import { useState, useEffect, useRef, useCallback } from 'react';
import { getSocket } from '../services/socket';

// WebRTC configuration with STUN servers
const rtcConfig = {
  iceServers: [
    { urls: 'stun:stun.l.google.com:19302' },
    { urls: 'stun:stun1.l.google.com:19302' },
    { urls: 'stun:stun2.l.google.com:19302' },
  ],
};

// File chunk size (16KB recommended for WebRTC DataChannel)
const CHUNK_SIZE = 16384;

/**
 * Custom hook for managing WebRTC peer-to-peer connections and file transfers
 *
 * @param {number} matchId - The match ID for this connection
 * @param {number} userId - Current user's ID
 * @returns {Object} WebRTC state and control functions
 */
export const useWebRTC = (matchId, userId) => {
  const [connectionState, setConnectionState] = useState('disconnected'); // disconnected, connecting, connected, failed
  const [transferProgress, setTransferProgress] = useState(0);
  const [isTransferring, setIsTransferring] = useState(false);
  const [receivingFile, setReceivingFile] = useState(null);

  const peerConnectionRef = useRef(null);
  const dataChannelRef = useRef(null);
  const socketRef = useRef(null);

  // File transfer state
  const fileTransferRef = useRef({
    file: null,
    fileName: '',
    fileSize: 0,
    fileType: '',
    chunks: [],
    currentChunk: 0,
    totalChunks: 0,
  });

  // Receiving file state
  const receivingBufferRef = useRef([]);
  const receivingMetadataRef = useRef(null);

  /**
   * Initialize peer connection
   */
  const initializePeerConnection = useCallback(() => {
    if (peerConnectionRef.current) {
      return peerConnectionRef.current;
    }

    const pc = new RTCPeerConnection(rtcConfig);
    peerConnectionRef.current = pc;

    // ICE candidate handler
    pc.onicecandidate = (event) => {
      if (event.candidate && socketRef.current) {
        socketRef.current.emit('webrtc_ice_candidate', {
          matchId,
          candidate: event.candidate,
        });
        console.log('📤 Sent ICE candidate');
      }
    };

    // Connection state change handler
    pc.onconnectionstatechange = () => {
      console.log('🔄 Connection state:', pc.connectionState);
      setConnectionState(pc.connectionState);

      if (pc.connectionState === 'failed') {
        console.error('❌ WebRTC connection failed');
        cleanupConnection();
      }
    };

    // ICE connection state handler
    pc.oniceconnectionstatechange = () => {
      console.log('🧊 ICE connection state:', pc.iceConnectionState);
    };

    console.log('✅ RTCPeerConnection initialized');
    return pc;
  }, [matchId]);

  /**
   * Create data channel for file transfer
   */
  const createDataChannel = useCallback((pc) => {
    const dc = pc.createDataChannel('fileTransfer', {
      ordered: true,
    });

    setupDataChannelHandlers(dc);
    dataChannelRef.current = dc;

    console.log('✅ DataChannel created');
    return dc;
  }, []);

  /**
   * Setup data channel event handlers
   */
  const setupDataChannelHandlers = useCallback((dc) => {
    dc.onopen = () => {
      console.log('✅ DataChannel opened');
      setConnectionState('connected');
    };

    dc.onclose = () => {
      console.log('❌ DataChannel closed');
      setConnectionState('disconnected');
    };

    dc.onerror = (error) => {
      console.error('❌ DataChannel error:', error);
      setConnectionState('failed');
    };

    dc.onmessage = (event) => {
      handleDataChannelMessage(event.data);
    };
  }, []);

