From 10ab3cdcacfb5b470b4e395d0964f7ab2b25f5ce Mon Sep 17 00:00:00 2001
From: David Zhao <david@davidzhao.com>
Date: Tue, 20 Jul 2021 15:45:10 -0700
Subject: [PATCH] implement RTCEngine.negotiate

---
 lib/src/rtc_engine.dart | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/lib/src/rtc_engine.dart b/lib/src/rtc_engine.dart
index d5af658..5a80a6b 100644
--- a/lib/src/rtc_engine.dart
+++ b/lib/src/rtc_engine.dart
@@ -105,7 +105,28 @@ class RTCEngine with SignalClientDelegate {
     return completer.future;
   }
 
-  negotiate() async {}
+  negotiate([Map<String, dynamic>? constraints]) async {
+    var pub = this.publisher;
+    if (pub == null) {
+      return;
+    }
+
+    var remoteDesc = await pub.pc.getRemoteDescription();
+    // handle cases that we couldn't create a new offer due to a pending answer
+    // that's lost in transit
+    if (remoteDesc != null &&
+        pub.pc.signalingState ==
+            RTCSignalingState.RTCSignalingStateHaveLocalOffer) {
+      await pub.pc.setRemoteDescription(remoteDesc);
+    }
+
+    if (constraints == null) {
+      constraints = {};
+    }
+    var offer = await pub.pc.createOffer(constraints);
+    await pub.pc.setLocalDescription(offer);
+    client.sendOffer(offer);
+  }
 
   _configurePeerConnections() async {
     if (publisher != null) {