package config

import (
	"fmt"
	"os"
	"strings"

	"github.com/spf13/viper"
)

type Config struct {
	Server   ServerConfig   `mapstructure:"server"`
	Database DatabaseConfig `mapstructure:"database"`
	Redis    RedisConfig    `mapstructure:"redis"`
	JWT      JWTConfig      `mapstructure:"jwt"`
	Log      LogConfig      `mapstructure:"log"`
	Plugin   PluginConfig   `mapstructure:"plugin"`
}

type ServerConfig struct {
	Port int    `mapstructure:"port"`
	Mode string `mapstructure:"mode"`
}

type DatabaseConfig struct {
	Host     string `mapstructure:"host"`
	Port     int    `mapstructure:"port"`
	User     string `mapstructure:"user"`
	Password string `mapstructure:"password"`
	DBName   string `mapstructure:"dbname"`
	SSLMode  string `mapstructure:"sslmode"`
}

type RedisConfig struct {
	Addr     string `mapstructure:"addr"`
	Password string `mapstructure:"password"`
	DB       int    `mapstructure:"db"`
}

type JWTConfig struct {
	Secret             string `mapstructure:"secret"`
	AccessExpiryMinutes int   `mapstructure:"access_expiry_minutes"`
	RefreshExpiryDays  int    `mapstructure:"refresh_expiry_days"`
	Issuer             string `mapstructure:"issuer"`
}

type LogConfig struct {
	Level  string `mapstructure:"level"`
	Format string `mapstructure:"format"`
}

type PluginConfig struct {
	Enabled []string `mapstructure:"enabled"`
}

func Load() (*Config, error) {
	v := viper.New()
	v.SetConfigName("config")
	v.SetConfigType("yaml")
	v.AddConfigPath("./configs/")
	v.AddConfigPath(".")

	v.SetEnvPrefix("MENGSTACK")
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	v.AutomaticEnv()

	setDefaults(v)

	if err := v.ReadInConfig(); err != nil {
		return nil, fmt.Errorf("failed to read config: %w", err)
	}

	// Check env var for mode override before merging env config
	env := v.GetString("server.mode")
	if envOverride := os.Getenv("MENGSTACK_SERVER_MODE"); envOverride != "" {
		env = envOverride
	}
	mergeEnvConfig(v, env)

	var cfg Config
	if err := v.Unmarshal(&cfg); err != nil {
		return nil, fmt.Errorf("failed to unmarshal config: %w", err)
	}

	return &cfg, nil
}

func setDefaults(v *viper.Viper) {
	v.SetDefault("server.port", 8080)
	v.SetDefault("server.mode", "debug")
	v.SetDefault("database.host", "127.0.0.1")
	v.SetDefault("database.port", 5432)
	v.SetDefault("database.user", "postgres")
	v.SetDefault("database.dbname", "mengstack")
	v.SetDefault("database.sslmode", "disable")
	v.SetDefault("redis.addr", "127.0.0.1:6379")
	v.SetDefault("redis.db", 0)
	v.SetDefault("jwt.access_expiry_minutes", 30)
	v.SetDefault("jwt.refresh_expiry_days", 7)
	v.SetDefault("jwt.issuer", "mengstack")
	v.SetDefault("log.level", "info")
	v.SetDefault("log.format", "json")
}

func mergeEnvConfig(v *viper.Viper, env string) {
	envFile := fmt.Sprintf("config.%s", env)
	v.SetConfigName(envFile)
	if err := v.MergeInConfig(); err != nil {
		// environment-specific config is optional
	}
	v.SetConfigName("config")
}