From 0df2630a70bc69cd1a79778f8e23ed5a1db1854a Mon Sep 17 00:00:00 2001
From: Ryan Zhao <ryanzhaors@qq.com>
Date: Tue, 7 Dec 2021 16:30:14 +1100
Subject: [PATCH] enable CBR

---
 SessionMessagingKit/Calls/WebRTCSession.swift         | 11 +++++++++--
 .../General/NSRegularExpression+SSK.swift             |  6 ++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/SessionMessagingKit/Calls/WebRTCSession.swift b/SessionMessagingKit/Calls/WebRTCSession.swift
index c2312cebc..ffe6b894a 100644
--- a/SessionMessagingKit/Calls/WebRTCSession.swift
+++ b/SessionMessagingKit/Calls/WebRTCSession.swift
@@ -139,7 +139,7 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
             if let error = error {
                 seal.reject(error)
             } else {
-                guard let self = self, let sdp = sdp else { preconditionFailure() }
+                guard let self = self, let sdp = self.correctSessionDescription(sdp: sdp) else { preconditionFailure() }
                 self.peerConnection.setLocalDescription(sdp) { error in
                     if let error = error {
                         print("Couldn't initiate call due to error: \(error).")
@@ -171,7 +171,7 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
             if let error = error {
                 seal.reject(error)
             } else {
-                guard let self = self, let sdp = sdp else { preconditionFailure() }
+                guard let self = self, let sdp = self.correctSessionDescription(sdp: sdp) else { preconditionFailure() }
                 self.peerConnection.setLocalDescription(sdp) { error in
                     if let error = error {
                         print("Couldn't accept call due to error: \(error).")
@@ -244,6 +244,13 @@ public final class WebRTCSession : NSObject, RTCPeerConnectionDelegate {
         return RTCMediaConstraints(mandatoryConstraints: mandatory, optionalConstraints: optional)
     }
     
+    private func correctSessionDescription(sdp: RTCSessionDescription?) -> RTCSessionDescription? {
+        guard let sdp = sdp else { return nil }
+        let cbrSdp = sdp.description.replace(regex: "(a=fmtp:111 ((?!cbr=).)*)\r?\n", with: "$1;cbr=1\r\n")
+        let finalSdp = cbrSdp.replace(regex: ".+urn:ietf:params:rtp-hdrext:ssrc-audio-level.*\r?\n", with: "")
+        return RTCSessionDescription(type: sdp.type, sdp: finalSdp)
+    }
+    
     // MARK: Peer connection delegate
     public func peerConnection(_ peerConnection: RTCPeerConnection, didChange state: RTCSignalingState) {
         print("[Calls] Signaling state changed to: \(state).")
diff --git a/SessionUtilitiesKit/General/NSRegularExpression+SSK.swift b/SessionUtilitiesKit/General/NSRegularExpression+SSK.swift
index c8eb33d21..891526aff 100644
--- a/SessionUtilitiesKit/General/NSRegularExpression+SSK.swift
+++ b/SessionUtilitiesKit/General/NSRegularExpression+SSK.swift
@@ -81,6 +81,12 @@ extension String {
     public var completeNSRange: NSRange {
         NSRange(completeRange, in: self)
     }
+    
+    public func replace(regex: String, with template: String) -> String {
+        let regex = try! NSRegularExpression(pattern: regex, options: .caseInsensitive)
+        let range = self.completeNSRange
+        return regex.stringByReplacingMatches(in: self, options: [], range: range, withTemplate: template)
+    }
 }
 
 extension NSTextCheckingResult {