set up action able to work with webrtc in localhost

app/assets/javascripts/signaling-server.js

@@ -0,0 +1,196 @@
+// Broadcast Types
+
+class Signaling {}
+
+const JOIN_ROOM = "JOIN_ROOM";
+const EXCHANGE = "EXCHANGE";
+const REMOVE_USER = "REMOVE_USER";
+
+// DOM Elements
+let currentUser;
+let localVideo;
+let remoteVideoContainer;
+
+// Objects
+let pcPeers = {}; // peer connection
+let localstream;
+
+window.onload = () => {
+  currentUser = document.getElementById("current-user").innerHTML;
+  localVideo = document.getElementById("local-video");
+  remoteVideoContainer = document.getElementById("remote-video-container");
+};
+
+// Ice Credentials
+const ice = { iceServers: [{urls: ['stun:stun.l.google.com:19302', 'stun:stun.1.google.com:19302']}]};
+
+// Initialize user's own video
+document.onreadystatechange = async () => {
+  if (document.readyState === "interactive") {
+    try {
+      const stream = await navigator.mediaDevices.getUserMedia({
+        audio: true,
+        video: true
+      })
+
+      localstream = stream;
+      localVideo.srcObject = stream
+      localVideo.muted = true
+    } catch (e) { console.error(e); }
+  }
+};
+
+
+const handleJoinSession = async () => {
+  App.session = await App.cable.subscriptions.create("VideoSessionChannel", {
+    connected: () => {
+      broadcastData({
+        type: JOIN_ROOM,
+        from: currentUser
+      });
+    },
+    received: data => {
+      console.log("received", data);
+      if (data.from === currentUser) return;
+      switch (data.type) {
+        case JOIN_ROOM:
+          return joinRoom(data);
+        case EXCHANGE:
+          if (data.to !== currentUser) return;
+          return exchange(data);
+        case REMOVE_USER:
+          return removeUser(data);
+        default:
+          return;
+      }
+    }
+  });
+};
+
+const handleLeaveSession = () => {
+  for (user in pcPeers) {
+    pcPeers[user].close();
+  }
+  pcPeers = {};
+
+  App.session.unsubscribe();
+
+  remoteVideoContainer.innerHTML = "";
+
+  broadcastData({
+    type: REMOVE_USER,
+    from: currentUser
+  });
+};
+
+const joinRoom = data => {
+  createPC(data.from, true);
+};
+
+const removeUser = data => {
+  console.log("removing user", data.from);
+  let video = document.getElementById(`remoteVideoContainer+${data.from}`);
+  video && video.remove();
+  delete pcPeers[data.from];
+};
+
+
+const broadcastData = data => {
+  fetch("sessions", {
+    method: "POST",
+    body: JSON.stringify(data),
+    headers: { "content-type": "application/json" }
+  });
+};
+
+const createPC = (userId, isOffer) => {
+  let pc = new RTCPeerConnection(ice);
+  pcPeers[userId] = pc;
+  pc.addStream(localstream);
+
+  if (isOffer) {
+    pc
+      .createOffer()
+      .then(offer => {
+        pc.setLocalDescription(offer);
+        broadcastData({
+          type: EXCHANGE,
+          from: currentUser,
+          to: userId,
+          sdp: JSON.stringify(pc.localDescription)
+        });
+      })
+      .catch(logError);
+  }
+
+  pc.onicecandidate = event => {
+    if (event.candidate) {
+      broadcastData({
+        type: EXCHANGE,
+        from: currentUser,
+        to: userId,
+        candidate: JSON.stringify(event.candidate)
+      });
+    }
+  };
+
+  pc.onaddstream = event => {
+    const element = document.createElement("video");
+    element.id = `remoteVideoContainer+${userId}`;  // why is the userId being interpolated?
+    element.autoplay = "autoplay";
+    element.srcObject = event.stream;
+    remoteVideoContainer.appendChild(element);
+  };
+
+  pc.oniceconnectionstatechange = event => {
+    if (pc.iceConnectionState == "disconnected") {
+      console.log("Disconnected:", userId);
+      broadcastData({
+        type: REMOVE_USER,
+        from: userId
+      });
+    }
+  };
+
+  return pc;
+};
+
+
+const exchange = data => {
+  let pc;
+
+  if (!pcPeers[data.from]) {
+    pc = createPC(data.from, false);
+  } else {
+    pc = pcPeers[data.from];
+  }
+
+  if (data.candidate) {
+    pc
+      .addIceCandidate(new RTCIceCandidate(JSON.parse(data.candidate)))
+      .then(() => console.log("Ice candidate added"))
+      .catch(logError);
+  }
+
+  if (data.sdp) {
+    sdp = JSON.parse(data.sdp);
+    pc
+      .setRemoteDescription(new RTCSessionDescription(sdp))
+      .then(() => {
+        if (sdp.type === "offer") {
+          pc.createAnswer().then(answer => {
+            pc.setLocalDescription(answer);
+            broadcastData({
+              type: EXCHANGE,
+              from: currentUser,
+              to: data.from,
+              sdp: JSON.stringify(pc.localDescription)
+            });
+          });
+        }
+      })
+      .catch(logError);
+  }
+};
+
+const logError = error => console.warn("Whoops! Error:", error);

