From 21871a387cbf1dc9a8355cc9c7ddf9605cb62321 Mon Sep 17 00:00:00 2001
From: Yonah <contrib@gensokyo.uk>
Date: Thu, 18 Sep 2025 06:06:46 +0900
Subject: [PATCH] generic: return content length alongside body

This increases efficiency for bigger response bodies.

Signed-off-by: Yonah <contrib@gensokyo.uk>
---
 cmd/msrfetch/net.go |  8 ++++----
 generic.go          |  2 +-
 song.go             |  2 +-
 song_test.go        | 14 +++++++-------
 4 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/cmd/msrfetch/net.go b/cmd/msrfetch/net.go
index 47022e8..805f22c 100644
--- a/cmd/msrfetch/net.go
+++ b/cmd/msrfetch/net.go
@@ -10,12 +10,12 @@ type netDirect struct {
 	c http.Client
 }
 
-func (n *netDirect) Get(ctx context.Context, url string) (io.ReadCloser, error) {
+func (n *netDirect) Get(ctx context.Context, url string) (io.ReadCloser, int64, error) {
 	var resp *http.Response
 	if req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil); err != nil {
-		return nil, err
+		return nil, -2, err
 	} else if resp, err = n.c.Do(req); err != nil {
-		return nil, err
+		return nil, -2, err
 	}
-	return resp.Body, nil
+	return resp.Body, resp.ContentLength, nil
 }
diff --git a/generic.go b/generic.go
index 2df3c4c..91dacf2 100644
--- a/generic.go
+++ b/generic.go
@@ -16,7 +16,7 @@ const (
 type Net interface {
 	// Get makes a get request to url and returns the response body.
 	// The caller must close the body after it finishes reading from it.
-	Get(ctx context.Context, url string) (body io.ReadCloser, err error)
+	Get(ctx context.Context, url string) (body io.ReadCloser, contentLength int64, err error)
 }
 
 // Response is a generic API response.
diff --git a/song.go b/song.go
index 1c0ad35..9d3ec94 100644
--- a/song.go
+++ b/song.go
@@ -47,7 +47,7 @@ func (s *Song) Enrich(ctx context.Context, n Net) error {
 	}
 
 	var v SongResponse
-	if body, err := n.Get(ctx, APIPrefix+"/song/"+s.CID.String()); err != nil {
+	if body, _, err := n.Get(ctx, APIPrefix+"/song/"+s.CID.String()); err != nil {
 		return err
 	} else {
 		if err = json.NewDecoder(body).Decode(&v); err != nil {
diff --git a/song_test.go b/song_test.go
index 83f1dbb..1909326 100644
--- a/song_test.go
+++ b/song_test.go
@@ -168,22 +168,22 @@ func TestSongEnrich(t *testing.T) {
 
 type stubNetSongEnrichErrorCloser stubNetSongEnrich
 
-func (n stubNetSongEnrichErrorCloser) Get(ctx context.Context, url string) (io.ReadCloser, error) {
-	r, err := stubNetSongEnrich(n).Get(ctx, url)
+func (n stubNetSongEnrichErrorCloser) Get(ctx context.Context, url string) (io.ReadCloser, int64, error) {
+	r, l, err := stubNetSongEnrich(n).Get(ctx, url)
 	if r != nil {
 		r = errorCloser{r}
 	}
-	return r, err
+	return r, l, err
 }
 
 type stubNetSongEnrich map[StringInt][]byte
 
-func (n stubNetSongEnrich) Get(_ context.Context, url string) (io.ReadCloser, error) {
+func (n stubNetSongEnrich) Get(_ context.Context, url string) (io.ReadCloser, int64, error) {
 	if i, err := strconv.Atoi(strings.TrimPrefix(url, APIPrefix+"/song/")); err != nil {
-		return nil, err
+		return nil, -2, err
 	} else if b, ok := n[StringInt(i)]; !ok {
-		return nil, fmt.Errorf("song cid %d requested, but is not present", i)
+		return nil, -2, fmt.Errorf("song cid %d requested, but is not present", i)
 	} else {
-		return nopCloser{bytes.NewReader(b)}, nil
+		return nopCloser{bytes.NewReader(b)}, int64(len(b)), nil
 	}
 }