package config

import (
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/spf13/viper"
)

// Config holds all configuration for the application
type Config struct {
	Server   ServerConfig
	Database DatabaseConfig
	Redis    RedisConfig
	Email    EmailConfig
	Push     PushConfig
	Worker   WorkerConfig
	Security SecurityConfig
}

type ServerConfig struct {
	Port         int
	Debug        bool
	AllowedHosts []string
	Timezone     string
}

type DatabaseConfig struct {
	Host         string
	Port         int
	User         string
	Password     string
	Database     string
	SSLMode      string
	MaxOpenConns int
	MaxIdleConns int
	MaxLifetime  time.Duration
}

type RedisConfig struct {
	URL      string
	Password string
	DB       int
}

type EmailConfig struct {
	Host     string
	Port     int
	User     string
	Password string
	From     string
	UseTLS   bool
}

type PushConfig struct {
	// Gorush server URL
	GorushURL string

	// APNs (iOS)
	APNSKeyPath   string
	APNSKeyID     string
	APNSTeamID    string
	APNSTopic     string
	APNSSandbox   bool

	// FCM (Android)
	FCMServerKey string
}

type WorkerConfig struct {
	// Scheduled job times (UTC)
	TaskReminderHour    int
	TaskReminderMinute  int
	OverdueReminderHour int
	DailyNotifHour      int
}

type SecurityConfig struct {
	SecretKey            string
	TokenCacheTTL        time.Duration
	PasswordResetExpiry  time.Duration
	ConfirmationExpiry   time.Duration
	MaxPasswordResetRate int // per hour
}

var cfg *Config

// Load reads configuration from environment variables
func Load() (*Config, error) {
	viper.SetEnvPrefix("")
	viper.AutomaticEnv()
	viper.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))

	// Set defaults
	setDefaults()

	cfg = &Config{
		Server: ServerConfig{
			Port:         viper.GetInt("PORT"),
			Debug:        viper.GetBool("DEBUG"),
			AllowedHosts: strings.Split(viper.GetString("ALLOWED_HOSTS"), ","),
			Timezone:     viper.GetString("TIMEZONE"),
		},
		Database: DatabaseConfig{
			Host:         viper.GetString("DB_HOST"),
			Port:         viper.GetInt("DB_PORT"),
			User:         viper.GetString("POSTGRES_USER"),
			Password:     viper.GetString("POSTGRES_PASSWORD"),
			Database:     viper.GetString("POSTGRES_DB"),
			SSLMode:      viper.GetString("DB_SSLMODE"),
			MaxOpenConns: viper.GetInt("DB_MAX_OPEN_CONNS"),
			MaxIdleConns: viper.GetInt("DB_MAX_IDLE_CONNS"),
			MaxLifetime:  viper.GetDuration("DB_MAX_LIFETIME"),
		},
		Redis: RedisConfig{
			URL:      viper.GetString("REDIS_URL"),
			Password: viper.GetString("REDIS_PASSWORD"),
			DB:       viper.GetInt("REDIS_DB"),
		},
		Email: EmailConfig{
			Host:     viper.GetString("EMAIL_HOST"),
			Port:     viper.GetInt("EMAIL_PORT"),
			User:     viper.GetString("EMAIL_HOST_USER"),
			Password: viper.GetString("EMAIL_HOST_PASSWORD"),
			From:     viper.GetString("DEFAULT_FROM_EMAIL"),
			UseTLS:   viper.GetBool("EMAIL_USE_TLS"),
		},
		Push: PushConfig{
			GorushURL:    viper.GetString("GORUSH_URL"),
			APNSKeyPath:  viper.GetString("APNS_AUTH_KEY_PATH"),
			APNSKeyID:    viper.GetString("APNS_AUTH_KEY_ID"),
			APNSTeamID:   viper.GetString("APNS_TEAM_ID"),
			APNSTopic:    viper.GetString("APNS_TOPIC"),
			APNSSandbox:  viper.GetBool("APNS_USE_SANDBOX"),
			FCMServerKey: viper.GetString("FCM_SERVER_KEY"),
		},
		Worker: WorkerConfig{
			TaskReminderHour:    viper.GetInt("CELERY_BEAT_REMINDER_HOUR"),
			TaskReminderMinute:  viper.GetInt("CELERY_BEAT_REMINDER_MINUTE"),
			OverdueReminderHour: 9,  // 9:00 AM UTC
			DailyNotifHour:      11, // 11:00 AM UTC
		},
		Security: SecurityConfig{
			SecretKey:            viper.GetString("SECRET_KEY"),
			TokenCacheTTL:        5 * time.Minute,
			PasswordResetExpiry:  15 * time.Minute,
			ConfirmationExpiry:   24 * time.Hour,
			MaxPasswordResetRate: 3,
		},
	}

