Improve logging around album art management

mpd-web-proxy/cmd/main.go

@@ -53,7 +53,7 @@ func (s *Server) PutChannel(rw http.ResponseWriter, req *http.Request) error {
 	defer req.Body.Close()
 	err := json.NewDecoder(req.Body).Decode(&envelope)
 	if err != nil {
-		WriteBadRequest(rw, fmt.Sprintf("bad json: %s", err.Error()))
+		WriteMPDErrorResponse(rw, fmt.Sprintf("bad json: %s", err.Error()))
 		return err
 	}
 	if envelope.Action == nil {
@@ -76,7 +76,7 @@ func (s *Server) PutChannel(rw http.ResponseWriter, req *http.Request) error {
 	}
 	err = action(envelope.Pin)
 	if err != nil {
-		WriteBadRequest(rw, err.Error())
+		WriteMPDErrorResponse(rw, err.Error())
 		return err
 	}
 	return nil
@@ -92,7 +92,7 @@ func (s *Server) Channels(rw http.ResponseWriter, req *http.Request) {
 	s.WriteResponse(rw)
 }
 
-func WriteBadRequest(rw http.ResponseWriter, msg string) {
+func WriteMPDErrorResponse(rw http.ResponseWriter, msg string) {
 	rw.WriteHeader(http.StatusBadRequest)
 	fmt.Fprintf(rw, "ACK: %s\n", msg)
 }
@@ -138,11 +138,11 @@ func (s *Server) MpdEvents(rw http.ResponseWriter, req *http.Request) {
 func MpdCommand(rw http.ResponseWriter, req *http.Request) {
 	qs, ok := req.URL.Query()["q"]
 	if !ok {
-		WriteBadRequest(rw, "query parameter `q` not defined")
+		WriteMPDErrorResponse(rw, "query parameter `q` not defined")
 		return
 	}
 	q := qs[0]
-	data := Must(internal.MpdQuery(q, MpdAuthority))
+	data := Must(internal.MpdQuery(MpdAuthority, q))
 	rw.Write(data)
 }
 
@@ -161,11 +161,13 @@ func MpdVersion(rw http.ResponseWriter, req *http.Request) {
 	json.NewEncoder(rw).Encode(&payload)
 }
 
+var AlbumNotFound = errors.New("no results for provided album ID")
+
 func chooseAFile(sc *bufio.Scanner) (string, error) {
 	for sc.Scan() {
 		line := strings.TrimSpace(sc.Text())
 		if line == "OK" {
-			return "", errors.New("no file label. how???")
+			return "", AlbumNotFound
 		}
 		parts := strings.Split(line, ": ")
 		if len(parts) == 2 && parts[0] == "file" {
@@ -186,11 +188,15 @@ func AlbumArt(rw http.ResponseWriter, req *http.Request) {
 	if sc.Err() != nil {
 		panic(sc.Err())
 	}
-	Must(fmt.Fprintf(conn, "search albumartist \"%s\" album \"%s\"\n", req.PathValue("albumartist"), req.PathValue("album")))
+	albumArtist := req.PathValue("albumartist")
+	album := req.PathValue("album")
+	Must(fmt.Fprintf(conn, "search albumartist \"%s\" album \"%s\"\n", albumArtist, album))
 	fname, err := chooseAFile(sc)
-	if err != nil {
+	if errors.Is(err, AlbumNotFound) {
 		rw.WriteHeader(404)
 		return
+	} else if err != nil {
+		panic(err)
 	}
 	fullPath := path.Join(MusicDir, fname)
 	fullDir, _ := path.Split(fullPath)
@@ -199,24 +205,39 @@ func AlbumArt(rw http.ResponseWriter, req *http.Request) {
 		panic(err)
 	}
 	if img != "" {
-		fmt.Println("found file:", img)
+		slog.Info(
+			"send folder image",
+			slog.String("albumartist", albumArtist),
+			slog.String("album", album),
+			slog.String("path", img),
+		)
 		rw.Header().Set("Content-Type", "image/jpeg")
 		f := Must(os.Open(img))
 		io.Copy(rw, f)
 		return
 	}
-	f, err := os.Open(fullPath)
-	if err != nil {
-		rw.WriteHeader(500)
-		return
-	}
+	f := Must(os.Open(fullPath))
 	defer f.Close()
 	mime, size, err := art.FindAPICInMP3(f)
-	fmt.Printf("%d\n", size)
 	if err != nil {
+		slog.Error(
+			"could not extract album art",
+			slog.String("albumartist", albumArtist),
+			slog.String("album", album),
+			slog.String("file", fullPath),
+			slog.String("message", err.Error()),
+		)
 		rw.WriteHeader(404)
 		return
 	}
+	slog.Info(
+		"send embedded album art",
+		slog.String("albumartist", albumArtist),
+		slog.String("album", album),
+		slog.String("type", mime),
+		slog.Int64("size", int64(size)),
+		slog.String("file", fullPath),
+	)
 	rw.Header().Set("Content-Type", mime)
 	_, err = io.CopyN(rw, f, int64(size))
 	if err != nil {

