From 53904ed3672cea2a74e1bd9b7c665faccf5b4034 Mon Sep 17 00:00:00 2001
From: Pierre HUBERT <pierre.git@communiquons.org>
Date: Sat, 11 Apr 2020 11:26:51 +0200
Subject: [PATCH] Thread-safely open & close channels

---
 relay.go | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 74 insertions(+), 4 deletions(-)

diff --git a/relay.go b/relay.go
index f4b02f8..6357421 100644
--- a/relay.go
+++ b/relay.go
@@ -6,8 +6,8 @@ package main
 
 import (
 	"encoding/json"
-	"fmt"
 	"log"
+	"time"
 
 	"github.com/pion/webrtc/v2"
 )
@@ -21,19 +21,28 @@ const (
 )
 
 type receivedSignal struct {
+	peerID    string
+	callHash  string
 	sigType   uint
 	offer     webrtc.SessionDescription
 	candidate webrtc.ICECandidateInit
 }
 
 /// We keep for each connection its channel
+var closeChan = make(chan string)
 var connections = make(map[string]chan receivedSignal)
 
 /// Process incoming messages
 func onSignal(callHash, peerID string, data map[string]interface{}) {
 
+	// Close all the channels that requested so
+	processCloseRequests()
+
 	// Decode received signal
-	newSignal := receivedSignal{}
+	newSignal := receivedSignal{
+		peerID:   peerID,
+		callHash: callHash,
+	}
 
 	if data["type"] == "SDP" {
 		newSignal.sigType = SDP
@@ -61,6 +70,67 @@ func onSignal(callHash, peerID string, data map[string]interface{}) {
 		log.Fatalf("Invalid signal type: %s !", data["type"])
 	}
 
-	println("Signal successfully processed!")
-	fmt.Println("sig:", newSignal)
+	// Check if we are attempting to connect as viewer to a non existing channel
+	if _, ok := connections[callHash]; !ok {
+		if peerID != "0" || newSignal.sigType != SDP {
+			println("Attempting to connect as viewer | send candidate to a non-ready broadcast!")
+			return
+		}
+	}
+
+	// Handle new offers
+	if newSignal.sigType == SDP && peerID == "0" {
+
+		// Check if we are overwriting another connection
+		if _, ok := connections[callHash]; ok {
+			closeConnection(callHash)
+		}
+
+		connections[callHash] = make(chan receivedSignal, 10)
+		go newCall(newSignal, connections[callHash])
+
+	} else {
+		// Forward the message to the channel
+		connections[callHash] <- newSignal
+	}
+}
+
+/// Close a connection
+func closeConnection(callHash string) {
+	log.Printf("Closing call %s", callHash)
+	if val, ok := connections[callHash]; ok {
+		close(val)
+		delete(connections, callHash)
+	}
+}
+
+// Ask for a channel to be closed
+func askForClose(callHash string) {
+	closeChan <- callHash
+}
+
+// Process channel close requests (in thread safe way)
+func processCloseRequests() {
+	for {
+		select {
+		case id := <-closeChan:
+			closeConnection(id)
+		case <-time.After(time.Millisecond * 10):
+			return
+		}
+	}
+}
+
+/// Start new call
+func newCall(mainOffer receivedSignal, ch chan receivedSignal) {
+
+	// Since we are answering use PayloadTypes declared by offerer
+	mediaEngine := webrtc.MediaEngine{}
+	err := mediaEngine.PopulateFromSDP(mainOffer.offer)
+	if err != nil {
+		log.Println("Error: invalid data in offer!", err)
+		askForClose(mainOffer.callHash)
+		return
+	}
+
 }