//go:build mysql
// +build mysql

// Package mysql is a database adapter for MySQL.
package mysql

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"hash/fnv"
	"sort"
	"strconv"
	"strings"
	"sync"
	"time"

	ms "github.com/go-sql-driver/mysql"
	"github.com/jmoiron/sqlx"
	"github.com/tinode/chat/server/auth"
	dbadapter "github.com/tinode/chat/server/db"
	"github.com/tinode/chat/server/db/common"
	"github.com/tinode/chat/server/store"
	t "github.com/tinode/chat/server/store/types"
)

// adapter holds MySQL connection data.
type adapter struct {
	db         *sqlx.DB
	registryDB *sqlx.DB
	dsn        string
	dbName     string
	// Maximum number of records to return
	maxResults int
	// Maximum number of message records to return
	maxMessageResults int
	version           int

	// Single query timeout.
	sqlTimeout time.Duration
	// DB transaction timeout.
	txTimeout time.Duration

	baseConfig       *configType
	tenantDBRouting  bool
	tenantScopedDB   bool
	tenantID         t.TenantID
	tenantRegistryDB string
	tenantAdapters   map[t.TenantID]*adapter
	tenantMu         sync.Mutex
	groupShardWindow string
}

const (
	adpVersion  = 123
	adapterName = "mysql"

	defaultDSN      = "root:@tcp(localhost:3306)/meeting_im?parseTime=true"
	defaultDatabase = "meeting_im"

	defaultMaxResults = 1024
	// This is capped by the Session's send queue limit (128).
	defaultMaxMessageResults = 100

	// If DB request timeout is specified,
	// we allocate txTimeoutMultiplier times more time for transactions.
	txTimeoutMultiplier = 1.5
)

const defaultTenantID = t.TenantID(1)

func quoteIdent(name string) string {
	return "`" + strings.ReplaceAll(name, "`", "``") + "`"
}

func parseFileUID(fid string) t.Uid {
	name := strings.TrimSpace(fid)
	id := t.ParseUid(name)
	if !id.IsZero() {
		return id
	}
	if dot := strings.LastIndexByte(name, '.'); dot > 0 {
		ext := name[dot+1:]
		if len(ext) == 0 || len(ext) > 16 {
			return t.ZeroUid
		}
		for _, r := range ext {
			if (r < 'A' || r > 'Z') && (r < 'a' || r > 'z') && (r < '0' || r > '9') {
				return t.ZeroUid
			}
		}
		return t.ParseUid(name[:dot])
	}
	return t.ZeroUid
}

type configType struct {
	// DB connection settings.
	// See https://pkg.go.dev/github.com/go-sql-driver/mysql#Config
	// for the full list of fields.
	ms.Config
	// Deprecated.
	DSN string `json:"dsn,omitempty"`

	// Connection pool settings.
	//
	// Maximum number of open connections to the database.
	MaxOpenConns int `json:"max_open_conns,omitempty"`
	// Maximum number of connections in the idle connection pool.
	MaxIdleConns int `json:"max_idle_conns,omitempty"`
	// Maximum amount of time a connection may be reused (in seconds).
	ConnMaxLifetime int `json:"conn_max_lifetime,omitempty"`

	// DB request timeout (in seconds).
	// If 0 (or negative), no timeout is applied.
	SqlTimeout int `json:"sql_timeout,omitempty"`

	// TenantRegistryDB is the public backend database, e.g. hotgo.
	TenantRegistryDB string `json:"tenant_registry_db,omitempty"`
	// TenantDBRouting enables "one tenant, one database" routing.
	TenantDBRouting bool `json:"tenant_db_routing,omitempty"`
}

func (a *adapter) getContext() (context.Context, context.CancelFunc) {
	if a.sqlTimeout > 0 {
		return context.WithTimeout(context.Background(), a.sqlTimeout)
	}
	return context.Background(), nil
}

func (a *adapter) getContextForTx() (context.Context, context.CancelFunc) {
	if a.txTimeout > 0 {
		return context.WithTimeout(context.Background(), a.txTimeout)
	}
	return context.Background(), nil
}

func normalizeMySQLDSN(dsn string) string {
	dsn = strings.TrimSpace(dsn)
	if strings.HasPrefix(dsn, "mysql://") {
		return strings.TrimPrefix(dsn, "mysql://")
	}
	if strings.HasPrefix(dsn, "mysql:") {
		credentials, _, _ := strings.Cut(strings.TrimPrefix(dsn, "mysql:"), "@")
		if strings.Count(credentials, ":") >= 1 {
			return strings.TrimPrefix(dsn, "mysql:")
		}
	}
	return dsn
}

func openMySQLDB(config configType, dsn, dbName string) (*sqlx.DB, string, error) {
	if strings.TrimSpace(dsn) != "" {
		cfg, err := ms.ParseDSN(normalizeMySQLDSN(dsn))
		if err != nil {
			return nil, "", err
		}
		if dbName != "" {
			cfg.DBName = dbName
		}
		dsn = cfg.FormatDSN()
		dbName = cfg.DBName
	} else {
		cfg := config.Config
		if dbName != "" {
			cfg.DBName = dbName
		}
		if cfg.DBName == "" {
			cfg.DBName = defaultDatabase
		}
		dsn = cfg.FormatDSN()
		dbName = cfg.DBName
	}
	db, err := sqlx.Open(instrumentedMySQLDriverName, dsn)
	if err != nil {
		return nil, "", err
	}
	if config.MaxOpenConns > 0 {
		db.SetMaxOpenConns(config.MaxOpenConns)
	}
	if config.MaxIdleConns > 0 {
		db.SetMaxIdleConns(config.MaxIdleConns)
	}
	if config.ConnMaxLifetime > 0 {
		db.SetConnMaxLifetime(time.Duration(config.ConnMaxLifetime) * time.Second)
	}
	return db, dbName, nil
}

func (a *adapter) HealthCheck(ctx context.Context) error {
	if a.db == nil {
		return errors.New("mysql database is not open")
	}
	if err := a.db.PingContext(ctx); err != nil {
		return err
	}
	if a.registryDB != nil {
		if err := a.registryDB.PingContext(ctx); err != nil {
			return errors.New("tenant registry mysql: " + err.Error())
		}
	}
	return nil
}

// Open initializes database session
func (a *adapter) Open(jsonconfig json.RawMessage) error {
	if a.db != nil {
		return errors.New("mysql adapter is already connected")
	}

	if len(jsonconfig) < 2 {
		return errors.New("adapter mysql missing config")
	}

	var err error
	defaultCfg := ms.NewConfig()
	config := configType{Config: *defaultCfg}
	if err = json.Unmarshal(jsonconfig, &config); err != nil {
		return errors.New("mysql adapter failed to parse config: " + err.Error())
	}

	if dsn := config.FormatDSN(); dsn != defaultCfg.FormatDSN() {
		// MySql config is specified. Use it.
		a.dbName = config.DBName
		a.dsn = dsn
		if config.DSN != "" {
			return errors.New("mysql config: conflicting config and DSN are provided")
		}
	} else {
		// Otherwise, use DSN to configure database connection.
		// Note: this method is deprecated.
		if config.DSN != "" {
			// Remove optional schema.
			a.dsn = normalizeMySQLDSN(config.DSN)
		} else {
			a.dsn = defaultDSN
		}

		// Parse out the database name from the DSN.
		if cfg, err := ms.ParseDSN(a.dsn); err == nil {
			a.dbName = cfg.DBName
		} else {
			return err
		}
	}

	if a.dbName == "" {
		a.dbName = defaultDatabase
	}
	if strings.EqualFold(strings.TrimSpace(a.dbName), "tinode") {
		return errors.New("mysql database tinode is deprecated; use meeting_im")
	}
	config.Config.DBName = a.dbName
	a.baseConfig = &config
	a.tenantDBRouting = config.TenantDBRouting
	a.tenantID = defaultTenantID
	a.tenantRegistryDB = strings.TrimSpace(config.TenantRegistryDB)
	a.tenantAdapters = make(map[t.TenantID]*adapter)

	if a.maxResults <= 0 {
		a.maxResults = defaultMaxResults
	}

	if a.maxMessageResults <= 0 {
		a.maxMessageResults = defaultMaxMessageResults
	}

	// This just initializes the driver but does not open the network connection.
	a.db, a.dbName, err = openMySQLDB(config, a.dsn, a.dbName)
	if err != nil {
		return err
	}

	// Actually opening the network connection.
	err = a.db.Ping()
	if err == nil {
		if config.SqlTimeout > 0 {
			a.sqlTimeout = time.Duration(config.SqlTimeout) * time.Second
			// We allocate txTimeoutMultiplier times sqlTimeout for transactions.
			a.txTimeout = time.Duration(float64(config.SqlTimeout)*txTimeoutMultiplier) * time.Second
		}
		if a.tenantRegistryDB != "" && a.tenantRegistryDB != a.dbName {
			a.registryDB, _, err = openMySQLDB(config, a.dsn, a.tenantRegistryDB)
			if err == nil {
				err = a.registryDB.Ping()
			}
			if err != nil {
				return errors.New("mysql adapter failed to open tenant registry database: " + err.Error())
			}
		}
		if err = ensureUserPrivacySchema(a.db); err != nil {
			return errors.New("mysql adapter failed to ensure user privacy schema: " + err.Error())
		}
	}
	return err
}

// Close closes the underlying database connection
func (a *adapter) Close() error {
	var err error
	a.tenantMu.Lock()
	for tenantID, tenantAdp := range a.tenantAdapters {
		if tenantAdp != nil && tenantAdp.db != nil && tenantAdp.db != a.db {
			if closeErr := tenantAdp.db.Close(); err == nil {
				err = closeErr
			}
		}
		delete(a.tenantAdapters, tenantID)
	}
	a.tenantMu.Unlock()
	if a.registryDB != nil {
		if closeErr := a.registryDB.Close(); err == nil {
			err = closeErr
		}
		a.registryDB = nil
	}
	if a.db != nil {
		if closeErr := a.db.Close(); err == nil {
			err = closeErr
		}
		a.db = nil
		a.version = -1
	}
	return err
}

// IsOpen returns true if connection to database has been established. It does not check if
// connection is actually live.
func (a *adapter) IsOpen() bool {
	return a.db != nil
}

// GetDbVersion returns current database version.
func (a *adapter) GetDbVersion() (int, error) {
	if a.version > 0 {
		return a.version, nil
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var vers int
	err := a.db.GetContext(ctx, &vers, "SELECT `value` FROM im_kvmeta WHERE `key`='version'")
	if err != nil {
		if isMissingDb(err) || isMissingTable(err) || err == sql.ErrNoRows {
			err = errors.New("Database not initialized")
		}
		return -1, err
	}

	a.version = vers

	return vers, nil
}

func (a *adapter) updateDbVersion(v int) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	a.version = -1
	if _, err := a.db.ExecContext(ctx, "UPDATE im_kvmeta SET `value`=? WHERE `key`='version'", v); err != nil {
		return err
	}
	return nil
}

// CheckDbVersion checks whether the actual DB version matches the expected version of this adapter.
func (a *adapter) CheckDbVersion() error {
	version, err := a.GetDbVersion()
	if err != nil {
		return err
	}

	if version != adpVersion {
		return errors.New("Invalid database version " + strconv.Itoa(version) +
			". Expected " + strconv.Itoa(adpVersion))
	}

	return nil
}

// Version returns adapter version.
func (*adapter) Version() int {
	return adpVersion
}

// DB connection stats object.
func (a *adapter) Stats() any {
	if a.db == nil {
		return nil
	}
	return a.db.Stats()
}

// GetName returns string that adapter uses to register itself with store.
func (a *adapter) GetName() string {
	return adapterName
}

// SetMaxResults configures how many results can be returned in a single DB call.
func (a *adapter) SetMaxResults(val int) error {
	if val <= 0 {
		a.maxResults = defaultMaxResults
	} else {
		a.maxResults = val
	}

	return nil
}

// TenantGetByCode resolves a tenant by its public enterprise code.
func (a *adapter) TenantGetByCode(code string) (*t.Tenant, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	var tenant t.Tenant
	db := a.db
	if a.registryDB != nil {
		db = a.registryDB
	}
	err := db.GetContext(ctx, &tenant,
		`SELECT id, code, name, tenant_desc, state, created_at, created_by, updated_at, updated_by
		 FROM im_tenant WHERE code=? LIMIT 1`, code)
	if err == sql.ErrNoRows {
		return nil, t.ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	return &tenant, nil
}

// TenantGetByID resolves a tenant registry row by internal ID.
func (a *adapter) TenantGetByID(id t.TenantID) (*t.Tenant, error) {
	if !id.IsValid() {
		return nil, t.ErrMalformed
	}
	return a.tenantByID(id)
}

func (a *adapter) TenantListActive(limit int) ([]t.Tenant, error) {
	if limit <= 0 {
		limit = 1000
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	db := a.db
	if a.registryDB != nil {
		db = a.registryDB
	}
	var tenants []t.Tenant
	err := db.SelectContext(ctx, &tenants,
		`SELECT id, code, name, tenant_desc, state, created_at, created_by, updated_at, updated_by
		 FROM im_tenant WHERE state=? ORDER BY id ASC LIMIT ?`, t.TenantStateActive, limit)
	return tenants, err
}

func (a *adapter) TenantAdapterFor(tenantID t.TenantID) (dbadapter.TenantBusinessAdapter, dbadapter.TenantAuthAdapter, error) {
	if !a.tenantDBRouting {
		if a.tenantID != defaultTenantID && a.tenantID != tenantID {
			return nil, nil, t.ErrMalformed
		}
		if a.registryDB != nil {
			tenant, err := a.tenantByID(tenantID)
			if err != nil {
				return nil, nil, err
			}
			if tenant.State != t.TenantStateActive {
				return nil, nil, t.ErrPermissionDenied
			}
		}
		return a, a, nil
	}
	tenant, err := a.tenantByID(tenantID)
	if err != nil {
		return nil, nil, err
	}
	if tenant.State != t.TenantStateActive {
		return nil, nil, t.ErrPermissionDenied
	}
	a.tenantMu.Lock()
	if tenantAdp := a.tenantAdapters[tenantID]; tenantAdp != nil {
		a.tenantMu.Unlock()
		return tenantAdp, tenantAdp, nil
	}
	a.tenantMu.Unlock()

	registryDB := a.registryDB
	if registryDB == nil {
		registryDB = a.db
	}
	tenantAdp := &adapter{
		db:                a.db,
		registryDB:        registryDB,
		dsn:               a.dsn,
		dbName:            a.dbName,
		maxResults:        a.maxResults,
		maxMessageResults: a.maxMessageResults,
		version:           a.version,
		sqlTimeout:        a.sqlTimeout,
		txTimeout:         a.txTimeout,
		baseConfig:        a.baseConfig,
		tenantDBRouting:   false,
		tenantID:          tenantID,
		// Tenant adapters share the same database. Keep tenant predicates and
		// explicit tenant_id writes enabled for logical isolation.
		tenantScopedDB: false,
	}
	a.tenantMu.Lock()
	if existing := a.tenantAdapters[tenantID]; existing != nil {
		a.tenantMu.Unlock()
		return existing, existing, nil
	}
	a.tenantAdapters[tenantID] = tenantAdp
	a.tenantMu.Unlock()
	return tenantAdp, tenantAdp, nil
}

func (a *adapter) tenantByID(tenantID t.TenantID) (*t.Tenant, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	db := a.db
	if a.registryDB != nil {
		db = a.registryDB
	}
	var tenant t.Tenant
	err := db.GetContext(ctx, &tenant,
		`SELECT id, code, name, tenant_desc, state, created_at, created_by, updated_at, updated_by
		 FROM im_tenant WHERE id=? LIMIT 1`, tenantID)
	if err == sql.ErrNoRows {
		return nil, t.ErrNotFound
	}
	if err != nil {
		return nil, err
	}
	if !tenant.IsActive() {
		return nil, t.ErrPermissionDenied
	}
	return &tenant, nil
}

func createTenantRegistry(tx *sql.Tx, registryDB, _ string) error {
	if _, err := tx.Exec("CREATE DATABASE IF NOT EXISTS " + quoteIdent(registryDB) + " CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci"); err != nil {
		return err
	}
	if _, err := tx.Exec("USE " + quoteIdent(registryDB)); err != nil {
		return err
	}
	if _, err := tx.Exec(
		`CREATE TABLE IF NOT EXISTS im_tenant(
			id                            BIGINT NOT NULL,
			code                          VARCHAR(64) NOT NULL,
			name                          VARCHAR(128) NOT NULL,
			tenant_desc                   VARCHAR(256),
			max_users                     BIGINT UNSIGNED NOT NULL DEFAULT 0,
			max_groups                    BIGINT UNSIGNED NOT NULL DEFAULT 0,
			max_group_members             INT UNSIGNED NOT NULL DEFAULT 0,
			realname_review_policy        TINYINT(1) NOT NULL DEFAULT 0,
			aliyun_moderation_enabled     TINYINT(1) NOT NULL DEFAULT 0,
			local_moderation_enabled      TINYINT(1) NOT NULL DEFAULT 0,
			message_encryption_enabled    TINYINT(1) NOT NULL DEFAULT 0,
			default_policy_group_id       BIGINT,
			security_policy_version       INT UNSIGNED NOT NULL DEFAULT 0,
			global_friend_enabled         TINYINT(1) NOT NULL DEFAULT 1,
			message_curfew_enabled        TINYINT(1) NOT NULL DEFAULT 0,
			state                         SMALLINT NOT NULL,
			created_at                    DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			created_by                    BIGINT NOT NULL,
			updated_at                    DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			updated_by                    BIGINT NOT NULL,
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_tenant_code(code)
		)`); err != nil {
		return err
	}
	_, err := tx.Exec(
		`INSERT INTO im_tenant(id,code,name,tenant_desc,state,created_by,updated_by)
		 VALUES(1,'default','Default Tenant',NULL,?,0,0)
		 ON DUPLICATE KEY UPDATE state=VALUES(state), updated_by=VALUES(updated_by)`,
		t.TenantStateActive)
	return err
}

// CreateDb is intentionally disabled for this deployment.
//
// Database creation, table creation, schema migration, indexes and seed data
// are handled by reviewed SQL files and the release process. The service and
// local database tools must not create or mutate schema implicitly.
func (a *adapter) CreateDb(reset bool) error {
	return errors.New("mysql schema auto-creation is disabled; apply reviewed SQL manually before starting the service")
}

