fix: Correct message viewtype before recoding image blob (#5496)

Otherwise, e.g. if a message is a large GIF, but its viewtype is set to `Image` by the app, this GIF
will be recoded to JPEG to reduce its size. GIFs and other special viewtypes must be always detected
and sent as is.

src/blob.rs

@@ -1330,6 +1330,42 @@ mod tests {
         Ok(img)
     }
 
+    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+    async fn test_send_big_gif_as_image() -> Result<()> {
+        let bytes = include_bytes!("../test-data/image/screenshot.gif");
+        let (width, height) = (1920u32, 1080u32);
+        let alice = TestContext::new_alice().await;
+        let bob = TestContext::new_bob().await;
+        alice
+            .set_config(
+                Config::MediaQuality,
+                Some(&(MediaQuality::Worse as i32).to_string()),
+            )
+            .await?;
+        let file = alice.get_blobdir().join("file").with_extension("gif");
+        fs::write(&file, &bytes)
+            .await
+            .context("failed to write file")?;
+        let mut msg = Message::new(Viewtype::Image);
+        msg.set_file(file.to_str().unwrap(), None);
+        let chat = alice.create_chat(&bob).await;
+        let sent = alice.send_msg(chat.id, &mut msg).await;
+        let bob_msg = bob.recv_msg(&sent).await;
+        // DC must detect the image as GIF and send it w/o reencoding.
+        assert_eq!(bob_msg.get_viewtype(), Viewtype::Gif);
+        assert_eq!(bob_msg.get_width() as u32, width);
+        assert_eq!(bob_msg.get_height() as u32, height);
+        let file_saved = bob
+            .get_blobdir()
+            .join("saved-".to_string() + &bob_msg.get_filename().unwrap());
+        bob_msg.save_file(&bob, &file_saved).await?;
+        let blob = BlobObject::new_from_path(&bob, &file_saved).await?;
+        let (file_size, _) = blob.metadata()?;
+        assert_eq!(file_size, bytes.len() as u64);
+        check_image_size(file_saved, width, height);
+        Ok(())
+    }
+
     #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
     async fn test_increation_in_blobdir() -> Result<()> {
         let t = TestContext::new_alice().await;

src/chat.rs

@@ -2505,36 +2505,14 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
             .await?
             .with_context(|| format!("attachment missing for message of type #{}", msg.viewtype))?;
 
-        let mut maybe_sticker = msg.viewtype == Viewtype::Sticker;
-        if msg.viewtype == Viewtype::Image
-            || maybe_sticker && !msg.param.exists(Param::ForceSticker)
-        {
-            blob.recode_to_image_size(context, &mut maybe_sticker)
-                .await?;
-
-            if !maybe_sticker {
-                msg.viewtype = Viewtype::Image;
-            }
-        }
-        msg.param.set(Param::File, blob.as_name());
-        if let (Some(filename), Some(blob_ext)) = (msg.param.get(Param::Filename), blob.suffix()) {
-            let stem = match filename.rsplit_once('.') {
-                Some((stem, _)) => stem,
-                None => filename,
-            };
-            msg.param
-                .set(Param::Filename, stem.to_string() + "." + blob_ext);
-        }
-
         if msg.viewtype == Viewtype::File || msg.viewtype == Viewtype::Image {
             // Correct the type, take care not to correct already very special
             // formats as GIF or VOICE.
             //
             // Typical conversions:
             // - from FILE to AUDIO/VIDEO/IMAGE
             // - from FILE/IMAGE to GIF */
-            if let Some((better_type, better_mime)) =
-                message::guess_msgtype_from_suffix(&blob.to_abs_path())
+            if let Some((better_type, _)) = message::guess_msgtype_from_suffix(&blob.to_abs_path())
             {
                 if better_type != Viewtype::Webxdc
                     || context
@@ -2543,9 +2521,6 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
                         .is_ok()
                 {
                     msg.viewtype = better_type;
-                    if !msg.param.exists(Param::MimeType) {
-                        msg.param.set(Param::MimeType, better_mime);
-                    }
                 }
             }
         } else if msg.viewtype == Viewtype::Webxdc {
@@ -2554,6 +2529,27 @@ async fn prepare_msg_blob(context: &Context, msg: &mut Message) -> Result<()> {
                 .await?;
         }
 
+        let mut maybe_sticker = msg.viewtype == Viewtype::Sticker;
+        if msg.viewtype == Viewtype::Image
+            || maybe_sticker && !msg.param.exists(Param::ForceSticker)
+        {
+            blob.recode_to_image_size(context, &mut maybe_sticker)
+                .await?;
+
+            if !maybe_sticker {
+                msg.viewtype = Viewtype::Image;
+            }
+        }
+        msg.param.set(Param::File, blob.as_name());
+        if let (Some(filename), Some(blob_ext)) = (msg.param.get(Param::Filename), blob.suffix()) {
+            let stem = match filename.rsplit_once('.') {
+                Some((stem, _)) => stem,
+                None => filename,
+            };
+            msg.param
+                .set(Param::Filename, stem.to_string() + "." + blob_ext);
+        }
+
         if !msg.param.exists(Param::MimeType) {
             if let Some((_, mime)) = message::guess_msgtype_from_suffix(&blob.to_abs_path()) {
                 msg.param.set(Param::MimeType, mime);