From 1f8157cc5a4d938c8ea0d21597def728a99265f8 Mon Sep 17 00:00:00 2001
From: "D. Berge" <dberge@aaltronav.eu>
Date: Sat, 10 Oct 2020 12:07:31 +0200
Subject: [PATCH] Add client-side RTC logic.

It tries to grab the microphone and open a
connection to every other user as soon as the
websocket connection is made. It shows audio
controls for every connection at the bottom
of the page for debugging purposes.
---
 lib/www/client/source/src/lib/rtc.js | 194 +++++++++++++++++++++++++++
 lib/www/client/source/src/main.js    |  10 +-
 2 files changed, 203 insertions(+), 1 deletion(-)
 create mode 100644 lib/www/client/source/src/lib/rtc.js

diff --git a/lib/www/client/source/src/lib/rtc.js b/lib/www/client/source/src/lib/rtc.js
new file mode 100644
index 0000000..041d8b4
--- /dev/null
+++ b/lib/www/client/source/src/lib/rtc.js
@@ -0,0 +1,194 @@
+
+let ws = null;
+let peerId = null;
+let peers = {};
+let stream = null;
+
+function init (socket) {
+  ws = socket;
+  ws.addEventListener("message", (ev) => {
+    try {
+      const payload = JSON.parse(ev.data);
+      if (payload.rtc === true) {
+        // Handle this message
+        handle (payload);
+      }
+    } catch (err) {
+      console.error("Invalid message", ev, err);
+    }
+  });
+}
+
+async function talk () {
+  try {
+    if (!stream) {
+      const constraints = { audio: true, video: false };
+      stream = await navigator.mediaDevices.getUserMedia(constraints);
+      console.log("Grabbed stream", stream);
+    }
+
+    if (peerId && Object.keys(peers).length) {
+      for (const track of stream.getTracks()) {
+        for (const peer in peers) {
+          peers[peer].addTrack(track, stream);
+        }
+      }
+    }
+  } catch (err) {
+    console.error("talk() error", err);
+  }
+}
+
+class PeerConnection {
+
+  constructor (otherPeerId) {
+    this.otherPeerId = otherPeerId;
+    this.makingOffer = false;
+    this.polite = this.otherPeerId > peerId;
+    this.start();
+  }
+
+  send (message) {
+    message.from = peerId;
+    message.to = this.otherPeerId;
+    send(message);
+  }
+
+  async handle (message) {
+    try {
+      let ignoreOffer = false;
+
+      if ("description" in message) {
+        const offerCollision = (message.description.type == "offer") &&
+          (this.makingOffer || this.conn.signalingState != "stable");
+
+        ignoreOffer = !this.polite && offerCollision;
+
+        if (ignoreOffer) {
+          return;
+        }
+
+        await this.conn.setRemoteDescription(message.description);
+        if (message.description.type == "offer") {
+          await this.conn.setLocalDescription();
+          this.send({ description: this.conn.localDescription });
+        }
+      }
+
+      if ("candidate" in message) {
+        try {
+          await this.conn.addIceCandidate(message.candidate);
+        } catch (err) {
+          if (!ignoreOffer) {
+            throw err;
+          }
+        }
+      }
+    } catch (err) {
+      console.error(err);
+    }
+  }
+
+  start () {
+    const config = { iceServers: [] };
+    this.conn = new RTCPeerConnection(config);
+    console.log("Have peer connection", this.conn);
+
+    this.conn.ontrack = ({track, streams}) => {
+      // FIXME Need to remove these elements when done
+      if (!this.remoteAudio) {
+        this.remoteAudio = document.createElement("audio");
+        this.remoteAudio.setAttribute("autoplay", "true");
+        this.remoteAudio.controls = true;
+        document.getElementsByTagName("footer")[0].appendChild(this.remoteAudio);
+        console.log("Added <audio> element", this.remoteAudio);
+      }
+
+      track.onunmute = () => {
+        if (this.remoteAudio.srcObject) {
+          return;
+        }
+        this.remoteAudio.srcObject = streams[0];
+        console.log("unmuted");
+      };
+    };
+
+    this.conn.onnegotiationneeded = async () => {
+      console.log("negotiation needed");
+      try {
+        this.makingOffer = true;
+        await this.conn.setLocalDescription();
+        this.send({ description: this.conn.localDescription });
+      } catch (err) {
+        console.error(err);
+      } finally {
+        this.makingOffer = false;
+      }
+    };
+
+    this.conn.oniceconnectionstatechange = () => {
+      console.log("state change");
+      if (this.conn.iceConnectionState == "failed") {
+        this.conn.restartIce();
+      }
+    }
+
+    this.conn.onicecandidate = async ({candidate}) => {
+      console.log("send candidate", candidate);
+      this.send({candidate});
+    };
+
+    if (stream) {
+      for (const track of stream.getAudioTracks()) {
+        this.addTrack(track, stream);
+      }
+    }
+
+  }
+
+  addTrack (track, stream) {
+    console.log("add track to connection", this.conn, track, stream);
+    if (this.conn) {
+      this.conn.addTrack(track, stream);
+    }
+  }
+
+
+};
+
+
+function send (message) {
+  console.log("Send message", message, "via", ws);
+  if (ws) {
+    message.rtc = true;
+    ws.send(JSON.stringify(message));
+  }
+}
+
+function handle (message) {
+  console.log("Handle message", message);
+
+  if ("peerId" in message) {
+    peerId = message.peerId;
+  }
+
+  if ("otherPeers" in message) {
+    for (const peer of message.otherPeers) {
+      if (peer in peers) continue;
+
+      peers[peer] = new PeerConnection(peer);
+    }
+  }
+
+  if ("newPeer" in message) {
+    peers[message.newPeer] = new PeerConnection(message.newPeer);
+  }
+
+  if ("to" in message && "from" in message && message.to == peerId) {
+    peers[message.from].handle(message);
+  }
+}
+
+export default {
+  init, talk
+};
diff --git a/lib/www/client/source/src/main.js b/lib/www/client/source/src/main.js
index 4f1c35e..672a8dc 100644
--- a/lib/www/client/source/src/main.js
+++ b/lib/www/client/source/src/main.js
@@ -6,6 +6,8 @@ import vuetify from './plugins/vuetify'
 import vueDebounce from 'vue-debounce'
 import { mapMutations } from 'vuex';
 
+import rtc from './lib/rtc';
+
 
 Vue.config.productionTip = false
 
@@ -51,12 +53,18 @@ new Vue({
 
       this.ws.addEventListener("message", (ev) => {
         const msg = JSON.parse(ev.data);
-        this.setServerEvent(msg);
+        if (msg.rtc === true) {
+          // Handle WebRTC message
+        } else {
+          this.setServerEvent(msg);
+        }
       });
 
       this.ws.addEventListener("open", (ev) => {
         console.log("WebSocket connection open", ev);
         this.setServerConnectionState(true);
+        rtc.init(this.ws);
+        rtc.talk();
       });
 
       this.ws.addEventListener("close", (ev) => {