package config

import (
	"fmt"
	"time"

	"github.com/spf13/viper"
)

// Config holds all configuration for the application
type Config struct {
	Server   ServerConfig   `mapstructure:"server"`
	Database DatabaseConfig `mapstructure:"database"`
	JWT      JWTConfig      `mapstructure:"jwt"`
	WeChat   WeChatConfig   `mapstructure:"wechat"`
}

// ServerConfig holds all server related configuration
type ServerConfig struct {
	Host            string        `mapstructure:"host"`
	Port            int           `mapstructure:"port"`
	ReadTimeout     time.Duration `mapstructure:"read_timeout"`
	WriteTimeout    time.Duration `mapstructure:"write_timeout"`
	ShutdownTimeout time.Duration `mapstructure:"shutdown_timeout"`
	Timeout         time.Duration `mapstructure:"timeout"` // Request processing timeout
}

// DatabaseConfig holds all database related configuration
type DatabaseConfig struct {
	Driver        string        `mapstructure:"driver"`
	DSN           string        `mapstructure:"dsn"`
	MaxOpenConns  int           `mapstructure:"max_open_conns"`
	MaxIdleConns  int           `mapstructure:"max_idle_conns"`
	MaxLifetime   time.Duration `mapstructure:"max_lifetime"`
	SkipMigration bool          `mapstructure:"skip_migration"`
}

// JWTConfig holds all JWT related configuration
type JWTConfig struct {
	Secret        string        `mapstructure:"secret"`
	ExpireDelta   time.Duration `mapstructure:"expire_delta"`
	RefreshDelta  time.Duration `mapstructure:"refresh_delta"`
	SigningMethod string        `mapstructure:"signing_method"`
	Issuer        string        `mapstructure:"issuer"`
	Audience      string        `mapstructure:"audience"`
}

// WeChatConfig holds all WeChat related configuration
type WeChatConfig struct {
	AppID     string `mapstructure:"app_id"`
	AppSecret string `mapstructure:"app_secret"`
}

// LoadConfig loads the configuration from file and environment variables
func LoadConfig() (*Config, error) {
	// Set default values
	setDefaults()

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

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

	// Validate config
	if err := validateConfig(&config); err != nil {
		return nil, fmt.Errorf("invalid configuration: %w", err)
	}

	return &config, nil
}

// setDefaults sets default values for configuration
func setDefaults() {
	// Server defaults
	viper.SetDefault("server.port", 8080)
	viper.SetDefault("server.read_timeout", "15s")
	viper.SetDefault("server.write_timeout", "15s")
	viper.SetDefault("server.shutdown_timeout", "5s")
	viper.SetDefault("server.timeout", "30s") // Default request processing timeout

	// Database defaults
	viper.SetDefault("database.driver", "sqlite3")
	viper.SetDefault("database.max_open_conns", 25)
	viper.SetDefault("database.max_idle_conns", 25)
	viper.SetDefault("database.max_lifetime", "5m")
	viper.SetDefault("database.skip_migration", false)

	// JWT defaults
	viper.SetDefault("jwt.expire_delta", "24h")
	viper.SetDefault("jwt.refresh_delta", "168h") // 7 days
	viper.SetDefault("jwt.signing_method", "HS256")
	viper.SetDefault("jwt.issuer", "otpm")
	viper.SetDefault("jwt.audience", "otpm-client")
}

// validateConfig validates the configuration
func validateConfig(config *Config) error {
	if config.Server.Port < 1 || config.Server.Port > 65535 {
		return fmt.Errorf("invalid port number: %d", config.Server.Port)
	}

	if config.Database.Driver == "" {
		return fmt.Errorf("database driver is required")
	}

	if config.Database.DSN == "" {
		return fmt.Errorf("database DSN is required")
	}

	if config.JWT.Secret == "" {
		return fmt.Errorf("JWT secret is required")
	}

	if config.WeChat.AppID == "" {
		return fmt.Errorf("WeChat AppID is required")
	}

	if config.WeChat.AppSecret == "" {
		return fmt.Errorf("WeChat AppSecret is required")
	}

	return nil
}