// UpgradeDb is intentionally schema-read-only.
//
// Automatic ALTER/CREATE upgrade steps are disabled. If the database version
// differs from the adapter version, prepare and apply a reviewed SQL migration,
// then update im_kvmeta.version as part of that migration.
func (a *adapter) UpgradeDb() error {
	if _, err := a.GetDbVersion(); err != nil {
		return err
	}

	if a.version == adpVersion {
		return nil
	}

	return errors.New("mysql schema auto-upgrade is disabled; apply reviewed SQL manually to upgrade from version " +
		strconv.Itoa(a.version) + " to " + strconv.Itoa(adpVersion))
}

func (a *adapter) ensureMessageTopicSeqIndex() error {
	const indexName = "messages_topic_seqid"
	var count int
	if err := a.db.QueryRow(
		`SELECT COUNT(*) FROM information_schema.statistics
		 WHERE table_schema=DATABASE() AND table_name='im_messages' AND index_name=?`,
		indexName).Scan(&count); err != nil {
		return err
	}
	if count > 0 {
		return nil
	}
	_, err := a.db.Exec("ALTER TABLE im_messages ADD UNIQUE INDEX messages_topic_seqid(topic, seqid)")
	return err
}

func (a *adapter) ensureTopicNameUniqueIndex() error {
	ctx := context.Background()
	conn, err := a.db.Connx(ctx)
	if err != nil {
		return err
	}
	defer conn.Close()

	tenantScoped, err := identityColumnExists(ctx, conn, "im_topics", "tenant_id")
	if err != nil {
		return err
	}

	var count int
	if tenantScoped {
		if err = conn.QueryRowContext(ctx,
			`SELECT COUNT(*) FROM information_schema.statistics
			 WHERE table_schema=DATABASE() AND table_name='im_topics' AND index_name='uk_topics_tenant_name' AND non_unique=0`,
		).Scan(&count); err != nil {
			return err
		}
		if count > 0 {
			return nil
		}
		if _, err = conn.ExecContext(ctx, `UPDATE im_topics AS keep_t
			JOIN (
				SELECT tenant_id,name,MIN(id) AS keep_id,
					MAX(seqid) AS seqid,MAX(delid) AS delid,
					MAX(COALESCE(touchedat,'1000-01-01')) AS touchedat,
					MAX(updatedat) AS updatedat
				FROM im_topics GROUP BY tenant_id,name HAVING COUNT(*)>1
			) AS dup ON dup.keep_id=keep_t.id
			SET keep_t.seqid=GREATEST(keep_t.seqid,dup.seqid),
				keep_t.delid=GREATEST(keep_t.delid,dup.delid),
				keep_t.touchedat=NULLIF(GREATEST(COALESCE(keep_t.touchedat,'1000-01-01'),dup.touchedat),'1000-01-01'),
				keep_t.updatedat=GREATEST(keep_t.updatedat,dup.updatedat)`); err != nil {
			return err
		}
		if _, err = conn.ExecContext(ctx, `DELETE t FROM im_topics AS t
			JOIN (
				SELECT tenant_id,name,MIN(id) AS keep_id
				FROM im_topics GROUP BY tenant_id,name HAVING COUNT(*)>1
			) AS dup ON dup.tenant_id=t.tenant_id AND dup.name=t.name AND t.id<>dup.keep_id`); err != nil {
			return err
		}
		_, err = conn.ExecContext(ctx, "ALTER TABLE im_topics ADD UNIQUE INDEX uk_topics_tenant_name(tenant_id, name)")
		if isDupe(err) {
			return nil
		}
		return err
	}

	if err = conn.QueryRowContext(ctx,
		`SELECT COUNT(*) FROM information_schema.statistics
		 WHERE table_schema=DATABASE() AND table_name='im_topics' AND index_name='topics_name' AND non_unique=0`,
	).Scan(&count); err != nil {
		return err
	}
	if count > 0 {
		return nil
	}
	if _, err = conn.ExecContext(ctx, `UPDATE im_topics AS keep_t
		JOIN (
			SELECT name,MIN(id) AS keep_id,
				MAX(seqid) AS seqid,MAX(delid) AS delid,
				MAX(COALESCE(touchedat,'1000-01-01')) AS touchedat,
				MAX(updatedat) AS updatedat
			FROM im_topics GROUP BY name HAVING COUNT(*)>1
		) AS dup ON dup.keep_id=keep_t.id
		SET keep_t.seqid=GREATEST(keep_t.seqid,dup.seqid),
			keep_t.delid=GREATEST(keep_t.delid,dup.delid),
			keep_t.touchedat=NULLIF(GREATEST(COALESCE(keep_t.touchedat,'1000-01-01'),dup.touchedat),'1000-01-01'),
			keep_t.updatedat=GREATEST(keep_t.updatedat,dup.updatedat)`); err != nil {
		return err
	}
	if _, err = conn.ExecContext(ctx, `DELETE t FROM im_topics AS t
		JOIN (
			SELECT name,MIN(id) AS keep_id
			FROM im_topics GROUP BY name HAVING COUNT(*)>1
		) AS dup ON dup.name=t.name AND t.id<>dup.keep_id`); err != nil {
		return err
	}
	if _, err = conn.ExecContext(ctx, "ALTER TABLE im_topics ADD UNIQUE INDEX topics_name(name)"); err != nil {
		if isDupe(err) {
			return nil
		}
		return err
	}
	return nil
}

func (a *adapter) ensureTopicSeqMatchesMessages() error {
	ctx := context.Background()
	conn, err := a.db.Connx(ctx)
	if err != nil {
		return err
	}
	defer conn.Close()

	topicsScoped, err := identityColumnExists(ctx, conn, "im_topics", "tenant_id")
	if err != nil {
		return err
	}
	messagesScoped, err := identityColumnExists(ctx, conn, "im_messages", "tenant_id")
	if err != nil {
		return err
	}
	if topicsScoped && messagesScoped {
		if _, err = conn.ExecContext(ctx, `UPDATE im_topics AS t
			JOIN (SELECT tenant_id,topic,MAX(seqid) AS max_seq FROM im_messages GROUP BY tenant_id,topic) AS m
				ON m.tenant_id=t.tenant_id AND m.topic COLLATE utf8mb4_unicode_ci=t.name
			SET t.seqid=GREATEST(t.seqid,m.max_seq)
			WHERE t.seqid<m.max_seq`); err != nil {
			return err
		}
	} else {
		if _, err = conn.ExecContext(ctx, `UPDATE im_topics AS t
			JOIN (SELECT topic,MAX(seqid) AS max_seq FROM im_messages GROUP BY topic) AS m ON m.topic COLLATE utf8mb4_unicode_ci=t.name
			SET t.seqid=GREATEST(t.seqid,m.max_seq)
			WHERE t.seqid<m.max_seq`); err != nil {
			return err
		}
	}
	groupMessagesExist, err := identityTableExists(ctx, conn, "im_group_messages")
	if err != nil || !groupMessagesExist {
		return err
	}
	groupMessagesScoped, err := identityColumnExists(ctx, conn, "im_group_messages", "tenant_id")
	if err != nil {
		return err
	}
	if topicsScoped && groupMessagesScoped {
		_, err = conn.ExecContext(ctx, `UPDATE im_topics AS t
			JOIN (SELECT tenant_id,topic,MAX(seqid) AS max_seq FROM im_group_messages GROUP BY tenant_id,topic) AS m
				ON m.tenant_id=t.tenant_id AND m.topic COLLATE utf8mb4_unicode_ci=t.name
			SET t.seqid=GREATEST(t.seqid,m.max_seq)
			WHERE t.seqid<m.max_seq`)
		return err
	}
	_, err = conn.ExecContext(ctx, `UPDATE im_topics AS t
		JOIN (SELECT topic,MAX(seqid) AS max_seq FROM im_group_messages GROUP BY topic) AS m ON m.topic COLLATE utf8mb4_unicode_ci=t.name
		SET t.seqid=GREATEST(t.seqid,m.max_seq)
		WHERE t.seqid<m.max_seq`)
	return err
}

func createIMNotificationTables(tx *sql.Tx) error {
	_, err := tx.Exec(
		`CREATE TABLE im_system_notifications(
			id          BIGINT NOT NULL AUTO_INCREMENT,
			user_id     BIGINT NOT NULL,
			event_id    VARCHAR(64) NOT NULL,
			event_type  VARCHAR(64) NOT NULL,
			title       VARCHAR(128) NOT NULL,
			summary     VARCHAR(512) NOT NULL,
			action      JSON,
			read_at     DATETIME(3),
			created_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_system_notifications_event(user_id, event_id),
			INDEX idx_im_system_notifications_inbox(user_id, id DESC)
		)`)
	return err
}

func createIMCallTables(tx *sql.Tx) error {
	_, err := tx.Exec(
		`CREATE TABLE im_call_records(
			id          BIGINT NOT NULL AUTO_INCREMENT,
			call_id     VARCHAR(64) NOT NULL,
			topic       CHAR(25) NOT NULL,
			seq_id      BIGINT NOT NULL,
			caller_id   BIGINT NOT NULL,
			callee_id   BIGINT NOT NULL,
			call_type   VARCHAR(16) NOT NULL,
			status      VARCHAR(32) NOT NULL,
			end_reason  VARCHAR(64) NOT NULL DEFAULT '',
			duration_ms BIGINT NOT NULL DEFAULT 0,
			started_at  DATETIME(3) NOT NULL,
			accepted_at DATETIME(3),
			finished_at DATETIME(3),
			created_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_call_records_call(call_id),
			UNIQUE INDEX uk_im_call_records_topic_seq(topic, seq_id),
			INDEX idx_im_call_records_caller(caller_id, id DESC),
			INDEX idx_im_call_records_callee(callee_id, id DESC),
			INDEX idx_im_call_records_status(status, updated_at)
		)`)
	return err
}

func createIMUserProductTables(tx *sql.Tx) error {
	statements := []string{
		`CREATE TABLE im_user_profiles(
			id             BIGINT NOT NULL,
			user_id        BIGINT NOT NULL,
			avatar_file_id VARCHAR(64) NOT NULL DEFAULT '',
			nickname       VARCHAR(64) NOT NULL DEFAULT '',
			birth_date     DATE,
			signature      VARCHAR(256) NOT NULL DEFAULT '',
			gender         VARCHAR(16) NOT NULL DEFAULT '',
			region         VARCHAR(128) NOT NULL DEFAULT '',
			email          VARCHAR(128) NOT NULL DEFAULT '',
			public_account VARCHAR(64) NOT NULL DEFAULT '',
			friend_add_enabled TINYINT NOT NULL DEFAULT 1,
			friend_add_disabled_reason VARCHAR(255) NOT NULL DEFAULT '',
			friend_add_policy_version INT NOT NULL DEFAULT 1,
			version        INT NOT NULL DEFAULT 1,
			created_at     DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at     DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_user_profiles_user(user_id)
		)`,
		`CREATE TABLE im_user_privacy_settings(
			id                   BIGINT NOT NULL,
			user_id              BIGINT NOT NULL,
			add_me_methods       JSON,
			profile_visibility   VARCHAR(32) NOT NULL DEFAULT 'friends',
			last_seen_visibility VARCHAR(32) NOT NULL DEFAULT 'friends',
			read_receipts        TINYINT NOT NULL DEFAULT 1,
			friend_request_verification TINYINT NOT NULL DEFAULT 1,
			group_invite_verification TINYINT NOT NULL DEFAULT 0,
			version              INT NOT NULL DEFAULT 1,
			created_at           DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at           DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_user_privacy_settings_user(user_id)
		)`,
		`CREATE TABLE im_device_push_tokens(
			id          BIGINT NOT NULL,
			device_id   VARCHAR(128) NOT NULL,
			user_id     BIGINT NOT NULL,
			provider    VARCHAR(32) NOT NULL,
			token       VARCHAR(512) NOT NULL,
			app_version VARCHAR(64) NOT NULL DEFAULT '',
			platform    VARCHAR(32) NOT NULL DEFAULT '',
			sdk_version VARCHAR(64) NOT NULL DEFAULT '',
			push_env    VARCHAR(32) NOT NULL DEFAULT '',
			notification_permission VARCHAR(32) NOT NULL DEFAULT '',
			created_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_device_push_tokens_device(device_id),
			UNIQUE INDEX uk_im_device_push_tokens_provider_token(provider, token),
			INDEX idx_im_device_push_tokens_user(user_id, updated_at)
		)`,
		`CREATE TABLE im_risk_challenges(
			id              BIGINT NOT NULL AUTO_INCREMENT,
			challenge_id    VARCHAR(64) NOT NULL,
			user_id         BIGINT NOT NULL,
			action          VARCHAR(64) NOT NULL,
			level           VARCHAR(16) NOT NULL,
			notice_code     VARCHAR(64) NOT NULL,
			notice_params   JSON,
			state           VARCHAR(16) NOT NULL DEFAULT 'pending',
			expires_at      DATETIME(3) NOT NULL,
			decision        VARCHAR(16) NOT NULL DEFAULT '',
			action_token_id VARCHAR(64) NOT NULL DEFAULT '',
			created_at      DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at      DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_risk_challenges_challenge(challenge_id),
			INDEX idx_im_risk_challenges_user_state(user_id, state, expires_at)
		)`,
		`CREATE TABLE im_abuse_reasons(
			id                   BIGINT NOT NULL AUTO_INCREMENT,
			target_type          VARCHAR(16) NOT NULL,
			reason_code          VARCHAR(64) NOT NULL,
			label                VARCHAR(128) NOT NULL,
			requires_description TINYINT NOT NULL DEFAULT 0,
			allows_evidence      TINYINT NOT NULL DEFAULT 1,
			sort_order           INT NOT NULL DEFAULT 0,
			enabled              TINYINT NOT NULL DEFAULT 1,
			created_at           DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at           DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_abuse_reasons_type_code(target_type, reason_code),
			INDEX idx_im_abuse_reasons_type_order(target_type, enabled, sort_order)
		)`,
		`CREATE TABLE im_abuse_reports(
			id                BIGINT NOT NULL AUTO_INCREMENT,
			report_id         VARCHAR(64) NOT NULL,
			reporter_id       BIGINT NOT NULL,
			target_type       VARCHAR(16) NOT NULL,
			target_user_id    BIGINT NOT NULL DEFAULT 0,
			target_topic      VARCHAR(32) NOT NULL DEFAULT '',
			target_seq        BIGINT NOT NULL DEFAULT 0,
			reason_code       VARCHAR(64) NOT NULL,
			description       TEXT NOT NULL,
			evidence_file_ids JSON,
			snapshot          JSON,
			idempotency_key   VARCHAR(128) NOT NULL,
			status            VARCHAR(32) NOT NULL DEFAULT 'received',
			created_at        DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at        DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_abuse_reports_report(report_id),
			UNIQUE INDEX uk_im_abuse_reports_idempotency(reporter_id, idempotency_key),
			INDEX idx_im_abuse_reports_target(target_type, target_topic, target_seq, target_user_id),
			INDEX idx_im_abuse_reports_reporter(reporter_id, id DESC)
		)`,
		`CREATE TABLE im_feedback_config(
			id                 BIGINT NOT NULL AUTO_INCREMENT,
			categories         JSON,
			max_length         INT NOT NULL DEFAULT 1000,
			attachment_policy  JSON,
			allow_contact      TINYINT NOT NULL DEFAULT 1,
			diagnostics_notice TEXT NOT NULL,
			created_at         DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at         DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id)
		)`,
		`CREATE TABLE im_feedback_submissions(
			id                  BIGINT NOT NULL AUTO_INCREMENT,
			feedback_id         VARCHAR(64) NOT NULL,
			user_id             BIGINT NOT NULL,
			category            VARCHAR(64) NOT NULL,
			content             TEXT NOT NULL,
			contact             VARCHAR(128) NOT NULL DEFAULT '',
			attachment_file_ids JSON,
			client_context      JSON,
			include_diagnostics TINYINT NOT NULL DEFAULT 0,
			idempotency_key     VARCHAR(128) NOT NULL,
			status              VARCHAR(32) NOT NULL DEFAULT 'received',
			created_at          DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at          DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_feedback_submissions_feedback(feedback_id),
			UNIQUE INDEX uk_im_feedback_submissions_idempotency(user_id, idempotency_key),
			INDEX idx_im_feedback_submissions_user(user_id, id DESC)
		)`,
	}
	for _, stmt := range statements {
		if _, err := tx.Exec(stmt); err != nil {
			return err
		}
	}
	return nil
}

func upgradeIMMessageActions(a *adapter) error {
	statements := []string{
		"ALTER TABLE im_messages ADD COLUMN version INT NOT NULL DEFAULT 1 AFTER client_msg_id",
		"ALTER TABLE im_messages ADD COLUMN recalled_at DATETIME(3) AFTER version",
		"ALTER TABLE im_messages ADD COLUMN recalled_by BIGINT AFTER recalled_at",
		`CREATE TABLE im_message_revisions(
			id          BIGINT NOT NULL AUTO_INCREMENT,
			createdat   DATETIME(3) NOT NULL,
			updatedat   DATETIME(3) NOT NULL,
			topic       CHAR(25) NOT NULL,
			seqid       BIGINT NOT NULL,
			version     INT NOT NULL,
			actor       BIGINT NOT NULL,
			head        JSON,
			content     JSON,
			reason      VARCHAR(256) NOT NULL DEFAULT '',
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_message_revisions_version(topic, seqid, version)
		)`,
	}
	for _, stmt := range statements {
		if _, err := a.db.Exec(stmt); err != nil {
			return err
		}
	}
	return nil
}

type sqlExecutor interface {
	Exec(query string, args ...any) (sql.Result, error)
}

func createIMRelationTables(exec sqlExecutor) error {
	statements := []string{
		`CREATE TABLE im_friend_requests(
			id               BIGINT NOT NULL AUTO_INCREMENT,
			request_id       VARCHAR(64) NOT NULL,
			applicant_id     BIGINT NOT NULL,
			target_id        BIGINT NOT NULL,
			message          VARCHAR(200) NOT NULL DEFAULT '',
			source           VARCHAR(32) NOT NULL DEFAULT '',
			source_topic     VARCHAR(64) NOT NULL DEFAULT '',
			status           VARCHAR(16) NOT NULL,
			idempotency_key  VARCHAR(128) NOT NULL DEFAULT '',
			expires_at       DATETIME(3) NOT NULL,
			handled_at       DATETIME(3),
			created_at       DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at       DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_friend_requests_request(request_id),
			UNIQUE INDEX uk_im_friend_requests_idempotency(applicant_id, idempotency_key),
			INDEX idx_im_friend_requests_pair(applicant_id, target_id, status, created_at),
			INDEX idx_im_friend_requests_inbox(target_id, status, created_at)
		)`,
		`CREATE TABLE im_friendships(
			id          BIGINT NOT NULL,
			user_id     BIGINT NOT NULL,
			peer_id     BIGINT NOT NULL,
			status      VARCHAR(16) NOT NULL,
			remark      VARCHAR(64) NOT NULL DEFAULT '',
			topic       CHAR(25) NOT NULL DEFAULT '',
			created_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_friendships_pair(user_id, peer_id),
			INDEX idx_im_friendships_peer(peer_id, status)
		)`,
		`CREATE TABLE im_user_blocks(
			id          BIGINT NOT NULL,
			blocker_id  BIGINT NOT NULL,
			blocked_id  BIGINT NOT NULL,
			created_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at  DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_user_blocks_pair(blocker_id, blocked_id),
			INDEX idx_im_user_blocks_blocked(blocked_id)
		)`,
		`CREATE TABLE im_favorites(
			id               BIGINT NOT NULL AUTO_INCREMENT,
			favorite_id      VARCHAR(64) NOT NULL,
			user_id          BIGINT NOT NULL,
			item_type        VARCHAR(16) NOT NULL,
			source_topic     CHAR(25) NOT NULL,
			source_seq       BIGINT NOT NULL,
			snapshot         JSON,
			attachment_refs  JSON,
			availability     VARCHAR(16) NOT NULL DEFAULT 'available',
			idempotency_key  VARCHAR(128) NOT NULL DEFAULT '',
			collected_at     DATETIME(3) NOT NULL,
			created_at       DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at       DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_favorites_favorite(favorite_id),
			UNIQUE INDEX uk_im_favorites_source(user_id, source_topic, source_seq),
			UNIQUE INDEX uk_im_favorites_idempotency(user_id, ((NULLIF(idempotency_key, '')))),
			INDEX idx_im_favorites_inbox(user_id, id DESC),
			INDEX idx_im_favorites_type(user_id, item_type, id DESC)
		)`,
	}
	for _, stmt := range statements {
		if _, err := exec.Exec(stmt); err != nil {
			return err
		}
	}
	return nil
}

