import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';

const String _llmApiKeyStorageKey = 'llm_api_key';
const String _llmBaseUrlStorageKey = 'llm_base_url';
const String _llmModelStorageKey = 'llm_model';
const String _llmProviderStorageKey = 'llm_provider';

String _providerApiKeyStorageKey(LlmProvider provider) {
  return 'llm_api_key_${provider.name}';
}

enum LlmProvider { openai, anthropic, google, ollama, openaiCompatible }

extension LlmProviderMetadata on LlmProvider {
  String get label {
    return switch (this) {
      LlmProvider.openai => 'OpenAI',
      LlmProvider.anthropic => 'Anthropic',
      LlmProvider.google => 'Google AI',
      LlmProvider.ollama => 'Ollama',
      LlmProvider.openaiCompatible => 'OpenAI-compatible',
    };
  }

  String get defaultBaseUrl {
    return switch (this) {
      LlmProvider.openai => 'https://api.openai.com/v1',
      LlmProvider.anthropic => 'https://api.anthropic.com/v1',
      LlmProvider.google => 'https://generativelanguage.googleapis.com/v1beta',
      LlmProvider.ollama => 'http://localhost:11434',
      LlmProvider.openaiCompatible => '',
    };
  }

  String get defaultModel {
    return switch (this) {
      LlmProvider.openai => 'gpt-4o-mini',
      LlmProvider.anthropic => 'claude-3-haiku-20240307',
      LlmProvider.google => 'gemini-2.0-flash',
      LlmProvider.ollama => '',
      LlmProvider.openaiCompatible => '',
    };
  }

  bool get requiresApiKey {
    return switch (this) {
      LlmProvider.openai || LlmProvider.anthropic || LlmProvider.google => true,
      LlmProvider.ollama || LlmProvider.openaiCompatible => false,
    };
  }

  bool get hasConfigurableBaseUrl {
    return this == LlmProvider.ollama || this == LlmProvider.openaiCompatible;
  }
}

class LlmConfigState {
  LlmConfigState({
    bool apiKeyConfigured = false,
    LlmProvider provider = LlmProvider.openai,
    String? baseUrl,
    String? model,
  }) : this._(
         apiKeyConfigured: apiKeyConfigured,
         provider: provider,
         baseUrl: _resolveBaseUrl(provider, baseUrl),
         model: _resolveModel(provider, model),
       );

  const LlmConfigState._({
    required this.apiKeyConfigured,
    required this.provider,
    required this.baseUrl,
    required this.model,
  });

  final bool apiKeyConfigured;
  final LlmProvider provider;
  final String baseUrl;
  final String model;

  bool get isConfigured {
    final bool hasKey = apiKeyConfigured || !provider.requiresApiKey;
    return hasKey && baseUrl.trim().isNotEmpty && model.trim().isNotEmpty;
  }

  LlmConfigState copyWith({
    bool? apiKeyConfigured,
    LlmProvider? provider,
    String? baseUrl,
    String? model,
  }) {
    final LlmProvider nextProvider = provider ?? this.provider;
    return LlmConfigState(
      apiKeyConfigured: apiKeyConfigured ?? this.apiKeyConfigured,
      provider: nextProvider,
      baseUrl: baseUrl ?? this.baseUrl,
      model: model ?? this.model,
    );
  }

  static String _resolveBaseUrl(LlmProvider provider, String? baseUrl) {
    final String? trimmed = baseUrl?.trim();
    if (trimmed != null && trimmed.isNotEmpty) {
      return trimmed;
    }
    return provider.defaultBaseUrl;
  }

  static String _resolveModel(LlmProvider provider, String? model) {
    final String? trimmed = model?.trim();
    if (trimmed != null && trimmed.isNotEmpty) {
      return trimmed;
    }
    return provider.defaultModel;
  }
}

class LlmConfigNotifier extends Notifier<LlmConfigState> {
  Future<void>? _initializeFuture;

  @override
  LlmConfigState build() {
    return LlmConfigState();
  }

  Future<void> initialize() async {
    final Future<void>? inFlight = _initializeFuture;
    if (inFlight != null) {
      return inFlight;
    }
    _initializeFuture = _initializeFromStorage();
    return _initializeFuture;
  }

