import 'package:flutter/foundation.dart';
import 'package:flutter_webrtc/flutter_webrtc.dart';

import '../config/ice_servers.dart';
import '../models/signal_message.dart';
import '../signaling/signaling_client.dart';

/// 封装 WebRTC 连接逻辑（对应 Android 端 WebRtcClient）。
///
/// 职责：
/// - 创建 PeerConnection（recvonly 视频 + 控制用 DataChannel）
/// - 创建 Offer 并通过信令发送
/// - 处理 Answer / ICE 候选
/// - 通过 DataChannel 发送控制指令（触摸/滑动/按键）
/// - 采集并解析连接统计信息
///
/// 本类同时兼容 Android 与 iOS（基于 flutter_webrtc）。
class WebRtcController {
  final SignalingClient signaling;
  final String deviceId;
  final String targetDeviceId;

  RTCPeerConnection? _pc;
  RTCDataChannel? _dataChannel;

  /// 远端视频渲染器，由调用方持有并显示。
  final RTCVideoRenderer renderer = RTCVideoRenderer();

  void Function()? onConnectionEstablished;
  void Function(String error)? onConnectionFailed;
  void Function()? onDisconnected;

  /// ICE 连接断开（如网络中断、被控端退出），用于提示用户并返回连接设置。
  void Function(String message)? onIceDisconnected;

  /// 远端视频流就绪（renderer 已绑定视频轨道）。
  void Function(RTCVideoRenderer renderer)? onRemoteStream;

  WebRtcController({
    required this.signaling,
    required this.deviceId,
    required this.targetDeviceId,
  });

  /// 初始化渲染器、PeerConnection，并创建 Offer。
  Future<void> initialize() async {
    await renderer.initialize();

    final configuration = {
      'iceServers': kIceServers,
      'sdpSemantics': 'unified-plan',
      'iceCandidatePoolSize': 10,
      // 增强复杂网络下的稳定性，参考 Android 端配置。
      'continualGatheringPolicy': 'gatherContinually',
      'iceTransportsType': 'all',
      'tcpCandidatePolicy': 'enabled',
    };

    _pc = await createPeerConnection(configuration);

    _pc!.onIceCandidate = _onIceCandidate;
    _pc!.onIceConnectionState = _onIceConnectionState;
    _pc!.onTrack = _onTrack;
    _pc!.onDataChannel = _onDataChannel;

    // 仅接收远端视频（recvonly）。
    await _pc!.addTransceiver(
      kind: RTCRtpMediaType.RTCRtpMediaTypeVideo,
      init: RTCRtpTransceiverInit(direction: TransceiverDirection.RecvOnly),
    );

    // 创建控制用 DataChannel。
    // 使用非可靠、无序模式以降低延迟，解决“不跟手”问题。
    final dcInit = RTCDataChannelInit()
      ..ordered = false
      ..maxRetransmits = 0;
    _dataChannel = await _pc!.createDataChannel(kDataChannelLabel, dcInit);
    _setupDataChannel(_dataChannel!);

    // 创建并发送 Offer。
    final constraints = {
      'mandatory': {
        'OfferToReceiveVideo': true,
        'OfferToReceiveAudio': false,
      },
      'optional': [],
    };
    final offer = await _pc!.createOffer(constraints);
    await _pc!.setLocalDescription(offer);
    _sendOffer(offer.sdp!);
  }

  void _onTrack(RTCTrackEvent event) {
    if (event.track.kind == 'video' && event.streams.isNotEmpty) {
      renderer.srcObject = event.streams[0];
      onRemoteStream?.call(renderer);
    }
  }

  void _onDataChannel(RTCDataChannel channel) {
    // 被控端也可能主动创建 DataChannel，统一处理。
    _setupDataChannel(channel);
  }

  void _setupDataChannel(RTCDataChannel channel) {
    channel.onMessage = (RTCDataChannelMessage message) {
      // 处理来自被控端的消息（本控制端主要发送，此处仅做日志记录）。
      // ignore: avoid_print
      print('DataChannel message: ${message.text}');
    };
    channel.onDataChannelState = (RTCDataChannelState state) {
      // ignore: avoid_print
      print('DataChannel state: $state');
    };
  }

