refactor: move actual transcoding into own fn

src/main.rs

@@ -1,7 +1,7 @@
 mod config;
 mod ui;
 
-use crate::config::Config;
+use crate::config::{Config, Transcode};
 use anyhow::{Context, Error, Result};
 use futures::{pin_mut, prelude::*};
 use glib::{subclass::prelude::*, GBoxed, GString};
@@ -68,7 +68,7 @@ fn gmake<T: IsA<Element>>(factory_name: &str) -> Result<T> {
 #[derive(Debug, Clone)]
 pub struct ConversionArgs {
     rel_from_path: PathBuf,
-    transcode: config::Transcode,
+    transcode: Transcode,
 }
 
 fn get_conversion_args(config: &Config) -> impl Iterator<Item = Result<ConversionArgs>> + '_ {
@@ -276,25 +276,49 @@ async fn transcode(
     // "whole" files to the intended file path, ignoring partial files in the mtime check
     let to_path_tmp = to_path.with_extension("tmp");
 
-    if let config::Transcode::Copy = args.transcode {
     rm_file_on_err(&to_path_tmp, async {
+        match args.transcode {
+            Transcode::Copy => {
                 fs::copy(&from_path, &to_path_tmp).await.with_context(|| {
                     format!(
                         "could not copy file from {} to {}",
                         from_path.display(),
                         to_path_tmp.display()
                     )
-            })
-        })
-        .await?;
-
-        fs::rename(&to_path_tmp, &to_path).await?;
-
-        return Ok(());
+                })?;
             }
-
+            _ => {
                 to_path.set_extension(args.transcode.extension());
 
+                transcode_gstreamer(
+                    &from_path,
+                    &to_path_tmp,
+                    args.transcode.clone(),
+                    task_id,
+                    queue,
+                )
+                .await?
+            }
+        }
+
+        fs::rename(&to_path_tmp, &to_path).await.with_context(|| {
+            format!(
+                "could not rename temporary file {} to {}",
+                to_path_tmp.display(),
+                to_path.display()
+            )
+        })
+    })
+    .await
+}
+
+async fn transcode_gstreamer(
+    from_path: &Path,
+    to_path: &Path,
+    transcode: Transcode,
+    task_id: usize,
+    queue: &ui::MsgQueue,
+) -> Result<()> {
     let file_src: Element = gmake("filesrc")?;
     file_src.set_property("location", &path_to_gstring(&from_path))?;
 
@@ -310,10 +334,7 @@ async fn transcode(
     // downgrade pipeline RC to a weak RC to break the reference cycle
     let pipeline_weak = pipeline.downgrade();
 
-    let transcode_args = args.transcode.clone();
-
-    let to_path_tmp_clone = to_path_tmp.clone();
-
+    let to_path_clone = to_path.to_owned();
     decodebin.connect_pad_added(move |decodebin, src_pad| {
         let insert_sink = || -> Result<()> {
             let pipeline = match pipeline_weak.upgrade() {
@@ -354,8 +375,8 @@ async fn transcode(
                 gmake("audioconvert")?,
             ];
 
-            match &transcode_args {
-                config::Transcode::Opus {
+            match &transcode {
+                Transcode::Opus {
                     bitrate,
                     bitrate_type,
                 } => {
@@ -378,13 +399,13 @@ async fn transcode(
                     dest_elems.push(gmake("oggmux")?);
                 }
 
-                config::Transcode::Flac { compression } => {
+                Transcode::Flac { compression } => {
                     let encoder: Element = gmake("flacenc")?;
                     encoder.set_property_from_str("quality", &compression.to_string());
                     dest_elems.push(encoder);
                 }
 
-                config::Transcode::Mp3 {
+                Transcode::Mp3 {
                     bitrate,
                     bitrate_type,
                 } => {
@@ -404,11 +425,14 @@ async fn transcode(
                     dest_elems.push(gmake("id3v2mux")?);
                 }
 
-                config::Transcode::Copy => unreachable!(),
+                Transcode::Copy => {
+                    // already handled outside this fn
+                    unreachable!();
+                }
             };
 
             let file_dest: gstreamer_base::BaseSink = gmake("filesink")?;
-            file_dest.set_property("location", &path_to_gstring(&to_path_tmp_clone))?;
+            file_dest.set_property("location", &path_to_gstring(&to_path_clone))?;
             file_dest.set_sync(false);
             dest_elems.push(file_dest.upcast());
 
@@ -446,7 +470,6 @@ async fn transcode(
 
     let bus = pipeline.get_bus().context("pipe get bus")?;
 
-    rm_file_on_err(&to_path_tmp, async {
     pipeline
         .set_state(gstreamer::State::Playing)
         .context("Unable to set the pipeline to the `Playing` state")?;
@@ -560,11 +583,7 @@ async fn transcode(
         .set_state(gstreamer::State::Null)
         .context("Unable to set the pipeline to the `Null` state")?;
 
-        fs::rename(&to_path_tmp, &to_path).await?;
-
     Ok(())
-    })
-    .await
 }
 
 async fn rm_file_on_err<F, T>(path: &Path, f: F) -> Result<T>