From 83c5698051e559618bd7669928bc16e15bf53d27 Mon Sep 17 00:00:00 2001
From: Lawrence Forooghian <lawrence@forooghian.com>
Date: Thu, 10 Oct 2024 15:46:44 -0300
Subject: [PATCH] Implement CHA-RL1d

(From the same spec as referenced in 25e5052.)
---
 Sources/AblyChat/RoomLifecycleManager.swift   |  5 ++
 .../RoomLifecycleManagerTests.swift           | 48 +++++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/Sources/AblyChat/RoomLifecycleManager.swift b/Sources/AblyChat/RoomLifecycleManager.swift
index 88f4bb6a..c13c894d 100644
--- a/Sources/AblyChat/RoomLifecycleManager.swift
+++ b/Sources/AblyChat/RoomLifecycleManager.swift
@@ -523,6 +523,11 @@ internal actor RoomLifecycleManager<Contributor: RoomLifecycleContributor> {
             break
         }
 
+        // CHA-RL1d
+        if let currentOperationID = status.operationID {
+            _ = await resultOfOperationWithID(currentOperationID, waitingOperationID: operationID)
+        }
+
         // CHA-RL1e
         changeStatus(to: .attaching(attachOperationID: operationID))
 
diff --git a/Tests/AblyChatTests/RoomLifecycleManagerTests.swift b/Tests/AblyChatTests/RoomLifecycleManagerTests.swift
index 51487901..45d3be84 100644
--- a/Tests/AblyChatTests/RoomLifecycleManagerTests.swift
+++ b/Tests/AblyChatTests/RoomLifecycleManagerTests.swift
@@ -125,6 +125,54 @@ struct RoomLifecycleManagerTests {
         }
     }
 
+    // @spec CHA-RL1d
+    @Test
+    func attach_ifOtherOperationInProgress_waitsForItToComplete() async throws {
+        // Given: A RoomLifecycleManager with a DETACH lifecycle operation in progress (the fact that it is a DETACH is not important; it is just an operation whose execution it is easy to prolong and subsequently complete, which is helpful for this test)
+        let contributorDetachOperation = SignallableChannelOperation()
+        let manager = await createManager(
+            contributors: [
+                createContributor(
+                    // Arbitrary, allows the ATTACH to eventually complete
+                    attachBehavior: .complete(.success),
+                    // This allows us to prolong the execution of the DETACH triggered in (1)
+                    detachBehavior: contributorDetachOperation.behavior
+                ),
+            ]
+        )
+
+        let detachOperationID = UUID()
+        let attachOperationID = UUID()
+
+        let statusChangeSubscription = await manager.onChange(bufferingPolicy: .unbounded)
+        // Wait for the manager to enter DETACHING; this our sign that the DETACH operation triggered in (1) has started
+        async let detachingStatusChange = statusChangeSubscription.first { $0.current == .detaching }
+
+        // (1) This is the "DETACH lifecycle operation in progress" mentioned in Given
+        async let _ = manager.performDetachOperation(testsOnly_forcingOperationID: detachOperationID)
+        _ = await detachingStatusChange
+
+        let operationWaitEventSubscription = await manager.testsOnly_subscribeToOperationWaitEvents()
+        async let attachedWaitingForDetachedEvent = operationWaitEventSubscription.first { operationWaitEvent in
+            operationWaitEvent == .init(waitingOperationID: attachOperationID, waitedOperationID: detachOperationID)
+        }
+
+        // When: `performAttachOperation()` is called on the lifecycle manager
+        async let attachResult: Void = manager.performAttachOperation(testsOnly_forcingOperationID: attachOperationID)
+
+        // Then:
+        // - the manager informs us that the ATTACH operation is waiting for the DETACH operation to complete
+        // - when the DETACH completes, the ATTACH operation proceeds (which we check here by verifying that it eventually completes) — note that (as far as I can tell) there is no way to test that the ATTACH operation would have proceeded _only if_ the DETACH had completed; the best we can do is allow the manager to tell us that that this is indeed what it’s doing (which is what we check for in the previous bullet)
+
+        _ = try #require(await attachedWaitingForDetachedEvent)
+
+        // Allow the DETACH to complete
+        contributorDetachOperation.complete(result: .success /* arbitrary */ )
+
+        // Check that ATTACH completes
+        try await attachResult
+    }
+
     // @spec CHA-RL1e
     @Test
     func attach_transitionsToAttaching() async throws {