Add mastodon posting

bin/server.dart

@@ -5,10 +5,18 @@ import 'package:shelf/shelf.dart';
 import 'package:shelf/shelf_io.dart';
 import 'package:shelf_router/shelf_router.dart';
 
+import 'package:dio/dio.dart' as dio_lib;
+
+var dio = dio_lib.Dio();
+
 // Load confirmation token from env
 final confirmationToken = Platform.environment['CONFIRMATION_TOKEN'];
 // Load secret key from env
 final secretKey = Platform.environment['SECRET_KEY'];
+// Load mastodon instance url from env
+final instanceUrl = Platform.environment['INSTANCE_URL'];
+// Load mastodon auth token from env
+final authToken = Platform.environment['MASTODON_TOKEN'];
 
 // Configure routes.
 final _router = Router()
@@ -38,6 +46,7 @@ Future<Response> _vkHandler(Request req) async {
   } else if (requestType == 'wall_post_new') {
     if (requestJson['secret'] == secretKey) {
       print(requestBody);
+      _postOnMastodon(requestJson);
       return Response.ok('ok');
     } else {
       return Response.ok('invalid secret');
@@ -47,16 +56,76 @@ Future<Response> _vkHandler(Request req) async {
   }
 }
 
-// Future<void> _postOnMastodon(reqJson) async {
-//   // Called to repost the post on Mastodon on vk.
-//   // reqJson contains the 'object' field of the VK post.
-//   // This object has the 'text' field with the post text.
-//   // Also it contains the 'attachments' field with the attachments.
-//   // The attachments field is an array of objects.
-// }
+Future<void> _postOnMastodon(reqJson) async {
+  // Called to repost the post on Mastodon on vk.
+  // reqJson contains the 'object' field of the VK post.
+  // This object has the 'text' field with the post text.
+  // Also it contains the 'attachments' field with the attachments.
+  // The attachments field is an array of objects.
+  // Each object has the 'type' field with the attachment type.
+  // We only want to post photos.
+  // The 'photo' type is 'photo'.
+  // The 'photo' type has the 'sizes' field with an array of objects.
+  // Each object has the 'url', 'height' and 'width' fields.
+  // We want to post the largest photo.
+  // The 'url' field is the url of the photo.
+  // The 'height' and 'width' fields are the height and width of the photo.
+  // We download all pictures with dio into a temporary directory.
+
+  final postText = reqJson['object']['text'] ?? '';
+
+  final attachments = reqJson['object']['attachments'];
+  final photos =
+      attachments.where((attachment) => attachment['type'] == 'photo');
+
+  final photoUrls = photos.map((photo) {
+    final photoUrl = photo['photo']['sizes'].last['url'];
+    final photoPath =
+        '${Directory.systemTemp.path}/${photoUrl.split('/').last}';
+    dio.download(photoUrl, photoPath);
+    return photoPath;
+  });
+
+  // Post the post on Mastodon.
+  // First we upload all photos with dio.
+  // Then we post the post with the uploaded photos and the text.
+  // We delete the photos after posting.
+  // Photos are uploaded to POST <instanceUrl>/api/v1/media in the 'file' form data field.
+  // We take the 'id' field of the response and add it to the post's 'media_ids' field.
+  // The 'media_ids' field is an array of media ids.
+  // We post the post with the media ids and the text in the 'status' field.
+  // Endpoint: POST <instanceUrl>/api/v1/statuses
+  // Headers: Authorization: Bearer <authToken>
+  // We use auth on all requests.
+
+  // if there are no photos, we don't fetch them
+  if (photos.isEmpty) {
+    await dio.post('$instanceUrl/api/v1/statuses',
+        data: {'status': postText},
+        options: dio_lib.Options(headers: {'Authorization': 'Bearer $authToken'}));
+  } else {
+    final mediaResponses = await Future.wait(
+        photoUrls.map((photoUrl) => dio.post('$instanceUrl/api/v1/media',
+            data: dio_lib.FormData.fromMap({'file': File(photoUrl)}),
+            options: dio_lib.Options(headers: {'Authorization': 'Bearer $authToken'}))));
+
+    final mediaIds = mediaResponses.map((mediaResponse) {
+      final mediaId = mediaResponse.data['id'];
+      return mediaId;
+    }).toList();
+
+    await dio.post('$instanceUrl/api/v1/statuses',
+        data: {
+          'status': postText,
+          'media_ids': mediaIds
+        },
+        options: dio_lib.Options(headers: {'Authorization': 'Bearer $authToken'}));
+
+    await Future.wait(photoUrls.map((photoUrl) => File(photoUrl).delete()));
+  }
+}
 
 void main(List<String> args) async {
-  
   // Use any available host or container IP (usually `0.0.0.0`).
   final ip = InternetAddress.anyIPv4;