From ea73efb0b0407bd22cf9d56a2740edb41f607455 Mon Sep 17 00:00:00 2001
From: Pierre HUBERT <pierre.git@communiquons.org>
Date: Sat, 11 Apr 2020 18:20:46 +0200
Subject: [PATCH] Respond to offers

---
 relay.go | 55 ++++++++++++++++++++++++++++++++++++++-----------------
 ws.go    |  5 +++++
 2 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/relay.go b/relay.go
index 6f8ef6c..5b901bc 100644
--- a/relay.go
+++ b/relay.go
@@ -22,6 +22,9 @@ const (
 	// CANDIDATE This is a candidate
 	CANDIDATE = iota
 
+	// RequestOffer for a broadcast receiver
+	RequestOffer = iota
+
 	// CloseConnection Requests the connection to be closed
 	CloseConnection = iota
 )
@@ -30,7 +33,7 @@ type receivedSignal struct {
 	peerID    string
 	callHash  string
 	sigType   uint
-	offer     webrtc.SessionDescription
+	sdp       webrtc.SessionDescription
 	candidate webrtc.ICECandidateInit
 }
 
@@ -70,7 +73,7 @@ func onSignal(callHash, peerID string, data map[string]interface{}) {
 			return
 		}
 
-		err = json.Unmarshal(enc, &newSignal.offer)
+		err = json.Unmarshal(enc, &newSignal.sdp)
 		if err != nil {
 			log.Printf("Discarding invalid candidate: %s", err)
 			return
@@ -93,6 +96,11 @@ func onSignal(callHash, peerID string, data map[string]interface{}) {
 			return
 		}
 
+	} else if data["type"] == "REQUEST_OFFER" {
+
+		// Request an offer
+		newSignal.sigType = RequestOffer
+
 	} else if data["type"] == "CLOSE_CONN" {
 
 		// Close connection
@@ -132,6 +140,13 @@ func onSignal(callHash, peerID string, data map[string]interface{}) {
 	}
 }
 
+/// Request an offer for a client of a broadcast
+func onRequestOffer(callHash, peerID string) {
+	onSignal(callHash, peerID, map[string]interface{}{
+		"type": "REQUEST_OFFER",
+	})
+}
+
 /// Request connections to be closed
 func onCloseConnection(callHash, peerID string) {
 	onSignal(callHash, peerID, map[string]interface{}{
@@ -173,7 +188,7 @@ func newCall(mainOffer receivedSignal, r activeRelay) {
 
 	// Since we are answering use PayloadTypes declared by offerer
 	mediaEngine := webrtc.MediaEngine{}
-	err := mediaEngine.PopulateFromSDP(mainOffer.offer)
+	err := mediaEngine.PopulateFromSDP(mainOffer.sdp)
 	if err != nil {
 		log.Println("Error: invalid data in offer!", err)
 		askForClose(r)
@@ -271,7 +286,7 @@ func newCall(mainOffer receivedSignal, r activeRelay) {
 	})
 
 	// Set the remote SessionDescription
-	err = mainPeerConnection.SetRemoteDescription(mainOffer.offer)
+	err = mainPeerConnection.SetRemoteDescription(mainOffer.sdp)
 	if err != nil {
 		log.Println("Set remote description error!", err)
 		askForClose(r)
@@ -339,7 +354,7 @@ func newCall(mainOffer receivedSignal, r activeRelay) {
 		}
 
 		// Check if we are creating a new connection
-		if newMessage.sigType == SDP {
+		if newMessage.sigType == RequestOffer {
 
 			// Close any previous connection of this client
 			if val, ok := clients[newMessage.peerID]; ok {
@@ -363,21 +378,14 @@ func newCall(mainOffer receivedSignal, r activeRelay) {
 				}
 			}
 
-			// Set remote description
-			err = newPeerConnection.SetRemoteDescription(newMessage.offer)
-			if err != nil {
-				log.Printf("Could not set remote description (remote peer): %s", err)
-				continue
-			}
-
-			// Create the answer
-			answer, err := newPeerConnection.CreateAnswer(nil)
+			// Create the offer
+			offer, err := newPeerConnection.CreateOffer(nil)
 			if err != nil {
 				log.Printf("Could not create answer: %s!", err)
 				continue
 			}
 
-			err = newPeerConnection.SetLocalDescription(answer)
+			err = newPeerConnection.SetLocalDescription(offer)
 			if err != nil {
 				log.Printf("Could not set local description: %s!", err)
 				continue
@@ -390,8 +398,21 @@ func newCall(mainOffer receivedSignal, r activeRelay) {
 				}
 			})
 
-			// Send answer
-			sendSignal(r.callHash, newMessage.peerID, answer)
+			// Send offer
+			sendSignal(r.callHash, newMessage.peerID, offer)
+
+		} else if newMessage.sigType == SDP {
+
+			// Got an answer from the client
+			if val, ok := clients[newMessage.peerID]; ok {
+				// Set remote description
+				if err := val.SetRemoteDescription(newMessage.sdp); err != nil {
+					log.Printf("Could not set remote description! %s", err)
+				}
+
+			} else {
+				log.Printf("Dropped un-usable answer: callHash %s / peer ID %s", newMessage.callHash, newMessage.peerID)
+			}
 
 		} else if newMessage.sigType == CANDIDATE {
 
diff --git a/ws.go b/ws.go
index 67bb22d..b955d15 100644
--- a/ws.go
+++ b/ws.go
@@ -82,6 +82,11 @@ func openWs(conf *Config) {
 			onSignal(msg.CallHash, msg.PeerID, msg.Data.(map[string]interface{}))
 			break
 
+		// Request an offer
+		case "request_offer":
+			onRequestOffer(msg.CallHash, msg.PeerID)
+			break
+
 		// Close a connection
 		case "close_conn":
 			onCloseConnection(msg.CallHash, msg.PeerID)