move media file read/write logic to a helper function

src/service/media.rs

@@ -63,9 +63,7 @@ impl Service {
         // Width, Height = 0 if it's not a thumbnail
         let key = self.db.create_file_metadata(mxc, 0, 0, &meta)?;
 
-        let path = services().globals.get_media_file(&key);
-        let mut f = File::create(path).await?;
-        f.write_all(file).await?;
+        self.write_content(&key, file).await?;
         Ok(meta)
     }
 
@@ -86,10 +84,7 @@ impl Service {
         };
         let key = self.db.create_file_metadata(mxc, width, height, &meta)?;
 
-        let path = services().globals.get_media_file(&key);
-        let mut f = File::create(path).await?;
-        f.write_all(file).await?;
-
+        self.write_content(&key, file).await?;
         Ok(meta)
     }
 
@@ -100,15 +95,7 @@ impl Service {
         mxc: OwnedMxcUri,
     ) -> Result<Option<(FileMeta, Vec<u8>)>> {
         if let Some((meta, key)) = self.db.search_file_metadata(mxc, 0, 0)? {
-            let path = services().globals.get_media_file(&key);
-            let mut file_data = Vec::new();
-            let Ok(mut file) = File::open(path).await else {
-                return Ok(None);
-            };
-
-            file.read_to_end(&mut file_data).await?;
-
-            Ok(Some((meta, file_data)))
+            Ok(self.read_content(&key).await?.map(|data| (meta, data)))
         } else {
             Ok(None)
         }
@@ -370,11 +357,48 @@ impl Service {
         // again next time
         let thumbnail_key =
             self.db.create_file_metadata(mxc, width, height, &meta)?;
-
-        let path = services().globals.get_media_file(&thumbnail_key);
-        let mut f = File::create(path).await?;
-        f.write_all(&thumbnail_bytes).await?;
+        self.write_content(&thumbnail_key, &thumbnail_bytes).await?;
 
         Ok(Some((meta, thumbnail_bytes.clone())))
     }
+
+    /// Writes contents for a media file to the fs.
+    ///
+    /// If a file already existed with the specified key, it is replaced.
+    async fn write_content(
+        &self,
+        key: &MediaFileKey,
+        data: &[u8],
+    ) -> Result<()> {
+        let path = services().globals.get_media_file(key);
+        let mut file = File::create(path).await?;
+
+        file.write_all(data).await?;
+
+        Ok(())
+    }
+
+    /// Returns the contents of a media file, read from the fs.
+    ///
+    /// If the file cannot be opened, returns `Ok(None)`. This is needed because
+    /// before media deletion admin commands were implemented, the only way to
+    /// delete abuse media was to remove the associated files from the fs. This
+    /// leaves the db in an inconsistent state, where media keys exist in the db
+    /// but their content files do not. We want to return `M_NOT_YET_UPLOADED`
+    /// in this case rather than the `M_UNKNOWN` we would normally use for db
+    /// consistency problems.
+    async fn read_content(
+        &self,
+        key: &MediaFileKey,
+    ) -> Result<Option<Vec<u8>>> {
+        let path = services().globals.get_media_file(key);
+        let Ok(mut file) = File::open(path).await else {
+            return Ok(None);
+        };
+
+        let mut data = Vec::new();
+        file.read_to_end(&mut data).await?;
+
+        Ok(Some(data))
+    }
 }