import 'package:flutter_dotenv/flutter_dotenv.dart';
import '../core/exceptions/invalid_environment_exception.dart';
import 'app_config.dart';
import '../data/firebase/models/firebase_config.dart';

/// Loads application configuration based on the specified environment.
/// 
/// This class provides a factory method to load configuration for either
/// 'dev' or 'prod' environments. It throws [InvalidEnvironmentException]
/// if an invalid environment is provided.
class ConfigLoader {
  /// Private constructor to prevent instantiation.
  ConfigLoader._();

  /// Loads configuration for the specified environment.
  /// 
  /// Reads from .env file if available, falls back to hardcoded defaults.
  /// 
  /// [environment] - The environment to load ('dev' or 'prod').
  /// 
  /// Returns an [AppConfig] instance for the specified environment.
  /// 
  /// Throws [InvalidEnvironmentException] if [environment] is not 'dev' or 'prod'.
  static AppConfig load(String environment) {
    final env = environment.toLowerCase();
    
    // Helper to get env var or fallback to default
    // Handles case where dotenv is not initialized (e.g., in tests)
    String getEnv(String key, String defaultValue) {
      try {
        return dotenv.env[key] ?? defaultValue;
      } catch (e) {
        // dotenv not initialized, use default
        return defaultValue;
      }
    }
    
    // Helper to parse boolean from env
    bool getBoolEnv(String key, bool defaultValue) {
      try {
        final value = dotenv.env[key];
        if (value == null) return defaultValue;
        return value.toLowerCase() == 'true';
      } catch (e) {
        // dotenv not initialized, use default
        return defaultValue;
      }
    }
    
    // Helper to parse comma-separated list from env
    List<String> getListEnv(String key, List<String> defaultValue) {
      try {
        final value = dotenv.env[key];
        if (value == null || value.isEmpty) return defaultValue;
        return value.split(',').map((s) => s.trim()).where((s) => s.isNotEmpty).toList();
      } catch (e) {
        // dotenv not initialized, use default
        return defaultValue;
      }
    }
    
    // Helper to create FirebaseConfig from environment variables
    FirebaseConfig createFirebaseConfig() {
      return FirebaseConfig(
        enabled: getBoolEnv('FIREBASE_ENABLED', false),
        firestoreEnabled: getBoolEnv('FIREBASE_FIRESTORE_ENABLED', true),
        storageEnabled: getBoolEnv('FIREBASE_STORAGE_ENABLED', true),
        authEnabled: getBoolEnv('FIREBASE_AUTH_ENABLED', true),
        messagingEnabled: getBoolEnv('FIREBASE_MESSAGING_ENABLED', true),
        analyticsEnabled: getBoolEnv('FIREBASE_ANALYTICS_ENABLED', true),
      );
    }

    switch (env) {
      case 'dev':
        return AppConfig(
          apiBaseUrl: getEnv('API_BASE_URL_DEV', 'https://api-dev.example.com'),
          enableLogging: getBoolEnv('ENABLE_LOGGING_DEV', true),
          immichBaseUrl: getEnv('IMMICH_BASE_URL', 'https://photos.satoshinakamoto.win'),
          immichApiKey: getEnv('IMMICH_API_KEY_DEV', 'your-dev-api-key-here'),
          immichEnabled: getBoolEnv('IMMICH_ENABLE', true),
          blossomServer: getEnv('BLOSSOM_SERVER', 'https://media.based21.com'),
          nostrRelays: getListEnv('NOSTR_RELAYS_DEV', [
            'wss://nostrum.satoshinakamoto.win',
            'wss://nos.lol',
          ]),
          firebaseConfig: createFirebaseConfig(),
        );
      case 'prod':
        return AppConfig(
          apiBaseUrl: getEnv('API_BASE_URL_PROD', 'https://api.example.com'),
          enableLogging: getBoolEnv('ENABLE_LOGGING_PROD', false),
          immichBaseUrl: getEnv('IMMICH_BASE_URL', 'https://photos.satoshinakamoto.win'),
          immichApiKey: getEnv('IMMICH_API_KEY_PROD', 'your-prod-api-key-here'),
          immichEnabled: getBoolEnv('IMMICH_ENABLE', true),
          blossomServer: getEnv('BLOSSOM_SERVER', 'https://media.based21.com'),
          nostrRelays: getListEnv('NOSTR_RELAYS_PROD', [
            'wss://relay.damus.io',
          ]),
          firebaseConfig: createFirebaseConfig(),
        );
      default:
        throw InvalidEnvironmentException(environment);
    }
  }
}