func createIMSecurityTables(tx *sql.Tx) error {
	if _, err := tx.Exec(
		`CREATE TABLE im_verification_codes(
			id                      BIGINT NOT NULL AUTO_INCREMENT,
			challenge_id            VARCHAR(64) NOT NULL,
			scene                   VARCHAR(32) NOT NULL,
			action                  VARCHAR(64) NOT NULL DEFAULT '',
			phone_hash              CHAR(64) NOT NULL,
			phone_mask              VARCHAR(32) NOT NULL,
			target_user             BIGINT,
			code_hash               CHAR(64) NOT NULL,
			verification_token_hash CHAR(64),
			state                   SMALLINT NOT NULL,
			attempts                INT NOT NULL DEFAULT 0,
			max_attempts            INT NOT NULL,
			expires_at              DATETIME(3) NOT NULL,
			resend_after            DATETIME(3) NOT NULL,
			verified_at             DATETIME(3),
			consumed_at             DATETIME(3),
			created_at              DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at              DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_verification_challenge(challenge_id),
			INDEX idx_im_verification_scene_phone_state(scene, phone_hash, state, expires_at)
		)`); err != nil {
		return err
	}
	if _, err := tx.Exec(
		`CREATE TABLE im_realname_verifications(
			id                BIGINT NOT NULL AUTO_INCREMENT,
			user_id           BIGINT NOT NULL,
			submission_id     VARCHAR(64) NOT NULL,
			status            VARCHAR(16) NOT NULL,
			name_cipher       TEXT NOT NULL,
			id_type           VARCHAR(32) NOT NULL,
			id_number_cipher  TEXT NOT NULL,
			id_number_hash    CHAR(64) NOT NULL,
			masked_name       VARCHAR(64) NOT NULL,
			masked_id_number  VARCHAR(64) NOT NULL,
			review_reason     VARCHAR(256),
			verified_at       DATETIME(3),
			created_at        DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at        DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_realname_submission(submission_id),
			INDEX idx_im_realname_user_latest(user_id, created_at),
			INDEX idx_im_realname_id_hash(id_number_hash)
		)`); err != nil {
		return err
	}
	if _, err := tx.Exec(
		`CREATE TABLE im_realname_appeals(
			id               BIGINT NOT NULL,
			appeal_id        VARCHAR(64) NOT NULL,
			user_id          BIGINT NOT NULL,
			reason           VARCHAR(500) NOT NULL DEFAULT '',
			attachments_json JSON,
			status           VARCHAR(32) NOT NULL DEFAULT 'pending',
			review_comment   VARCHAR(500) NOT NULL DEFAULT '',
			created_at       DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at       DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_realname_appeals_appeal(appeal_id),
			INDEX idx_im_realname_appeals_user(user_id, created_at),
			INDEX idx_im_realname_appeals_status(status, created_at)
		)`); err != nil {
		return err
	}
	_, err := tx.Exec(
		`CREATE TABLE im_youth_mode_settings(
			id              BIGINT NOT NULL,
			user_id         BIGINT NOT NULL,
			purpose         VARCHAR(64) NOT NULL,
			password_hash   VARBINARY(255) NOT NULL,
			enabled         TINYINT NOT NULL DEFAULT 0,
			policy_version  INT NOT NULL DEFAULT 1,
			restrictions    JSON,
			enabled_at      DATETIME(3),
			failed_attempts INT NOT NULL DEFAULT 0,
			locked_until    DATETIME(3),
			created_at      DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
			updated_at      DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
			PRIMARY KEY(id),
			UNIQUE INDEX uk_im_youth_mode_settings_user_purpose(user_id, purpose)
		)`)
	return err
}

// Create system topic 'sys'.
func createSystemTopic(tx *sql.Tx) error {
	now := t.TimeNow()
	query := `INSERT INTO im_topics(createdat,updatedat,state,touchedat,name,access,public)
				VALUES(?,?,?,?,'sys','{"Auth": "N","Anon": "N"}','{"fn": "System"}')`
	_, err := tx.Exec(query, now, now, t.StateOK, now)
	return err
}

func addTags(tx *sqlx.Tx, table, keyName string, keyVal any, tags []string, ignoreDups bool) error {
	if len(tags) == 0 {
		return nil
	}

	insert, err := tx.Prepare("INSERT INTO " + table + "(" + keyName + ",tag) VALUES(?,?)")
	if err != nil {
		return err
	}

	for _, tag := range tags {
		if _, err = insert.Exec(keyVal, tag); err != nil {
			if isDupe(err) {
				if ignoreDups {
					err = nil
					continue
				}
				return t.ErrDuplicate
			}
			return err
		}
	}
	return nil
}

func addTenantTags(tx *sqlx.Tx, tenantID t.TenantID, table, keyName string, keyVal any,
	tags []string, ignoreDups bool) error {
	if len(tags) == 0 {
		return nil
	}

	insert, err := tx.Prepare("INSERT INTO " + table + "(tenant_id," + keyName + ",tag) VALUES(?,?,?)")
	if err != nil {
		return err
	}
	defer insert.Close()

	for _, tag := range tags {
		if _, err = insert.Exec(tenantID, keyVal, tag); err != nil {
			if isDupe(err) && ignoreDups {
				continue
			}
			if isDupe(err) {
				return t.ErrDuplicate
			}
			return err
		}
	}
	return nil
}

func removeTags(tx *sqlx.Tx, table, keyName string, keyVal any, tags []string) error {
	if len(tags) == 0 {
		return nil
	}

	var args []any
	for _, tag := range tags {
		args = append(args, tag)
	}

	query, args, _ := sqlx.In("DELETE FROM "+table+" WHERE "+keyName+"=? AND tag IN (?)", keyVal, args)
	_, err := tx.Exec(tx.Rebind(query), args...)

	return err
}

// UserCreate creates a new user. Returns error and true if error is due to duplicate user name,
// false for any other error
func (a *adapter) UserCreate(user *t.User) error {
	if user == nil || strings.TrimSpace(user.Username) == "" {
		return t.ErrMalformed
	}
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	decoded_uid := store.DecodeUid(user.Uid())
	securityID, err := nextSnowflakeID()
	if err != nil {
		return err
	}
	profileID, err := nextSnowflakeID()
	if err != nil {
		return err
	}
	var phone any
	if strings.TrimSpace(user.Phone) != "" {
		canonicalPhone, err := normalizeUserPhone(user.Phone)
		if err != nil {
			return err
		}
		user.Phone = canonicalPhone
		phone = canonicalPhone
	}
	accountNo, hasAccountNo, err := nextUserAccountNo(ctx, tx)
	if err != nil {
		return err
	}
	nickname, avatarFileID := profileSeedFromPublic(user.Public)
	insert := "INSERT INTO im_users(id,username,createdat,updatedat,state,access,phone,trusted) VALUES(?,?,?,?,?,?,?,?)"
	args := []any{decoded_uid, user.Username, user.CreatedAt, user.UpdatedAt, user.State, user.Access, phone,
		common.ToJSON(user.Trusted)}
	if hasAccountNo {
		insert = "INSERT INTO im_users(id,account_no,username,createdat,updatedat,state,access,phone,trusted) VALUES(?,?,?,?,?,?,?,?,?)"
		args = []any{decoded_uid, accountNo, user.Username, user.CreatedAt, user.UpdatedAt, user.State, user.Access, phone,
			common.ToJSON(user.Trusted)}
	}
	if _, err = tx.Exec(insert, args...); err != nil {
		if isDupe(err) {
			return t.ErrDuplicate
		}
		return err
	}

	if _, err = tx.Exec("INSERT INTO im_user_security(id,user_id,auth_version,created_at,updated_at) VALUES(?,?,?,?,?)",
		securityID, decoded_uid, 1, user.CreatedAt, user.UpdatedAt); err != nil {
		return err
	}
	if _, err = tx.Exec(`INSERT IGNORE INTO im_user_profiles(id,user_id,avatar_file_id,nickname,public_account,created_at,updated_at)
		VALUES(?,?,?,?,?,?,?)`, profileID, decoded_uid, avatarFileID, nickname, user.Uid().UserId(), user.CreatedAt, user.UpdatedAt); err != nil {
		return err
	}
	user.Tags = nil

	return tx.Commit()
}

// nextUserAccountNo allocates a tenant-local, human-facing account number.
// The sequence row serializes concurrent registrations across server nodes.
func nextUserAccountNo(ctx context.Context, tx *sqlx.Tx) (uint32, bool, error) {
	var columns int
	if err := tx.GetContext(ctx, &columns, `SELECT COUNT(*) FROM information_schema.COLUMNS
		WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME='im_users' AND COLUMN_NAME='account_no'`); err != nil {
		return 0, false, err
	}
	if columns == 0 {
		return 0, false, nil
	}

	if _, err := tx.ExecContext(ctx, `INSERT IGNORE INTO im_user_account_sequences(id,next_value)
		SELECT 1,GREATEST(COALESCE(MAX(account_no),999),999) FROM im_users WHERE account_no>0`); err != nil {
		return 0, true, err
	}
	if _, err := tx.ExecContext(ctx, `UPDATE im_user_account_sequences
		SET next_value=GREATEST(next_value,(SELECT GREATEST(COALESCE(MAX(account_no),999),999) FROM im_users WHERE account_no>0))
		WHERE id=1`); err != nil {
		return 0, true, err
	}

	result, err := tx.ExecContext(ctx, `UPDATE im_user_account_sequences
		SET next_value=LAST_INSERT_ID(next_value+1) WHERE id=1`)
	if err != nil {
		return 0, true, err
	}
	if affected, affectedErr := result.RowsAffected(); affectedErr != nil {
		return 0, true, affectedErr
	} else if affected != 1 {
		return 0, true, errors.New("mysql: user account sequence is not initialized")
	}
	var next uint64
	if err = tx.GetContext(ctx, &next, "SELECT LAST_INSERT_ID()"); err != nil {
		return 0, true, err
	}
	if next > uint64(^uint32(0)) {
		return 0, true, errors.New("mysql: user account number exhausted")
	}
	return uint32(next), true, nil
}

// TenantAuthAddRecord adds the user's Basic authentication record.
func (a *adapter) TenantAuthAddRecord(tenantID t.TenantID, uid t.Uid,
	authLvl auth.Level, secret []byte, expires time.Time) error {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantAuthAddRecord(tenantID, uid, authLvl, secret, expires)
	}
	var exp *time.Time
	if !expires.IsZero() {
		exp = &expires
	}
	var username string
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	if err = a.db.GetContext(ctx, &username, "SELECT username FROM im_users WHERE tenant_id=? AND id=?", tenantID, store.DecodeUid(uid)); err != nil {
		if err == sql.ErrNoRows {
			return t.ErrNotFound
		}
		return err
	}
	authID, err := nextSnowflakeID()
	if err != nil {
		return err
	}
	_, err = a.db.ExecContext(ctx, "INSERT INTO im_auth(tenant_id,id,userid,authLvl,secret,expires) VALUES(?,?,?,?,?,?)",
		tenantID, authID, store.DecodeUid(uid), authLvl, secret, exp)
	if isIDOutOfRange(err) {
		_, err = a.db.ExecContext(ctx, "INSERT INTO im_auth(tenant_id,userid,authLvl,secret,expires) VALUES(?,?,?,?,?)",
			tenantID, store.DecodeUid(uid), authLvl, secret, exp)
	}
	if isDupe(err) {
		return t.ErrDuplicate
	}
	return err
}

// TenantAuthDeleteRecord deletes the Basic authentication record.
func (a *adapter) TenantAuthDeleteRecord(tenantID t.TenantID, uid t.Uid) error {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantAuthDeleteRecord(tenantID, uid)
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err = a.db.ExecContext(ctx, "DELETE FROM im_auth WHERE tenant_id=? AND userid=?", tenantID, store.DecodeUid(uid))
	return err
}

// TenantAuthUpdateRecord updates the Basic authentication record and optional username.
func (a *adapter) TenantAuthUpdateRecord(tenantID t.TenantID, uid t.Uid, username string,
	authLvl auth.Level, secret []byte, expires time.Time) error {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantAuthUpdateRecord(tenantID, uid, username, authLvl, secret, expires)
	}
	params := []string{"authLvl=?"}
	args := []any{authLvl}
	if len(secret) > 0 {
		params = append(params, "secret=?")
		args = append(args, secret)
	}
	if !expires.IsZero() {
		params = append(params, "expires=?")
		args = append(args, expires)
	}
	decodedUID := store.DecodeUid(uid)
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	if username != "" {
		if _, err = tx.ExecContext(ctx, "UPDATE im_users SET username=?,updatedat=? WHERE tenant_id=? AND id=?", username, t.TimeNow(), tenantID, decodedUID); err != nil {
			if isDupe(err) {
				return t.ErrDuplicate
			}
			return err
		}
	}
	args = append(args, tenantID, decodedUID)
	resp, err := tx.ExecContext(ctx, "UPDATE im_auth SET "+strings.Join(params, ",")+" WHERE tenant_id=? AND userid=?", args...)
	if err != nil {
		return err
	}
	if count, _ := resp.RowsAffected(); count <= 0 {
		return t.ErrNotFound
	}
	return tx.Commit()
}

// TenantAuthGetRecord retrieves a user's Basic authentication record.
func (a *adapter) TenantAuthGetRecord(tenantID t.TenantID, uid t.Uid) (string,
	auth.Level, []byte, time.Time, error) {
	var expires time.Time
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return "", auth.LevelNone, nil, expires, t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantAuthGetRecord(tenantID, uid)
	}
	var record struct {
		Username string
		Authlvl  auth.Level
		Secret   []byte
		Expires  *time.Time
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	err = a.db.GetContext(ctx, &record, `SELECT u.username,a.secret,a.expires,a.authlvl
		FROM im_auth AS a JOIN im_users AS u ON u.tenant_id=a.tenant_id AND u.id=a.userid
		WHERE a.tenant_id=? AND a.userid=?`, tenantID, store.DecodeUid(uid))
	if err == sql.ErrNoRows {
		return "", auth.LevelNone, nil, expires, t.ErrNotFound
	}
	if err != nil {
		return "", auth.LevelNone, nil, expires, err
	}
	if record.Expires != nil {
		expires = *record.Expires
	}
	return record.Username, record.Authlvl, record.Secret, expires, nil
}

// TenantAuthGetByLogin retrieves a Basic authentication record by tenant-local login.
func (a *adapter) TenantAuthGetByLogin(tenantID t.TenantID, login string) (t.Uid,
	auth.Level, []byte, time.Time, error) {
	var expires time.Time
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ZeroUid, auth.LevelNone, nil, expires, t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantAuthGetByLogin(tenantID, login)
	}
	var record struct {
		Userid  int64
		Authlvl auth.Level
		Secret  []byte
		Expires *time.Time
	}
	lookup := login
	if len(login) == 11 && asciiDigits(login) {
		lookup = "+86" + login
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	err = a.db.GetContext(ctx, &record, `SELECT a.userid,a.secret,a.expires,a.authlvl
		FROM im_users AS u JOIN im_auth AS a ON a.tenant_id=u.tenant_id AND a.userid=u.id
		WHERE u.tenant_id=? AND (u.username=? OR (u.phone IS NOT NULL AND u.phone=?))
		ORDER BY (u.username=?) DESC LIMIT 1`, tenantID, login, lookup, login)
	if err == sql.ErrNoRows {
		return t.ZeroUid, auth.LevelNone, nil, expires, nil
	}
	if err != nil {
		return t.ZeroUid, auth.LevelNone, nil, expires, err
	}
	if record.Expires != nil {
		expires = *record.Expires
	}
	return store.EncodeUid(record.Userid), record.Authlvl, record.Secret, expires, nil
}

// Add user's authentication record
func (a *adapter) AuthAddRecord(uid t.Uid, scheme, unique string, authLvl auth.Level,
	secret []byte, expires time.Time) error {

	var exp *time.Time
	if !expires.IsZero() {
		exp = &expires
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	var storedUsername string
	if err := a.db.GetContext(ctx, &storedUsername, "SELECT username FROM im_users WHERE id=?", store.DecodeUid(uid)); err != nil {
		if err == sql.ErrNoRows {
			return t.ErrNotFound
		}
		return err
	} else if unique != storedUsername {
		return t.ErrMalformed
	}
	authID, err := nextSnowflakeID()
	if err != nil {
		return err
	}
	if _, err := a.db.ExecContext(ctx, "INSERT INTO im_auth(id,userid,authLvl,secret,expires) VALUES(?,?,?,?,?)",
		authID, store.DecodeUid(uid), authLvl, secret, exp); isIDOutOfRange(err) {
		_, err = a.db.ExecContext(ctx, "INSERT INTO im_auth(userid,authLvl,secret,expires) VALUES(?,?,?,?)",
			store.DecodeUid(uid), authLvl, secret, exp)
		if err != nil && isDupe(err) {
			return t.ErrDuplicate
		}
		return err
	} else if err != nil {
		if isDupe(err) {
			return t.ErrDuplicate
		}
		return err
	}
	return nil
}

// AuthDelScheme deletes an existing authentication scheme for the user.
func (a *adapter) AuthDelScheme(user t.Uid, scheme string) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err := a.db.ExecContext(ctx, "DELETE FROM im_auth WHERE userid=?", store.DecodeUid(user))
	return err
}

// AuthDelAllRecords deletes all authentication records for the user.
func (a *adapter) AuthDelAllRecords(user t.Uid) (int, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	res, err := a.db.ExecContext(ctx, "DELETE FROM im_auth WHERE userid=?", store.DecodeUid(user))
	if err != nil {
		return 0, err
	}
	count, _ := res.RowsAffected()

	return int(count), nil
}

// Update user's authentication unique, secret, auth level.
func (a *adapter) AuthUpdRecord(uid t.Uid, scheme, unique string, authLvl auth.Level,
	secret []byte, expires time.Time) error {
	params := []string{"authLvl=?"}
	args := []any{authLvl}
	if len(secret) > 0 {
		params = append(params, "secret=?")
		args = append(args, secret)
	}
	if !expires.IsZero() {
		params = append(params, "expires=?")
		args = append(args, expires)
	}
	decodedUID := store.DecodeUid(uid)
	args = append(args, decodedUID)

