import 'dart:async';
import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_webrtc/flutter_webrtc.dart';

import '../services/signalling.dart';

class ViewerScreen extends StatefulWidget {
  final String serverUrl;
  const ViewerScreen({super.key, required this.serverUrl});

  @override
  State<ViewerScreen> createState() => _ViewerScreenState();
}

class _ViewerScreenState extends State<ViewerScreen> {
  final _sig = SignallingService();
  RTCPeerConnection? _pc;
  RTCDataChannel? _dataChannel;
  final _remoteRenderer = RTCVideoRenderer();

  final _roomCodeCtrl = TextEditingController();
  String _status = 'Enter a room code to connect';
  bool _streaming = false;
  bool _joining = false;

  StreamSubscription? _sigSub;

  // size of the rendered video widget, used to normalise pointer coords
  Size _videoSize = Size.zero;
  final _videoKey = GlobalKey();

  @override
  void initState() {
    super.initState();
    _remoteRenderer.initialize();
  }

  @override
  void dispose() {
    _sigSub?.cancel();
    _sig.dispose();
    _pc?.close();
    _remoteRenderer.dispose();
    _roomCodeCtrl.dispose();
    super.dispose();
  }

  Future<void> _join() async {
    final roomId = _roomCodeCtrl.text.trim().toUpperCase();
    if (roomId.isEmpty) return;

    setState(() {
      _joining = true;
      _status = 'Connecting...';
    });

    try {
      _sig.connect(widget.serverUrl);
    } catch (e) {
      setState(() {
        _status = 'Failed to connect: $e';
        _joining = false;
      });
      return;
    }

    _sig.send({'type': 'join', 'roomId': roomId});

    _sigSub = _sig.messages.listen(
      (msg) => _onSignal(msg, roomId),
      onError: (e) {
        setState(() => _status = 'Signal error: $e');
      },
    );
  }

  Future<void> _onSignal(Map<String, dynamic> msg, String roomId) async {
    final type = msg['type'] as String?;

    switch (type) {
      case 'joined':
        setState(() => _status = 'Waiting for host offer...');
        await _initPeerConnection(roomId);
        break;

      case 'signal':
        final data = msg['data'] as Map<String, dynamic>;
        await _handleSignalData(data, roomId);
        break;

      case 'host_disconnected':
        setState(() {
          _status = 'Host disconnected';
          _streaming = false;
        });
        break;

      case 'error':
        setState(() {
          _status = 'Error: ${msg['message']}';
          _joining = false;
        });
        break;
    }
  }

  Future<void> _initPeerConnection(String roomId) async {
    final config = {
      'iceServers': [
        {'urls': 'stun:stun.l.google.com:19302'},
      ],
    };

    _pc = await createPeerConnection(config);

    _pc!.onIceCandidate = (candidate) {
      _sig.send({
        'type': 'signal',
        'roomId': roomId,
        'data': {
          'type': 'candidate',
          'candidate': candidate.toMap(),
        },
      });
    };

    _pc!.onConnectionState = (state) {
      if (state == RTCPeerConnectionState.RTCPeerConnectionStateConnected) {
        setState(() => _status = 'Connected');
      } else if (state == RTCPeerConnectionState.RTCPeerConnectionStateFailed ||
          state == RTCPeerConnectionState.RTCPeerConnectionStateDisconnected) {
        setState(() {
          _status = 'Connection lost';
          _streaming = false;
        });
      }
    };

    _pc!.onTrack = (event) {
      if (event.track.kind == 'video') {
        setState(() {
          _remoteRenderer.srcObject = event.streams[0];
          _streaming = true;
          _status = 'Streaming';
        });
      }
    };

    _pc!.onDataChannel = (channel) {
      _dataChannel = channel;
    };
  }

  Future<void> _handleSignalData(Map<String, dynamic> data, String roomId) async {
    final sigType = data['type'] as String?;

    if (sigType == 'offer') {
      final offer = RTCSessionDescription(data['sdp'] as String, 'offer');
      await _pc?.setRemoteDescription(offer);

      final answer = await _pc!.createAnswer();
      await _pc!.setLocalDescription(answer);

