add support for preview images

deltachat-ios/AppDelegate.swift

@@ -323,12 +323,24 @@ extension AppDelegate: UNUserNotificationCenterDelegate {
                     content.userInfo = ui
                     content.sound = .default
 
-                    /*if let url = msg.fileURL,
-                       let attachment = try? UNNotificationAttachment(identifier: Constants.notificationIdentifier, url: url, options: nil) {
-                        content.attachments = [attachment]
-                    }*/
-
-                    let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 3, repeats: false)
+                    if msg.type == DC_MSG_IMAGE || msg.type == DC_MSG_GIF,
+                       let url = msg.fileURL {
+                        do {
+                            // make a copy of the file first since UNNotificationAttachment will move attached files into the attachment data store
+                            // so that they can be accessed by all of the appropriate processes
+                            let tempUrl = url.deletingLastPathComponent()
+                                .appendingPathComponent("notification_tmp")
+                                .appendingPathExtension(url.pathExtension)
+                            try FileManager.default.copyItem(at: url, to: tempUrl)
+                            if let attachment = try? UNNotificationAttachment(identifier: Constants.notificationIdentifier, url: tempUrl, options: nil) {
+                                content.attachments = [attachment]
+                            }
+                        } catch let error {
+                            logger.error("Failed to copy file \(url) for notification preview generation: \(error)")
+                        }
+                    }
+
+                    let trigger = UNTimeIntervalNotificationTrigger(timeInterval: 0.1, repeats: false)
                     let request = UNNotificationRequest(identifier: Constants.notificationIdentifier, content: content, trigger: trigger)
                     UNUserNotificationCenter.current().add(request, withCompletionHandler: nil)
                     DcContext.shared.logger?.info("notifications: added \(content)")