Add TranscriptionReceived event to track publication (#449)

* Add TranscriptionReceived event to track publication

* spotless

+/*
+ * Copyright 2024 LiveKit, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.livekit.android.events
+
+import io.livekit.android.room.track.TrackPublication
+import io.livekit.android.room.types.TranscriptionSegment
+
+sealed class TrackPublicationEvent(val publication: TrackPublication) : Event() {
+    class TranscriptionReceived(
+        /**
+         * The applicable track publication these transcriptions apply to.
+         */
+        publication: TrackPublication,
+        /**
+         * The transcription segments.
+         */
+        val transcriptions: List<TranscriptionSegment>,
+    ) : TrackPublicationEvent(publication)
+}

@@ -1022,7 +1022,7 @@ constructor(
         )
         eventBus.tryPostEvent(event)
         participant?.onTranscriptionReceived(event)
-        // TODO: Emit for publication
+        publication?.onTranscriptionReceived(event)
     }
 
     /**

 /*
- * Copyright 2023 LiveKit, Inc.
+ * Copyright 2023-2024 LiveKit, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,9 @@
 
 package io.livekit.android.room.track
 
+import io.livekit.android.events.BroadcastEventBus
+import io.livekit.android.events.RoomEvent
+import io.livekit.android.events.TrackPublicationEvent
 import io.livekit.android.room.participant.Participant
 import io.livekit.android.util.FlowObservable
 import io.livekit.android.util.flowDelegate
@@ -44,6 +47,9 @@ open class TrackPublication(
             return trackInfo?.encryption ?: LivekitModels.Encryption.Type.NONE
         }
 
+    protected val eventBus = BroadcastEventBus<TrackPublicationEvent>()
+    val events = eventBus.readOnly()
+
     @FlowObservable
     @get:FlowObservable
     open var muted: Boolean by flowDelegate(false)
@@ -87,4 +93,16 @@ open class TrackPublication(
 
         trackInfo = info
     }
+
+    internal fun onTranscriptionReceived(transcription: RoomEvent.TranscriptionReceived) {
+        if (transcription.publication != this) {
+            return
+        }
+        eventBus.tryPostEvent(
+            TrackPublicationEvent.TranscriptionReceived(
+                publication = this,
+                transcriptions = transcription.transcriptionSegments,
+            ),
+        )
+    }
 }

@@ -316,6 +316,7 @@ object TestData {
                     startTime = 1
                     endTime = 10
                     final = true
+                    trackId = LOCAL_AUDIO_TRACK.sid
                     build()
                 },
             )

@@ -16,10 +16,16 @@
 
 package io.livekit.android.room
 
+import io.livekit.android.events.ParticipantEvent
 import io.livekit.android.events.RoomEvent
+import io.livekit.android.events.TrackPublicationEvent
+import io.livekit.android.room.participant.AudioTrackPublishOptions
+import io.livekit.android.room.track.LocalAudioTrack
+import io.livekit.android.room.track.Track
 import io.livekit.android.test.MockE2ETest
 import io.livekit.android.test.assert.assertIsClass
 import io.livekit.android.test.events.EventCollector
+import io.livekit.android.test.mock.MockAudioStreamTrack
 import io.livekit.android.test.mock.MockDataChannel
 import io.livekit.android.test.mock.MockPeerConnection
 import io.livekit.android.test.mock.TestData
@@ -33,26 +39,57 @@ class RoomTranscriptionMockE2ETest : MockE2ETest() {
     @Test
     fun transcriptionReceived() = runTest {
         connect()
+        room.localParticipant.publishAudioTrack(
+            LocalAudioTrack(
+                "",
+                MockAudioStreamTrack(id = TestData.LOCAL_TRACK_PUBLISHED.trackPublished.cid),
+            ),
+            options = AudioTrackPublishOptions(
+                source = Track.Source.MICROPHONE,
+            ),
+        )
         val subPeerConnection = component.rtcEngine().getSubscriberPeerConnection() as MockPeerConnection
         val subDataChannel = MockDataChannel(RTCEngine.RELIABLE_DATA_CHANNEL_LABEL)
         subPeerConnection.observer?.onDataChannel(subDataChannel)
 
-        val collector = EventCollector(room.events, coroutineRule.scope)
+        val roomCollector = EventCollector(room.events, coroutineRule.scope)
+        val participantCollector = EventCollector(room.localParticipant.events, coroutineRule.scope)
+        val publicationCollector = EventCollector(room.localParticipant.getTrackPublication(Track.Source.MICROPHONE)!!.events, coroutineRule.scope)
+
         val dataBuffer = TestData.DATA_PACKET_TRANSCRIPTION.toDataChannelBuffer()
 
         subDataChannel.observer?.onMessage(dataBuffer)
-        val events = collector.stopCollecting()
 
-        assertEquals(1, events.size)
-        assertIsClass(RoomEvent.TranscriptionReceived::class.java, events[0])
+        val roomEvents = roomCollector.stopCollecting()
+        val participantEvents = participantCollector.stopCollecting()
+        val publicationEvents = publicationCollector.stopCollecting()
+
+        // Verify room events
+        run {
+            assertEquals(1, roomEvents.size)
+            assertIsClass(RoomEvent.TranscriptionReceived::class.java, roomEvents[0])
+
+            val event = roomEvents.first() as RoomEvent.TranscriptionReceived
+            assertEquals(room, event.room)
+            assertEquals(room.localParticipant, event.participant)
+            assertEquals(room.localParticipant.getTrackPublication(Track.Source.MICROPHONE)!!, event.publication)
+
+            val expectedSegment = TestData.DATA_PACKET_TRANSCRIPTION.transcription.getSegments(0)
+            val receivedSegment = event.transcriptionSegments.first()
+            assertEquals(expectedSegment.id, receivedSegment.id)
+            assertEquals(expectedSegment.text, receivedSegment.text)
+        }
 
-        val event = events.first() as RoomEvent.TranscriptionReceived
-        assertEquals(room, event.room)
-        assertEquals(room.localParticipant, event.participant)
+        // Verify participant events
+        run {
+            assertEquals(1, participantEvents.size)
+            assertIsClass(ParticipantEvent.TranscriptionReceived::class.java, participantEvents[0])
+        }
 
-        val expectedSegment = TestData.DATA_PACKET_TRANSCRIPTION.transcription.getSegments(0)
-        val receivedSegment = event.transcriptionSegments.first()
-        assertEquals(expectedSegment.id, receivedSegment.id)
-        assertEquals(expectedSegment.text, receivedSegment.text)
+        // Verify publication events
+        run {
+            assertEquals(1, publicationEvents.size)
+            assertIsClass(TrackPublicationEvent.TranscriptionReceived::class.java, publicationEvents[0])
+        }
     }
 }