	// Validate required fields
	if err := validate(cfg); err != nil {
		return nil, err
	}

	return cfg, nil
}

// Get returns the current configuration
func Get() *Config {
	return cfg
}

func setDefaults() {
	// Server defaults
	viper.SetDefault("PORT", 8000)
	viper.SetDefault("DEBUG", false)
	viper.SetDefault("ALLOWED_HOSTS", "localhost,127.0.0.1")
	viper.SetDefault("TIMEZONE", "UTC")

	// Database defaults
	viper.SetDefault("DB_HOST", "localhost")
	viper.SetDefault("DB_PORT", 5432)
	viper.SetDefault("POSTGRES_USER", "postgres")
	viper.SetDefault("POSTGRES_DB", "mycrib")
	viper.SetDefault("DB_SSLMODE", "disable")
	viper.SetDefault("DB_MAX_OPEN_CONNS", 25)
	viper.SetDefault("DB_MAX_IDLE_CONNS", 10)
	viper.SetDefault("DB_MAX_LIFETIME", 600*time.Second)

	// Redis defaults
	viper.SetDefault("REDIS_URL", "redis://localhost:6379/0")
	viper.SetDefault("REDIS_DB", 0)

	// Email defaults
	viper.SetDefault("EMAIL_HOST", "smtp.gmail.com")
	viper.SetDefault("EMAIL_PORT", 587)
	viper.SetDefault("EMAIL_USE_TLS", true)
	viper.SetDefault("DEFAULT_FROM_EMAIL", "MyCrib <noreply@mycrib.com>")

	// Push notification defaults
	viper.SetDefault("GORUSH_URL", "http://localhost:8088")
	viper.SetDefault("APNS_TOPIC", "com.example.mycrib")
	viper.SetDefault("APNS_USE_SANDBOX", true)

	// Worker defaults
	viper.SetDefault("CELERY_BEAT_REMINDER_HOUR", 20)
	viper.SetDefault("CELERY_BEAT_REMINDER_MINUTE", 0)
}

func validate(cfg *Config) error {
	if cfg.Security.SecretKey == "" {
		// In development, use a default key
		if cfg.Server.Debug {
			cfg.Security.SecretKey = "development-secret-key-change-in-production"
		} else {
			return fmt.Errorf("SECRET_KEY is required in production")
		}
	}

	if cfg.Database.Password == "" && !cfg.Server.Debug {
		return fmt.Errorf("POSTGRES_PASSWORD is required")
	}

	return nil
}

// DSN returns the database connection string
func (d *DatabaseConfig) DSN() string {
	return fmt.Sprintf(
		"host=%s port=%d user=%s password=%s dbname=%s sslmode=%s",
		d.Host, d.Port, d.User, d.Password, d.Database, d.SSLMode,
	)
}

// ReadAPNSKey reads the APNs key from file if path is provided
func (p *PushConfig) ReadAPNSKey() (string, error) {
	if p.APNSKeyPath == "" {
		return "", nil
	}

	content, err := os.ReadFile(p.APNSKeyPath)
	if err != nil {
		return "", fmt.Errorf("failed to read APNs key: %w", err)
	}

	return string(content), nil
}