class MeshNet {
  constructor() {
    this.myPeerId = generatePeerId();
    this.connections = new Map();
    this.isHost = false;
    this._pendingPeer = null;
    this._currentQRData = null;

    this.onpeerconnect = null;
    this.onpeerdisconnect = null;
    this.ondata = null;
    this.onqrupdate = null;
    this.onanswerready = null;
  }

  createRoom() {
    this.isHost = true;
    this._createPendingPeer();
  }

  _createPendingPeer() {
    if (this._pendingPeer) {
      try { this._pendingPeer.peer.destroy(); } catch (e) {}
    }

    const peer = new SimplePeer({ initiator: true, trickle: false });
    let signalSent = false;
    let connected = false;

    peer.on('signal', signal => {
      if (signalSent) return;
      signalSent = true;
      this._currentQRData = JSON.stringify({ v: 1, id: this.myPeerId, s: signal });
      if (this.onqrupdate) this.onqrupdate(this._currentQRData);
    });

    peer.on('connect', () => {
      connected = true;
      peer.send(JSON.stringify({ type: 'identity', peerId: this.myPeerId }));
    });

    peer.on('data', data => {
      try {
        const msg = JSON.parse(data.toString());
        this._handleMessage(msg, peer);
      } catch (e) {
        console.error('p2p data parse error:', e);
      }
    });

    peer.on('close', () => {
      this._cleanupPeer(peer);
    });

    peer.on('error', err => {
      console.error('p2p error:', err);
    });

    this._pendingPeer = { peer, signalSent, connected, peerId: null };
  }

  feedAnswer(answerStr) {
    if (!this._pendingPeer || this._pendingPeer.signalReceived) return;
    try {
      const data = JSON.parse(answerStr);
      this._pendingPeer.peerId = data.id;
      this._pendingPeer.peer.signal(data.s);
      this._pendingPeer.signalReceived = true;
    } catch (e) {
      console.error('feedAnswer error:', e);
    }
  }

  joinFromQR(qrContent) {
    const data = JSON.parse(qrContent);
    const remoteId = data.id;
    const offer = data.s;

    const peer = new SimplePeer({ initiator: false, trickle: false });
    let answerSent = false;
    let connected = false;

    peer.on('signal', signal => {
      if (answerSent) return;
      answerSent = true;
      const answerData = JSON.stringify({
        v: 1, id: this.myPeerId, s: signal, to: remoteId
      });
      if (this.onanswerready) this.onanswerready(answerData);
    });

    peer.on('connect', () => {
      connected = true;
      this.connections.set(remoteId, peer);
      peer.send(JSON.stringify({ type: 'identity', peerId: this.myPeerId }));
      if (this.onpeerconnect) this.onpeerconnect(remoteId);
    });

    peer.on('data', data => {
      try {
        const msg = JSON.parse(data.toString());
        this._handleMessage(msg, peer);
      } catch (e) {
        console.error('p2p data parse error:', e);
      }
    });

    peer.on('close', () => {
      this._cleanupPeer(peer);
    });

    peer.on('error', err => {
      console.error('p2p error:', err);
    });

    peer.signal(offer);
    this.connections.set(remoteId, peer);
    this._pendingPeer = { peer, peerId: remoteId, connected };
  }

  _handleMessage(msg, peer) {
    if (msg.type === 'identity') {
      const existing = this._findPeerId(peer);
      if (existing && existing !== msg.peerId) {
        this.connections.delete(existing);
      }
      this.connections.set(msg.peerId, peer);

      if (this._pendingPeer && this._pendingPeer.peer === peer) {
        this._pendingPeer.peerId = msg.peerId;
        this._pendingPeer.connected = true;
        if (this.onpeerconnect) this.onpeerconnect(msg.peerId);
        if (this.isHost) {
          setTimeout(() => this._createPendingPeer(), 300);
        }
      } else {
        if (this.onpeerconnect) this.onpeerconnect(msg.peerId);
      }
      return;
    }

    if (msg.type === 'signal_relay') {
      const target = this.connections.get(msg.to);
      if (target) {
        target.send(JSON.stringify({
          type: 'signal_relayed',
          from: msg.from,
          signal: msg.signal
        }));
      }
      return;
    }

    if (this.ondata) {
      const peerId = this._findPeerId(peer) || 'unknown';
      this.ondata(peerId, msg);
    }
  }

  _findPeerId(peer) {
    for (const [id, p] of this.connections) {
      if (p === peer) return id;
    }
    return null;
  }

  _cleanupPeer(peer) {
    const peerId = this._findPeerId(peer);
    if (peerId) {
      this.connections.delete(peerId);
      if (this.onpeerdisconnect) this.onpeerdisconnect(peerId);
    }
    if (this._pendingPeer && this._pendingPeer.peer === peer) {
      this._pendingPeer = null;
    }
  }

  broadcast(msg) {
    const str = JSON.stringify(msg);
    for (const [id, peer] of this.connections) {
      try { peer.send(str); } catch (e) { console.error('broadcast to', id, 'failed:', e); }
    }
  }

  sendTo(peerId, msg) {
    const peer = this.connections.get(peerId);
    if (peer) {
      try { peer.send(JSON.stringify(msg)); } catch (e) { console.error('sendTo', peerId, 'failed:', e); }
    }
  }

  relaySignal(from, to, signal) {
    const target = this.connections.get(to);
    if (target) {
      target.send(JSON.stringify({ type: 'signal_relay', from, to, signal }));
    }
  }

  getPeerIds() {
    return Array.from(this.connections.keys());
  }

  getCount() {
    return this.connections.size;
  }

  destroy() {
    for (const peer of this.connections.values()) {
      try { peer.destroy(); } catch (e) {}
    }
    this.connections.clear();
    if (this._pendingPeer) {
      try { this._pendingPeer.peer.destroy(); } catch (e) {}
      this._pendingPeer = null;
    }
  }
}