Fix LivestreamChannelController not connecting chat after coming from background (#3778)

* Fix livestream controller not resuming chat after coming from background

* Update CHANGELOG.md

* Add comment explaining the reason

Author: nuno-vieira

CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Add a completion block to `LivestreamChannelController.resume()` to observe possible errors [#3774](https://github.com/GetStream/stream-chat-swift/pull/3774)
 ### 🐞 Fixed
 - Fix pending message being added to `LivestreamChannelController.messages` when in paused state [#3774](https://github.com/GetStream/stream-chat-swift/pull/3774)
+- Fix `LivestreamChannelController` not connecting chat after coming from background [#3778](https://github.com/GetStream/stream-chat-swift/pull/3778)
 ### 🔄 Changed
 - The `LivestreamChannelController.resume()` should be manually called, previously, it was automatically called on a new message [#3774](https://github.com/GetStream/stream-chat-swift/pull/3774)
 

Sources/StreamChat/Controllers/ChannelController/LivestreamChannelController.swift

@@ -760,6 +760,15 @@ public class LivestreamChannelController: DataStoreProvider, EventsControllerDel
         loadFirstPage()
     }
 
+    public func applicationDidMoveToForeground() {
+        // The livestream controller is not impacted by the syncing of missing events.
+        // Since it won't get notified about messages updated from the DB.
+        // So we need to manually reset the channel once the user is connected again.
+        if client.connectionStatus != .connected {
+            loadFirstPage()
+        }
+    }
+
     // MARK: - Private Methods
 
     private func updateChannelData(

TestTools/StreamChatTestTools/Mocks/StreamChat/ChatClient_Mock.swift

@@ -27,7 +27,7 @@ final class ChatClient_Mock: ChatClient {
         mockedAppSettings
     }
 
-    var mockedEventNotificationCenter: EventNotificationCenter_Mock? = nil
+    var mockedEventNotificationCenter: EventNotificationCenter_Mock?
 
     override var eventNotificationCenter: EventNotificationCenter {
         mockedEventNotificationCenter ?? super.eventNotificationCenter
@@ -64,7 +64,7 @@ final class ChatClient_Mock: ChatClient {
     }
 
     override var currentUserId: UserId? {
-        return currentUserId_mock
+        currentUserId_mock
     }
 
     public var currentUserId_mock: UserId? {
@@ -76,6 +76,16 @@ final class ChatClient_Mock: ChatClient {
         }
     }
 
+    public var connectionStatus_mock: ConnectionStatus?
+    override var connectionStatus: ConnectionStatus {
+        get {
+            connectionStatus_mock ?? super.connectionStatus
+        }
+        set {
+            connectionStatus_mock = newValue
+        }
+    }
+
     override func createBackgroundWorkers() {
         createBackgroundWorkers_called = true
 

Tests/StreamChatTests/Controllers/ChannelController/LivestreamChannelController_Tests.swift

@@ -906,7 +906,35 @@ extension LivestreamChannelController_Tests {
         let expectedEndpoint = Endpoint<ChannelPayload>.updateChannel(query: expectedQuery)
         XCTAssertEqual(apiClient.request_endpoint, AnyEndpoint(expectedEndpoint))
     }
-    
+
+    func test_applicationDidMoveToForeground_whenNotConnected_callsLoadFirstPage() {
+        // Given
+        let apiClient = client.mockAPIClient
+        client.connectionStatus_mock = .disconnected(error: ClientError())
+
+        // When
+        controller.applicationDidMoveToForeground()
+
+        // Then
+        let expectedPagination = MessagesPagination(pageSize: 25, parameter: nil)
+        var expectedQuery = channelQuery!
+        expectedQuery.pagination = expectedPagination
+        let expectedEndpoint = Endpoint<ChannelPayload>.updateChannel(query: expectedQuery)
+        XCTAssertEqual(apiClient.request_endpoint, AnyEndpoint(expectedEndpoint))
+    }
+
+    func test_applicationDidMoveToForeground_whenConnected_doesNotCallLoadFirstPage() {
+        // Given
+        let apiClient = client.mockAPIClient
+        client.connectionStatus_mock = .connected
+
+        // When
+        controller.applicationDidMoveToForeground()
+
+        // Then
+        XCTAssertNil(apiClient.request_endpoint)
+    }
+
     func test_didReceiveEvent_messageNewEvent_addsMessageToArray() {
         let newMessage = ChatMessage.mock(id: "new", cid: controller.cid!, text: "New message")
         let event = MessageNewEvent(