rework ytdlp in terms of start/wait, fix audio transcode error

ytdlp/ytdlp.go

@@ -2,25 +2,66 @@ package ytdlp
 
 import (
 	"bytes"
+	"context"
 	"os/exec"
 	"strings"
 )
 
 // runs ffprobe with the provided args and returns (stdout, stderr, error)
 func Run(args ...string) ([]byte, []byte, error) {
-	ytdlp := "yt-dlp"
-	log.Infoln(ytdlp, strings.Join(args, " "))
-	cmd := exec.Command(ytdlp, args...)
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	cmd.Stdout = &stdout
-	cmd.Stderr = &stderr
-	err := cmd.Run()
-
+	cmd, cancel, err := Start(args...)
+	defer cancel()
 	if err != nil {
-		log.Errorf("yt-dlp error: %v", err)
+		return nil, nil, err
 	}
-	log.Infoln("stdout:", stdout.String())
-	log.Infoln("stderr:", stderr.String())
-	return stdout.Bytes(), stderr.Bytes(), err
+	return cmd.Wait()
+}
+
+type Cmd struct {
+	ctx context.Context
+	cmd *exec.Cmd
+
+	stdout *bytes.Buffer
+	stderr *bytes.Buffer
+}
+
+func Start(args ...string) (*Cmd, context.CancelFunc, error) {
+
+	ytdlp := "yt-dlp"
+	stdout := new(bytes.Buffer)
+	stderr := new(bytes.Buffer)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cmd := exec.CommandContext(ctx, ytdlp, args...)
+	cmd.Stdout = stdout
+	cmd.Stderr = stderr
+
+	log.Infoln(ytdlp, strings.Join(args, " "))
+	err := cmd.Start()
+	if err != nil {
+		return nil, cancel, err // FIXME: okay to just return this cancel thing?
+	}
+
+	return &Cmd{
+		ctx:    ctx,
+		cmd:    cmd,
+		stdout: stdout,
+		stderr: stderr,
+	}, cancel, nil
+}
+
+func (c *Cmd) Wait() ([]byte, []byte, error) {
+	err := c.cmd.Wait()
+	if err != nil {
+		if c.ctx.Err() == context.Canceled {
+			log.Debugln("command canceled")
+		} else {
+			log.Errorln("yt-dlp error", err)
+		}
+	} else {
+		log.Infoln("stdout:", c.stdout.String())
+		log.Infoln("stderr:", c.stderr.String())
+	}
+
+	return c.stdout.Bytes(), c.stderr.Bytes(), err
 }