feat: Refresh app in the background

Mail/Helpers/AppAssembly.swift

@@ -132,6 +132,9 @@ enum ApplicationAssembly {
                     contactCache.countLimit = Constants.contactCacheExtensionMaxCount
                 }
                 return contactCache
+            },
+            Factory(type: RefreshAppBackgroundTask.self) { _, _ in
+                RefreshAppBackgroundTask()
             }
         ]
 

Mail/MailApp.swift

@@ -36,6 +36,7 @@ struct MailApp: App {
     @LazyInjectService private var appLockHelper: AppLockHelper
     @LazyInjectService private var accountManager: AccountManager
     @LazyInjectService private var appLaunchCounter: AppLaunchCounter
+    @LazyInjectService private var refreshAppBackgroundTask: RefreshAppBackgroundTask
 
     @UIApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
 
@@ -49,6 +50,7 @@ struct MailApp: App {
 
     init() {
         DDLogInfo("Application starting in foreground ? \(UIApplication.shared.applicationState != .background)")
+        refreshAppBackgroundTask.register()
     }
 
     var body: some Scene {
@@ -74,6 +76,7 @@ struct MailApp: App {
                         navigationState.transitionToLockViewIfNeeded()
                         UserDefaults.shared.openingUntilReview -= 1
                     case .background:
+                        refreshAppBackgroundTask.scheduleForBackgroundLaunchIfNeeded()
                         if UserDefaults.shared.isAppLockEnabled && navigationState.state != .appLocked {
                             appLockHelper.setTime()
                         }

MailCore/Cache/RefreshAppBackgroundTask.swift

@@ -0,0 +1,101 @@
+/*
+ Infomaniak Mail - iOS App
+ Copyright (C) 2022 Infomaniak Network SA
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+import BackgroundTasks
+import CocoaLumberjackSwift
+import Foundation
+import InfomaniakDI
+import SwiftUI
+
+/// A type that represents a [task that can be executed in the background](https://developer.apple.com/documentation/uikit/app_and_environment/scenes/preparing_your_ui_to_run_in_the_background/using_background_tasks_to_update_your_app)
+public protocol BackgroundTaskable {
+    /// Schedule the task for next background launch, only if needed
+    func scheduleForBackgroundLaunchIfNeeded()
+
+    /// Schedule the task for next background launch
+    func scheduleForBackgroundLaunch()
+
+    /// Ask the system to register the task
+    func register()
+
+    /// The method that actually executes when background task is called
+    func run() async
+}
+
+public class RefreshAppBackgroundTask: BackgroundTaskable {
+    let backgroundTaskIdentifier = "com.infomaniak.mail.background-refresh"
+
+    @LazyInjectService var accountManager: AccountManager
+
+    public init() {
+        // Exposed for DI
+    }
+
+    public func scheduleForBackgroundLaunchIfNeeded() {
+        guard !accountManager.accounts.isEmpty else { return }
+        scheduleForBackgroundLaunch()
+    }
+
+    public func scheduleForBackgroundLaunch() {
+        let request = BGAppRefreshTaskRequest(identifier: backgroundTaskIdentifier)
+        // Fetch no earlier than 15 minutes from now
+        request.earliestBeginDate = Date(timeIntervalSinceNow: 15 * 60)
+
+        do {
+            try BGTaskScheduler.shared.submit(request)
+        } catch {
+            DDLogError("Could not schedule app refresh: \(error)")
+        }
+    }
+
+    public func run() async {
+        guard let currentMailboxManager = accountManager.currentMailboxManager,
+              let inboxFolder = currentMailboxManager.getFolder(with: .inbox),
+              inboxFolder.cursor != nil else {
+            // We do nothing if we don't have an initial cursor
+            BGTaskScheduler.shared.cancelAllTaskRequests()
+            return
+        }
+
+        // Every time we execute a task we schedule a new task for next time
+        scheduleForBackgroundLaunch()
+
+        await currentMailboxManager.refreshFolderContent(inboxFolder.freezeIfNeeded())
+
+        await NotificationsHelper.clearAlreadyReadNotifications()
+
+        await NotificationsHelper.updateUnreadCountBadge()
+    }
+
+    @available(iOS, deprecated: 16, message: "Use Scene.backgroundTask")
+    public func register() {
+        BGTaskScheduler.shared
+            .register(forTaskWithIdentifier: backgroundTaskIdentifier, using: nil) { task in
+                guard let refreshTask = task as? BGAppRefreshTask else { return }
+
+                let handleAppRefresh = Task {
+                    await self.run()
+                    refreshTask.setTaskCompleted(success: true)
+                }
+
+                refreshTask.expirationHandler = {
+                    handleAppRefresh.cancel()
+                }
+            }
+    }
+}