From e22429af17460bfe9ada52ecb6208bb506a8d3b1 Mon Sep 17 00:00:00 2001
From: bbaldino <bbaldino@cisco.com>
Date: Thu, 9 Sep 2021 13:04:48 -0700
Subject: [PATCH] fix: support ice gathering already being complete in
 getLocalDescriptionWithIceCandidates (#40)

---
 src/peer-connection-utils.spec.ts | 25 ++++++++++++++++++-------
 src/peer-connection-utils.ts      | 23 +++++++++++++++++------
 src/peer-connection.ts            |  9 +++++++++
 3 files changed, 44 insertions(+), 13 deletions(-)

diff --git a/src/peer-connection-utils.spec.ts b/src/peer-connection-utils.spec.ts
index 40a6718..77671e9 100644
--- a/src/peer-connection-utils.spec.ts
+++ b/src/peer-connection-utils.spec.ts
@@ -6,15 +6,16 @@ import { mocked } from './mocks/mock';
 
 jest.mock('./peer-connection');
 
+const dummyLocalDesc = {
+  type: 'offer',
+  sdp: 'sdp with candidates',
+  toJSON: () => undefined,
+} as RTCSessionDescription;
+
 describe('getLocalDescriptionWithIceCandidates', () => {
   const mockPc = mocked(new PeerConnection(), true);
   test('return the correct offer after ice gathering has finished', (done) => {
-    const localDesc = {
-      type: 'offer',
-      sdp: 'sdp with candidates',
-      toJSON: () => undefined,
-    } as RTCSessionDescription;
-    mockPc.getLocalDescription.mockReturnValueOnce(localDesc);
+    mockPc.getLocalDescription.mockReturnValueOnce(dummyLocalDesc);
 
     const promise = new PromiseHelper(
       getLocalDescriptionWithIceCandidates(mockPc as unknown as PeerConnection)
@@ -46,11 +47,12 @@ describe('getLocalDescriptionWithIceCandidates', () => {
       Promise.resolve().then(() => {
         expect(mockPc.getLocalDescription.mock.calls).toHaveLength(1);
         expect(promise.isFinished()).toBe(true);
-        expect(promise.resolvedValue).toBe(localDesc);
+        expect(promise.resolvedValue).toBe(dummyLocalDesc);
         done();
       });
     });
   });
+
   test('rejects if the local description is null', async () => {
     mockPc.getLocalDescription.mockReturnValueOnce(null);
     const promise = getLocalDescriptionWithIceCandidates(mockPc as unknown as PeerConnection);
@@ -62,6 +64,15 @@ describe('getLocalDescriptionWithIceCandidates', () => {
     });
     await expect(promise).rejects.toStrictEqual(expect.any(Error));
   });
+
+  test('resolves immediately if the ICE candidates have already been gathered', () => {
+    mockPc.getLocalDescription.mockReturnValueOnce(dummyLocalDesc);
+    Object.defineProperty(mockPc, 'iceGatheringState', {
+      get: () => 'complete',
+    });
+
+    return getLocalDescriptionWithIceCandidates(mockPc as unknown as PeerConnection);
+  });
 });
 
 /**
diff --git a/src/peer-connection-utils.ts b/src/peer-connection-utils.ts
index 2a99ad4..1fecc0d 100644
--- a/src/peer-connection-utils.ts
+++ b/src/peer-connection-utils.ts
@@ -11,16 +11,27 @@ export function getLocalDescriptionWithIceCandidates(
   peerConnection: PeerConnection
 ): Promise<RTCSessionDescription> {
   return new Promise((resolve, reject) => {
+    /**
+     * A helper method to retrieve the local description and resolve, if one is found, or reject
+     * with an error if it's not.
+     */
+    const getLocalDescAndResolve = () => {
+      const localDesc = peerConnection.getLocalDescription();
+      if (localDesc) {
+        resolve(localDesc);
+      } else {
+        reject(new Error('Local description was null'));
+      }
+    };
     peerConnection.on(PeerConnection.Events.IceGatheringStateChange, (e) => {
       if (e.target.iceGatheringState === 'complete') {
-        const localDesc = peerConnection.getLocalDescription();
-        if (localDesc) {
-          resolve(localDesc);
-        } else {
-          reject(new Error('Local description was null'));
-        }
+        getLocalDescAndResolve();
       }
       // TODO(brian): throw an error if we see an error iceGatheringState
     });
+    // It's possible ICE gathering is already done
+    if (peerConnection.iceGatheringState === 'complete') {
+      getLocalDescAndResolve();
+    }
   });
 }
diff --git a/src/peer-connection.ts b/src/peer-connection.ts
index 39dc6de..e5fed76 100644
--- a/src/peer-connection.ts
+++ b/src/peer-connection.ts
@@ -179,6 +179,15 @@ class PeerConnection extends EventEmitter {
   getTransceivers(): RTCRtpTransceiver[] {
     return this.pc.getTransceivers();
   }
+
+  /**
+   * Returns a string that describes the connections' ICE gathering state.
+   *
+   * @returns - The ICE gathering state.
+   */
+  get iceGatheringState(): RTCIceGathererState {
+    return this.pc.iceGatheringState;
+  }
 }
 
 export { MediaStreamTrackKind, PeerConnection };