import 'dart:convert';
import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:path/path.dart' as p;
import 'package:path_provider/path_provider.dart';

/// Which backend answers chat requests. Embeddings (knowledge base) always
/// stay on the local Nomic server regardless of this choice.
enum AiProvider { local, ollama, lmstudio, anthropic, openai, gemini, openrouter }

extension AiProviderX on AiProvider {
  String get label => switch (this) {
    AiProvider.local => 'Built-in (Qwen3 4B)',
    AiProvider.ollama => 'Ollama (local)',
    AiProvider.lmstudio => 'LM Studio (local)',
    AiProvider.anthropic => 'Anthropic (Claude)',
    AiProvider.openai => 'OpenAI (GPT)',
    AiProvider.gemini => 'Google (Gemini)',
    AiProvider.openrouter => 'OpenRouter',
  };

  String get defaultModel => switch (this) {
    AiProvider.local => 'local',
    AiProvider.ollama => 'qwen3:4b',
    AiProvider.lmstudio => 'local-model',
    AiProvider.anthropic => 'claude-opus-4-8',
    AiProvider.openai => 'gpt-5.1',
    AiProvider.gemini => 'gemini-2.5-flash',
    // OpenRouter routes to any model — IDs like "anthropic/claude-opus-4.8",
    // "openai/gpt-4o", "meta-llama/llama-3.3-70b-instruct".
    AiProvider.openrouter => 'openai/gpt-4o',
  };

  /// Self-hosted OpenAI-compatible servers reachable over a base URL.
  bool get isSelfHosted =>
      this == AiProvider.ollama || this == AiProvider.lmstudio;

  String get defaultBaseUrl => switch (this) {
    AiProvider.ollama => 'http://localhost:11434',
    AiProvider.lmstudio => 'http://localhost:1234',
    _ => '',
  };

  bool get needsApiKey => switch (this) {
    AiProvider.anthropic ||
    AiProvider.openai ||
    AiProvider.gemini ||
    AiProvider.openrouter => true,
    _ => false,
  };
}

class AiSettings {
  const AiSettings({
    this.provider = AiProvider.local,
    this.apiKeys = const {},
    this.models = const {},
    this.baseUrls = const {},
  });

  final AiProvider provider;

  /// API key per provider name — kept separately so switching providers
  /// doesn't lose previously entered keys.
  final Map<String, String> apiKeys;

  /// Model override per provider name; falls back to [AiProviderX.defaultModel].
  final Map<String, String> models;

  /// Base URL override per provider name (Ollama / LM Studio);
  /// falls back to [AiProviderX.defaultBaseUrl].
  final Map<String, String> baseUrls;

  String? apiKeyFor(AiProvider p) {
    final key = apiKeys[p.name]?.trim();
    return (key == null || key.isEmpty) ? null : key;
  }

  String modelFor(AiProvider p) {
    final model = models[p.name]?.trim();
    return (model == null || model.isEmpty) ? p.defaultModel : model;
  }

  String baseUrlFor(AiProvider p) {
    final url = baseUrls[p.name]?.trim();
    final resolved = (url == null || url.isEmpty) ? p.defaultBaseUrl : url;
    // Tolerate a trailing slash pasted in by the user.
    return resolved.endsWith('/')
        ? resolved.substring(0, resolved.length - 1)
        : resolved;
  }

  /// True when [provider] can serve chat: self-hosted and built-in servers
  /// need no key, cloud providers do.
  bool get isProviderConfigured =>
      !provider.needsApiKey || apiKeyFor(provider) != null;

  AiSettings copyWith({
    AiProvider? provider,
    Map<String, String>? apiKeys,
    Map<String, String>? models,
    Map<String, String>? baseUrls,
  }) {
    return AiSettings(
      provider: provider ?? this.provider,
      apiKeys: apiKeys ?? this.apiKeys,
      models: models ?? this.models,
      baseUrls: baseUrls ?? this.baseUrls,
    );
  }

  Map<String, dynamic> toJson() => {
    'provider': provider.name,
    'apiKeys': apiKeys,
    'models': models,
    'baseUrls': baseUrls,
  };

  factory AiSettings.fromJson(Map<String, dynamic> json) {
    return AiSettings(
      provider: AiProvider.values.firstWhere(
        (p) => p.name == json['provider'],
        orElse: () => AiProvider.local,
      ),
      apiKeys: Map<String, String>.from(json['apiKeys'] as Map? ?? {}),
      models: Map<String, String>.from(json['models'] as Map? ?? {}),
      baseUrls: Map<String, String>.from(json['baseUrls'] as Map? ?? {}),
    );
  }
}

/// Loads and persists [AiSettings] as a JSON file in the app documents dir.
class AiSettingsService extends ChangeNotifier {
  static const _fileName = 'trainhub_ai_settings.json';

  AiSettings _settings = const AiSettings();
  AiSettings get settings => _settings;

  Future<File> _file() async {
    final dir = await getApplicationDocumentsDirectory();
    return File(p.join(dir.path, _fileName));
  }

  Future<void> load() async {
    try {
      final file = await _file();
      if (!file.existsSync()) return;
      final json = jsonDecode(await file.readAsString());
      _settings = AiSettings.fromJson(json as Map<String, dynamic>);
      notifyListeners();
    } catch (e) {
      if (kDebugMode) debugPrint('Failed to load AI settings: $e');
    }
  }

  Future<void> save(AiSettings settings) async {
    _settings = settings;
    notifyListeners();
    try {
      final file = await _file();
      await file.writeAsString(jsonEncode(settings.toJson()));
    } catch (e) {
      if (kDebugMode) debugPrint('Failed to save AI settings: $e');
    }
  }
}