app/assets/stylesheets/pages/_home.scss

@@ -1 +1,6 @@
 // Specific CSS for your home-page
+video {
+  transform: rotateY(180deg);
+  -webkit-transform:rotateY(180deg); /* Safari and Chrome */
+  -moz-transform:rotateY(180deg); /* Firefox */
+}

app/channels/video_session_channel.rb

@@ -1,6 +1,7 @@
 class VideoSessionChannel < ApplicationCable::Channel
   def subscribed
     # video session
+    stream_from "video_session_channel"
     # stream_from "chat_room_#{params[:chat_room_id]}"
   end
 

app/controllers/application_controller.rb

@@ -1,4 +1,5 @@
 class ApplicationController < ActionController::Base
   protect_from_forgery with: :exception
   before_action :authenticate_user!
+  protect_from_forgery unless: -> { request.format.json? } # Only accept json
 end

app/controllers/video_sessions_controller.rb

@@ -0,0 +1,15 @@
+class VideoSessionsController < ApplicationController
+  def create
+    #  HTTP status code 200 with an empty body
+    head :no_content
+    ActionCable.server.broadcast "video_session_channel", session_params
+  end
+
+  private
+
+  def session_params
+    # SDP = Session description protocol (codec info from client)
+    # Candidate = ICE candidates (e.g. TURN and STUN server)
+    params.permit(:type, :from, :to, :sdp, :candidate)
+  end
+end

app/views/pages/home.html.erb

@@ -1,2 +1,18 @@
-<h1>Pages#home</h1>
-<p>Find me in app/views/pages/home.html.erb</p>
+<h1>Action Cable Signaling Server</h1>
+
+<div>Random User ID:
+  <span id="current-user"><%= rand(0..10000) %></span>
+</div>
+
+<div id="remote-video-container"></div>
+<video id="local-video" autoplay></video>
+
+<hr />
+
+<button onclick="handleJoinSession()">
+  Join Room
+</button>
+
+<button onclick="handleLeaveSession()">
+  Leave Room
+</button>

app/views/video_sessions/create.html.erb

@@ -0,0 +1,2 @@
+<h1>VideoSessions#create</h1>
+<p>Find me in app/views/video_sessions/create.html.erb</p>

config/routes.rb

@@ -1,5 +1,10 @@
 Rails.application.routes.draw do
+  get 'video_sessions/create'
   devise_for :users
   root to: 'pages#home'
+
+  post '/sessions', to: 'video_sessions#create'
+
+  mount ActionCable.server, at: '/cable'
   # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
 end

test/controllers/video_sessions_controller_test.rb

@@ -0,0 +1,9 @@
+require 'test_helper'
+
+class VideoSessionsControllerTest < ActionDispatch::IntegrationTest
+  test "should get create" do
+    get video_sessions_create_url
+    assert_response :success
+  end
+
+end