feat: Store sending attachment in temporary file storage

This could make retrying to send
files more easy as the file is
stored in the file storage.

This just replaces the current approach to store
the file in the memory instead so they are gone
on the next session.
For this we need a deleteFile() method for the
database.

lib/src/event.dart

@@ -420,12 +420,29 @@ class Event extends MatrixEvent {
       MessageTypes.Audio,
       MessageTypes.File,
     }.contains(messageType)) {
-      final file = room.sendingFilePlaceholders[eventId];
+      final bytes = await room.client.database?.getFile(
+        Uri.parse('com.famedly.sendingAttachment://file/$eventId'),
+      );
+      final file = bytes == null
+          ? null
+          : MatrixFile(
+              bytes: bytes,
+              name: content.tryGet<String>('filename') ?? 'image',
+            );
       if (file == null) {
         await cancelSend();
         throw Exception('Can not try to send again. File is no longer cached.');
       }
-      final thumbnail = room.sendingFileThumbnails[eventId];
+      final thumbnailBytes = await room.client.database?.getFile(
+        Uri.parse('com.famedly.sendingAttachment://thumbnail/$txid'),
+      );
+      final thumbnail = thumbnailBytes == null
+          ? null
+          : MatrixImageFile(
+              bytes: thumbnailBytes,
+              name:
+                  'thumbnail_${content.tryGet<String>('filename') ?? 'image'}',
+            );
       final credentials = FileSendRequestCredentials.fromJson(unsigned ?? {});
       final inReplyTo = credentials.inReplyTo == null
           ? null
@@ -708,7 +725,15 @@ class Event extends MatrixEvent {
       throw ("This event has the type '$type' and so it can't contain an attachment.");
     }
     if (status.isSending) {
-      final localFile = room.sendingFilePlaceholders[eventId];
+      final bytes = await room.client.database?.getFile(
+        Uri.parse('com.famedly.sendingAttachment://file/$eventId'),
+      );
+      final localFile = bytes == null
+          ? null
+          : MatrixImageFile(
+              bytes: bytes,
+              name: content.tryGet<String>('filename') ?? 'image',
+            );
       if (localFile != null) return localFile;
     }
     final database = room.client.database;

lib/src/room.dart

@@ -687,9 +687,6 @@ class Room {
     return sendEvent(event, txid: txid);
   }
 
-  final Map<String, MatrixFile> sendingFilePlaceholders = {};
-  final Map<String, MatrixImageFile> sendingFileThumbnails = {};
-
   /// Sends a [file] to this room after uploading it. Returns the mxc uri of
   /// the uploaded file. If [waitUntilSent] is true, the future will wait until
   /// the message event has received the server. Otherwise the future will only
@@ -713,10 +710,6 @@ class Room {
     String? threadLastEventId,
   }) async {
     txid ??= client.generateUniqueTransactionId();
-    sendingFilePlaceholders[txid] = file;
-    if (thumbnail != null) {
-      sendingFileThumbnails[txid] = thumbnail;
-    }
 
     // Create a fake Event object as a placeholder for the uploading file:
     final syncUpdate = SyncUpdate(
@@ -753,6 +746,22 @@ class Room {
         },
       ),
     );
+    await _handleFakeSync(syncUpdate);
+
+    if (client.database?.supportsFileStoring == true) {
+      await client.database?.storeFile(
+        Uri.parse('com.famedly.sendingAttachment://file/$txid'),
+        file.bytes,
+        DateTime.now().millisecondsSinceEpoch,
+      );
+      if (thumbnail != null) {
+        await client.database?.storeFile(
+          Uri.parse('com.famedly.sendingAttachment://thumbnail/$txid'),
+          file.bytes,
+          DateTime.now().millisecondsSinceEpoch,
+        );
+      }
+    }
 
     MatrixFile uploadFile = file; // ignore: omit_local_variable_types
     // computing the thumbnail in case we can
@@ -838,12 +847,22 @@ class Room {
         syncUpdate.rooms!.join!.values.first.timeline!.events!.first
             .unsigned![messageSendingStatusKey] = EventStatus.error.intValue;
         await _handleFakeSync(syncUpdate);
+
+        if (client.database?.supportsFileStoring != true) {
+          final sendEvent = await getEventById(txid);
+          await sendEvent?.cancelSend();
+        }
         rethrow;
       } catch (_) {
         if (DateTime.now().isAfter(timeoutDate)) {
           syncUpdate.rooms!.join!.values.first.timeline!.events!.first
               .unsigned![messageSendingStatusKey] = EventStatus.error.intValue;
           await _handleFakeSync(syncUpdate);
+
+          if (client.database?.supportsFileStoring != true) {
+            final sendEvent = await getEventById(txid);
+            await sendEvent?.cancelSend();
+          }
           rethrow;
         }
         Logs().v('Send File into room failed. Try again...');
@@ -907,8 +926,13 @@ class Room {
       threadRootEventId: threadRootEventId,
       threadLastEventId: threadLastEventId,
     );
-    sendingFilePlaceholders.remove(txid);
-    sendingFileThumbnails.remove(txid);
+    await client.database?.deleteFile(
+      Uri.parse('com.famedly.sendingAttachment://file/$txid'),
+    );
+    await client.database?.deleteFile(
+      Uri.parse('com.famedly.sendingAttachment://thumbnail/$txid'),
+    );
+
     return eventId;
   }