  void _onIceCandidate(RTCIceCandidate candidate) {
    final payload = {
      'sdpMid': candidate.sdpMid,
      'sdpMLineIndex': candidate.sdpMLineIndex,
      'candidate': candidate.candidate,
    };
    final msg = SignalMessage.withPayload(
      type: 'ICE_CANDIDATE',
      fromDeviceId: deviceId,
      toDeviceId: targetDeviceId,
      deviceType: 'CONTROLLER',
      payload: payload,
    );
    signaling.send(msg);
  }

  void _onIceConnectionState(RTCIceConnectionState state) {
    // ignore: avoid_print
    print('ICE connection state: $state');
    if (state == RTCIceConnectionState.RTCIceConnectionStateConnected) {
      onConnectionEstablished?.call();
    } else if (state == RTCIceConnectionState.RTCIceConnectionStateDisconnected) {
      onIceDisconnected?.call('ICE 连接已断开');
    } else if (state == RTCIceConnectionState.RTCIceConnectionStateFailed) {
      onConnectionFailed?.call('ICE 连接失败');
      onDisconnected?.call();
    }
  }

  void _sendOffer(String sdp) {
    final payload = {'sdp': sdp};
    final msg = SignalMessage.withPayload(
      type: 'OFFER',
      fromDeviceId: deviceId,
      toDeviceId: targetDeviceId,
      deviceType: 'CONTROLLER',
      payload: payload,
    );
    signaling.send(msg);
  }

  /// 处理来自信令服务器的 Answer。
  Future<void> handleAnswer(String sdp) async {
    final answer = RTCSessionDescription(sdp, 'answer');
    await _pc?.setRemoteDescription(answer);
  }

  /// 处理来自信令服务器的 ICE 候选。
  Future<void> handleIceCandidate(Map<String, dynamic> payload) async {
    final candidate = RTCIceCandidate(
      payload['candidate'] as String,
      payload['sdpMid'] as String?,
      payload['sdpMLineIndex'] as int?,
    );
    await _pc?.addCandidate(candidate);
  }

  /// 通过 DataChannel 发送控制指令（JSON 字符串）。
  void sendControlCommand(String commandJson) {
    if (_dataChannel?.state == RTCDataChannelState.RTCDataChannelOpen) {
      debugPrint('WebRtcController: Sending command -> $commandJson');
      _dataChannel!.send(RTCDataChannelMessage(commandJson));
    }
  }

  /// 采集连接统计信息，回调格式化后的文本（对应 Android 端 updateStats）。
  Future<String> getStatsText() async {
    if (_pc == null) return '';
    final reports = await _pc!.getStats();

    dynamic width = '-';
    dynamic height = '-';
    dynamic fps = '-';
    dynamic delay = '-';
    dynamic codec = '-';

    for (final report in reports) {
      final values = report.values;
      if (report.type == 'inbound-rtp' && values['kind'] == 'video') {
        width = values['frameWidth'] ?? '-';
        height = values['frameHeight'] ?? '-';
        fps = values['framesPerSecond'] ?? '-';

        final codecId = values['codecId'];
        if (codecId != null) {
          final codecReport = reports.where((r) => r.id == codecId).firstOrNull;
          final mime = codecReport?.values['mimeType'];
          if (mime is String && mime.startsWith('video/')) {
            codec = mime.substring(6);
          }
        }
      } else if (report.type == 'candidate-pair') {
        if (values['nominated'] == true) {
          final rtt = values['currentRoundTripTime'];
          if (rtt is num) {
            delay = (rtt * 1000).toStringAsFixed(0);
          }
        }
      }
    }

    return '分辨率: ${width}x$height  帧率: $fps  延迟: $delay ms\n'
        '解码格式: $codec';
  }

  /// 释放所有资源。
  Future<void> close() async {
    try {
      await _dataChannel?.close();
    } catch (_) {}
    try {
      await _pc?.close();
    } catch (_) {}
    try {
      await renderer.dispose();
    } catch (_) {}
    _dataChannel = null;
    _pc = null;
  }
}