	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	if unique != "" {
		if _, err = tx.ExecContext(ctx, "UPDATE im_users SET username=?,updatedat=? WHERE id=?", unique, t.TimeNow(), decodedUID); err != nil {
			if isDupe(err) {
				return t.ErrDuplicate
			}
			return err
		}
	}
	query := "UPDATE im_auth SET " + strings.Join(params, ",") + " WHERE userid=?"
	resp, err := tx.ExecContext(ctx, query, args...)
	if isDupe(err) {
		return t.ErrDuplicate
	}
	if err != nil {
		return err
	}

	if count, _ := resp.RowsAffected(); count <= 0 {
		var exists int
		if err = tx.GetContext(ctx, &exists, "SELECT COUNT(*) FROM im_auth WHERE userid=?", decodedUID); err != nil {
			return err
		}
		if exists == 0 {
			return t.ErrNotFound
		}
	}

	return tx.Commit()
}

// Retrieve user's authentication record
func (a *adapter) AuthGetRecord(uid t.Uid, scheme string) (string, auth.Level, []byte, time.Time, error) {
	var expires time.Time

	var record struct {
		Username string
		Authlvl  auth.Level
		Secret   []byte
		Expires  *time.Time
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	if err := a.db.GetContext(ctx, &record, `SELECT u.username,a.secret,a.expires,a.authlvl
		FROM im_auth AS a JOIN im_users AS u ON u.id=a.userid WHERE a.userid=?`, store.DecodeUid(uid)); err != nil {
		if err == sql.ErrNoRows {
			// Nothing found - use standard error.
			err = t.ErrNotFound
		}
		return "", 0, nil, expires, err
	}

	if record.Expires != nil {
		expires = *record.Expires
	}

	return record.Username, record.Authlvl, record.Secret, expires, nil
}

// Retrieve user's authentication record
func (a *adapter) AuthGetUniqueRecord(unique string) (t.Uid, auth.Level, []byte, time.Time, error) {
	var expires time.Time

	var record struct {
		Userid  int64
		Authlvl auth.Level
		Secret  []byte
		Expires *time.Time
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	lookup := unique
	if len(unique) == 11 && asciiDigits(unique) {
		lookup = "+86" + unique
	}
	if err := a.db.GetContext(ctx, &record, `SELECT a.userid,a.secret,a.expires,a.authlvl
		FROM im_users AS u JOIN im_auth AS a ON a.userid=u.id
		WHERE u.username=? OR (u.phone IS NOT NULL AND u.phone=?) ORDER BY (u.username=?) DESC LIMIT 1`,
		unique, lookup, unique); err != nil {
		if err == sql.ErrNoRows {
			// Nothing found - clear the error
			err = nil
		}
		return t.ZeroUid, 0, nil, expires, err
	}

	if record.Expires != nil {
		expires = *record.Expires
	}

	return store.EncodeUid(record.Userid), record.Authlvl, record.Secret, expires, nil
}

// UserGet fetches a single user by user id. If user is not found it returns (nil, nil)
func (a *adapter) UserGet(uid t.Uid) (*t.User, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var row profileUserRow
	err := a.db.GetContext(ctx, &row, `SELECT u.id,u.username,u.createdat,u.updatedat,u.state,u.stateat,u.access,u.lastseen,u.useragent,
		COALESCE(u.phone,'') AS phone,u.trusted,
		p.nickname AS profile_nickname,p.avatar_file_id AS profile_avatar_file_id,p.signature AS profile_signature,
		p.gender AS profile_gender,p.region AS profile_region,p.public_account AS profile_public_account,p.updated_at AS profile_updated_at
		FROM im_users AS u LEFT JOIN im_user_profiles AS p ON p.user_id=u.id
		WHERE u.id=? AND u.state!=?`, store.DecodeUid(uid), t.StateDeleted)
	if err == nil {
		user := profileUserFromRow(row)
		user.SetUid(uid)
		return &user, nil
	}

	if err == sql.ErrNoRows {
		// Clear the error if user does not exist or marked as soft-deleted.
		return nil, nil
	}

	return nil, err
}

func (a *adapter) UserGetAll(ids ...t.Uid) ([]t.User, error) {
	uids := make([]any, len(ids))
	for i, id := range ids {
		if id.IsZero() {
			continue
		}
		uids[i] = store.DecodeUid(id)
	}

	users := []t.User{}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	q, uids, _ := sqlx.In(`SELECT u.id,u.username,u.createdat,u.updatedat,u.state,u.stateat,u.access,u.lastseen,u.useragent,
		COALESCE(u.phone,'') AS phone,u.trusted,
		p.nickname AS profile_nickname,p.avatar_file_id AS profile_avatar_file_id,p.signature AS profile_signature,
		p.gender AS profile_gender,p.region AS profile_region,p.public_account AS profile_public_account,p.updated_at AS profile_updated_at
		FROM im_users AS u LEFT JOIN im_user_profiles AS p ON p.user_id=u.id
		WHERE u.id IN (?) AND u.state!=?`, uids, t.StateDeleted)
	rows, err := a.db.QueryxContext(ctx, a.db.Rebind(q), uids...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var row profileUserRow
		if err = rows.StructScan(&row); err != nil {
			users = nil
			break
		}
		user := profileUserFromRow(row)

		users = append(users, user)
	}
	if err == nil {
		err = rows.Err()
	}

	return users, err
}

// UserDelete deletes specified user: wipes completely (hard-delete) or marks as deleted.
// TODO: report when the user is not found.
func (a *adapter) UserDelete(uid t.Uid, hard bool) error {
	query := "SELECT name FROM im_topics WHERE owner=?"
	args := []any{store.DecodeUid(uid)}
	// In case of hard delete, delete all topics, even those which were
	// soft-deleted previsously.
	if !hard {
		query += " AND state!=?"
		args = append(args, t.StateDeleted)
	}
	// Get a list of topic names owned by the user (as 'grp' and 'chn').
	ownTopics, err := a.topicNamesForUser(query, true, args...)
	if err != nil {
		return err
	}

	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	now := t.TimeNow()
	decoded_uid := store.DecodeUid(uid)

	if hard {
		// Delete user's devices
		// t.ErrNotFound = user has no devices.
		if err = deviceDelete(tx, uid, ""); err != nil && err != t.ErrNotFound {
			return err
		}

		// Delete user's subscriptions in all topics.
		if err = subsDelForUser(tx, decoded_uid, true); err != nil {
			return err
		}

		// Delete records of messages soft-deleted for the user in all topics.
		if _, err = tx.Exec("DELETE FROM im_dellog WHERE deletedfor=?", decoded_uid); err != nil {
			return err
		}

		// Can't delete user's messages in all topics because we cannot notify topics of such deletion.
		// Just leave the messages there marked as sent by "not found" user.

		// Delete topics where the user is the owner.
		if len(ownTopics) > 0 {
			// First delete all messages in those topics.
			if _, err = tx.Exec("DELETE im_dellog FROM im_dellog JOIN im_topics ON im_topics.name=im_dellog.topic WHERE im_topics.owner=?",
				decoded_uid); err != nil {
				return err
			}

			// Deletion of messages will cascade to filemsglinks and so to fileuploads.
			if _, err = tx.Exec("DELETE im_messages FROM im_messages JOIN im_topics ON im_topics.name=im_messages.topic WHERE im_topics.owner=?",
				decoded_uid); err != nil {
				return err
			}

			// Delete subscriptions for all users where the user is the owner of the topic.
			sql, args, _ := sqlx.In("DELETE FROM im_subscriptions AS s WHERE topic IN (?)", ownTopics)
			if _, err = tx.Exec(tx.Rebind(sql), args); err != nil {
				return err
			}

			// Delete topic tags.
			if _, err = tx.Exec("DELETE tt FROM im_topictags AS tt JOIN im_topics AS t ON t.name=tt.topic WHERE t.owner=?",
				decoded_uid); err != nil {
				return err
			}

			// And finally delete the topics.
			if _, err = tx.Exec("DELETE FROM im_topics WHERE owner=?", decoded_uid); err != nil {
				return err
			}
		}

		// Delete user's authentication records.
		if _, err = tx.Exec("DELETE FROM im_auth WHERE userid=?", decoded_uid); err != nil {
			return err
		}

		// Delete all credentials.
		if err = credDel(tx, uid, "", ""); err != nil && err != t.ErrNotFound {
			return err
		}

		if _, err = tx.Exec("DELETE FROM im_users WHERE id=?", decoded_uid); err != nil {
			return err
		}
	} else {
		// Disable all user's subscriptions. That includes p2p subscriptions. No need to delete them.
		if err = subsDelForUser(tx, decoded_uid, false); err != nil {
			return err
		}

		if len(ownTopics) > 0 {
			// Disable all subscriptions to topics where the user is the owner.
			sql, args, _ := sqlx.In("UPDATE im_subscriptions SET updatedat=?,deletedat=? WHERE topic IN (?)", now, now, ownTopics)
			if _, err = tx.Exec(tx.Rebind(sql), args...); err != nil {
				return err
			}
		}

		// Disable group topics where the user is the owner.
		if _, err = tx.Exec("UPDATE im_topics SET updatedat=?,touchedat=?,state=?,stateat=? WHERE owner=?",
			now, now, t.StateDeleted, now, decoded_uid); err != nil {
			return err
		}

		// Disable p2p topics with the user (p2p topic's owner is 0).
		if _, err = tx.Exec("UPDATE im_topics AS t JOIN im_subscriptions AS s ON t.name=s.topic "+
			"SET t.updatedat=?,t.touchedat=?,t.state=?,t.stateat=? "+
			"WHERE t.owner=0 AND s.userid=? AND t.name LIKE 'p2p%'",
			now, now, t.StateDeleted, now, decoded_uid); err != nil {
			return err
		}

		// Disable the other user's subscription to a disabled p2p topic.
		if _, err = tx.Exec("UPDATE im_subscriptions AS s_one JOIN im_subscriptions AS s_two "+
			"ON s_one.topic=s_two.topic "+
			"SET s_two.updatedat=?, s_two.deletedat=? WHERE s_one.userid=? AND s_one.topic LIKE 'p2p%'",
			now, now, decoded_uid); err != nil {
			return err
		}

		// Finally disable user.
		if _, err = tx.Exec("UPDATE im_users SET updatedat=?,state=?,stateat=? WHERE id=?",
			now, t.StateDeleted, now, decoded_uid); err != nil {
			return err
		}
	}

	return tx.Commit()
}

// topicStateForUser is called by UserUpdate when the update contains state change.
// Soft-deleted topics remain soft-deleted.
func (a *adapter) topicStateForUser(tx *sqlx.Tx, decoded_uid int64, now time.Time, update any) error {
	var err error

	state, ok := update.(t.ObjState)
	if !ok {
		return t.ErrMalformed
	}

	if now.IsZero() {
		now = t.TimeNow()
	}

	// Change state of all topics where the user is the owner.
	if _, err = tx.Exec("UPDATE im_topics SET state=?, stateat=? WHERE owner=? AND state!=?",
		state, now, decoded_uid, t.StateDeleted); err != nil {
		return err
	}

	// Change state of p2p topics with the user (p2p topic's owner is 0)
	if _, err = tx.Exec("UPDATE im_topics JOIN im_subscriptions ON im_topics.name=im_subscriptions.topic "+
		"SET im_topics.state=?, im_topics.stateat=? WHERE im_topics.owner=0 AND im_subscriptions.userid=? AND im_topics.state!=?",
		state, now, decoded_uid, t.StateDeleted); err != nil {
		return err
	}

	// Subscriptions don't need to be updated:
	// subscriptions of a disabled user are not disabled and still can be manipulated.
	return nil
}

// UserUpdate updates user object.
func (a *adapter) UserUpdate(uid t.Uid, update map[string]any) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	update = sanitizeUserUpdate(update)
	cols, args := common.UpdateByMap(update)
	if len(cols) == 0 {
		return tx.Commit()
	}
	decoded_uid := store.DecodeUid(uid)
	args = append(args, decoded_uid)
	_, err = tx.Exec("UPDATE im_users SET "+strings.Join(cols, ",")+" WHERE id=?", args...)
	if err != nil {
		return err
	}

	if state, ok := update["State"]; ok {
		now, _ := update["StateAt"].(time.Time)
		err = a.topicStateForUser(tx, decoded_uid, now, state)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// UserUpdateTags is retained for adapter compatibility; user tags are disabled.
func (a *adapter) UserUpdateTags(uid t.Uid, add, remove, reset []string) ([]string, error) {
	return nil, nil
}

// UserGetByCred returns user ID for the given validated credential.
func (a *adapter) UserGetByCred(method, value string) (t.Uid, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var decoded_uid int64
	var err error
	if method == "tel" {
		err = a.db.GetContext(ctx, &decoded_uid, "SELECT id FROM im_users WHERE phone=? AND state!=?", value, t.StateDeleted)
	} else {
		err = a.db.GetContext(ctx, &decoded_uid, "SELECT userid FROM im_credentials WHERE synthetic=?", method+":"+value)
	}
	if err == nil {
		return store.EncodeUid(decoded_uid), nil
	}

	if err == sql.ErrNoRows {
		// Clear the error if user does not exist
		return t.ZeroUid, nil
	}
	return t.ZeroUid, err
}

// TenantUserGetByCred returns a user ID for a validated credential in one tenant.
func (a *adapter) TenantUserGetByCred(tenantID t.TenantID, method, value string) (t.Uid, error) {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ZeroUid, t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantUserGetByCred(tenantID, method, value)
	}
	if method == "tel" {
		ctx, cancel := a.getContext()
		if cancel != nil {
			defer cancel()
		}
		var decodedUID int64
		err = a.db.GetContext(ctx, &decodedUID,
			"SELECT id FROM im_users WHERE tenant_id=? AND phone=? AND state!=?", tenantID, value, t.StateDeleted)
		if err == sql.ErrNoRows {
			return t.ZeroUid, nil
		}
		if err != nil {
			return t.ZeroUid, err
		}
		return store.EncodeUid(decodedUID), nil
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var decodedUID int64
	err = a.db.GetContext(ctx, &decodedUID,
		"SELECT userid FROM im_credentials WHERE tenant_id=? AND synthetic=?", tenantID, method+":"+value)
	if err == sql.ErrNoRows {
		return t.ZeroUid, nil
	}
	if err != nil {
		return t.ZeroUid, err
	}
	return store.EncodeUid(decodedUID), nil
}

// UserUnreadCount returns the total number of unread messages in all topics with
// the R permission. If read fails, the counts are still returned with the original
// user IDs but with the unread count undefined and non-nil error.
// UserUnreadCount does not count unread messages in channels although it should.
func (a *adapter) UserUnreadCount(ids ...t.Uid) (map[t.Uid]int, error) {
	uids := make([]any, len(ids))
	counts := make(map[t.Uid]int, len(ids))
	for i, id := range ids {
		uids[i] = store.DecodeUid(id)
		// Ensure all original uids are always present.
		counts[id] = 0
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	// FIXME: support channels (for channels subscriptions.topic != topics.name).
	q, args, _ := sqlx.In("SELECT s.userid, SUM(t.seqid)-SUM(s.readseqid) AS unreadcount FROM im_topics AS t, im_subscriptions AS s "+
		"WHERE s.userid IN (?) AND t.name=s.topic AND s.deletedat IS NULL AND t.state!=? AND "+
		"INSTR(s.modewant, 'R')>0 AND INSTR(s.modegiven, 'R')>0 GROUP BY s.userid", uids, int(t.StateDeleted))
	rows, err := a.db.QueryxContext(ctx, a.db.Rebind(q), args...)
	if err != nil {
		return counts, err
	}
	defer rows.Close()

	var userId int64
	var unreadCount int
	for rows.Next() {
		if err = rows.Scan(&userId, &unreadCount); err != nil {
			break
		}
		counts[store.EncodeUid(userId)] = unreadCount
	}
	if err == nil {
		err = rows.Err()
	}

	return counts, err
}

// UserGetUnvalidated returns a list of uids which have never logged in, have no
// validated credentials and haven't been updated since lastUpdatedBefore.
func (a *adapter) UserGetUnvalidated(lastUpdatedBefore time.Time, limit int) ([]t.Uid, error) {
	var uids []t.Uid

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	rows, err := a.db.QueryxContext(ctx,
		"SELECT u.id, IFNULL(SUM(c.done),0) AS total FROM im_users AS u "+
			"LEFT JOIN im_credentials AS c ON u.id=c.userid WHERE u.lastseen IS NULL AND u.updatedat<? "+
			"GROUP BY u.id, u.updatedat HAVING total=0 ORDER BY u.updatedat ASC LIMIT ?", lastUpdatedBefore, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var userId int64
		var unused int
		if err = rows.Scan(&userId, &unused); err != nil {
			break
		}
		uids = append(uids, store.EncodeUid(userId))
	}
	if err == nil {
		err = rows.Err()
	}

	return uids, err
}

func (a *adapter) topicCreate(tx *sqlx.Tx, topic *t.Topic) error {
	_, err := tx.Exec("INSERT INTO im_topics(createdat,updatedat,touchedat,state,name,usebt,owner,access,public,trusted,tags,aux) "+
		"VALUES(?,?,?,?,?,?,?,?,?,?,?,?)",
		topic.CreatedAt, topic.UpdatedAt, topic.TouchedAt, topic.State, topic.Id, topic.UseBt,
		store.DecodeUid(t.ParseUid(topic.Owner)), topic.Access, common.ToJSON(topic.Public), common.ToJSON(topic.Trusted),
		topic.Tags, common.ToJSON(topic.Aux))
	if err != nil {
		return err
	}

	// Save topic's tags to a separate table to make topic findable.
	return addTags(tx, "im_topictags", "topic", topic.Id, topic.Tags, false)
}

// TopicCreate saves topic object to database.
func (a *adapter) TopicCreate(topic *t.Topic) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	err = a.topicCreate(tx, topic)
	if err != nil {
		return err
	}
	return tx.Commit()
}

// If undelete = true - update subscription on duplicate key, otherwise ignore the duplicate.
func createSubscription(tx *sqlx.Tx, sub *t.Subscription, undelete bool) error {
	if sub == nil {
		return t.ErrMalformed
	}
	isOwner := (sub.ModeGiven & sub.ModeWant).IsOwner()

	jpriv := common.ToJSON(sub.Private)
	decoded_uid := store.DecodeUid(t.ParseUid(sub.User))

	existing := struct {
		ID        int64        `db:"id"`
		DeletedAt sql.NullTime `db:"deletedat"`
	}{}
	err := tx.Get(&existing, "SELECT id,deletedat FROM im_subscriptions WHERE topic=? AND userid=? ORDER BY deletedat IS NULL DESC,id ASC LIMIT 1",
		sub.Topic, decoded_uid)
	if err != nil && err != sql.ErrNoRows {
		return err
	}
	if err == nil {
		if existing.DeletedAt.Valid {
			_, err = tx.Exec("UPDATE im_subscriptions SET createdat=?,updatedat=?,deletedat=NULL,modeWant=?,modeGiven=?,"+
				"delid=0,recvseqid=0,readseqid=0,private=? WHERE id=?",
				sub.CreatedAt, sub.UpdatedAt, sub.ModeWant.String(), sub.ModeGiven.String(), jpriv, existing.ID)
		} else {
			_, err = tx.Exec("UPDATE im_subscriptions SET updatedat=?,modeWant=?,modeGiven=?,private=? WHERE id=?",
				sub.UpdatedAt, sub.ModeWant.String(), sub.ModeGiven.String(), jpriv, existing.ID)
		}
		if err != nil {
			return err
		}
		if isOwner {
			_, err = tx.Exec("UPDATE im_topics SET owner=? WHERE name=?", decoded_uid, sub.Topic)
		}
		return err
	}

	subID, err := nextSnowflakeID()
	if err != nil {
		return err
	}
	_, err = tx.Exec(
		"INSERT INTO im_subscriptions(id,createdat,updatedat,deletedat,userid,topic,modeWant,modeGiven,private) "+
			"VALUES(?,?,?,NULL,?,?,?,?,?)",
		subID, sub.CreatedAt, sub.UpdatedAt, decoded_uid, sub.Topic, sub.ModeWant.String(), sub.ModeGiven.String(), jpriv)
	if isIDOutOfRange(err) {
		_, err = tx.Exec(
			"INSERT INTO im_subscriptions(createdat,updatedat,deletedat,userid,topic,modeWant,modeGiven,private) "+
				"VALUES(?,?,NULL,?,?,?,?,?)",
			sub.CreatedAt, sub.UpdatedAt, decoded_uid, sub.Topic, sub.ModeWant.String(), sub.ModeGiven.String(), jpriv)
	}

	if err != nil && isDupe(err) {
		if undelete {
			_, err = tx.Exec("UPDATE im_subscriptions SET createdat=?,updatedat=?,deletedat=NULL,modeWant=?,modeGiven=?,"+
				"delid=0,recvseqid=0,readseqid=0 WHERE topic=? AND userid=?",
				sub.CreatedAt, sub.UpdatedAt, sub.ModeWant.String(), sub.ModeGiven.String(), sub.Topic, decoded_uid)
		} else {
			_, err = tx.Exec("UPDATE im_subscriptions SET createdat=?,updatedat=?,deletedat=NULL,modeWant=?,modeGiven=?,"+
				"delid=0,recvseqid=0,readseqid=0,private=? WHERE topic=? AND userid=?",
				sub.CreatedAt, sub.UpdatedAt, sub.ModeWant.String(), sub.ModeGiven.String(), jpriv, sub.Topic, decoded_uid)
		}
	}

	if err == nil && isOwner {
		// Update topic owner if the subscription is with owner rights.
		// Don't increment subscriber count here - it's done in TopicShare in bulk.
		_, err = tx.Exec("UPDATE im_topics SET owner=? WHERE name=?", decoded_uid, sub.Topic)
	}
	return err
}

