add support for sending media

Still needs camera support.

lib/controllers/attachment.dart

@@ -0,0 +1,41 @@
+import "package:file_selector/file_selector.dart";
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:nexus/controllers/client.dart";
+import "package:nexus/controllers/rooms.dart";
+import "package:nexus/models/content/content.dart";
+import "package:nexus/models/content/message.dart";
+import "package:path/path.dart";
+
+class AttachmentController extends Notifier<(String, MessageContent?)?> {
+  final String roomId;
+  AttachmentController(this.roomId);
+
+  @override
+  Null build() => null;
+
+  Future<void> add(XFile file) async {
+    final filename = basename(file.path);
+    state = (filename, null);
+
+    final room = ref.watch(
+      RoomsController.provider.select((value) => value[roomId]),
+    );
+
+    final content = await ref
+        .watch(ClientController.provider.notifier)
+        .uploadMedia(
+          .new(
+            path: file.path,
+            encrypted:
+                room?.state[EventType.encryption.name]?.isNotEmpty == true,
+          ),
+        );
+
+    state = (filename, content);
+  }
+
+  static final provider = NotifierProvider.family
+      .autoDispose<AttachmentController, (String, MessageContent?)?, String>(
+        AttachmentController.new,
+      );
+}

lib/controllers/client.dart

@@ -14,6 +14,7 @@ import "package:nexus/controllers/sync_status.dart";
 import "package:nexus/controllers/top_level_spaces.dart";
 import "package:nexus/helpers/extensions/gomuks_buffer.dart";
 import "package:nexus/main.dart";
+import "package:nexus/models/content/message.dart";
 import "package:nexus/models/event.dart";
 import "package:nexus/models/oauth_auth_code_response.dart";
 import "package:nexus/models/paginate.dart";
@@ -32,6 +33,7 @@ import "package:nexus/models/requests/send_event.dart";
 import "package:nexus/models/requests/send_message.dart";
 import "package:nexus/models/requests/set_membership.dart";
 import "package:nexus/models/requests/set_state.dart";
+import "package:nexus/models/requests/upload_media.dart";
 import "package:nexus/models/room.dart";
 import "package:nexus/models/sync_data.dart";
 import "package:nexus/src/third_party/gomuks.g.dart";
@@ -266,6 +268,9 @@ class ClientController extends AsyncNotifier<int> {
   Future<void> setMembership(SetMembershipRequest request) =>
       _sendCommand("set_membership", request.toJson());
 
+  Future<MessageContent> uploadMedia(UploadMediaRequest request) async =>
+      .fromJson(await _sendCommand("upload_media", request.toJson()));
+
   Future<void> logout() => _sendCommand("logout");
 
   Future<void> markRead(Room room) async {

lib/controllers/image_picker.dart

@@ -0,0 +1,11 @@
+import "package:flutter_riverpod/flutter_riverpod.dart";
+import "package:image_picker/image_picker.dart";
+
+class ImagePickerController extends Notifier<ImagePicker> {
+  @override
+  ImagePicker build() => .new();
+
+  static final provider = NotifierProvider<ImagePickerController, ImagePicker>(
+    ImagePickerController.new,
+  );
+}

lib/controllers/room_chat.dart

@@ -4,6 +4,7 @@ import "package:collection/collection.dart";
 import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:flutter_riverpod/flutter_riverpod.dart";
 import "package:fluttertagger/fluttertagger.dart";
+import "package:nexus/controllers/attachment.dart";
 import "package:nexus/controllers/client.dart";
 import "package:nexus/controllers/rooms.dart";
 import "package:nexus/models/content/content.dart";
@@ -120,6 +121,10 @@ class RoomChatController extends AsyncNotifier<IList<Event>?> {
     required RelationType relationType,
     Event? relation,
   }) async {
+    final attachment = ref.watch(AttachmentController.provider(roomId));
+
+    if (attachment != null && attachment.$2 == null) return;
+
     var taggedMessage = text;
 
     for (final tag in tags) {
@@ -136,6 +141,7 @@ class RoomChatController extends AsyncNotifier<IList<Event>?> {
     final event = await client.sendMessage(
       SendMessageRequest(
         roomId: roomId,
+        baseContent: attachment?.$2,
         mentions: Mentions(
           userIds: [
             if (shouldMention == true &&
@@ -152,6 +158,8 @@ class RoomChatController extends AsyncNotifier<IList<Event>?> {
       ),
     );
 
+    ref.invalidate(AttachmentController.provider(roomId));
+
     ref
         .watch(RoomsController.provider.notifier)
         .update(