  /**
   * Handle incoming data channel messages
   */
  const handleDataChannelMessage = useCallback((data) => {
    // Check if it's metadata (JSON string)
    if (typeof data === 'string') {
      try {
        const metadata = JSON.parse(data);

        if (metadata.type === 'file_metadata') {
          // Receiving file metadata
          receivingMetadataRef.current = metadata;
          receivingBufferRef.current = [];
          setReceivingFile({
            name: metadata.fileName,
            size: metadata.fileSize,
            type: metadata.fileType,
          });
          setIsTransferring(true);
          setTransferProgress(0);
          console.log('📥 Receiving file:', metadata.fileName);
        } else if (metadata.type === 'file_end') {
          // File transfer complete
          const blob = new Blob(receivingBufferRef.current, {
            type: receivingMetadataRef.current.fileType
          });

          // Trigger download
          const url = URL.createObjectURL(blob);
          const a = document.createElement('a');
          a.href = url;
          a.download = receivingMetadataRef.current.fileName;
          document.body.appendChild(a);
          a.click();
          document.body.removeChild(a);
          URL.revokeObjectURL(url);

          console.log('✅ File received and downloaded:', receivingMetadataRef.current.fileName);

          // Reset state
          setIsTransferring(false);
          setTransferProgress(0);
          setReceivingFile(null);
          receivingBufferRef.current = [];
          receivingMetadataRef.current = null;
        }
      } catch (error) {
        console.error('Failed to parse metadata:', error);
      }
    } else {
      // Binary data - file chunk
      receivingBufferRef.current.push(data);

      const received = receivingBufferRef.current.length;
      const total = Math.ceil(receivingMetadataRef.current.fileSize / CHUNK_SIZE);
      const progress = Math.round((received / total) * 100);

      setTransferProgress(progress);
      console.log(`📥 Received chunk ${received}/${total} (${progress}%)`);
    }
  }, []);

  /**
   * Create and send offer to peer
   */
  const createOffer = useCallback(async () => {
    try {
      setConnectionState('connecting');

      const pc = initializePeerConnection();
      createDataChannel(pc);

      const offer = await pc.createOffer();
      await pc.setLocalDescription(offer);

      socketRef.current.emit('webrtc_offer', {
        matchId,
        offer: pc.localDescription,
      });

      console.log('📤 Sent WebRTC offer');
    } catch (error) {
      console.error('Failed to create offer:', error);
      setConnectionState('failed');
    }
  }, [matchId, initializePeerConnection, createDataChannel]);

  /**
   * Handle incoming offer and create answer
   */
  const handleOffer = useCallback(async (offer) => {
    try {
      setConnectionState('connecting');

      const pc = initializePeerConnection();

      // Setup data channel handler for incoming connections
      pc.ondatachannel = (event) => {
        console.log('✅ DataChannel received');
        dataChannelRef.current = event.channel;
        setupDataChannelHandlers(event.channel);
      };

      await pc.setRemoteDescription(new RTCSessionDescription(offer));

      const answer = await pc.createAnswer();
      await pc.setLocalDescription(answer);

      socketRef.current.emit('webrtc_answer', {
        matchId,
        answer: pc.localDescription,
      });

      console.log('📤 Sent WebRTC answer');
    } catch (error) {
      console.error('Failed to handle offer:', error);
      setConnectionState('failed');
    }
  }, [matchId, initializePeerConnection, setupDataChannelHandlers]);

  /**
   * Handle incoming answer
   */
  const handleAnswer = useCallback(async (answer) => {
    try {
      const pc = peerConnectionRef.current;
      if (!pc) {
        console.error('No peer connection found');
        return;
      }

      await pc.setRemoteDescription(new RTCSessionDescription(answer));
      console.log('✅ Remote description set');
    } catch (error) {
      console.error('Failed to handle answer:', error);
      setConnectionState('failed');
    }
  }, []);

  /**
   * Handle incoming ICE candidate
   */
  const handleIceCandidate = useCallback(async (candidate) => {
    try {
      const pc = peerConnectionRef.current;
      if (!pc) {
        console.error('No peer connection found');
        return;
      }

      await pc.addIceCandidate(new RTCIceCandidate(candidate));
      console.log('✅ Added ICE candidate');
    } catch (error) {
      console.error('Failed to add ICE candidate:', error);
    }
  }, []);