// TopicCreateP2P given two users creates a p2p topic.
func (a *adapter) TopicCreateP2P(initiator, invited *t.Subscription) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	err = createSubscription(tx, initiator, false)
	if err != nil {
		return err
	}

	// If the second subscription exists, don't overwrite it. Just make sure it's not deleted.
	err = createSubscription(tx, invited, true)
	if err != nil {
		return err
	}

	topic := &t.Topic{ObjHeader: t.ObjHeader{Id: initiator.Topic}}
	topic.ObjHeader.MergeTimes(&initiator.ObjHeader)
	topic.TouchedAt = initiator.GetTouchedAt()
	var existingTopicID int64
	err = tx.Get(&existingTopicID, "SELECT id FROM im_topics WHERE name=? ORDER BY id ASC LIMIT 1", topic.Id)
	if err != nil && err != sql.ErrNoRows {
		return err
	}
	if err == sql.ErrNoRows {
		err = a.topicCreate(tx, topic)
		if err != nil {
			return err
		}
	} else if _, err = tx.Exec("UPDATE im_topics SET updatedat=?,touchedat=?,state=? WHERE id=?",
		topic.UpdatedAt, topic.TouchedAt, t.StateOK, existingTopicID); err != nil {
		return err
	}

	return tx.Commit()
}

// TopicGet loads a single topic by name, if it exists. If the topic does not exist the call returns (nil, nil)
func (a *adapter) TopicGet(topic string) (*t.Topic, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	// Fetch topic by name
	var tt = new(t.Topic)
	if err := a.db.GetContext(ctx, tt,
		"SELECT createdat,updatedat,state,stateat,touchedat,name AS id,usebt,access,owner,seqid,delid,subcnt,IFNULL(mutation_version,0) AS mutation_version,public,trusted,tags,aux "+
			"FROM im_topics WHERE name=?", topic); err != nil {
		if err == sql.ErrNoRows {
			// Nothing found - clear the error
			err = nil
		}
		return nil, err
	}

	if t.GetTopicCat(topic) == t.TopicCatGrp {
		// Topic found, get subsription count (ignoring the value set in topics.subcnt). Try both topic and channel names.
		var subCnt int
		if err := a.db.GetContext(ctx, &subCnt,
			"SELECT COUNT(*) FROM im_subscriptions WHERE topic IN (?,?) AND deletedat IS NULL", topic, t.GrpToChn(topic)); err != nil {
			return nil, err
		}

		if subCnt != tt.SubCnt {
			// Update the topic with the correct subscription count.
			tt.SubCnt = subCnt
			if _, err := a.db.ExecContext(ctx, "UPDATE im_topics SET subcnt=? WHERE name=?", subCnt, topic); err != nil {
				return nil, err
			}
		}
	}

	tt.Owner = common.EncodeUidString(tt.Owner).String()
	tt.Public = common.FromJSON(tt.Public)
	tt.Trusted = common.FromJSON(tt.Trusted)

	return tt, nil
}

// TopicsForUser loads user's contact list: p2p and grp topics, except for 'me' & 'fnd' subscriptions.
// Reads and denormalizes Public & Trusted values.
func (a *adapter) TopicsForUser(uid t.Uid, keepDeleted bool, opts *t.QueryOpt) ([]t.Subscription, error) {
	// Fetch ALL user's subscriptions, even those which has not been modified recently.
	// We are going to use these subscriptions to fetch topics and users which may have been modified recently.
	q := `SELECT createdat,updatedat,deletedat,topic,delid,recvseqid,
		readseqid,modewant,modegiven,private FROM im_subscriptions WHERE userid=?`
	args := []any{store.DecodeUid(uid)}
	if !keepDeleted {
		// Filter out deleted rows.
		q += " AND deletedat IS NULL"
	}

	limit := 0
	ims := time.Time{}
	if opts != nil {
		if opts.Topic != "" {
			q += " AND topic=?"
			args = append(args, opts.Topic)
		}

		// Apply the limit only when the client does not manage the cache (or cold start).
		// Otherwise have to get all subscriptions and do a manual join with users/topics.
		if opts.IfModifiedSince == nil {
			if opts.Limit > 0 && opts.Limit < a.maxResults {
				limit = opts.Limit
			} else {
				limit = a.maxResults
			}
		} else {
			ims = *opts.IfModifiedSince
		}
	} else {
		limit = a.maxResults
	}

	q += " ORDER BY topic ASC, deletedat IS NULL DESC, updatedat DESC, id DESC"
	if limit > 0 {
		q += " LIMIT ?"
		args = append(args, limit)
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	// Must close rows manually as we will be reusing it.

	// Fetch subscriptions. Two queries are needed: users table (p2p) and topics table (grp).
	// Prepare a list of separate subscriptions to users vs topics
	join := make(map[string]t.Subscription) // Keeping these to make a join with table for .private and .access
	p2pResolved := make(map[string]bool)
	topq := make([]any, 0, 16)
	usrq := make([]any, 0, 16)
	for rows.Next() {
		var sub t.Subscription
		if err = rows.StructScan(&sub); err != nil {
			break
		}
		tname := sub.Topic
		sub.User = uid.String()
		if !t.ParseUserId(tname).IsZero() {
			// Legacy self-user subscriptions are not conversation entries.
			continue
		}
		tcat := t.GetTopicCat(tname)
		peerID := ""

		if tcat == t.TopicCatMe || tcat == t.TopicCatFnd {
			// One of 'me', 'fnd' subscriptions, skip.
			// Don't skip 'sys' subscription.
			continue
		} else if tcat == t.TopicCatP2P {
			// P2P subscription, find the other user to get user.Public and user.Trusted.
			uid1, uid2, _ := t.ParseP2P(tname)
			p2pResolved[tname] = false
			if uid1 == uid {
				usrq = append(usrq, store.DecodeUid(uid2))
				peerID = uid2.UserId()
				sub.SetWith(peerID)
			} else {
				usrq = append(usrq, store.DecodeUid(uid1))
				peerID = uid1.UserId()
				sub.SetWith(peerID)
			}
		} else if tcat == t.TopicCatGrp {
			// Maybe convert channel name to group topic name.
			tname = t.ChnToGrp(tname)
		}
		if _, exists := join[tname]; exists {
			continue
		}
		// No special handling needed for 'slf', 'sys' subscriptions.

		topq = append(topq, tname)
		sub.Private = common.FromJSON(sub.Private)
		if tcat == t.TopicCatP2P {
			sub.Private = ensureP2PPrivatePeer(sub.Private, peerID)
		}
		join[tname] = sub
	}
	if err == nil {
		err = rows.Err()
	}
	rows.Close()

	if err != nil {
		return nil, err
	}

	var subs []t.Subscription
	if len(join) == 0 {
		return subs, nil
	}

	// Fetch grp topics and join to subscriptions.
	if len(topq) > 0 {
		q = "SELECT updatedat,state,touchedat,name AS id,usebt,access,seqid,delid,subcnt,IFNULL(mutation_version,0) AS mutation_version,public,trusted " +
			"FROM im_topics WHERE name IN (?)"
		q, args, _ = sqlx.In(q, topq)

		if !keepDeleted {
			// Optionally skip deleted topics.
			q += " AND state!=?"
			args = append(args, t.StateDeleted)
		}

		if !ims.IsZero() {
			// Use cache timestamp if provided: get newer entries only.
			q += " AND touchedat>?"
			args = append(args, ims)

			if limit > 0 && limit < len(topq) {
				// No point in fetching more than the requested limit.
				q += " ORDER BY touchedat LIMIT ?"
				args = append(args, limit)
			}
		}

		ctx2, cancel2 := a.getContext()
		if cancel2 != nil {
			defer cancel2()
		}
		rows, err = a.db.QueryxContext(ctx2, a.db.Rebind(q), args...)
		if err != nil {
			return nil, err
		}

		var top t.Topic
		for rows.Next() {
			if err = rows.StructScan(&top); err != nil {
				break
			}
			sub := join[top.Id]
			// Check if sub.UpdatedAt needs to be adjusted to earlier or later time.
			sub.UpdatedAt = common.SelectLatestTime(sub.UpdatedAt, top.UpdatedAt)
			sub.SetState(top.State)
			sub.SetTouchedAt(top.TouchedAt)
			sub.SetSeqId(top.SeqId)
			sub.Private = ensurePrivateMutationVersion(sub.Private, top.MutationVersion)
			if t.GetTopicCat(sub.Topic) == t.TopicCatGrp {
				sub.SetSubCnt(top.SubCnt)
				sub.SetPublic(common.FromJSON(top.Public))
				sub.SetTrusted(common.FromJSON(top.Trusted))
			}
			// Put back the updated value of a subsription, will process further below
			join[top.Id] = sub
		}
		if err == nil {
			err = rows.Err()
		}
		rows.Close()

		if err != nil {
			return nil, err
		}
	}

	// Fetch p2p users and join to p2p subscriptions.
	if len(usrq) > 0 {
		q = `SELECT u.id,u.updatedat,u.state,u.access,u.lastseen,u.useragent,u.trusted,
			p.nickname AS profile_nickname,p.avatar_file_id AS profile_avatar_file_id,p.signature AS profile_signature,
			p.gender AS profile_gender,p.region AS profile_region,p.public_account AS profile_public_account,p.updated_at AS profile_updated_at,
			fs.remark AS friendship_remark
			FROM im_users AS u
			LEFT JOIN im_user_profiles AS p ON p.user_id=u.id
			LEFT JOIN im_friendships AS fs ON fs.user_id=? AND fs.peer_id=u.id AND fs.status=?
			WHERE u.id IN (?)`
		q, args, _ = sqlx.In(q, store.DecodeUid(uid), t.RelationshipFriend, usrq)
		if !keepDeleted {
			// Optionally skip deleted users.
			q += " AND u.state!=?"
			args = append(args, t.StateDeleted)
		}

		// Ignoring ims: we need all users to get LastSeen and UserAgent.

		ctx3, cancel3 := a.getContext()
		if cancel3 != nil {
			defer cancel3()
		}
		rows, err = a.db.QueryxContext(ctx3, a.db.Rebind(q), args...)
		if err != nil {
			return nil, err
		}

		for rows.Next() {
			var usr2 profileUserRow
			if err = rows.StructScan(&usr2); err != nil {
				break
			}

			joinOn := uid.P2PName(common.EncodeUidString(usr2.ID))
			if sub, ok := join[joinOn]; ok {
				sub.UpdatedAt = common.SelectLatestTime(sub.UpdatedAt, usr2.effectiveUpdatedAt())
				sub.SetState(usr2.State)
				sub.SetPublic(usr2.profilePublic())
				sub.SetTrusted(common.FromJSON(usr2.Trusted))
				sub.SetDefaultAccess(usr2.Access.Auth, usr2.Access.Anon)
				sub.SetLastSeenAndUA(usr2.lastSeen(), usr2.UserAgent)
				sub.Private = ensureP2PPrivatePeerRemark(sub.Private, common.EncodeUidString(usr2.ID).UserId(), usr2.FriendshipRemark.String)
				join[joinOn] = sub
				p2pResolved[joinOn] = true
			}
		}
		if err == nil {
			err = rows.Err()
		}
		rows.Close()

		if err != nil {
			return nil, err
		}
	}

	subs = make([]t.Subscription, 0, len(join))
	for _, sub := range join {
		if t.GetTopicCat(sub.Topic) == t.TopicCatP2P && !p2pResolved[sub.Topic] {
			continue
		}
		subs = append(subs, sub)
	}

	return common.SelectEarliestUpdatedSubs(subs, opts, a.maxResults), nil
}

// UsersForTopic loads users subscribed to the given topic (not channel readers).
// The difference between UsersForTopic vs SubsForTopic is that the former loads user.Public,
// the latter does not.
func (a *adapter) UsersForTopic(topic string, keepDeleted bool, opts *t.QueryOpt) ([]t.Subscription, error) {
	tcat := t.GetTopicCat(topic)

	// Fetch all subscribed users. The number of users is not large.
	q := `SELECT s.createdat,s.updatedat,s.deletedat,s.userid,s.topic,s.delid,s.recvseqid,
		s.readseqid,s.modewant,s.modegiven,u.trusted,u.lastseen,u.useragent,s.private,
		p.nickname AS profile_nickname,p.avatar_file_id AS profile_avatar_file_id,pu.location AS profile_avatar_url,p.signature AS profile_signature,
		p.gender AS profile_gender,p.region AS profile_region,p.public_account AS profile_public_account
		FROM im_subscriptions AS s JOIN im_users AS u ON s.userid=u.id
		LEFT JOIN im_user_profiles AS p ON p.user_id=s.userid
		LEFT JOIN im_public_uploads AS pu ON pu.file_id=p.avatar_file_id
		WHERE s.topic=?`
	args := []any{topic}
	if !keepDeleted {
		// Filter out rows with users deleted
		q += " AND u.state!=?"
		args = append(args, t.StateDeleted)

		// For p2p topics we must load all subscriptions including deleted.
		// Otherwise it will be impossible to swipe Public values.
		if tcat != t.TopicCatP2P {
			// Filter out deleted subscriptions.
			q += " AND s.deletedat IS NULL"
		}
	}

	limit := a.maxResults
	var oneUser t.Uid
	if opts != nil {
		// Ignore IfModifiedSince: loading all entries because a topic cannot have too many subscribers.
		// Those unmodified will be stripped of Public & Private.

		if !opts.User.IsZero() {
			// For p2p topics we have to fetch both users otherwise public cannot be swapped.
			if tcat != t.TopicCatP2P {
				q += " AND s.userid=?"
				args = append(args, store.DecodeUid(opts.User))
			}
			oneUser = opts.User
		}
		if opts.Limit > 0 && opts.Limit < limit {
			limit = opts.Limit
		}
	}
	q += " LIMIT ?"
	args = append(args, limit)

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	// Fetch subscriptions.
	var sub t.Subscription
	var subs []t.Subscription
	var lastSeen sql.NullTime
	var userAgent string
	var trusted any
	var profileNickname, profileAvatarFileID, profileAvatarURL, profileSignature, profileGender, profileRegion, profilePublicAccount sql.NullString
	for rows.Next() {
		if err = rows.Scan(
			&sub.CreatedAt, &sub.UpdatedAt, &sub.DeletedAt,
			&sub.User, &sub.Topic, &sub.DelId, &sub.RecvSeqId,
			&sub.ReadSeqId, &sub.ModeWant, &sub.ModeGiven,
			&trusted, &lastSeen, &userAgent, &sub.Private,
			&profileNickname, &profileAvatarFileID, &profileAvatarURL, &profileSignature,
			&profileGender, &profileRegion, &profilePublicAccount); err != nil {
			break
		}

		sub.User = common.EncodeUidString(sub.User).String()
		sub.Private = common.FromJSON(sub.Private)
		sub.SetPublic(profilePublicFromFieldsWithAvatarURL(profileNickname, profileAvatarFileID, profileAvatarURL, profileSignature, profileGender, profileRegion, profilePublicAccount))
		sub.SetTrusted(common.FromJSON(trusted))
		sub.SetLastSeenAndUA(&lastSeen.Time, userAgent)
		subs = append(subs, sub)
	}
	if err == nil {
		err = rows.Err()
	}

	if err == nil && tcat == t.TopicCatP2P && len(subs) > 0 {
		// Swap public & lastSeen values of P2P topics as expected.
		if len(subs) == 1 {
			// The other user is deleted, nothing we can do.
			subs[0].SetPublic(nil)
			subs[0].SetTrusted(nil)
			subs[0].SetLastSeenAndUA(nil, "")
		} else {
			tmp := subs[0].GetPublic()
			subs[0].SetPublic(subs[1].GetPublic())
			subs[1].SetPublic(tmp)

			tmp = subs[0].GetTrusted()
			subs[0].SetTrusted(subs[1].GetTrusted())
			subs[1].SetTrusted(tmp)

			lastSeen := subs[0].GetLastSeen()
			userAgent = subs[0].GetUserAgent()
			subs[0].SetLastSeenAndUA(subs[1].GetLastSeen(), subs[1].GetUserAgent())
			subs[1].SetLastSeenAndUA(lastSeen, userAgent)
		}

		// Remove deleted and unneeded subscriptions
		if !keepDeleted || !oneUser.IsZero() {
			var xsubs []t.Subscription
			for i := range subs {
				if (subs[i].DeletedAt != nil && !keepDeleted) || (!oneUser.IsZero() && subs[i].Uid() != oneUser) {
					continue
				}
				xsubs = append(xsubs, subs[i])
			}
			subs = xsubs
		}
	}

	return subs, err
}

// topicNamesForUser reads a slice of strings using provided query.
// if includeChan is true, the query is expected to add channel names as well as group topic names.
func (a *adapter) topicNamesForUser(sqlQuery string, includeChan bool, args ...any) ([]string, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, sqlQuery, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var names []string
	for rows.Next() {
		var name string
		if err = rows.Scan(&name); err != nil {
			break
		}
		names = append(names, name)
		// If the name is a group topic, also add the channel name if requested.
		if includeChan {
			if channel := t.GrpToChn(name); channel != "" {
				names = append(names, channel)
			}
		}
	}
	if err == nil {
		err = rows.Err()
	}

	return names, err
}

// OwnTopics loads a slice of topic names where the user is the owner.
func (a *adapter) OwnTopics(uid t.Uid) ([]string, error) {
	return a.topicNamesForUser("SELECT name FROM im_topics WHERE owner=? AND state!=?",
		false, store.DecodeUid(uid), t.StateDeleted)
}

