package config

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"strconv"
	"strings"
	"time"
)

type Config struct {
	Listen       string        `json:"listen"`
	MySQL        MySQLConfig   `json:"mysql"`
	Redis        RedisConfig   `json:"redis"`
	Kafka        KafkaConfig   `json:"kafka"`
	Auth         AuthConfig    `json:"auth"`
	ReadTimeout  time.Duration `json:"-"`
	WriteTimeout time.Duration `json:"-"`
}

type MySQLConfig struct {
	DSN string `json:"dsn"`
}

type RedisConfig struct {
	Addr      string `json:"addr"`
	Username  string `json:"username"`
	Password  string `json:"password"`
	DB        int    `json:"db"`
	KeyPrefix string `json:"key_prefix"`
}

type KafkaConfig struct {
	Enabled   bool     `json:"enabled"`
	Brokers   []string `json:"brokers"`
	Topic     string   `json:"topic"`
	Username  string   `json:"username"`
	Password  string   `json:"password"`
	SASL      string   `json:"sasl"`
	ClientID  string   `json:"client_id"`
	BatchSize int      `json:"batch_size"`
}

type AuthConfig struct {
	APIKeys             []string `json:"api_keys"`
	SessionKeyPattern   string   `json:"session_key_pattern"`
	AllowDevHeaderAuth  bool     `json:"allow_dev_header_auth"`
	RequiredTenantCode  bool     `json:"required_tenant_code"`
	RequiredAPIKey      bool     `json:"required_api_key"`
	SkipSessionInDev    bool     `json:"skip_session_in_dev"`
	TrustedInternalAddr string   `json:"trusted_internal_addr"`
}

func Load() (*Config, error) {
	cfg := defaultConfig()
	if path := strings.TrimSpace(os.Getenv("IM_WORKBENCH_CONFIG")); path != "" {
		data, err := os.ReadFile(path)
		if err != nil {
			return nil, err
		}
		if err := json.Unmarshal(data, cfg); err != nil {
			return nil, err
		}
	}
	applyEnv(cfg)
	if err := cfg.validate(); err != nil {
		return nil, err
	}
	return cfg, nil
}

func defaultConfig() *Config {
	return &Config{
		Listen: ":6061",
		MySQL: MySQLConfig{
			DSN: "root:root@tcp(127.0.0.1:3306)/tinode?parseTime=true&charset=utf8mb4,utf8&loc=Local",
		},
		Redis: RedisConfig{
			Addr:      "127.0.0.1:6379",
			KeyPrefix: "im:",
		},
		Kafka: KafkaConfig{
			Topic:    "im.workbench.event",
			ClientID: "im_workbench",
		},
		Auth: AuthConfig{
			SessionKeyPattern:  "im:session:token:%s",
			RequiredTenantCode: true,
			RequiredAPIKey:     true,
		},
		ReadTimeout:  8 * time.Second,
		WriteTimeout: 8 * time.Second,
	}
}

func applyEnv(cfg *Config) {
	setString(&cfg.Listen, "IM_WORKBENCH_LISTEN")
	setString(&cfg.MySQL.DSN, "IM_WORKBENCH_MYSQL_DSN")
	setString(&cfg.Redis.Addr, "IM_WORKBENCH_REDIS_ADDR")
	setString(&cfg.Redis.Username, "IM_WORKBENCH_REDIS_USERNAME")
	setString(&cfg.Redis.Password, "IM_WORKBENCH_REDIS_PASSWORD")
	setString(&cfg.Redis.KeyPrefix, "IM_WORKBENCH_REDIS_KEY_PREFIX")
	setString(&cfg.Kafka.Topic, "IM_WORKBENCH_KAFKA_TOPIC")
	setString(&cfg.Kafka.Username, "IM_WORKBENCH_KAFKA_USERNAME")
	setString(&cfg.Kafka.Password, "IM_WORKBENCH_KAFKA_PASSWORD")
	setString(&cfg.Kafka.SASL, "IM_WORKBENCH_KAFKA_SASL")
	setString(&cfg.Kafka.ClientID, "IM_WORKBENCH_KAFKA_CLIENT_ID")
	setString(&cfg.Auth.SessionKeyPattern, "IM_WORKBENCH_SESSION_KEY_PATTERN")
	setString(&cfg.Auth.TrustedInternalAddr, "IM_WORKBENCH_TRUSTED_INTERNAL_ADDR")
	if brokers := strings.TrimSpace(os.Getenv("IM_WORKBENCH_KAFKA_BROKERS")); brokers != "" {
		cfg.Kafka.Brokers = splitCSV(brokers)
	}
	if keys := strings.TrimSpace(os.Getenv("IM_WORKBENCH_API_KEYS")); keys != "" {
		cfg.Auth.APIKeys = splitCSV(keys)
	}
	if value := strings.TrimSpace(os.Getenv("IM_WORKBENCH_KAFKA_BATCH_SIZE")); value != "" {
		if parsed, err := strconv.Atoi(value); err == nil {
			cfg.Kafka.BatchSize = parsed
		}
	}
	if value := strings.TrimSpace(os.Getenv("IM_WORKBENCH_REDIS_DB")); value != "" {
		if parsed, err := strconv.Atoi(value); err == nil {
			cfg.Redis.DB = parsed
		}
	}
	setBool(&cfg.Auth.AllowDevHeaderAuth, "IM_WORKBENCH_ALLOW_DEV_HEADER_AUTH")
	setBool(&cfg.Auth.RequiredTenantCode, "IM_WORKBENCH_REQUIRED_TENANT_CODE")
	setBool(&cfg.Auth.RequiredAPIKey, "IM_WORKBENCH_REQUIRED_API_KEY")
	setBool(&cfg.Auth.SkipSessionInDev, "IM_WORKBENCH_SKIP_SESSION_IN_DEV")
	setBool(&cfg.Kafka.Enabled, "IM_WORKBENCH_KAFKA_ENABLED")
}

func (c *Config) validate() error {
	if strings.TrimSpace(c.Listen) == "" {
		return errors.New("listen is required")
	}
	if strings.TrimSpace(c.MySQL.DSN) == "" {
		return errors.New("mysql dsn is required")
	}
	if strings.TrimSpace(c.Redis.Addr) == "" && !c.Auth.SkipSessionInDev {
		return errors.New("redis addr is required")
	}
	if strings.TrimSpace(c.Auth.SessionKeyPattern) == "" {
		return errors.New("session key pattern is required")
	}
	if !strings.Contains(c.Auth.SessionKeyPattern, "%s") {
		return fmt.Errorf("session key pattern must include %%s")
	}
	return nil
}

func setString(target *string, key string) {
	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
		*target = value
	}
}

func setBool(target *bool, key string) {
	switch strings.ToLower(strings.TrimSpace(os.Getenv(key))) {
	case "1", "true", "yes", "on":
		*target = true
	case "0", "false", "no", "off":
		*target = false
	}
}

func splitCSV(value string) []string {
	parts := strings.Split(value, ",")
	items := make([]string, 0, len(parts))
	for _, part := range parts {
		if item := strings.TrimSpace(part); item != "" {
			items = append(items, item)
		}
	}
	return items
}