  /**
   * Send file via data channel
   */
  const sendFile = useCallback(async (file) => {
    if (!file) {
      console.error('No file provided');
      return;
    }

    const dc = dataChannelRef.current;
    if (!dc || dc.readyState !== 'open') {
      console.error('DataChannel is not open');
      alert('Connection not established. Please wait and try again.');
      return;
    }

    try {
      setIsTransferring(true);
      setTransferProgress(0);

      // Send file metadata
      const metadata = {
        type: 'file_metadata',
        fileName: file.name,
        fileSize: file.size,
        fileType: file.type,
      };

      dc.send(JSON.stringify(metadata));
      console.log('📤 Sent file metadata:', metadata);

      // Read file and send in chunks
      const arrayBuffer = await file.arrayBuffer();
      const totalChunks = Math.ceil(arrayBuffer.byteLength / CHUNK_SIZE);

      for (let i = 0; i < totalChunks; i++) {
        const start = i * CHUNK_SIZE;
        const end = Math.min(start + CHUNK_SIZE, arrayBuffer.byteLength);
        const chunk = arrayBuffer.slice(start, end);

        // Wait if buffer is getting full
        while (dc.bufferedAmount > CHUNK_SIZE * 10) {
          await new Promise(resolve => setTimeout(resolve, 10));
        }

        dc.send(chunk);

        const progress = Math.round(((i + 1) / totalChunks) * 100);
        setTransferProgress(progress);
        console.log(`📤 Sent chunk ${i + 1}/${totalChunks} (${progress}%)`);
      }

      // Send end marker
      dc.send(JSON.stringify({ type: 'file_end' }));
      console.log('✅ File transfer complete:', file.name);

      setIsTransferring(false);
      setTransferProgress(0);
    } catch (error) {
      console.error('Failed to send file:', error);
      setIsTransferring(false);
      setTransferProgress(0);
      alert('Failed to send file: ' + error.message);
    }
  }, []);

  /**
   * Cleanup connection
   */
  const cleanupConnection = useCallback(() => {
    if (dataChannelRef.current) {
      dataChannelRef.current.close();
      dataChannelRef.current = null;
    }

    if (peerConnectionRef.current) {
      peerConnectionRef.current.close();
      peerConnectionRef.current = null;
    }

    setConnectionState('disconnected');
    setIsTransferring(false);
    setTransferProgress(0);
    setReceivingFile(null);
    receivingBufferRef.current = [];
    receivingMetadataRef.current = null;

    console.log('🧹 WebRTC connection cleaned up');
  }, []);

  /**
   * Setup Socket.IO event listeners
   */
  useEffect(() => {
    const socket = getSocket();
    if (!socket) {
      console.error('Socket not available');
      return;
    }

    socketRef.current = socket;

    // Listen for WebRTC signaling events
    socket.on('webrtc_offer', ({ from, offer }) => {
      console.log('📥 Received WebRTC offer from:', from);
      if (from !== userId) {
        handleOffer(offer);
      }
    });

    socket.on('webrtc_answer', ({ from, answer }) => {
      console.log('📥 Received WebRTC answer from:', from);
      if (from !== userId) {
        handleAnswer(answer);
      }
    });

    socket.on('webrtc_ice_candidate', ({ from, candidate }) => {
      console.log('📥 Received ICE candidate from:', from);
      if (from !== userId) {
        handleIceCandidate(candidate);
      }
    });

    // Cleanup on unmount
    return () => {
      socket.off('webrtc_offer');
      socket.off('webrtc_answer');
      socket.off('webrtc_ice_candidate');
      cleanupConnection();
    };
  }, [userId, handleOffer, handleAnswer, handleIceCandidate, cleanupConnection]);

  return {
    connectionState,
    isTransferring,
    transferProgress,
    receivingFile,
    createOffer,
    sendFile,
    cleanupConnection,
  };
};