  Future<void> _initializeFromStorage() async {
    const FlutterSecureStorage secureStorage = FlutterSecureStorage();
    final String? storedProvider = await secureStorage.read(
      key: _llmProviderStorageKey,
    );
    final String? storedBaseUrl = await secureStorage.read(
      key: _llmBaseUrlStorageKey,
    );
    final String? storedModel = await secureStorage.read(
      key: _llmModelStorageKey,
    );

    final LlmProvider provider = storedProvider != null
        ? LlmProvider.values.firstWhere(
            (LlmProvider p) => p.name == storedProvider,
            orElse: () => LlmProvider.openai,
          )
        : LlmProvider.openai;
    String? storedKey = await _readApiKey(secureStorage, provider: provider);
    if (storedKey == null || storedKey.isEmpty) {
      final String? legacyKey = await secureStorage.read(
        key: _llmApiKeyStorageKey,
      );
      if (legacyKey != null && legacyKey.isNotEmpty) {
        await secureStorage.write(
          key: _providerApiKeyStorageKey(provider),
          value: legacyKey,
        );
        storedKey = legacyKey;
      }
    }

    state = LlmConfigState(
      apiKeyConfigured: storedKey != null && storedKey.isNotEmpty,
      provider: provider,
      baseUrl: storedBaseUrl,
      model: storedModel,
    );
  }

  Future<void> setApiKey(String apiKey) async {
    const FlutterSecureStorage secureStorage = FlutterSecureStorage();
    final String key = _providerApiKeyStorageKey(state.provider);
    if (apiKey.isEmpty) {
      await secureStorage.delete(key: key);
    } else {
      await secureStorage.write(key: key, value: apiKey);
    }
    state = state.copyWith(apiKeyConfigured: apiKey.isNotEmpty);
  }

  Future<void> setProvider(LlmProvider provider) async {
    const FlutterSecureStorage secureStorage = FlutterSecureStorage();
    await secureStorage.write(
      key: _llmProviderStorageKey,
      value: provider.name,
    );
    await secureStorage.write(
      key: _llmBaseUrlStorageKey,
      value: provider.defaultBaseUrl,
    );
    await secureStorage.write(
      key: _llmModelStorageKey,
      value: provider.defaultModel,
    );
    final String? storedKey = await _readApiKey(
      secureStorage,
      provider: provider,
    );
    state = state.copyWith(
      apiKeyConfigured: storedKey != null && storedKey.isNotEmpty,
      provider: provider,
      baseUrl: provider.defaultBaseUrl,
      model: provider.defaultModel,
    );
  }

  Future<void> saveConfiguration({
    required LlmProvider provider,
    required String baseUrl,
    required String model,
    String? apiKey,
    bool clearApiKey = false,
  }) async {
    const FlutterSecureStorage secureStorage = FlutterSecureStorage();
    await secureStorage.write(
      key: _llmProviderStorageKey,
      value: provider.name,
    );
    await secureStorage.write(
      key: _llmBaseUrlStorageKey,
      value: baseUrl.trim(),
    );
    await secureStorage.write(key: _llmModelStorageKey, value: model.trim());

    final String? storedProviderKey = await _readApiKey(
      secureStorage,
      provider: provider,
    );
    bool apiKeyConfigured =
        storedProviderKey != null && storedProviderKey.isNotEmpty;
    if (clearApiKey) {
      await secureStorage.delete(key: _providerApiKeyStorageKey(provider));
      apiKeyConfigured = false;
    } else if (apiKey != null) {
      final String trimmedApiKey = apiKey.trim();
      if (trimmedApiKey.isEmpty) {
        await secureStorage.delete(key: _providerApiKeyStorageKey(provider));
        apiKeyConfigured = false;
      } else {
        await secureStorage.write(
          key: _providerApiKeyStorageKey(provider),
          value: trimmedApiKey,
        );
        apiKeyConfigured = true;
      }
    }

    state = LlmConfigState(
      apiKeyConfigured: apiKeyConfigured,
      provider: provider,
      baseUrl: baseUrl,
      model: model,
    );
  }

  Future<String?> getApiKey({LlmProvider? provider}) async {
    const FlutterSecureStorage secureStorage = FlutterSecureStorage();
    return _readApiKey(secureStorage, provider: provider ?? state.provider);
  }

  Future<void> clearApiKey() async {
    const FlutterSecureStorage secureStorage = FlutterSecureStorage();
    await secureStorage.delete(key: _providerApiKeyStorageKey(state.provider));
    state = state.copyWith(apiKeyConfigured: false);
  }

  Future<String?> _readApiKey(
    FlutterSecureStorage secureStorage, {
    required LlmProvider provider,
  }) async {
    final String? providerKey = await secureStorage.read(
      key: _providerApiKeyStorageKey(provider),
    );
    if (providerKey != null && providerKey.isNotEmpty) {
      return providerKey;
    }

    return null;
  }
}

final llmConfigProvider = NotifierProvider<LlmConfigNotifier, LlmConfigState>(
  LlmConfigNotifier.new,
);