Fetch and thumbnail original media if fetching thumbnail fails

E.g. because the remote server's thumbnail endpoint is broken in
hilarious ways: https://github.com/element-hq/synapse/issues/17518

book/changelog.md

@@ -125,6 +125,9 @@ This will be the first release of Grapevine since it was forked from Conduit
 10. **BREAKING:** Reorganize config into sections.
     ([!49](https://gitlab.computer.surgery/matrix/grapevine-fork/-/merge_requests/49))
     * Details on how to migrate can be found in the merge request's description.
+11. Try to generate thumbnails for remote media ourselves if the federation
+    thumbnail request fails.
+    ([!58](https://gitlab.computer.surgery/matrix/grapevine-fork/-/merge_requests/58))
 
 ### Fixed
 

src/api/client_server/media.rs

@@ -804,6 +804,13 @@ async fn get_content_thumbnail_route_ruma(
         Error::BadRequest(ErrorKind::InvalidParam, "Height is invalid.")
     })?;
 
+    let make_response = |file, content_type| {
+        authenticated_media_client::get_content_thumbnail::v1::Response {
+            file,
+            content_type,
+        }
+    };
+
     if let Some(FileMeta {
         content_type,
         file,
@@ -811,13 +818,10 @@ async fn get_content_thumbnail_route_ruma(
     }) =
         services().media.get_thumbnail(mxc.to_string(), width, height).await?
     {
-        Ok(authenticated_media_client::get_content_thumbnail::v1::Response {
+        return Ok(make_response(file, content_type));
-            file,
+    }
-            content_type,
+
-        })
+    if &*body.server_name != services().globals.server_name() && allow_remote {
-    } else if &*body.server_name != services().globals.server_name()
-        && allow_remote
-    {
         let get_thumbnail_response = get_remote_thumbnail(
             &body.server_name,
             authenticated_media_fed::get_content_thumbnail::v1::Request {
@@ -832,25 +836,50 @@ async fn get_content_thumbnail_route_ruma(
                 animated: Some(false),
             },
         )
-        .await?;
+        .await;
 
+        match get_thumbnail_response {
+            Ok(resp) => {
                 services()
                     .media
                     .upload_thumbnail(
                         mxc.to_string(),
                         None,
-                get_thumbnail_response.content.content_type.as_deref(),
+                        resp.content.content_type.as_deref(),
                         width,
                         height,
-                &get_thumbnail_response.content.file,
+                        &resp.content.file,
                     )
                     .await?;
 
-        Ok(authenticated_media_client::get_content_thumbnail::v1::Response {
+                return Ok(make_response(
-            file: get_thumbnail_response.content.file,
+                    resp.content.file,
-            content_type: get_thumbnail_response.content.content_type,
+                    resp.content.content_type,
-        })
+                ));
-    } else {
+            }
+            Err(error) => warn!(
+                %error,
+                "Failed to fetch thumbnail via federation, trying to fetch \
+                 original media and create thumbnail ourselves"
+            ),
+        }
+
+        get_remote_content(&mxc).await?;
+
+        if let Some(FileMeta {
+            content_type,
+            file,
+            ..
+        }) = services()
+            .media
+            .get_thumbnail(mxc.to_string(), width, height)
+            .await?
+        {
+            return Ok(make_response(file, content_type));
+        }
+
+        error!("Source media doesn't exist even after fetching it from remote");
+    }
+
     Err(Error::BadRequest(ErrorKind::NotYetUploaded, "Media not found."))
 }
-}