import 'dart:io';

import 'package:flutter/foundation.dart';
import 'package:package_info_plus/package_info_plus.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:uuid/uuid.dart';

import 'events/events.dart';
import 'queue/event_queue.dart';
import 'sender.dart';

class AnalyticsTracker {
  static AnalyticsTracker? _instance;

  late final AnalyticsSender _sender;
  late final EventQueue _queue;
  late final String _deviceId;
  late final String _sessionId;
  late final String _platform;
  late final String _appVersion;
  late final String? _appBuild;
  late final String _env;

  String? _userId;

  AnalyticsTracker._();

  static AnalyticsTracker get instance {
    if (_instance == null) {
      throw StateError('AnalyticsTracker not initialized. Call init() first.');
    }
    return _instance!;
  }

  static Future<void> init({
    required String endpoint,
    required String deviceId,
  }) async {
    if (_instance != null) return;

    final packageInfo = await PackageInfo.fromPlatform();

    final sessionId = await _getOrCreateSessionId();
    final platform = Platform.isAndroid ? 'android' : 'ios';
    final env = kDebugMode ? 'dev' : 'prod';

    final tracker = AnalyticsTracker._();
    tracker._sender = AnalyticsSender(endpoint: endpoint);
    tracker._queue = EventQueue(
      maxSize: 50,
      flushInterval: const Duration(seconds: 30),
      onFlush: tracker._handleFlush,
    );
    tracker._deviceId = deviceId;
    tracker._sessionId = sessionId;
    tracker._platform = platform;
    tracker._appVersion = packageInfo.version;
    tracker._appBuild = packageInfo.buildNumber.isNotEmpty
        ? packageInfo.buildNumber
        : null;
    tracker._env = env;

    tracker._queue.start();
    _instance = tracker;
  }

  static Future<String> _getOrCreateSessionId() async {
    const uuid = Uuid();
    final prefs = await SharedPreferences.getInstance();
    var sessionId = prefs.getString('_analytics_session_id');
    if (sessionId == null) {
      sessionId = 'sess_${uuid.v4()}';
      await prefs.setString('_analytics_session_id', sessionId);
    }
    return sessionId;
  }

  void setUserId(String? userId) {
    _userId = userId;
  }

  String get userId => _userId ?? 'anonymous';

  String get sessionId => _sessionId;

  void track(BaseAnalyticsEvent event) {
    _queue.add(event);
  }

  void trackLogin({
    required String method,
    String? traceId,
    String? requestId,
    AnalyticsContext? context,
  }) {
    track(
      SessionLoginEvent(
        eventId: _generateEventId(),
        timestamp: DateTime.now(),
        userId: userId,
        deviceId: _deviceId,
        sessionId: _sessionId,
        platform: _platform,
        appVersion: _appVersion,
        appBuild: _appBuild,
        env: _env,
        pageName: 'login',
        traceId: traceId,
        requestId: requestId,
        method: method,
        context: context,
      ),
    );
  }

  void trackLogout({
    String? reason,
    int? sessionDurationS,
    String? pageName,
    String? traceId,
    AnalyticsContext? context,
  }) {
    track(
      SessionLogoutEvent(
        eventId: _generateEventId(),
        timestamp: DateTime.now(),
        userId: userId,
        deviceId: _deviceId,
        sessionId: _sessionId,
        platform: _platform,
        appVersion: _appVersion,
        appBuild: _appBuild,
        env: _env,
        pageName: pageName,
        traceId: traceId,
        reason: reason,
        sessionDurationS: sessionDurationS,
        context: context,
      ),
    );
  }

  void trackAgentChatCompleted({
    required String conversationId,
    String? scenario,
    int? messageCount,
    int? responseTimeMs,
    String? traceId,
    String? requestId,
    AnalyticsContext? context,
  }) {
    track(
      AgentChatCompletedEvent(
        eventId: _generateEventId(),
        timestamp: DateTime.now(),
        userId: userId,
        deviceId: _deviceId,
        sessionId: _sessionId,
        platform: _platform,
        appVersion: _appVersion,
        appBuild: _appBuild,
        env: _env,
        pageName: 'chat',
        traceId: traceId,
        requestId: requestId,
        conversationId: conversationId,
        scenario: scenario,
        messageCount: messageCount,
        responseTimeMs: responseTimeMs,
        context: context,
      ),
    );
  }

  void trackPageView({
    required String pageName,
    String? pageFrom,
    int? stayDurationMs,
    int? clickCount,
    String? traceId,
    AnalyticsContext? context,
  }) {
    track(
      PageViewEvent(
        eventId: _generateEventId(),
        timestamp: DateTime.now(),
        userId: userId,
        deviceId: _deviceId,
        sessionId: _sessionId,
        platform: _platform,
        appVersion: _appVersion,
        appBuild: _appBuild,
        env: _env,
        pageName: pageName,
        pageFrom: pageFrom,
        stayDurationMs: stayDurationMs,
        clickCount: clickCount,
        traceId: traceId,
        context: context,
      ),
    );
  }

  void trackClick({
    required String pageName,
    required String elementId,
    String? elementType,
    String? traceId,
    AnalyticsContext? context,
  }) {
    track(
      UiClickEvent(
        eventId: _generateEventId(),
        timestamp: DateTime.now(),
        userId: userId,
        deviceId: _deviceId,
        sessionId: _sessionId,
        platform: _platform,
        appVersion: _appVersion,
        appBuild: _appBuild,
        env: _env,
        pageName: pageName,
        elementId: elementId,
        elementType: elementType,
        traceId: traceId,
        context: context,
      ),
    );
  }

  String _generateEventId() {
    return const Uuid().v4();
  }

  Future<void> _handleFlush(List<BaseAnalyticsEvent> events) async {
    try {
      await _sender.send(events);
    } catch (e) {
      // TODO: 失败时落盘本地，下次启动重试
      debugPrint('Analytics send failed: $e');
    }
  }

  void dispose() {
    _queue.stop();
  }
}