mpd-web-proxy/internal/art/art_test.go

@@ -28,7 +28,6 @@ func BenchmarkFindAPICInMP3(b *testing.B) {
 	if err != nil {
 		panic(err)
 	}
-	nul, err := os.Open("/dev/null")
 	defer f.Close()
 	for range b.N {
 		_, err := f.Seek(0, io.SeekStart)
@@ -39,6 +38,6 @@ func BenchmarkFindAPICInMP3(b *testing.B) {
 		if err != nil {
 			panic(err)
 		}
-		io.CopyN(nul, f, int64(sz))
+		io.CopyN(io.Discard, f, int64(sz))
 	}
 }

mpd-web-proxy/internal/gpio/gpio.go

@@ -1,7 +1,7 @@
 package gpio
 
 import (
-	"fmt"
+	"log/slog"
 )
 
 // PhysicalState represents the physical voltage value
@@ -35,11 +35,11 @@ func (n *NopBackend) Set(pin int, state PhysicalState) error {
 	if state {
 		newState = "HIGH"
 	}
-	fmt.Printf("\u001b[32mSet pin %d to %s\u001b[0m\n", pin, newState)
+	slog.Info("set gpio pin state", slog.Int("pin", pin), slog.String("state", newState))
 	return nil
 }
 
 func (n *NopBackend) Close() error {
-	fmt.Println("GPIO Close called")
+	slog.Info("gpio close called")
 	return nil
 }

mpd-web-proxy/internal/mpd.go

@@ -3,7 +3,6 @@ package internal
 import (
 	"bufio"
 	"bytes"
-	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -14,40 +13,27 @@ import (
 // MpdQuery connects and queries the MPD server
 // with the given command. Returns the response body
 // or any connection error.
-func MpdQuery(cmd string, authority string) ([]byte, error) {
+func MpdQuery(authority string, cmd string, args ...any) ([]byte, error) {
 	mpd, err := net.Dial("tcp", authority)
 	if err != nil {
 		return nil, err
 	}
 	defer mpd.Close()
-	return mpdQuery(cmd, mpd)
-}
-
-// A cancellable MPD Query.
-func MpdQueryContext(cmd string, authority string, ctx context.Context) ([]byte, error) {
-	mpd, err := net.Dial("tcp", authority)
-	if err != nil {
-		return nil, err
-	}
-	go func() {
-		<-ctx.Done()
-		fmt.Println("client gone. closing mpd")
-		mpd.Close()
-	}()
-	return mpdQuery(cmd, mpd)
+	return mpdQuery(mpd, cmd, args...)
 }
 
 // mpdQuery reads and parses a response stream
 // to verify that the response is valid.
-func mpdQuery(cmd string, mpd io.ReadWriter) ([]byte, error) {
+func mpdQuery(mpd io.ReadWriter, cmd string, args ...any) ([]byte, error) {
+	q := fmt.Sprintf(cmd, args...)
 	scanner := bufio.NewScanner(mpd)
 	if !scanner.Scan() {
 		if err := scanner.Err(); err != nil {
 			return nil, err
 		}
 		return nil, errors.New("unexpected EOF")
 	}
-	if _, err := io.WriteString(mpd, strings.TrimSpace(cmd)+"\n"); err != nil {
+	if _, err := io.WriteString(mpd, strings.TrimSpace(q)+"\n"); err != nil {
 		return nil, err
 	}
 	var ret bytes.Buffer