class Entropy {
   static localVideo = null;
   static localStream = null;
   static remoteVideo = null;
   static peerConnection = null;
   static uuid = null;
   static serverConnection = null;
   static peerConnectionConfig = {
     'iceServers': [
       {'urls': 'stun:stun.stunprotocol.org:3478'},
       {'urls': 'stun:stun.l.google.com:19302'},
     ]
   };
   
   static getCookie(cname) {
     var name = cname + "=";
     var decodedCookie = decodeURIComponent(document.cookie);
     var ca = decodedCookie.split(';');
     for(var i = 0; i <ca.length; i++) {
       var c = ca[i];
       while (c.charAt(0) == ' ') {
         c = c.substring(1);
       }
       if (c.indexOf(name) == 0) {
         return c.substring(name.length, c.length);
       }
     }
     return "";
   }
   
   static setCookie(cname, cvalue) {
     var d = new Date();
     d.setTime(d.getTime() + (1*24*60*60*1000));
     var expires = "expires="+ d.toUTCString();
     document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
   }
   
   static pageReady() {
     Entropy.uuid = Entropy.getCookie("uuid");
     if (!Entropy.uuid) {
       Entropy.uuid = Entropy.createUUID();
       Entropy.setCookie("uuid", Entropy.uuid);
     }
   
     Entropy.localVideo = document.getElementById('localVideo');
     Entropy.remoteVideo = document.getElementById('remoteVideo');
   
     Entropy.serverConnection = new WebSocket('wss://' + window.location.hostname + '/abc');
     Entropy.serverConnection.onmessage = Entropy.gotMessageFromServer;
   
     var constraints = {
       video: true,
       audio: false,
     };
   
     if(navigator.mediaDevices.getUserMedia) {
       navigator.mediaDevices.getUserMedia(constraints).then(Entropy.getUserMediaSuccess).catch(Entropy.errorHandler);
     } else {
       alert('Your browser does not support getUserMedia API');
     }
   }
   
   static getUserMediaSuccess(stream) {
     Entropy.localStream = stream;
     Entropy.localVideo.srcObject = stream;
   }
   
   static start(isCaller) {
     Entropy.peerConnection = new RTCPeerConnection(Entropy.peerConnectionConfig);
     Entropy.peerConnection.onicecandidate = Entropy.gotIceCandidate;
     Entropy.peerConnection.ontrack = Entropy.gotRemoteStream;
     Entropy.peerConnection.addStream(Entropy.localStream);
   
     if(isCaller) {
       Entropy.peerConnection
         .createOffer({
           'iceRestart': true,
           'voiceActivityDetection': true,
         })
         .then(Entropy.createdDescription)
         .catch(Entropy.errorHandler);
     }
   }
   
   static gotMessageFromServer(message) {
     if(!Entropy.peerConnection) Entropy.start(false);
   
     var signal = JSON.parse(message.data);
   
     // Ignore messages from ourself
     if(signal.uuid == Entropy.uuid) return;
   
     if(signal.sdp) {
       Entropy.peerConnection.setRemoteDescription(new RTCSessionDescription(signal.sdp)).then(function() {
         // Only create answers in response to offers
         if(signal.sdp.type == 'offer') {
           Entropy.peerConnection.createAnswer().then(Entropy.createdDescription).catch(Entropy.errorHandler);
         }
       }).catch(Entropy.errorHandler);
     } else if(signal.ice) {
       Entropy.peerConnection.addIceCandidate(new RTCIceCandidate(signal.ice)).catch(Entropy.errorHandler);
     }
   }
   
   static gotIceCandidate(event) {
     if(event.candidate != null) {
       Entropy.serverConnection.send(JSON.stringify({'ice': event.candidate, 'uuid': Entropy.uuid}));
     }
   }
   
   static createdDescription(description) {
     console.log('got description');
   
     Entropy.peerConnection
       .setLocalDescription(description)
       .then(function() {
         Entropy.serverConnection.send(JSON.stringify({
            'sdp': Entropy.peerConnection.localDescription, 
            'uuid': Entropy.uuid,
         }));
       })
       .catch(errorHandler);
   }
   
   static gotRemoteStream(event) {
     console.log('got remote stream');
     Entropy.remoteVideo.srcObject = event.streams[0];
   }
   
   static errorHandler(error) {
     console.log(error);
   }
   
   // Taken from http://stackoverflow.com/a/105074/515584
   // Strictly speaking, it's not a real UUID, but it gets the job done here
   static createUUID() {
     function s4() {
       return Math.floor((1 + Math.random()) * 0x10000).toString(16).substring(1);
     }
   
     return s4() + s4() + '-' + s4() + '-' + s4() + '-' + s4() + '-' + s4() + s4() + s4();
   }
}

function pageReady() {
   Entropy.pageReady();
}