Discard duplicate messages delivered by sockets

GliaWidgets/Sources/ViewModel/Chat/ChatViewModel.swift

@@ -46,6 +46,10 @@ class ChatViewModel: EngagementViewModel, ViewModel {
     var isViewLoaded: Bool = false
     var isChoiceCardInputModeEnabled: Bool = false
     private (set) var siteConfiguration: CoreSdkClient.Site?
+    // Stored message ids retrieved from history.
+    // They are used to discard messages received from socket
+    // to avoid duplication.
+    private (set) var historyMessageIds: Set<ChatMessage.MessageId> = []
 
     var mediaPickerButtonVisibility: MediaPickerButtonVisibility {
         guard let site = siteConfiguration else { return .disabled }
@@ -372,6 +376,10 @@ extension ChatViewModel {
         environment.fetchChatHistory { [weak self] result in
             guard let self else { return }
             let messages = (try? result.get()) ?? []
+            // Store message ids from history,
+            // to be able to discard duplicates
+            // delivered by sockets.
+            self.historyMessageIds = Set(messages.map(\.id))
             let items = messages.compactMap {
                 ChatItem(
                     with: $0,
@@ -548,6 +556,11 @@ extension ChatViewModel {
     }
 
     private func receivedMessage(_ message: CoreSdkClient.Message) {
+        // Discard messages that have been already received from history
+        // to avoid duplication.
+        guard !historyMessageIds.contains(message.id) else {
+            return
+        }
         switch message.sender.type {
         case .operator, .system:
             let message = ChatMessage(

GliaWidgets/Sources/ViewModel/Chat/Data/ChatMessage.swift

@@ -25,7 +25,8 @@ enum ChatMessageSender: Int, Codable {
 }
 
 class ChatMessage: Codable {
-    let id: String
+    typealias MessageId = String
+    let id: MessageId
     var queueID: String?
     let `operator`: ChatOperator?
     let sender: ChatMessageSender

GliaWidgetsTests/Sources/ChatViewModel/ChatViewModelTests.swift

@@ -477,6 +477,74 @@ class ChatViewModelTests: XCTestCase {
         }
         XCTAssertEqual(calls, [.scrollToBottom(animated: true)])
     }
+
+    func test_messagesIdsFromHistoryAreStoredInHistoryMessageIds() {
+        var viewModelEnv = ChatViewModel.Environment.failing()
+        viewModelEnv.createFileUploadListModel = { _ in .mock() }
+        viewModelEnv.fileManager.urlsForDirectoryInDomainMask = { _, _ in [.mock] }
+        viewModelEnv.fileManager.createDirectoryAtUrlWithIntermediateDirectories = { _, _, _ in }
+        viewModelEnv.loadChatMessagesFromHistory = { true }
+        viewModelEnv.fetchSiteConfigurations = { _ in }
+        let expectedMessageId = "expected_message_id"
+        viewModelEnv.fetchChatHistory = { callback in
+            callback(.success([.mock(id: expectedMessageId)]))
+        }
+        let viewModel: ChatViewModel = .mock(environment: viewModelEnv)
+        viewModel.start()
+        XCTAssertEqual(viewModel.historyMessageIds, [expectedMessageId])
+    }
+
+    func test_messageReceivedFromSocketIsDiscarded() {
+        var viewModelEnv = ChatViewModel.Environment.failing()
+        viewModelEnv.createFileUploadListModel = { _ in .mock() }
+        viewModelEnv.fileManager.urlsForDirectoryInDomainMask = { _, _ in [.mock] }
+        viewModelEnv.fileManager.createDirectoryAtUrlWithIntermediateDirectories = { _, _, _ in }
+        viewModelEnv.loadChatMessagesFromHistory = { true }
+        viewModelEnv.fetchSiteConfigurations = { _ in }
+        let expectedMessageId = "expected_message_id"
+        viewModelEnv.fetchChatHistory = { callback in
+            callback(.success([.mock(id: expectedMessageId)]))
+        }
+        let viewModel: ChatViewModel = .mock(environment: viewModelEnv)
+        viewModel.start()
+        var actions: [ChatViewModel.Action] = []
+        viewModel.action = {
+            actions.append($0)
+        }
+        viewModel.interactorEvent(.receivedMessage(.mock(id: expectedMessageId)))
+        XCTAssertTrue(actions.isEmpty)
+    }
+
+    func test_messageReceivedFromSocketIsNotDiscarded() {
+        var viewModelEnv = ChatViewModel.Environment.failing()
+        viewModelEnv.createFileUploadListModel = { _ in .mock() }
+        viewModelEnv.fileManager.urlsForDirectoryInDomainMask = { _, _ in [.mock] }
+        viewModelEnv.fileManager.createDirectoryAtUrlWithIntermediateDirectories = { _, _, _ in }
+        viewModelEnv.loadChatMessagesFromHistory = { true }
+        viewModelEnv.fetchSiteConfigurations = { _ in }
+        viewModelEnv.fetchChatHistory = { _ in }
+
+        let messageId = "message_id"
+        let viewModel: ChatViewModel = .mock(environment: viewModelEnv)
+        viewModel.start()
+        var actions: [ChatViewModel.Action] = []
+        viewModel.action = {
+            actions.append($0)
+        }
+        viewModel.interactorEvent(.receivedMessage(.mock(id: messageId)))
+        enum Call {
+            case quickReplyPropsUpdatedHidden
+        }
+        var calls: [Call] = []
+        switch actions[0] {
+        case .quickReplyPropsUpdated(.hidden):
+            calls.append(.quickReplyPropsUpdatedHidden)
+        default:
+            break
+        }
+        XCTAssertEqual(actions.count, 1)
+        XCTAssertEqual(calls, [.quickReplyPropsUpdatedHidden])
+    }
 }
 
 extension ChatChoiceCardOption {