streamer/audio: ProbeText now also returns the 'comment' tag

Also implemented a WriteMetadata that writes the given songs metadata
to the file given and returns the new file in-memory.

streamer/audio/ffprobe.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"context"
 	"io"
+	"os"
 	"os/exec"
 	"regexp"
 	"strconv"
@@ -53,13 +54,14 @@ type Info struct {
 	Title      string
 	Artist     string
 	Album      string
+	Comment    string
 	Bitrate    int
 }
 
 var ffprobeTextArgs = []string{
 	"-loglevel", "fatal",
 	"-hide_banner",
-	"-show_entries", "format_tags=title,artist,album:stream_tags=title,artist,album:stream=duration,bit_rate:format=format_name,bit_rate",
+	"-show_entries", "format_tags=title,artist,album,comment:stream_tags=title,artist,album,comment:stream=duration,bit_rate:format=format_name,bit_rate",
 	"-of", "default=noprint_wrappers=1",
 }
 
@@ -77,6 +79,21 @@ func ProbeText(ctx context.Context, filename string) (*Info, error) {
 	return parseProbeText(ctx, bytes.NewReader(out))
 }
 
+func probeText(ctx context.Context, file *os.File) (*Info, error) {
+	const op errors.Op = "streamer/audio.Probe"
+
+	cmd := exec.CommandContext(ctx, "ffprobe",
+		append(ffprobeTextArgs, "-i", "-")...)
+	cmd.Stdin = file
+
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, errors.E(op, err, errors.Info(cmd.String()))
+	}
+
+	return parseProbeText(ctx, bytes.NewReader(out))
+}
+
 func parseProbeText(ctx context.Context, out io.Reader) (*Info, error) {
 	const op errors.Op = "streamer/audio.parseProbeText"
 	var err error
@@ -107,6 +124,8 @@ func parseProbeText(ctx context.Context, out io.Reader) (*Info, error) {
 			info.Artist = value
 		case "album":
 			info.Album = value
+		case "comment":
+			info.Comment = value
 		case "bit_rate":
 			if value != "N/A" { // could not exist
 				info.Bitrate, err = strconv.Atoi(value)

streamer/audio/metadata.go

@@ -0,0 +1,71 @@
+package audio
+
+import (
+	"context"
+	"io"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	radio "github.com/R-a-dio/valkyrie"
+	"github.com/R-a-dio/valkyrie/errors"
+	"github.com/spf13/afero"
+)
+
+// DeleteID3Tags runs `id3v2 --delete-all <filename>` this removes any id3 tags
+// in the file.
+func DeleteID3Tags(ctx context.Context, filename string) {
+	exec.CommandContext(ctx, "id3v2", "--delete-all", filename)
+}
+
+// WithMetadata puts the metadata of song into the file given by filename and returns
+// it as an in-memory file.
+func WriteMetadata(ctx context.Context, f afero.File, song radio.Song) (*MemoryBuffer, error) {
+	const op errors.Op = "streamer/audio.WriteMetadata"
+
+	args := []string{
+		"-hide_banner",
+		"-loglevel", "error",
+		"-i", "-",
+		"-c:a", "copy", // copy audio stream
+		"-id3v2_version", "3", // windows apparently doesn't support v2.4
+	}
+	if song.Title != "" {
+		args = append(args, "-metadata", "title="+song.Title)
+	}
+	if song.Artist != "" {
+		args = append(args, "-metadata", "artist="+song.Artist)
+	}
+	if song.Album != "" {
+		args = append(args, "-metadata", "album="+song.Album)
+	}
+	if song.Tags != "" {
+		args = append(args, "-metadata", "comment="+song.Tags)
+	}
+
+	switch strings.ToLower(filepath.Ext(f.Name())) {
+	case ".flac":
+		args = append(args, "-f", "flac")
+	case ".mp3":
+		args = append(args, "-f", "mp3")
+	case ".ogg":
+		args = append(args, "-f", "ogg")
+	default:
+		return nil, errors.E(op, errors.InvalidArgument)
+	}
+	args = append(args, "-")
+
+	ff, err := newFFmpegCmd("metadata-"+song.TrackID.String(), args)
+	if err != nil {
+		return nil, errors.E(op, err)
+	}
+	ff.Cmd.Stdin = f
+
+	out, err := ff.Run()
+	if err != nil {
+		return nil, errors.E(op, err)
+	}
+	// seek the output to the start
+	_, _ = out.Seek(0, io.SeekStart)
+	return out, nil
+}

streamer/audio/metadata_test.go

@@ -0,0 +1,38 @@
+package audio
+
+import (
+	"context"
+	"testing"
+
+	radio "github.com/R-a-dio/valkyrie"
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWriteMetadata(t *testing.T) {
+	fsys := afero.NewOsFs()
+	f, err := fsys.Open("testdata/MP3_2MG.mp3")
+	require.NoError(t, err)
+
+	song := radio.Song{
+		DatabaseTrack: &radio.DatabaseTrack{
+			Title:  "test",
+			Artist: "some kind of artist",
+			Album:  "a kind of album",
+			Tags:   "test effective very",
+		},
+	}
+
+	out, err := WriteMetadata(context.Background(), f, song)
+	require.NoError(t, err)
+
+	// probe the output file
+	info, err := probeText(context.Background(), out.Memfd.File)
+	require.NoError(t, err)
+
+	assert.Equal(t, song.Title, info.Title)
+	assert.Equal(t, song.Artist, info.Artist)
+	assert.Equal(t, song.Album, info.Album)
+	assert.Equal(t, song.Tags, info.Comment)
+}