//go:build mysql
// +build mysql

package mysql

import (
	"context"

	"github.com/jmoiron/sqlx"
)

const userPrivacyMigrationLock = "CONCAT('im_user_privacy:', LEFT(SHA2(DATABASE(), 256), 40))"

// ensureUserPrivacySchema adds columns of im_user_privacy_settings that were
// introduced after the table's initial release. Databases created fresh by
// createIMUserProductTables already have them; legacy databases are upgraded
// in place. A missing table is skipped: it is created by the fresh-install
// path and there is nothing to upgrade yet.
func ensureUserPrivacySchema(db *sqlx.DB) error {
	ctx := context.Background()
	conn, err := db.Connx(ctx)
	if err != nil {
		return err
	}
	defer conn.Close()

	// Fast path: check for missing columns without taking the migration lock.
	// Databases created by createIMUserProductTables already have every column,
	// so this is the common case and avoids GET_LOCK entirely (prohibited on
	// Percona XtraDB Cluster with pxc_strict_mode=ENFORCING).
	added, err := ensureUserPrivacyColumns(ctx, conn)
	if err != nil || added {
		return err
	}

	_, unlock, err := acquireMigrationLock(ctx, conn, userPrivacyMigrationLock)
	if err != nil {
		return err
	}
	if unlock != nil {
		defer unlock()
	}

	// Double-check under the lock: another instance may have migrated while we
	// were waiting. Without a lock (PXC fallback) this simply runs idempotently.
	_, err = ensureUserPrivacyColumns(ctx, conn)
	return err
}

// ensureUserPrivacyColumns adds any columns of im_user_privacy_settings that
// are missing and reports whether nothing was missing. A missing table is
// skipped: it is created by the fresh-install path and there is nothing to
// upgrade yet. Column definitions mirror createIMUserProductTables; the SELECT
// in userPrivacyByUID references every one of them.
func ensureUserPrivacyColumns(ctx context.Context, conn *sqlx.Conn) (bool, error) {
	tableExists, err := identityTableExists(ctx, conn, "im_user_privacy_settings")
	if err != nil || !tableExists {
		return true, err
	}

	columns := []struct{ name, ddl string }{
		{"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"},
	}
	missing := false
	for _, col := range columns {
		exists, err := identityColumnExists(ctx, conn, "im_user_privacy_settings", col.name)
		if err != nil {
			return false, err
		}
		if exists {
			continue
		}
		missing = true
		if _, err = conn.ExecContext(ctx, "ALTER TABLE im_user_privacy_settings ADD COLUMN "+col.name+" "+col.ddl); err != nil {
			return false, err
		}
	}
	return !missing, nil
}