package config

import (
	"errors"
	"fmt"
	"net"
	"os"
	"time"

	"github.com/spf13/viper"
)

// Config holds the application configuration
type Config struct {
	DatabaseURL        string        `mapstructure:"database_url"`      // Primary database URL (used for writes, and reads if DatabaseReadURL not set)
	DatabaseReadURL    string        `mapstructure:"database_read_url"` // Optional: read-only database URL (falls back to DatabaseURL if not set)
	JWTSecret          string        `mapstructure:"jwt_secret"`
	JWTExpiration      time.Duration `mapstructure:"jwt_expiration"`
	ServerPort         int           `mapstructure:"server_port"`
	ServerHost         string        `mapstructure:"server_host"`          // IP address or hostname to bind to (mutually exclusive with server_interface)
	ServerInterface    string        `mapstructure:"server_interface"`     // Network interface name to bind to (mutually exclusive with server_host)
	ArchiveStoragePath string        `mapstructure:"archive_storage_path"` // Path to store archived files
	EnableAccessLog    bool          `mapstructure:"enable_access_log"`    // Enable HTTP access logging middleware
}

// Load loads configuration from file or environment variables
func Load(configPath string) (*Config, error) {
	v := viper.New()

	// Set defaults
	v.SetDefault("database_url", "sqlite://devdata/hako.db")
	v.SetDefault("server_port", 8080)
	v.SetDefault("jwt_expiration", "24h")
	v.SetDefault("archive_storage_path", "devdata/archives")
	v.SetDefault("enable_access_log", true)

	// Environment variables
	v.SetEnvPrefix("")
	v.AutomaticEnv()

	// Bind environment variables
	_ = v.BindEnv("database_url", "DATABASE_URL")
	_ = v.BindEnv("database_read_url", "DATABASE_READ_URL")
	_ = v.BindEnv("jwt_secret", "JWT_SECRET")
	_ = v.BindEnv("jwt_expiration", "JWT_EXPIRATION")
	_ = v.BindEnv("server_port", "SERVER_PORT")
	_ = v.BindEnv("server_host", "SERVER_HOST")
	_ = v.BindEnv("server_interface", "SERVER_INTERFACE")
	_ = v.BindEnv("archive_storage_path", "ARCHIVE_STORAGE_PATH")
	_ = v.BindEnv("enable_access_log", "ENABLE_ACCESS_LOG")

	// If config file is provided, read from it
	if configPath != "" {
		v.SetConfigFile(configPath)
		v.SetConfigType("yaml") // Default to yaml, but viper can auto-detect

		if err := v.ReadInConfig(); err != nil {
			// Allow missing config file (configuration can come from env vars)
			// but return error for other issues like permission denied
			if !errors.Is(err, os.ErrNotExist) {
				return nil, fmt.Errorf("failed to read config file: %w", err)
			}
			// Config file not found, continue with env vars and defaults
		}
	}

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

	// Validate required fields
	if cfg.DatabaseURL == "" {
		return nil, fmt.Errorf("database_url is required")
	}
	// If DatabaseReadURL is not specified, use DatabaseURL for reads
	if cfg.DatabaseReadURL == "" {
		cfg.DatabaseReadURL = cfg.DatabaseURL
	}
	if cfg.JWTSecret == "" {
		return nil, fmt.Errorf("jwt_secret is required")
	}

	// Validate that server_host and server_interface are not both set
	if cfg.ServerHost != "" && cfg.ServerInterface != "" {
		return nil, fmt.Errorf("server_host and server_interface cannot be defined at the same time")
	}

	// Parse JWT expiration if it's a string
	if cfg.JWTExpiration == 0 {
		expStr := v.GetString("jwt_expiration")
		if expStr != "" {
			duration, err := time.ParseDuration(expStr)
			if err != nil {
				return nil, fmt.Errorf("invalid jwt_expiration format: %w", err)
			}
			cfg.JWTExpiration = duration
		} else {
			cfg.JWTExpiration = 24 * time.Hour // Default to 24 hours
		}
	}

	return &cfg, nil
}

// GetBindAddress returns the address to bind the server to (host:port or interface IP:port)
func (c *Config) GetBindAddress() (string, error) {
	port := c.ServerPort
	if port == 0 {
		port = 8080 // Default port
	}

	var host string
	if c.ServerInterface != "" {
		// Get IP address from interface name
		iface, err := net.InterfaceByName(c.ServerInterface)
		if err != nil {
			return "", fmt.Errorf("failed to find interface %s: %w", c.ServerInterface, err)
		}

		addrs, err := iface.Addrs()
		if err != nil {
			return "", fmt.Errorf("failed to get addresses for interface %s: %w", c.ServerInterface, err)
		}

		// Find the first IPv4 address
		for _, addr := range addrs {
			var ip net.IP
			switch v := addr.(type) {
			case *net.IPNet:
				ip = v.IP
			case *net.IPAddr:
				ip = v.IP
			}

			if ip != nil && ip.To4() != nil {
				host = ip.String()
				break
			}
		}

		if host == "" {
			return "", fmt.Errorf("no IPv4 address found on interface %s", c.ServerInterface)
		}
	} else if c.ServerHost != "" {
		host = c.ServerHost
	} else {
		// Default: bind to all interfaces
		host = ""
	}

	return fmt.Sprintf("%s:%d", host, port), nil
}

// GetServerURL returns the URL to access the server
func (c *Config) GetServerURL() (string, error) {
	port := c.ServerPort
	if port == 0 {
		port = 8080 // Default port
	}

	var host string
	if c.ServerInterface != "" {
		// Get IP address from interface name
		iface, err := net.InterfaceByName(c.ServerInterface)
		if err != nil {
			return "", fmt.Errorf("failed to find interface %s: %w", c.ServerInterface, err)
		}

		addrs, err := iface.Addrs()
		if err != nil {
			return "", fmt.Errorf("failed to get addresses for interface %s: %w", c.ServerInterface, err)
		}

		// Find the first IPv4 address
		for _, addr := range addrs {
			var ip net.IP
			switch v := addr.(type) {
			case *net.IPNet:
				ip = v.IP
			case *net.IPAddr:
				ip = v.IP
			}

			if ip != nil && ip.To4() != nil {
				host = ip.String()
				break
			}
		}

		if host == "" {
			return "", fmt.Errorf("no IPv4 address found on interface %s", c.ServerInterface)
		}
	} else if c.ServerHost != "" {
		host = c.ServerHost
	} else {
		// Default: localhost
		host = "localhost"
	}

	return fmt.Sprintf("http://%s:%d", host, port), nil
}