// ChannelsForUser loads a slice of topic names where the user is a channel reader and notifications (P) are enabled.
func (a *adapter) ChannelsForUser(uid t.Uid) ([]string, error) {
	return a.topicNamesForUser("SELECT topic FROM im_subscriptions WHERE userid=? AND topic LIKE 'chn%' "+
		"AND INSTR(modewant,'P')>0 AND INSTR(modegiven,'P')>0 AND deletedat IS NULL",
		false, store.DecodeUid(uid))
}

// TopicShare adds subscriptions to a topic and increments the topic's subcnt.
func (a *adapter) TopicShare(topic string, shares []*t.Subscription) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	for _, sub := range shares {
		err = createSubscription(tx, sub, true)
		if err != nil {
			return err
		}
	}

	if topic != "" {
		// Update topic's subscription count.
		if _, err = tx.Exec("UPDATE im_topics SET subcnt=subcnt+? WHERE name=?", len(shares), topic); err != nil {
			return err
		}
	}

	return tx.Commit()
}

// TopicDelete deletes topic, subscriptions, messages.
func (a *adapter) TopicDelete(topic string, isChan, hard bool) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// If the topic is a channel, must try to delete subscriptions under both grpXXX and chnXXX names.
	args := []any{topic}
	if isChan {
		args = append(args, t.GrpToChn(topic))
	}

	if hard {
		// Delete subscriptions. If this is a channel, delete both group subscriptions and channel subscriptions.
		q, args, _ := sqlx.In("DELETE FROM im_subscriptions WHERE topic IN (?)", args)
		if _, err = tx.Exec(tx.Rebind(q), args...); err != nil {
			return err
		}

		if err = messageDeleteList(tx, topic, nil); err != nil {
			return err
		}

		if _, err = tx.Exec("DELETE FROM im_topictags WHERE topic=?", topic); err != nil {
			return err
		}

		if _, err = tx.Exec("DELETE FROM im_topics WHERE name=?", topic); err != nil {
			return err
		}
	} else {
		now := t.TimeNow()

		q, args, _ := sqlx.In("UPDATE im_subscriptions SET updatedat=?,deletedat=? WHERE topic IN (?)", now, now, args)
		if _, err = tx.Exec(tx.Rebind(q), args...); err != nil {
			return err
		}

		if _, err = tx.Exec("UPDATE im_topics SET updatedat=?,touchedat=?,state=?,stateat=? WHERE name=?",
			now, now, t.StateDeleted, now, topic); err != nil {
			return err
		}
	}
	return tx.Commit()
}

// TopicUpdateOnMessage updates topic's seqid and touchedat when a new message is posted.
func (a *adapter) TopicUpdateOnMessage(topic string, msg *t.Message) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err := a.db.ExecContext(ctx, "UPDATE im_topics SET seqid=?,touchedat=? WHERE name=?", msg.SeqId, msg.CreatedAt, topic)

	return err
}

// TopicUpdateSubCnt updates subscriber count denormalized in topic.
func (a *adapter) TopicUpdateSubCnt(topic string) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err := a.db.ExecContext(ctx,
		"UPDATE im_topics SET subcnt=(SELECT COUNT(*) FROM im_subscriptions WHERE topic IN (?,?) AND deletedat IS NULL) WHERE name=?",
		topic, t.GrpToChn(topic), topic)
	return err
}

// TopicUpdate updates topic's fields given in the update map.
// If update contains UpdatedAt but not TouchedAt, TouchedAt is set to Updated
func (a *adapter) TopicUpdate(topic string, update map[string]any) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	if t, u := update["TouchedAt"], update["UpdatedAt"]; t == nil && u != nil {
		update["TouchedAt"] = u
	}
	cols, args := common.UpdateByMap(update)
	args = append(args, topic)
	_, err = tx.Exec("UPDATE im_topics SET "+strings.Join(cols, ",")+" WHERE name=?", args...)
	if err != nil {
		return err
	}

	// Tags are also stored in a separate table
	if tags := common.ExtractTags(update); tags != nil {
		// First delete all user tags
		_, err = tx.Exec("DELETE FROM im_topictags WHERE topic=?", topic)
		if err != nil {
			return err
		}
		// Now insert new tags
		err = addTags(tx, "im_topictags", "topic", topic, tags, false)
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

func (a *adapter) TopicOwnerChange(topic string, newOwner t.Uid) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err := a.db.ExecContext(ctx, "UPDATE im_topics SET owner=? WHERE name=?", store.DecodeUid(newOwner), topic)
	return err
}

// Get a subscription of a user to a topic.
func (a *adapter) SubscriptionGet(topic string, user t.Uid, keepDeleted bool) (*t.Subscription, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	query := `SELECT createdat,updatedat,deletedat,userid AS user,topic,delid,recvseqid,
		readseqid,modewant,modegiven,private FROM im_subscriptions WHERE topic=? AND userid=?`
	if !keepDeleted {
		query += " AND deletedat IS NULL"
	}
	var sub t.Subscription
	err := a.db.GetContext(ctx, &sub, query, topic, store.DecodeUid(user))
	if err != nil {
		if err == sql.ErrNoRows {
			// Nothing found - clear the error
			err = nil
		}
		return nil, err
	}

	sub.User = user.String()
	sub.Private = common.FromJSON(sub.Private)

	return &sub, nil
}

// SubsForUser loads all user's subscriptions. Does NOT load Public or Private values and does
// not load deleted subscriptions.
func (a *adapter) SubsForUser(forUser t.Uid) ([]t.Subscription, error) {
	q := `SELECT createdat,updatedat,deletedat,userid AS user,topic,delid,recvseqid,
		readseqid,modewant,modegiven FROM im_subscriptions WHERE userid=? AND deletedat IS NULL`
	args := []any{store.DecodeUid(forUser)}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var subs []t.Subscription
	var sub t.Subscription
	for rows.Next() {
		if err = rows.StructScan(&sub); err != nil {
			break
		}
		sub.User = forUser.String()
		subs = append(subs, sub)
	}
	if err == nil {
		err = rows.Err()
	}

	return subs, err
}

// SubsForTopic fetches all subsciptions for a topic. Does NOT load Public value and does not load channel readers.
// The difference between UsersForTopic vs SubsForTopic is that the former loads user.public+trusted,
// the latter does not.
func (a *adapter) SubsForTopic(topic string, keepDeleted bool, opts *t.QueryOpt) ([]t.Subscription, error) {
	q := `SELECT createdat,updatedat,deletedat,userid AS user,topic,delid,recvseqid,
		readseqid,modewant,modegiven,private FROM im_subscriptions WHERE topic=?`

	args := []any{topic}
	if !keepDeleted {
		// Filter out deleted rows.
		q += " AND deletedat IS NULL"
	}
	limit := 0
	if opts != nil {
		// Ignore IfModifiedSince - we must return all entries
		// Those unmodified will be stripped of Public & Private.

		if !opts.User.IsZero() {
			q += " AND userid=?"
			args = append(args, store.DecodeUid(opts.User))
		}
		limit = a.maxResults
		if opts.Limit > 0 && opts.Limit < limit {
			limit = opts.Limit
		}
	}

	if limit > 0 {
		q += " LIMIT ?"
		args = append(args, limit)
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var subs []t.Subscription
	var sub t.Subscription
	for rows.Next() {
		if err = rows.StructScan(&sub); err != nil {
			break
		}

		sub.User = common.EncodeUidString(sub.User).String()
		sub.Private = common.FromJSON(sub.Private)
		subs = append(subs, sub)
	}
	if err == nil {
		err = rows.Err()
	}

	return subs, err
}

// SubsUpdate updates one or multiple subscriptions to a topic.
func (a *adapter) SubsUpdate(topic string, user t.Uid, update map[string]any) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	cols, args := common.UpdateByMap(update)
	q := "UPDATE im_subscriptions SET " + strings.Join(cols, ",") + " WHERE topic=?"
	args = append(args, topic)
	if !user.IsZero() {
		// Update just one topic subscription
		q += " AND userid=?"
		args = append(args, store.DecodeUid(user))
	}

	if _, err = tx.Exec(q, args...); err != nil {
		return err
	}

	return tx.Commit()
}

// SubsDelete marks at most one subscription as deleted (soft-deleting).
func (a *adapter) SubsDelete(topic string, user t.Uid) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}

	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	decoded_id := store.DecodeUid(user)
	now := t.TimeNow()

	// Mark subscription as deleted.
	res, err := tx.ExecContext(ctx,
		"UPDATE im_subscriptions SET updatedat=?,deletedat=? WHERE topic=? AND userid=? AND deletedat IS NULL",
		now, now, topic, decoded_id)
	if err != nil {
		return err
	}

	affected, err := res.RowsAffected()
	if err == nil && affected == 0 {
		// ensure tx.Rollback() above is ran
		err = t.ErrNotFound
		return err
	}

	// Channel readers cannot delete messages.
	if !t.IsChannel(topic) {
		// Remove records of messages soft-deleted by this user.
		_, err = tx.Exec("DELETE FROM im_dellog WHERE topic=? AND deletedfor=?", topic, decoded_id)
		if err != nil {
			return err
		}
	}

	if t.GetTopicCat(topic) == t.TopicCatGrp {
		// Decrement topic subscription count (only one subscription is	deleted).
		_, err = tx.Exec("UPDATE im_topics SET subcnt=subcnt-1 WHERE name=?", t.ChnToGrp(topic))
		if err != nil {
			return err
		}
	}

	return tx.Commit()
}

// subsDelForUser marks user's subscriptions as deleted.
func subsDelForUser(tx *sqlx.Tx, decoded_uid int64, hard bool) error {
	// Decrement subscription count for all topics the user is subscribed to.
	rows, err := tx.Query("SELECT topic FROM im_subscriptions WHERE userid=? AND deletedat IS NULL", decoded_uid)
	if err != nil {
		return err
	}
	var topics []any
	for rows.Next() {
		var name string
		if err = rows.Scan(&name); err != nil {
			break
		}
		if t.IsChannel(name) {
			// Convert channel name to group name.
			name = t.ChnToGrp(name)
		}
		topics = append(topics, name)
	}
	if err == nil {
		err = rows.Err()
	}
	rows.Close()
	if err != nil {
		return err
	}
	if len(topics) > 0 {
		sql, args, err := sqlx.In("UPDATE im_topics SET subcnt=subcnt-1 WHERE name IN (?)", topics)
		_, err = tx.Exec(tx.Rebind(sql), args...)
		if err != nil {
			return err
		}
	}

	if hard {
		_, err = tx.Exec("DELETE FROM im_subscriptions WHERE userid=?", decoded_uid)
	} else {
		now := t.TimeNow()
		_, err = tx.Exec("UPDATE im_subscriptions SET updatedat=?,deletedat=? WHERE userid=? AND deletedat IS NULL",
			now, now, decoded_uid)
	}
	return err
}

// SubsDelForUser marks user's subscriptions as deleted.
func (a *adapter) SubsDelForUser(user t.Uid, hard bool) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}

	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	if err = subsDelForUser(tx, store.DecodeUid(user), hard); err != nil {
		return err
	}

	return tx.Commit()
}

// Find returns group topics which match the requested discovery tags.
func (a *adapter) Find(caller, promoPrefix string, req [][]string, opt []string, activeOnly bool) ([]t.Subscription, error) {
	index := make(map[string]struct{})
	allReq := t.FlattenDoubleSlice(req)
	allTags := append(append([]string{}, allReq...), opt...)
	if len(allTags) == 0 {
		return nil, nil
	}
	var args []any
	stateConstraint := ""
	if activeOnly {
		args = append(args, t.StateOK)
		stateConstraint = "t.state=? AND "
	}
	for _, tag := range allTags {
		args = append(args, tag)
		index[tag] = struct{}{}
	}

	var matcher string
	if promoPrefix != "" {
		// The max number of tags is 16. Using 20 to make sure one prefix match is greater than all non-prefix matches.
		matcher = "SUM(CASE WHEN LOCATE('" + promoPrefix + "', tg.tag)=1 THEN 20 ELSE 1 END)"
	} else {
		matcher = "COUNT(*)"
	}

	query := "SELECT t.name AS topic,t.createdat,t.updatedat,t.usebt,t.access,t.subcnt,t.public,t.trusted,t.tags," + matcher + " AS matches " +
		"FROM im_topics AS t JOIN im_topictags AS tg ON t.name=tg.topic " +
		"WHERE " + stateConstraint + "tg.tag IN (?" + strings.Repeat(",?", len(allTags)-1) + ") " +
		"GROUP BY t.name,t.createdat,t.updatedat,t.usebt,t.access,t.subcnt,t.public,t.trusted,t.tags "
	if len(allReq) > 0 {
		q, a := common.DisjunctionSql(req, "tg.tag")
		query += q
		args = append(args, a...)
	}
	query += "ORDER BY matches DESC, subcnt DESC LIMIT ?"
	args = append(args, a.maxResults)

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	// Get users matched by tags, sort by number of matches from high to low.
	rows, err := a.db.QueryxContext(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	// Read results as subscriptions.
	var public, trusted any
	var access t.DefaultAccess
	var subcnt int
	var setTags t.StringSlice
	var ignored int
	var isChan bool
	var sub t.Subscription
	var subs []t.Subscription
	for rows.Next() {
		if err = rows.Scan(&sub.Topic, &sub.CreatedAt, &sub.UpdatedAt, &isChan, &access, &subcnt,
			&public, &trusted, &setTags, &ignored); err != nil {
			subs = nil
			break
		}

		if id, err := strconv.ParseInt(sub.Topic, 10, 64); err == nil {
			sub.Topic = store.EncodeUid(id).UserId()
			if sub.Topic == caller {
				// Skip the caller.
				continue
			}
		}

		if isChan {
			// This is a channel, convert grp to chn name: all channel-capable
			// topics should appear as channels in search results.
			sub.Topic = t.GrpToChn(sub.Topic)
		}

		sub.SetSubCnt(subcnt)
		sub.SetPublic(common.FromJSON(public))
		sub.SetTrusted(common.FromJSON(trusted))
		sub.SetDefaultAccess(access.Auth, access.Anon)
		// Indicating that the mode is not set, not 'N'.
		sub.ModeGiven = t.ModeUnset
		sub.ModeWant = t.ModeUnset
		sub.Private = common.FilterFoundTags(setTags, index)
		subs = append(subs, sub)
	}
	if err == nil {
		err = rows.Err()
	}

	return subs, err
}

// FindOne returns the first topic which matches the given tag.
func (a *adapter) FindOne(tag string) (string, error) {
	query := "SELECT t.name AS topic FROM im_topics AS t LEFT JOIN im_topictags AS tt ON t.name=tt.topic " +
		"WHERE tt.tag=? LIMIT 1"

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	rows, err := a.db.QueryxContext(ctx, query, tag)
	if err != nil {
		return "", err
	}
	defer rows.Close()

	var found string
	if rows.Next() {
		if err = rows.Scan(&found); err != nil {
			return "", err
		}

		// Check if the found value is a topic name or a user ID.
		// User IDs are returned as decoded decimal strings.
		if id, err := strconv.ParseInt(found, 10, 64); err == nil {
			found = store.EncodeUid(id).UserId()
		}
	}
	if err == nil {
		err = rows.Err()
	}

	return found, err
}

// Messages
func (a *adapter) MessageSave(msg *t.Message) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	// store assignes message ID, but we don't use it. Message IDs are not used anywhere.
	// Using a sequential ID provided by the database.
	clientMsgID := sql.NullString{String: msg.ClientMsgID, Valid: msg.ClientMsgID != ""}
	res, err := a.db.ExecContext(ctx,
		"INSERT INTO im_messages(createdAt,updatedAt,seqid,topic,`from`,client_msg_id,version,head,content,content_nonce,key_version) VALUES(?,?,?,?,?,?,?,?,?,?,?)",
		msg.CreatedAt, msg.UpdatedAt, msg.SeqId, msg.Topic,
		store.DecodeUid(t.ParseUid(msg.From)), clientMsgID, messageVersion(msg.Version), msg.Head, common.ToJSON(msg.Content), msg.ContentNonce, msg.KeyVersion)
	if isDupe(err) {
		return t.ErrDuplicate
	}
	if err == nil {
		id, _ := res.LastInsertId()
		// Replacing ID given by store by ID given by the DB.
		msg.SetUid(t.Uid(id))
	}
	return err
}

// MessageGetAll returns messages matching the query.
func (a *adapter) MessageGetAll(topic string, forUser t.Uid, opts *t.QueryOpt) ([]t.Message, error) {
	var limit = a.maxMessageResults

	args := []any{store.DecodeUid(forUser), topic}
	seqIdConstraint := ""
	if opts != nil {
		seqIdConstraint = "AND m.seqid "
		if len(opts.IdRanges) > 0 {
			constr, newargs := common.RangesToSql(opts.IdRanges)
			seqIdConstraint += constr
			args = append(args, newargs...)
		} else {
			seqIdConstraint += "BETWEEN ? AND ?"
			if opts.Since > 0 {
				args = append(args, opts.Since)
			} else {
				args = append(args, 0)
			}
			if opts.Before > 1 {
				// MySQL BETWEEN is inclusive-inclusive, Tinode API requires inclusive-exclusive, thus -1
				args = append(args, opts.Before-1)
			} else {
				args = append(args, 1<<31-1)
			}
		}

		if opts.Limit > 0 && opts.Limit < limit {
			limit = opts.Limit
		}
	}

	args = append(args, limit)

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	rows, err := a.db.QueryxContext(
		ctx,
		"SELECT m.createdat,m.updatedat,m.deletedat,m.delid,m.seqid,m.topic,m.`from`,m.head,m.content,m.content_nonce,m.key_version"+
			" FROM im_messages AS m LEFT JOIN im_dellog AS d"+
			" ON d.topic=m.topic AND m.seqid BETWEEN d.low AND d.hi-1 AND d.deletedfor=?"+
			" WHERE m.delid=0 AND m.topic=? "+seqIdConstraint+" AND d.deletedfor IS NULL"+
			" ORDER BY m.seqid DESC LIMIT ?",
		args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	msgs := make([]t.Message, 0, limit)
	for rows.Next() {
		var msg t.Message
		if err = rows.StructScan(&msg); err != nil {
			break
		}
		msg.From = common.EncodeUidString(msg.From).String()
		msg.Content = common.FromJSON(msg.Content)
		msgs = append(msgs, msg)
	}
	if err == nil {
		err = rows.Err()
	}

	return msgs, err
}

// Get ranges of deleted messages
func (a *adapter) MessageGetDeleted(topic string, forUser t.Uid, opts *t.QueryOpt) ([]t.DelMessage, error) {
	var limit = a.maxResults
	var lower int64 = 0
	var upper int64 = 1<<31 - 1

	if opts != nil {
		if opts.Since > 0 {
			lower = opts.Since
		}
		if opts.Before > 1 {
			// DelRange is inclusive-exclusive, while BETWEEN is inclusive-inclisive.
			upper = opts.Before - 1
		}

		if opts.Limit > 0 && opts.Limit < limit {
			limit = opts.Limit
		}
	}

	// Fetch log of deletions
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, "SELECT topic,deletedfor,delid,low,hi FROM im_dellog WHERE topic=? AND delid BETWEEN ? AND ?"+
		" AND (deletedFor=0 OR deletedFor=?)"+
		" ORDER BY delid LIMIT ?", topic, lower, upper, store.DecodeUid(forUser), limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var dellog struct {
		Topic      string
		Deletedfor int64
		Delid      int
		Low        int64
		Hi         int64
	}
	var dmsgs []t.DelMessage
	var dmsg t.DelMessage
	for rows.Next() {
		if err = rows.StructScan(&dellog); err != nil {
			dmsgs = nil
			break
		}

		if dellog.Delid != dmsg.DelId {
			if dmsg.DelId > 0 {
				dmsgs = append(dmsgs, dmsg)
			}
			dmsg.DelId = dellog.Delid
			dmsg.Topic = dellog.Topic
			if dellog.Deletedfor > 0 {
				dmsg.DeletedFor = store.EncodeUid(dellog.Deletedfor).String()
			} else {
				dmsg.DeletedFor = ""
			}
			dmsg.SeqIdRanges = nil
		}
		if dellog.Hi <= dellog.Low+1 {
			dellog.Hi = 0
		}
		dmsg.SeqIdRanges = append(dmsg.SeqIdRanges, t.Range{Low: dellog.Low, Hi: dellog.Hi})
	}
	if err == nil {
		err = rows.Err()
	}

	if err == nil {
		if dmsg.DelId > 0 {
			dmsgs = append(dmsgs, dmsg)
		}
	}

	return dmsgs, err
}

func messageDeleteList(tx *sqlx.Tx, topic string, toDel *t.DelMessage) error {
	var err error

	if toDel == nil {
		// Whole topic is being deleted, thus also deleting all messages.
		_, err = tx.Exec("DELETE FROM im_dellog WHERE topic=?", topic)
		if err == nil {
			_, err = tx.Exec("DELETE FROM im_messages WHERE topic=?", topic)
		}
		// filemsglinks will be deleted because of ON DELETE CASCADE
		return err
	}

