Transcription events CLT-343 (#406)

- [x] Events for RoomDelegate
- [x] Events for ParticipantDelegate
- [ ] State management

Sources/LiveKit/Core/Room+EngineDelegate.swift

@@ -194,4 +194,32 @@ extension Room {
             }
         }
     }
+
+    func room(didReceiveTranscriptionPacket packet: Livekit_Transcription) {
+        // Try to find matching Participant.
+        guard let participant = allParticipants[Participant.Identity(from: packet.transcribedParticipantIdentity)] else {
+            log("[Transcription] Could not find participant: \(packet.transcribedParticipantIdentity)", .warning)
+            return
+        }
+
+        guard let publication = participant._state.read({ $0.trackPublications[Track.Sid(from: packet.trackID)] }) else {
+            log("[Transcription] Could not find publication: \(packet.trackID)", .warning)
+            return
+        }
+
+        let segments = packet.segments.map { $0.toLKType() }
+
+        guard !segments.isEmpty else {
+            log("[Transcription] Received segments are empty", .warning)
+            return
+        }
+
+        delegates.notify {
+            $0.room?(self, participant: participant, trackPublication: publication, didReceiveTranscriptionSegments: segments)
+        }
+
+        participant.delegates.notify {
+            $0.participant?(participant, trackPublication: publication, didReceiveTranscriptionSegments: segments)
+        }
+    }
 }

Sources/LiveKit/Core/Room.swift

@@ -521,6 +521,7 @@ extension Room: DataChannelDelegate {
         switch dataPacket.value {
         case let .speaker(update): engine(self, didUpdateSpeakers: update.speakers)
         case let .user(userPacket): engine(self, didReceiveUserPacket: userPacket)
+        case let .transcription(packet): room(didReceiveTranscriptionPacket: packet)
         default: return
         }
     }

Sources/LiveKit/Protocols/ParticipantDelegate.swift

@@ -65,6 +65,10 @@ public protocol ParticipantDelegate: AnyObject {
     @objc optional
     func participant(_ participant: Participant, trackPublication: TrackPublication, didUpdateIsMuted isMuted: Bool)
 
+    /// Received transcription segments.
+    @objc optional
+    func participant(_ participant: Participant, trackPublication: TrackPublication, didReceiveTranscriptionSegments segments: [TranscriptionSegment])
+
     // MARK: - LocalTrackPublication
 
     /// The ``LocalParticipant`` has published a ``LocalTrackPublication``.

Sources/LiveKit/Protocols/RoomDelegate.swift

@@ -102,6 +102,10 @@ public protocol RoomDelegate: AnyObject {
     @objc optional
     func room(_ room: Room, participant: Participant, didUpdateAttributes attributes: [String: String])
 
+    /// Received transcription segments.
+    @objc optional
+    func room(_ room: Room, participant: Participant, trackPublication: TrackPublication, didReceiveTranscriptionSegments segments: [TranscriptionSegment])
+
     // MARK: - Track Publications
 
     /// The ``LocalParticipant`` has published a ``LocalTrack``.

Sources/LiveKit/Types/TranscriptionSegment.swift

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2024 LiveKit
+ *
+ * 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.
+ */
+
+import Foundation
+
+@objc
+public class TranscriptionSegment: NSObject {
+    public let id: String
+    public let text: String
+    public let language: String
+    public let startTime: UInt64
+    public let endTime: UInt64
+    public let isFinal: Bool
+
+    init(id: String,
+         text: String,
+         language: String,
+         startTime: UInt64,
+         endTime: UInt64,
+         isFinal: Bool)
+    {
+        self.id = id
+        self.text = text
+        self.language = language
+        self.startTime = startTime
+        self.endTime = endTime
+        self.isFinal = isFinal
+    }
+
+    // MARK: - Equal
+
+    override public func isEqual(_ object: Any?) -> Bool {
+        guard let other = object as? Self else { return false }
+        return id == other.id
+    }
+
+    override public var hash: Int {
+        var hasher = Hasher()
+        hasher.combine(id)
+        return hasher.finalize()
+    }
+}
+
+// MARK: - Internal
+
+extension Livekit_TranscriptionSegment {
+    func toLKType() -> TranscriptionSegment {
+        TranscriptionSegment(id: id,
+                             text: text,
+                             language: language,
+                             startTime: startTime,
+                             endTime: endTime,
+                             isFinal: final)
+    }
+}