package config

import (
	"fmt"
	"os"
	"strconv"
)

// Config holds all application configuration
type Config struct {
	Server   ServerConfig
	Database DatabaseConfig
	OAuth    OAuthConfig
	Session  SessionConfig
}

// ServerConfig holds server-related configuration
type ServerConfig struct {
	Port string
	Host string
}

// DatabaseConfig holds DynamoDB configuration
type DatabaseConfig struct {
	Region          string
	Endpoint        string // For DynamoDB local
	TablePrefix     string
	UseLocalDB      bool
}

// OAuthConfig holds OAuth provider configurations
type OAuthConfig struct {
	Google GoogleOAuthConfig
}

// GoogleOAuthConfig holds Google OAuth configuration
type GoogleOAuthConfig struct {
	ClientID     string
	ClientSecret string
	RedirectURL  string
}

// SessionConfig holds session management configuration
type SessionConfig struct {
	SecretKey string
	MaxAge    int // in seconds
}

// Load loads configuration from environment variables
func Load() (*Config, error) {
	cfg := &Config{
		Server: ServerConfig{
			Port: getEnv("PORT", "8080"),
			Host: getEnv("HOST", "localhost"),
		},
		Database: DatabaseConfig{
			Region:      getEnv("AWS_REGION", "us-east-1"),
			Endpoint:    getEnv("DYNAMODB_ENDPOINT", "http://localhost:8000"),
			TablePrefix: getEnv("TABLE_PREFIX", "startpage_"),
			UseLocalDB:  getEnvBool("USE_LOCAL_DB", true),
		},
		OAuth: OAuthConfig{
			Google: GoogleOAuthConfig{
				ClientID:     getEnv("GOOGLE_CLIENT_ID", ""),
				ClientSecret: getEnv("GOOGLE_CLIENT_SECRET", ""),
				RedirectURL:  getEnv("GOOGLE_REDIRECT_URL", "http://localhost:8080/auth/callback/google"),
			},
		},
		Session: SessionConfig{
			SecretKey: getEnv("SESSION_SECRET", "change-me-in-production"),
			MaxAge:    getEnvInt("SESSION_MAX_AGE", 86400*7), // 7 days default
		},
	}

	// Validate required fields
	if cfg.OAuth.Google.ClientID == "" {
		return nil, fmt.Errorf("GOOGLE_CLIENT_ID is required")
	}
	if cfg.OAuth.Google.ClientSecret == "" {
		return nil, fmt.Errorf("GOOGLE_CLIENT_SECRET is required")
	}

	return cfg, nil
}

// getEnv gets an environment variable or returns a default value
func getEnv(key, defaultValue string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return defaultValue
}

// getEnvBool gets a boolean environment variable or returns a default value
func getEnvBool(key string, defaultValue bool) bool {
	if value := os.Getenv(key); value != "" {
		boolVal, err := strconv.ParseBool(value)
		if err == nil {
			return boolVal
		}
	}
	return defaultValue
}

// getEnvInt gets an integer environment variable or returns a default value
func getEnvInt(key string, defaultValue int) int {
	if value := os.Getenv(key); value != "" {
		intVal, err := strconv.Atoi(value)
		if err == nil {
			return intVal
		}
	}
	return defaultValue
}