	// Only some messages are being deleted.

	delRanges := toDel.SeqIdRanges

	if toDel.DeletedFor == "" {
		// Hard-deleting messages requires updates to the messages table.
		where := "m.topic=?"
		args := []any{topic}

		if len(delRanges) > 0 {
			rSql, rArgs := common.RangesToSql(delRanges)
			where += " AND m.seqid " + rSql
			args = append(args, rArgs...)
		}

		where += " AND m.deletedat IS NULL"

		// We are asked to delete messages no older than newerThan.
		if newerThan := toDel.GetNewerThan(); newerThan != nil {
			where += " AND m.createdat>?"
			args = append(args, newerThan)
		}

		// Find the actual IDs still present in the database.
		var seqIDs []int64
		err = tx.Select(&seqIDs, "SELECT seqid FROM im_messages AS m WHERE "+where, args...)
		if err != nil {
			return err
		}

		if len(seqIDs) == 0 {
			// Nothing to delete. No need to make a log entry. All done.
			return nil
		}

		// Recalculate the actual ranges to delete.
		sort.Slice(seqIDs, func(i, j int) bool { return seqIDs[i] < seqIDs[j] })
		delRanges = t.SliceToRanges(seqIDs)

		// Compose a new query with the new ranges.
		where = "m.topic=?"
		args = []any{topic}
		rSql, rArgs := common.RangesToSql(delRanges)
		where += " AND m.seqid " + rSql
		args = append(args, rArgs...)

		// No need to add anything else: deletedat etc is already accounted for.

		_, err = tx.Exec("DELETE fml.* FROM im_filemsglinks AS fml INNER JOIN im_messages AS m ON m.id=fml.msgid WHERE "+
			where, args...)
		if err != nil {
			return err
		}

		// Instead of deleting messages, clear all content.
		_, err = tx.Exec("UPDATE im_messages AS m SET m.deletedat=?,m.delId=?,m.`from`=0,m.head=NULL,m.content=NULL WHERE "+
			where, append([]any{t.TimeNow(), toDel.DelId}, args...)...)
		if err != nil {
			return err
		}
	}

	// Now make log entries. Needed for both hard- and soft-deleting.
	var insert *sql.Stmt
	if insert, err = tx.Prepare(
		"INSERT INTO im_dellog(topic,deletedfor,delid,low,hi) VALUES(?,?,?,?,?)"); err != nil {
		return err
	}

	forUser := common.DecodeUidString(toDel.DeletedFor)
	for _, rng := range delRanges {
		if rng.Hi == 0 {
			// Dellog must contain valid Low and *Hi*.
			rng.Hi = rng.Low + 1
		}
		// A log entry for each range.
		if _, err = insert.Exec(topic, forUser, toDel.DelId, rng.Low, rng.Hi); err != nil {
			break
		}
	}

	return err
}

// MessageDeleteList deletes messages in the given topic with seqIds from the list.
func (a *adapter) MessageDeleteList(topic string, toDel *t.DelMessage) (err error) {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}

	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	if err = messageDeleteList(tx, topic, toDel); err != nil {
		return err
	}

	return tx.Commit()
}

func deviceHasher(deviceID string) string {
	// Generate custom key as [64-bit hash of device id] to ensure predictable
	// length of the key
	hasher := fnv.New64()
	hasher.Write([]byte(deviceID))
	return strconv.FormatUint(uint64(hasher.Sum64()), 16)
}

// Device management for push notifications.

// DeviceUpsert creates or updates a device record.
func (a *adapter) DeviceUpsert(uid t.Uid, def *t.DeviceDef) error {
	hash := deviceHasher(def.DeviceId)

	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// Ensure uniqueness of the device ID: delete all records of the device ID
	_, err = tx.Exec("DELETE FROM im_devices WHERE hash=?", hash)
	if err != nil {
		return err
	}

	// Actually add/update DeviceId for the new user
	_, err = tx.Exec("INSERT INTO im_devices(userid, hash, deviceId, platform, lastseen, lang) VALUES(?,?,?,?,?,?)",
		store.DecodeUid(uid), hash, def.DeviceId, def.Platform, def.LastSeen, def.Lang)
	if err != nil {
		return err
	}

	return tx.Commit()
}

// DeviceGetAll returns all devices for a given set of users.
func (a *adapter) DeviceGetAll(uids ...t.Uid) (map[t.Uid][]t.DeviceDef, int, error) {
	var unums []any
	for _, uid := range uids {
		unums = append(unums, store.DecodeUid(uid))
	}

	q, unums, _ := sqlx.In("SELECT userid,deviceid,platform,lastseen,lang FROM im_devices WHERE userid IN (?)", unums)
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	rows, err := a.db.QueryxContext(ctx, q, unums...)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	var device struct {
		Userid   int64
		Deviceid string
		Platform string
		Lastseen time.Time
		Lang     string
	}

	result := make(map[t.Uid][]t.DeviceDef)
	count := 0
	for rows.Next() {
		if err = rows.StructScan(&device); err != nil {
			break
		}
		uid := store.EncodeUid(device.Userid)
		udev := result[uid]
		udev = append(udev, t.DeviceDef{
			DeviceId: device.Deviceid,
			Platform: device.Platform,
			LastSeen: device.Lastseen,
			Lang:     device.Lang,
		})
		result[uid] = udev
		count++
	}
	if err == nil {
		err = rows.Err()
	}

	return result, count, err
}

func deviceDelete(tx *sqlx.Tx, uid t.Uid, deviceID string) error {
	var err error
	var res sql.Result
	if deviceID == "" {
		res, err = tx.Exec("DELETE FROM im_devices WHERE userid=?", store.DecodeUid(uid))
	} else {
		res, err = tx.Exec("DELETE FROM im_devices WHERE userid=? AND hash=?", store.DecodeUid(uid), deviceHasher(deviceID))
	}

	if err == nil {
		if count, _ := res.RowsAffected(); count == 0 {
			err = t.ErrNotFound
		}
	}

	return err
}

// DeviceDelete deletes a device record (push token).
func (a *adapter) DeviceDelete(uid t.Uid, deviceID string) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	err = deviceDelete(tx, uid, deviceID)
	if err != nil {
		return err
	}

	return tx.Commit()
}

// Credential management

// CredUpsert adds or updates a validation record. Returns true if inserted, false if updated.
// 1. if credential is validated:
// 1.1 Hard-delete unconfirmed equivalent record, if exists.
// 1.2 Insert new. Report error if duplicate.
// 2. if credential is not validated:
// 2.1 Check if validated equivalent exist. If so, report an error.
// 2.2 Soft-delete all unvalidated records of the same method.
// 2.3 Undelete existing credential. Return if successful.
// 2.4 Insert new credential record.
func (a *adapter) CredUpsert(cred *t.Credential) (bool, error) {
	var err error
	if cred == nil {
		return false, t.ErrMalformed
	}
	if cred.Method == "tel" {
		cred.Value, err = normalizeUserPhone(cred.Value)
		if err != nil {
			return false, err
		}
	}

	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return false, err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	now := t.TimeNow()
	userId := common.DecodeUidString(cred.User)

	// Enforce uniqueness: if credential is confirmed, "method:value" must be unique.
	// if credential is not yet confirmed, "userid:method:value" is unique.
	synth := cred.Method + ":" + cred.Value

	if !cred.Done {
		// Check if this credential is already validated.
		var done bool
		err = tx.Get(&done, "SELECT done FROM im_credentials WHERE synthetic=?", synth)
		if err == nil {
			// Assign err to ensure closing of a transaction.
			err = t.ErrDuplicate
			return false, err
		}
		if err != sql.ErrNoRows {
			return false, err
		}
		// We are going to insert new record.
		synth = cred.User + ":" + synth

		// Adding new unvalidated credential. Deactivate all unvalidated records of this user and method.
		_, err = tx.Exec("UPDATE im_credentials SET deletedat=? WHERE userid=? AND method=? AND done=FALSE",
			now, userId, cred.Method)
		if err != nil {
			return false, err
		}
		// Assume that the record exists and try to update it: undelete, update timestamp and response value.
		res, err := tx.Exec("UPDATE im_credentials SET updatedat=?,deletedat=NULL,resp=?,done=FALSE WHERE synthetic=?",
			cred.UpdatedAt, cred.Resp, synth)
		if err != nil {
			return false, err
		}
		// If record was updated, then all is fine.
		if numrows, _ := res.RowsAffected(); numrows > 0 {
			return false, tx.Commit()
		}
	} else {
		// Hard-deleting unconformed record if it exists.
		_, err = tx.Exec("DELETE FROM im_credentials WHERE synthetic=?", cred.User+":"+synth)
		if err != nil {
			return false, err
		}
	}
	// Add new record.
	credID, err := nextSnowflakeID()
	if err != nil {
		return false, err
	}
	_, err = tx.Exec("INSERT INTO im_credentials(id,createdat,updatedat,method,value,synthetic,userid,resp,done) "+
		"VALUES(?,?,?,?,?,?,?,?,?)",
		credID, cred.CreatedAt, cred.UpdatedAt, cred.Method, cred.Value, synth, userId, cred.Resp, cred.Done)
	if isIDOutOfRange(err) {
		_, err = tx.Exec("INSERT INTO im_credentials(createdat,updatedat,method,value,synthetic,userid,resp,done) "+
			"VALUES(?,?,?,?,?,?,?,?)",
			cred.CreatedAt, cred.UpdatedAt, cred.Method, cred.Value, synth, userId, cred.Resp, cred.Done)
	}
	if err != nil {
		if isDupe(err) {
			return true, t.ErrDuplicate
		}
		return true, err
	}
	if cred.Done && cred.Method == "tel" {
		if _, err = tx.Exec("UPDATE im_users SET phone=? WHERE id=? AND (phone IS NULL OR phone='')", cred.Value, userId); err != nil {
			return true, err
		}
	}
	return true, tx.Commit()
}

// TenantCredUpsert adds or updates a credential scoped to a tenant.
func (a *adapter) TenantCredUpsert(tenantID t.TenantID, cred *t.Credential) (bool, error) {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil || cred == nil {
		return false, t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantCredUpsert(tenantID, cred)
	}
	if cred.Method == "tel" {
		cred.Value, err = normalizeUserPhone(cred.Value)
		if err != nil {
			return false, err
		}
	}
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return false, err
	}
	defer tx.Rollback()
	now := t.TimeNow()
	userID := common.DecodeUidString(cred.User)
	synth := cred.Method + ":" + cred.Value
	if !cred.Done {
		var done bool
		err = tx.Get(&done, "SELECT done FROM im_credentials WHERE tenant_id=? AND synthetic=?", tenantID, synth)
		if err == nil {
			return false, t.ErrDuplicate
		}
		if err != sql.ErrNoRows {
			return false, err
		}
		synth = cred.User + ":" + synth
		if _, err = tx.Exec("UPDATE im_credentials SET deletedat=? WHERE tenant_id=? AND userid=? AND method=? AND done=FALSE",
			now, tenantID, userID, cred.Method); err != nil {
			return false, err
		}
		res, updateErr := tx.Exec("UPDATE im_credentials SET updatedat=?,deletedat=NULL,resp=?,done=FALSE WHERE tenant_id=? AND synthetic=?",
			cred.UpdatedAt, cred.Resp, tenantID, synth)
		if updateErr != nil {
			return false, updateErr
		}
		if rows, _ := res.RowsAffected(); rows > 0 {
			return false, tx.Commit()
		}
	} else if _, err = tx.Exec("DELETE FROM im_credentials WHERE tenant_id=? AND synthetic=?", tenantID, cred.User+":"+synth); err != nil {
		return false, err
	}
	credID, err := nextSnowflakeID()
	if err != nil {
		return false, err
	}
	_, err = tx.Exec(`INSERT INTO im_credentials(tenant_id,id,createdat,updatedat,method,value,synthetic,userid,resp,done)
		VALUES(?,?,?,?,?,?,?,?,?,?)`, tenantID, credID, cred.CreatedAt, cred.UpdatedAt, cred.Method, cred.Value, synth, userID, cred.Resp, cred.Done)
	if isIDOutOfRange(err) {
		_, err = tx.Exec(`INSERT INTO im_credentials(tenant_id,createdat,updatedat,method,value,synthetic,userid,resp,done)
			VALUES(?,?,?,?,?,?,?,?,?)`, tenantID, cred.CreatedAt, cred.UpdatedAt, cred.Method, cred.Value, synth, userID, cred.Resp, cred.Done)
	}
	if err != nil {
		if isDupe(err) {
			return true, t.ErrDuplicate
		}
		return true, err
	}
	if cred.Done && cred.Method == "tel" {
		if _, err = tx.Exec("UPDATE im_users SET phone=? WHERE tenant_id=? AND id=? AND (phone IS NULL OR phone='')", cred.Value, tenantID, userID); err != nil {
			return true, err
		}
	}
	return true, tx.Commit()
}

func tenantCredDel(tx *sqlx.Tx, tenantID t.TenantID, uid t.Uid, method, value string) error {
	constraints := " WHERE tenant_id=? AND userid=?"
	args := []any{tenantID, store.DecodeUid(uid)}
	if method != "" {
		constraints += " AND method=?"
		args = append(args, method)
		if value != "" {
			constraints += " AND value=?"
			args = append(args, value)
		}
	}

	if method == "" {
		res, err := tx.Exec("DELETE FROM im_credentials"+constraints, args...)
		if err != nil {
			return err
		}
		if count, _ := res.RowsAffected(); count == 0 {
			return t.ErrNotFound
		}
		return nil
	}

	res, err := tx.Exec("DELETE FROM im_credentials"+constraints+" AND (done=TRUE OR retries=0)", args...)
	if err != nil {
		return err
	}
	if count, _ := res.RowsAffected(); count > 0 {
		return nil
	}

	args = append([]any{t.TimeNow()}, args...)
	res, err = tx.Exec("UPDATE im_credentials SET deletedat=?"+constraints, args...)
	if err != nil {
		return err
	}
	if count, _ := res.RowsAffected(); count == 0 {
		return t.ErrNotFound
	}
	return nil
}

// credDel deletes given validation method or all methods of the given user.
// 1. If user is being deleted, hard-delete all records (method == "")
// 2. If one value is being deleted:
// 2.1 Delete it if it's valiated or if there were no attempts at validation
// (otherwise it could be used to circumvent the limit on validation attempts).
// 2.2 In that case mark it as soft-deleted.
func credDel(tx *sqlx.Tx, uid t.Uid, method, value string) error {
	constraints := " WHERE userid=?"
	args := []any{store.DecodeUid(uid)}

	if method != "" {
		constraints += " AND method=?"
		args = append(args, method)

		if value != "" {
			constraints += " AND value=?"
			args = append(args, value)
		}
	}

	var err error
	var res sql.Result
	if method == "" {
		// Case 1
		res, err = tx.Exec("DELETE FROM im_credentials"+constraints, args...)
		if err == nil {
			if count, _ := res.RowsAffected(); count == 0 {
				err = t.ErrNotFound
			}
		}
		return err
	}

	// Case 2.1
	res, err = tx.Exec("DELETE FROM im_credentials"+constraints+" AND (done=TRUE OR retries=0)", args...)
	if err != nil {
		return err
	}
	if count, _ := res.RowsAffected(); count > 0 {
		return nil
	}

	// Case 2.2
	args = append([]any{t.TimeNow()}, args...)
	res, err = tx.Exec("UPDATE im_credentials SET deletedat=?"+constraints, args...)
	if err == nil {
		if count, _ := res.RowsAffected(); count >= 0 {
			err = t.ErrNotFound
		}
	}

	return err
}

// CredDel deletes either credentials of the given user. If method is blank all
// credentials are removed. If value is blank all credentials of the given the
// method are removed.
func (a *adapter) CredDel(uid t.Uid, method, value string) error {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	err = credDel(tx, uid, method, value)
	if err != nil {
		return err
	}

	return tx.Commit()
}

// TenantCredDel deletes credentials only in the selected tenant.
func (a *adapter) TenantCredDel(tenantID t.TenantID, uid t.Uid, method, value string) error {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantCredDel(tenantID, uid, method, value)
	}
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	if err = tenantCredDel(tx, tenantID, uid, method, value); err != nil {
		tx.Rollback()
		return err
	}
	return tx.Commit()
}

// CredConfirm marks given credential method as confirmed.
func (a *adapter) CredConfirm(uid t.Uid, method string) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	res, err := a.db.ExecContext(
		ctx,
		"UPDATE im_credentials SET updatedat=?,done=TRUE,synthetic=CONCAT(method,':',value) "+
			"WHERE userid=? AND method=? AND deletedat IS NULL AND done=FALSE",
		t.TimeNow(), store.DecodeUid(uid), method)
	if err != nil {
		if isDupe(err) {
			return t.ErrDuplicate
		}
		return err
	}
	if numrows, _ := res.RowsAffected(); numrows < 1 {
		return t.ErrNotFound
	}
	return nil
}

// TenantCredConfirm confirms a credential only in the selected tenant.
func (a *adapter) TenantCredConfirm(tenantID t.TenantID, uid t.Uid, method string) error {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantCredConfirm(tenantID, uid, method)
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	res, err := a.db.ExecContext(ctx,
		"UPDATE im_credentials SET updatedat=?,done=TRUE,synthetic=CONCAT(method,':',value) "+
			"WHERE tenant_id=? AND userid=? AND method=? AND deletedat IS NULL AND done=FALSE",
		t.TimeNow(), tenantID, store.DecodeUid(uid), method)
	if isDupe(err) {
		return t.ErrDuplicate
	}
	if err != nil {
		return err
	}
	if numRows, _ := res.RowsAffected(); numRows < 1 {
		return t.ErrNotFound
	}
	return nil
}

