/*
 * libdatachannel example web client
 * Copyright (C) 2020 Lara Mackey
 * Copyright (C) 2020 Paul-Louis Ageneau
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; If not, see <http://www.gnu.org/licenses/>.
 */

window.addEventListener('load', () => {

const config = {
  iceServers: [{
    urls: 'stun:stun.l.google.com:19302', // change to your STUN server
  }],
};

const localId = randomId(8);

const url = `ws://localhost:8000/${localId}`;

const peerConnectionMap = {};
const dataChannelMap = {};

const offerId = document.getElementById('offerId');
const offerBtn = document.getElementById('offerBtn');
const sendMsg = document.getElementById('sendMsg');
const sendBtn = document.getElementById('sendBtn');
const _localId = document.getElementById('localId');
_localId.textContent = localId;

console.log('Connecting to signaling...');
openSignaling(url)
  .then((ws) => {
    console.log('WebSocket connected, signaling ready');
    offerId.disabled = false;
    offerBtn.disabled = false;
    offerBtn.onclick = () => offerPeerConnection(ws, offerId.value);
  })
  .catch((err) => console.error(err));


function openSignaling(url) {
  return new Promise((resolve, reject) => {
    const ws = new WebSocket(url);
    ws.onopen = () => resolve(ws);
    ws.onerror = () => reject(new Error('WebSocket error'));
    ws.onclosed = () => console.error('WebSocket disconnected');
    ws.onmessage = (e) => {
      if(typeof(e.data) != 'string') return;
      const message = JSON.parse(e.data);
      const { id, type } = message;

      let pc = peerConnectionMap[id];
      if(!pc) {
		    if(type != 'offer') return;

			  // Create PeerConnection for answer
			  console.log(`Answering to ${id}`);
			  pc = createPeerConnection(ws, id);
		  }

      switch(type) {
      case 'offer':
      case 'answer':
			  pc.setRemoteDescription({
			    sdp: message.description,
			    type: message.type,
			  })
			  .then(() => {
          if(type == 'offer') {
			      // Send answer
            sendLocalDescription(ws, id, pc, 'answer');
          }
			  });
			  break;

			case 'candidate':
		    pc.addIceCandidate({
          candidate: message.candidate,
          sdpMid: message.mid,
		    });
		    break;
		  }
    }
  });
}

function offerPeerConnection(ws, id) {
	// Create PeerConnection
	console.log(`Offering to ${id}`);
	pc = createPeerConnection(ws, id);

  // Create DataChannel
  const label = "test";
  console.log(`Creating DataChannel with label "${label}"`);
  const dc = pc.createDataChannel(label);
  setupDataChannel(dc, id);

  // Send offer
  sendLocalDescription(ws, id, pc, 'offer');
}

// Create and setup a PeerConnection
function createPeerConnection(ws, id) {
  const pc = new RTCPeerConnection(config);
  pc.onconnectionstatechange = () => console.log(`Connection state: ${pc.connectionState}`);
  pc.onicegatheringstatechange = () => console.log(`Gathering state: ${pc.iceGatheringState}`);
  pc.onicecandidate = (e) => {
    if (e.candidate) {
      // Send candidate
      sendLocalCandidate(ws, id, e.candidate);
    }
  };
  pc.ondatachannel = (e) => {
    const dc = e.channel;
    console.log(`"DataChannel from ${id} received with label "${dc.label}"`);
    setupDataChannel(dc, id);

		dc.send(`Hello from ${localId}`);

    sendMsg.disabled = false;
    sendBtn.disabled = false;
    sendBtn.onclick = () => dc.send(sendMsg.value);
  };

  peerConnectionMap[id] = pc;
  return pc;
}

// Setup a DataChannel
function setupDataChannel(dc, id) {
  dc.onopen = () => {
    console.log(`DataChannel from ${id} open`);

    sendMsg.disabled = false;
    sendBtn.disabled = false;
    sendBtn.onclick = () => dc.send(sendMsg.value);
  };
  dc.onclose = () => {
    console.log(`DataChannel from ${id} closed`);
  };
	dc.onmessage = (e) => {
    if(typeof(e.data) != 'string') return;
		console.log(`Message from ${id} received: ${e.data}`);
    document.body.appendChild(document.createTextNode(e.data));
	};

  dataChannelMap[id] = dc;
  return dc;
}

function sendLocalDescription(ws, id, pc, type) {
  (type == 'offer' ? pc.createOffer() : pc.createAnswer())
    .then((desc) => pc.setLocalDescription(desc))
    .then(() => {
      const { sdp, type } = pc.localDescription;
      ws.send(JSON.stringify({
        id,
        type,
        description: sdp,
      }));
    });
}

function sendLocalCandidate(ws, id, cand) {
  const {candidate, sdpMid} = cand;
  ws.send(JSON.stringify({
    id,
    type: 'candidate',
    candidate,
    mid: sdpMid,
  }));
}

// Helper function to generate a random ID
function randomId(length) {
  const characters = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
  const pickRandom = () => characters.charAt(Math.floor(Math.random() * characters.length));
  return [...Array(length)].map(pickRandom).join('');
}

});