      _sig.send({
        'type': 'signal',
        'roomId': roomId,
        'data': {'type': 'answer', 'sdp': answer.sdp},
      });

    } else if (sigType == 'candidate') {
      final raw = data['candidate'] as Map<String, dynamic>;
      final candidate = RTCIceCandidate(
        raw['candidate'] as String,
        raw['sdpMid'] as String?,
        raw['sdpMLineIndex'] as int?,
      );
      await _pc?.addCandidate(candidate);
    }
  }

  void _sendInput(Map<String, dynamic> ev) {
    if (_dataChannel == null) return;
    try {
      _dataChannel!.send(RTCDataChannelMessage(jsonEncode(ev)));
    } catch (_) {}
  }

  // get video widget size via the global key
  void _updateVideoSize() {
    final ctx = _videoKey.currentContext;
    if (ctx != null) {
      final box = ctx.findRenderObject() as RenderBox?;
      if (box != null) _videoSize = box.size;
    }
  }

  Offset _normalise(Offset local) {
    _updateVideoSize();
    if (_videoSize.isEmpty) return Offset.zero;
    return Offset(
      (local.dx / _videoSize.width).clamp(0.0, 1.0),
      (local.dy / _videoSize.height).clamp(0.0, 1.0),
    );
  }

  // ---- input capture

  void _onPointerMove(PointerMoveEvent e) {
    final n = _normalise(e.localPosition);
    _sendInput({'type': 'move', 'x': n.dx, 'y': n.dy});
  }

  void _onPointerDown(PointerDownEvent e) {
    final n = _normalise(e.localPosition);
    // button 0 = left, 1 = right (PointerDeviceKind bit not directly available)
    _sendInput({'type': 'click', 'x': n.dx, 'y': n.dy, 'button': 0});
  }

  void _onKeyEvent(KeyEvent e) {
    if (e is KeyDownEvent) {
      _sendInput({'type': 'keydown', 'keyCode': e.logicalKey.keyId});
    } else if (e is KeyUpEvent) {
      _sendInput({'type': 'keyup', 'keyCode': e.logicalKey.keyId});
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Pulsar — Viewer'),
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
      ),
      body: _streaming ? _buildStream() : _buildJoinView(),
    );
  }

  Widget _buildJoinView() {
    return Center(
      child: ConstrainedBox(
        constraints: const BoxConstraints(maxWidth: 360),
        child: Padding(
          padding: const EdgeInsets.all(32),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              const Icon(Icons.connected_tv, size: 64, color: Colors.indigo),
              const SizedBox(height: 24),
              TextField(
                controller: _roomCodeCtrl,
                textCapitalization: TextCapitalization.characters,
                maxLength: 6,
                textAlign: TextAlign.center,
                style: const TextStyle(
                  fontSize: 28,
                  fontFamily: 'monospace',
                  letterSpacing: 8,
                  fontWeight: FontWeight.bold,
                ),
                decoration: const InputDecoration(
                  labelText: 'Room Code',
                  border: OutlineInputBorder(),
                  counterText: '',
                ),
                onSubmitted: (_) => _joining ? null : _join(),
              ),

              const SizedBox(height: 16),

              FilledButton(
                onPressed: _joining ? null : _join,
                child: _joining
                    ? const SizedBox(
                        height: 20,
                        width: 20,
                        child: CircularProgressIndicator(strokeWidth: 2, color: Colors.white),
                      )
                    : const Text('Connect'),
              ),

              const SizedBox(height: 16),
              Text(
                _status,
                textAlign: TextAlign.center,
                style: const TextStyle(color: Colors.grey),
              ),
            ],
          ),
        ),
      ),
    );
  }

  Widget _buildStream() {
    return Focus(
      autofocus: true,
      onKeyEvent: (_, e) {
        _onKeyEvent(e);
        return KeyEventResult.handled;
      },
      child: Listener(
        onPointerMove: _onPointerMove,
        onPointerDown: _onPointerDown,
        child: RTCVideoView(
          _remoteRenderer,
          key: _videoKey,
          objectFit: RTCVideoViewObjectFit.RTCVideoViewObjectFitContain,
        ),
      ),
    );
  }
}