// CredFail increments failure count of the given validation method.
func (a *adapter) CredFail(uid t.Uid, method string) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err := a.db.ExecContext(ctx, "UPDATE im_credentials SET updatedat=?,retries=retries+1 WHERE userid=? AND method=? AND done=FALSE",
		t.TimeNow(), store.DecodeUid(uid), method)
	return err
}

// TenantCredFail increments credential failures only in the selected tenant.
func (a *adapter) TenantCredFail(tenantID t.TenantID, uid t.Uid, method string) error {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantCredFail(tenantID, uid, method)
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	_, err = a.db.ExecContext(ctx, "UPDATE im_credentials SET updatedat=?,retries=retries+1 "+
		"WHERE tenant_id=? AND userid=? AND method=? AND done=FALSE",
		t.TimeNow(), tenantID, store.DecodeUid(uid), method)
	return err
}

// CredGetActive returns currently active unvalidated credential of the given user and method.
func (a *adapter) CredGetActive(uid t.Uid, method string) (*t.Credential, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var cred t.Credential
	err := a.db.GetContext(ctx, &cred, "SELECT createdat,updatedat,method,value,resp,done,retries "+
		"FROM im_credentials WHERE userid=? AND deletedat IS NULL AND method=? AND done=FALSE",
		store.DecodeUid(uid), method)
	if err != nil {
		if err == sql.ErrNoRows {
			err = nil
		}
		return nil, err
	}
	cred.User = uid.String()

	return &cred, nil
}

// TenantCredGetActive returns the active credential in the selected tenant.
func (a *adapter) TenantCredGetActive(tenantID t.TenantID, uid t.Uid, method string) (*t.Credential, error) {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return nil, t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantCredGetActive(tenantID, uid, method)
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var cred t.Credential
	err = a.db.GetContext(ctx, &cred, `SELECT createdat,updatedat,method,value,resp,done,retries
		FROM im_credentials WHERE tenant_id=? AND userid=? AND deletedat IS NULL AND method=? AND done=FALSE`,
		tenantID, store.DecodeUid(uid), method)
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	cred.User = uid.String()
	return &cred, nil
}

// CredGetAll returns credential records for the given user and method, all or validated only.
func (a *adapter) CredGetAll(uid t.Uid, method string, validatedOnly bool) ([]t.Credential, error) {
	query := "SELECT createdat,updatedat,method,value,resp,done,retries FROM im_credentials WHERE userid=? AND deletedat IS NULL"
	args := []any{store.DecodeUid(uid)}
	if method != "" {
		query += " AND method=?"
		args = append(args, method)
	}
	if validatedOnly {
		query += " AND done=TRUE"
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var credentials []t.Credential
	err := a.db.SelectContext(ctx, &credentials, query, args...)
	if err != nil {
		return nil, err
	}

	user := uid.String()
	for i := range credentials {
		credentials[i].User = user
	}

	return credentials, err
}

// TenantCredGetAll returns credentials only from the selected tenant.
func (a *adapter) TenantCredGetAll(tenantID t.TenantID, uid t.Uid, method string,
	validatedOnly bool) ([]t.Credential, error) {
	tenantAdp, err := a.routedTenantAdapter(tenantID)
	if err != nil {
		return nil, t.ErrMalformed
	}
	if tenantAdp != a {
		return tenantAdp.TenantCredGetAll(tenantID, uid, method, validatedOnly)
	}
	query := `SELECT createdat,updatedat,method,value,resp,done,retries
		FROM im_credentials WHERE tenant_id=? AND userid=? AND deletedat IS NULL`
	args := []any{tenantID, store.DecodeUid(uid)}
	if method != "" {
		query += " AND method=?"
		args = append(args, method)
	}
	if validatedOnly {
		query += " AND done=TRUE"
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var credentials []t.Credential
	if err = a.db.SelectContext(ctx, &credentials, query, args...); err != nil {
		return nil, err
	}
	for i := range credentials {
		credentials[i].User = uid.String()
	}
	return credentials, nil
}

// FileUploads

// FileStartUpload initializes a file upload
func (a *adapter) FileStartUpload(fd *t.FileDef) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var user any
	if fd.User != "" {
		user = store.DecodeUid(t.ParseUid(fd.User))
	} else {
		user = 0
	}
	_, err := a.db.ExecContext(ctx,
		"INSERT INTO im_fileuploads(id,createdat,updatedat,userid,status,mimetype,size,etag,location) "+
			"VALUES(?,?,?,?,?,?,?,?,?)",
		store.DecodeUid(fd.Uid()), fd.CreatedAt, fd.UpdatedAt, user,
		fd.Status, fd.MimeType, fd.Size, fd.ETag, fd.Location)
	return err
}

// FileFinishUpload marks file upload as completed, successfully or otherwise
func (a *adapter) FileFinishUpload(fd *t.FileDef, success bool, size int64) (*t.FileDef, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	now := t.TimeNow()
	if success {
		_, err = tx.ExecContext(ctx, "UPDATE im_fileuploads SET updatedat=?,status=?,size=?,etag=?,location=? WHERE id=?",
			now, t.UploadCompleted, size, fd.ETag, fd.Location, store.DecodeUid(fd.Uid()))
		if err != nil {
			return nil, err
		}
		fd.UpdatedAt = now
		fd.Size = size
		if err = insertFileReviewTasks(ctx, tx, fd); err != nil {
			return nil, err
		}

		fd.Status = t.UploadCompleted
	} else {
		// Deleting the record: there is no value in keeping it in the DB.
		_, err = tx.ExecContext(ctx, "DELETE FROM im_fileuploads WHERE id=?", store.DecodeUid(fd.Uid()))
		if err != nil {
			return nil, err
		}

		fd.Status = t.UploadFailed
		fd.Size = 0
	}
	fd.UpdatedAt = now

	return fd, tx.Commit()
}

// FileGet fetches a record of a specific file
func (a *adapter) FileGet(fid string) (*t.FileDef, error) {
	id := parseFileUID(fid)
	if id.IsZero() {
		return nil, t.ErrMalformed
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var fd t.FileDef
	err := a.db.GetContext(ctx, &fd, "SELECT id,createdat,updatedat,userid AS user,status,mimetype,size,IFNULL(etag,'') AS etag,location "+
		"FROM im_fileuploads WHERE id=?", store.DecodeUid(id))
	if err == sql.ErrNoRows {
		storageName := id.String32()
		err = a.db.GetContext(ctx, &fd, "SELECT id,createdat,updatedat,userid AS user,status,mimetype,size,IFNULL(etag,'') AS etag,location "+
			"FROM im_fileuploads WHERE location=? OR location LIKE ? ORDER BY createdat DESC LIMIT 1", storageName, "%/"+storageName)
	}
	if err == sql.ErrNoRows {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}

	fd.Id = common.EncodeUidString(fd.Id).String()
	fd.User = common.EncodeUidString(fd.User).String()

	return &fd, nil
}

// FileDeleteUnused deletes records where UseCount is zero. If olderThan is non-zero, deletes
// unused records with UpdatedAt before olderThan.
// Returns array of FileDef.Location of deleted filerecords so actual files can be deleted too.
func (a *adapter) FileDeleteUnused(olderThan time.Time, limit int) ([]string, error) {
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// Garbage collecting entries which as either marked as deleted, or lack message references, or have no user assigned.
	query := "SELECT fu.id,fu.location FROM im_fileuploads AS fu LEFT JOIN im_filemsglinks AS fml ON fml.fileid=fu.id " +
		"WHERE fml.id IS NULL"
	var args []any
	if !olderThan.IsZero() {
		query += " AND fu.updatedat<?"
		args = append(args, olderThan)
	}
	if limit > 0 {
		query += " LIMIT ?"
		args = append(args, limit)
	}

	rows, err := tx.Query(query, args...)
	if err != nil {
		return nil, err
	}

	type gcCandidate struct {
		id       int
		location string
	}
	var candidates []gcCandidate
	for rows.Next() {
		var id int
		var loc string
		if err = rows.Scan(&id, &loc); err != nil {
			break
		}
		candidates = append(candidates, gcCandidate{id: id, location: loc})
	}
	if err == nil {
		err = rows.Err()
	}
	rows.Close()

	if err != nil {
		return nil, err
	}

	var locations []string
	var ids []any
	for _, candidate := range candidates {
		if candidate.location != "" {
			locations = append(locations, candidate.location)
		}
		ids = append(ids, candidate.id)
	}

	if err != nil {
		return nil, err
	}

	if len(ids) > 0 {
		query, ids, _ = sqlx.In("DELETE FROM im_fileuploads WHERE id IN (?)", ids)
		_, err = tx.Exec(query, ids...)
		if err != nil {
			return nil, err
		}
	}

	return locations, tx.Commit()
}

// FileLinkAttachments connects given topic or message to the file record IDs from the list.
func (a *adapter) FileLinkAttachments(topic string, userId, msgId t.Uid, fids []string) error {
	if len(fids) == 0 || (topic == "" && msgId.IsZero() && userId.IsZero()) {
		return t.ErrMalformed
	}
	now := t.TimeNow()

	var args []any
	var linkId any
	var linkBy string
	if !msgId.IsZero() {
		linkBy = "msgid"
		linkId = int64(msgId)
	} else if topic != "" {
		linkBy = "topic"
		linkId = topic
		// Only one attachment per topic is permitted at this time.
		fids = fids[0:1]
	} else {
		linkBy = "userid"
		linkId = store.DecodeUid(userId)
		// Only one attachment per user is permitted at this time.
		fids = fids[0:1]
	}

	// Decoded ids
	var dids []any
	for _, fid := range fids {
		id := t.ParseUid(fid)
		if id.IsZero() {
			return t.ErrMalformed
		}
		dids = append(dids, store.DecodeUid(id))
	}
	var existing int
	query, queryArgs, err := sqlx.In("SELECT COUNT(*) FROM im_fileuploads WHERE id IN (?) AND status=?", dids, t.UploadCompleted)
	if err != nil {
		return err
	}
	ctx, cancel := a.getContextForTx()
	if cancel != nil {
		defer cancel()
	}
	if err = a.db.GetContext(ctx, &existing, a.db.Rebind(query), queryArgs...); err != nil {
		return err
	}
	if existing != len(dids) {
		return t.ErrNotFound
	}

	for _, id := range dids {
		// createdat,fileid,[msgid|topic|userid]
		args = append(args, now, id, linkId)
	}

	tx, err := a.db.BeginTxx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			tx.Rollback()
		}
	}()

	// Unlink earlier uploads on the same topic or user allowing them to be garbage-collected.
	if msgId.IsZero() {
		sql := "DELETE FROM im_filemsglinks WHERE " + linkBy + "=?"
		_, err = tx.Exec(sql, linkId)
		if err != nil {
			return err
		}
	}

	sql := "INSERT INTO im_filemsglinks(createdat,fileid," + linkBy + ") VALUES (?,?,?)"
	_, err = tx.Exec(sql+strings.Repeat(",(?,?,?)", len(dids)-1), args...)
	if err != nil {
		return err
	}

	return tx.Commit()
}

func (a *adapter) FileUserHasAccess(fid string, uid t.Uid) (bool, error) {
	if uid.IsZero() {
		return false, t.ErrMalformed
	}
	fileID := parseFileUID(fid)
	if fileID.IsZero() {
		return false, t.ErrMalformed
	}
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}
	var allowed int
	buildQuery := func() (string, []any) {
		args := []any{
			store.DecodeUid(fileID), fileID.String32(), "%/" + fileID.String32(), t.UploadCompleted,
			store.DecodeUid(uid), store.DecodeUid(uid), store.DecodeUid(uid), t.RelationshipFriend,
			store.DecodeUid(uid), store.DecodeUid(uid), t.GroupMemberStatusActive, store.DecodeUid(uid), store.DecodeUid(uid),
			store.DecodeUid(uid), fid, fid,
		}
		return `
		SELECT COUNT(*) FROM im_fileuploads AS fu
		WHERE (fu.id=? OR fu.location=? OR fu.location LIKE ?) AND fu.status=? AND (
			fu.userid=?
			OR EXISTS (
				SELECT 1 FROM im_filemsglinks AS fml
				WHERE fml.fileid=fu.id AND fml.topic LIKE 'cvp%'
			)
			OR EXISTS (
				SELECT 1 FROM im_filemsglinks AS fml
				WHERE fml.fileid=fu.id AND fml.userid=?
			)
			OR EXISTS (
				SELECT 1 FROM im_filemsglinks AS fml
				INNER JOIN im_friendships AS fs
					ON fs.user_id=? AND fs.peer_id=fml.userid AND fs.status=?
				WHERE fml.fileid=fu.id AND fml.userid IS NOT NULL
			)
			OR EXISTS (
				SELECT 1 FROM im_filemsglinks AS fml
				INNER JOIN im_subscriptions AS s
					ON s.topic=fml.topic AND s.userid=?
				WHERE fml.fileid=fu.id AND fml.topic IS NOT NULL
					AND s.deletedat IS NULL AND INSTR(s.modewant,'R')>0 AND INSTR(s.modegiven,'R')>0
			)
			OR EXISTS (
				SELECT 1 FROM im_filemsglinks AS fml
				INNER JOIN im_group_members AS gm
					ON gm.topic=fml.topic AND gm.user_id=? AND gm.member_status=?
				WHERE fml.fileid=fu.id AND fml.topic IS NOT NULL
			)
			OR EXISTS (
				SELECT 1 FROM im_filemsglinks AS fml
				INNER JOIN im_messages AS m
					ON m.id=fml.msgid
				INNER JOIN im_subscriptions AS s
					ON s.topic=m.topic AND s.userid=?
				WHERE fml.fileid=fu.id AND fml.msgid IS NOT NULL
					AND m.deletedat IS NULL AND m.recalled_at IS NULL
					AND s.deletedat IS NULL AND INSTR(s.modewant,'R')>0 AND INSTR(s.modegiven,'R')>0
					AND NOT EXISTS (
						SELECT 1 FROM im_dellog AS d
						WHERE d.topic=m.topic AND d.deletedfor=?
							AND d.low<=m.seqid AND (d.hi=0 OR d.hi>m.seqid)
					)
			)
			OR EXISTS (
				SELECT 1 FROM im_group_files AS gf
				INNER JOIN im_subscriptions AS s
					ON s.topic=gf.topic AND s.userid=?
			WHERE (gf.file_id=? OR gf.file_id LIKE CONCAT(?,'.%')) AND gf.status='active'
					AND s.deletedat IS NULL AND INSTR(s.modewant,'R')>0 AND INSTR(s.modegiven,'R')>0
			)
		) LIMIT 1`, args
	}
	run := func() error {
		query, args := buildQuery()
		return a.db.GetContext(ctx, &allowed, query, args...)
	}
	err := run()
	for attempt := 0; isRetryableMySQLError(err) && attempt < 2; attempt++ {
		time.Sleep(time.Duration(attempt+1) * 25 * time.Millisecond)
		err = run()
	}
	if err != nil {
		return false, err
	}
	return allowed > 0, nil
}

// PCacheGet reads a persistet cache entry.
func (a *adapter) PCacheGet(key string) (string, error) {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	var value string
	if err := a.db.GetContext(ctx, &value, "SELECT `value` FROM im_kvmeta WHERE `key`=? LIMIT 1", key); err != nil {
		if err == sql.ErrNoRows {
			return "", t.ErrNotFound
		}
		return "", err
	}
	return value, nil
}

// PCacheUpsert creates or updates a persistent cache entry.
func (a *adapter) PCacheUpsert(key string, value string, failOnDuplicate bool) error {
	if strings.Contains(key, "%") {
		// Do not allow % in keys: it interferes with LIKE query.
		return t.ErrMalformed
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	var action string
	if failOnDuplicate {
		action = "INSERT"
	} else {
		action = "REPLACE"
	}

	id, err := nextSnowflakeID()
	if err != nil {
		return err
	}
	_, err = a.db.ExecContext(ctx, action+" INTO im_kvmeta(id,`key`,createdat,`value`) VALUES(?,?,?,?)", id, key, t.TimeNow(), value)
	if isDupe(err) {
		return t.ErrDuplicate
	}
	return err
}

// PCacheDelete deletes one persistent cache entry.
func (a *adapter) PCacheDelete(key string) error {
	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	_, err := a.db.ExecContext(ctx, "DELETE FROM im_kvmeta WHERE `key`=?", key)
	return err
}

// PCacheExpire expires old entries with the given key prefix.
func (a *adapter) PCacheExpire(keyPrefix string, olderThan time.Time) error {
	if keyPrefix == "" {
		return t.ErrMalformed
	}

	ctx, cancel := a.getContext()
	if cancel != nil {
		defer cancel()
	}

	_, err := a.db.ExecContext(ctx, "DELETE FROM im_kvmeta WHERE `key` LIKE ? AND createdat<?", keyPrefix+"%", olderThan)
	return err
}

// GetTestDB returns a currently open database connection.
func (a *adapter) GetTestDB() any {
	return a.db
}

// Helper functions

// Check if MySQL error is a Error Code: 1062. Duplicate entry ... for key ...
func isDupe(err error) bool {
	if err == nil {
		return false
	}

	myerr, ok := err.(*ms.MySQLError)
	return ok && myerr.Number == 1062
}

func isMissingTable(err error) bool {
	if err == nil {
		return false
	}

	myerr, ok := err.(*ms.MySQLError)
	return ok && myerr.Number == 1146
}

func isMissingDb(err error) bool {
	if err == nil {
		return false
	}

	myerr, ok := err.(*ms.MySQLError)
	return ok && myerr.Number == 1049
}

func isUnknownColumn(err error) bool {
	if err == nil {
		return false
	}
	myerr, ok := err.(*ms.MySQLError)
	return ok && myerr.Number == 1054
}

func isDuplicateColumn(err error) bool {
	if err == nil {
		return false
	}
	myerr, ok := err.(*ms.MySQLError)
	return ok && myerr.Number == 1060
}

func isIDOutOfRange(err error) bool {
	if err == nil {
		return false
	}
	myerr, ok := err.(*ms.MySQLError)
	return ok && myerr.Number == 1264 && strings.Contains(strings.ToLower(myerr.Message), "id")
}

func isRetryableMySQLError(err error) bool {
	if err == nil {
		return false
	}
	var myerr *ms.MySQLError
	if !errors.As(err, &myerr) {
		return false
	}
	if myerr.Number == 1213 || myerr.Number == 1205 {
		return true
	}
	return strings.EqualFold(string(myerr.SQLState[:]), "40001")
}

func isPXCStrictModeNamedLockError(err error) bool {
	if err == nil {
		return false
	}
	myerr, ok := err.(*ms.MySQLError)
	if !ok || myerr.Number != 1105 {
		return false
	}
	msg := strings.ToLower(myerr.Message)
	return strings.Contains(msg, "percona-xtradb-cluster") &&
		strings.Contains(msg, "pxc_strict_mode") &&
		(strings.Contains(msg, "get_lock") || strings.Contains(msg, "release_lock"))
}

func mysqlDefaultString(value, fallback string) string {
	if strings.TrimSpace(value) == "" {
		return fallback
	}
	return strings.TrimSpace(value)
}

// GetTestAdapter returns an adapter object. Useful for running tests.
func GetTestAdapter() *adapter {
	return &adapter{}
}

func init() {
	store.RegisterAdapter(&adapter{})
}