good progress with server and client back and forth

- getting there slowly with console logs and understanding the steps along the way

packages/api/routes/rtc.ts

@@ -0,0 +1,78 @@
+import express, { Application, Request, Response } from "express";
+
+const webrtc = require("wrtc");
+
+export default function getRtcRoutes() {
+  const router = express.Router();
+
+  router.use(express.json());
+
+  // get user details based on id token
+  router.post("/join/:lineId", handleJoin);
+
+  return router;
+}
+
+// a mapping between a certain line and the streams for it
+const linesStreams: {
+  [lineId: string]: any[];
+} = {};
+
+async function handleJoin(req: Request, res: Response) {
+  try {
+    const { lineId } = req.params;
+    const { sdp } = req.body;
+
+    const peer = new webrtc.RTCPeerConnection({
+      iceServers: [
+        {
+          urls: "stun:stun.stunprotocol.org",
+        },
+      ],
+    });
+
+    // allow this peer connection to receive other peoples' streams
+    peer.ontrack = (e: any) => handleStreams(e, peer, lineId);
+
+    // allow this peer connection for this specific line to get tracks for this line already
+    linesStreams[lineId]?.forEach((stream: any) => {
+      stream.getTracks().forEach((track: any) => {
+        console.log(`have tracks in this line`, track, stream);
+        peer.addTrack(track, stream);
+      });
+    });
+
+    // create connection between server and client who hit this endpoint
+    const desc = new webrtc.RTCSessionDescription(sdp);
+    await peer.setRemoteDescription(desc);
+    const answer = await peer.createAnswer();
+    await peer.setLocalDescription(answer);
+
+    const payload = {
+      sdp: peer.localDescription,
+    };
+
+    res
+      .status(200)
+      .json({ message: `You can now broadcast to ${lineId}!`, data: payload });
+  } catch (error) {
+    console.log(error);
+
+    res.status(500).json({
+      message: "Problem in setting up peer connection with media server",
+      error,
+    });
+  }
+}
+
+function handleStreams(e: any, peer: any, lineId: string) {
+  // if the room/line exists already, then add to the list of streams
+  if (lineId in linesStreams) {
+    const newStreamsForLine = [...(linesStreams[lineId] ?? []), ...e.streams];
+
+    linesStreams[lineId] = newStreamsForLine;
+  } else {
+    // create a new list of streams
+    linesStreams[lineId] = [...e.streams];
+  }
+}