feat(client-presence): Create Acknowledgment message interface and ackRequested flow

packages/framework/presence/src/internalTypes.ts

@@ -34,7 +34,9 @@ export type IEphemeralRuntime = Pick<
 	(IContainerRuntime & IRuntimeInternal) | IFluidDataStoreRuntime,
 	"clientId" | "connected" | "getAudience" | "getQuorum" | "off" | "on" | "submitSignal"
 > &
-	Partial<Pick<IFluidDataStoreRuntime, "logger">>;
+	Partial<Pick<IFluidDataStoreRuntime, "logger">> & {
+		ILayerCompatDetails?: unknown;
+	};
 
 /**
  * @internal

packages/framework/presence/src/presenceDatastoreManager.ts

@@ -3,6 +3,7 @@
  * Licensed under the MIT License.
  */
 
+import type { ILayerCompatDetails } from "@fluid-internal/client-utils";
 import type { IEmitter } from "@fluidframework/core-interfaces/internal";
 import { assert } from "@fluidframework/core-utils/internal";
 import type { IInboundSignalMessage } from "@fluidframework/runtime-definitions/internal";
@@ -75,6 +76,7 @@ interface DatastoreUpdateMessage extends IInboundSignalMessage {
 		sendTimestamp: number;
 		avgLatency: number;
 		isComplete?: true;
+		acknowledgementId?: number;
 		data: DatastoreMessageContent;
 	};
 }
@@ -90,11 +92,33 @@ interface ClientJoinMessage extends IInboundSignalMessage {
 	};
 }
 
+// Message type identifier for presence acknowledgment messages.
+const acknowledgementMessageType = "Pres:Ack";
+
+// Signal message format used to acknowledge receipt of presence-related messages.
+// These are lightweight and typically contain only the messageId being acknowledged.
+interface AcknowledgementMessage extends IInboundSignalMessage {
+	type: typeof acknowledgementMessageType;
+	content: {
+		id: number;
+	};
+}
+
 function isPresenceMessage(
 	message: IInboundSignalMessage,
-): message is DatastoreUpdateMessage | ClientJoinMessage {
+): message is DatastoreUpdateMessage | ClientJoinMessage | AcknowledgementMessage {
 	return message.type.startsWith("Pres:");
 }
+
+function isLayerCompatDetails(value: unknown): value is ILayerCompatDetails {
+	return (
+		typeof value === "object" &&
+		value !== null &&
+		"supportedFeatures" in value &&
+		value.supportedFeatures instanceof Set
+	);
+}
+
 /**
  * @internal
  */
@@ -356,14 +380,27 @@ export class PresenceDatastoreManagerImpl implements PresenceDatastoreManager {
 		// IExtensionMessage is a subset of IInboundSignalMessage so this is safe.
 		// Change types of DatastoreUpdateMessage | ClientJoinMessage to
 		// IExtensionMessage<> derivatives to see the issues.
-		message: IInboundSignalMessage | DatastoreUpdateMessage | ClientJoinMessage,
+		message:
+			| IInboundSignalMessage
+			| DatastoreUpdateMessage
+			| ClientJoinMessage
+			| AcknowledgementMessage,
 		local: boolean,
 	): void {
 		const received = Date.now();
 		assert(message.clientId !== null, 0xa3a /* Map received signal without clientId */);
 		if (!isPresenceMessage(message)) {
 			return;
 		}
+
+		if (message.type === acknowledgementMessageType) {
+			// TODO: Handle acknowledgement messages here.
+			// Placeholder for future implementation.
+			// These acknowledgement messages will be used to confirm receipt
+			// of pending messages that were previously sent.
+			return;
+		}
+
 		if (local) {
 			const deliveryDelta = received - message.content.sendTimestamp;
 			// Limit returnedMessages count to 256 such that newest message
@@ -395,6 +432,20 @@ export class PresenceDatastoreManagerImpl implements PresenceDatastoreManager {
 			if (message.content.isComplete) {
 				this.refreshBroadcastRequested = false;
 			}
+			// If the message requests an acknowledgement, we will send one back.
+			if (
+				message.content.acknowledgementId !== undefined &&
+				isLayerCompatDetails(this.runtime.ILayerCompatDetails) &&
+				this.runtime.ILayerCompatDetails?.supportedFeatures?.has("submit_signals_v2") === true
+			) {
+				this.runtime.submitSignal(
+					acknowledgementMessageType,
+					{
+						id: message.content.acknowledgementId,
+					} satisfies AcknowledgementMessage["content"],
+					message.clientId,
+				);
+			}
 		}
 
 		// Handle activation of unregistered workspaces before processing updates.