Improve error handling for the API

cmd/go2tv-lite/go2tv.go

@@ -34,6 +34,9 @@ var (
 	transcodePtr = flag.Bool("tc", false, "Use ffmpeg to transcode input video file.")
 	listPtr      = flag.Bool("l", false, "List all available UPnP/DLNA Media Renderer models and URLs.")
 	versionPtr   = flag.Bool("version", false, "Print version.")
+
+	ErrNoCombi    = errors.New("can't combine -l with other flags")
+	ErrFailtoList = errors.New("failed to list devices")
 )
 
 type dummyScreen struct {
@@ -194,12 +197,12 @@ func listFlagFunction() error {
 	})
 
 	if flagsEnabled > 1 {
-		return errors.New("can't combine -l with other flags")
+		return ErrNoCombi
 	}
 
 	deviceList, err := devices.LoadSSDPservices(1)
 	if err != nil {
-		return errors.New("failed to list devices")
+		return ErrFailtoList
 	}
 
 	fmt.Println()

cmd/go2tv/go2tv.go

@@ -36,6 +36,9 @@ var (
 	transcodePtr = flag.Bool("tc", false, "Use ffmpeg to transcode input video file.")
 	listPtr      = flag.Bool("l", false, "List all available UPnP/DLNA Media Renderer models and URLs.")
 	versionPtr   = flag.Bool("version", false, "Print version.")
+
+	ErrNoCombi    = errors.New("can't combine -l with other flags")
+	ErrFailtoList = errors.New("failed to list devices")
 )
 
 type flagResults struct {
@@ -188,12 +191,12 @@ func listFlagFunction() error {
 	})
 
 	if flagsEnabled > 1 {
-		return errors.New("can't combine -l with other flags")
+		return ErrNoCombi
 	}
 
 	deviceList, err := devices.LoadSSDPservices(1)
 	if err != nil {
-		return errors.New("failed to list devices")
+		return ErrFailtoList
 	}
 
 	fmt.Println()

devices/devices.go

@@ -9,7 +9,11 @@ import (
 	"github.com/pkg/errors"
 )
 
-var ErrNoDeviceAvailable = errors.New("loadSSDPservices: No available Media Renderers")
+var (
+	ErrNoDeviceAvailable  = errors.New("loadSSDPservices: No available Media Renderers")
+	ErrDeviceNotAvailable = errors.New("devicePicker: Requested device not available")
+	ErrSomethingWentWrong = errors.New("devicePicker: Something went terribly wrong")
+)
 
 // LoadSSDPservices returns a map with all the devices that support the
 // AVTransport service.
@@ -45,7 +49,7 @@ func LoadSSDPservices(delay int) (map[string]string, error) {
 // DevicePicker will pick the nth device from the devices input map.
 func DevicePicker(devices map[string]string, n int) (string, error) {
 	if n > len(devices) || len(devices) == 0 || n <= 0 {
-		return "", errors.New("devicePicker: Requested device not available")
+		return "", ErrDeviceNotAvailable
 	}
 
 	keys := make([]string, 0)
@@ -60,5 +64,6 @@ func DevicePicker(devices map[string]string, n int) (string, error) {
 			return devices[k], nil
 		}
 	}
-	return "", errors.New("devicePicker: Something went terribly wrong")
+
+	return "", ErrSomethingWentWrong
 }

soapcalls/soapbuilders.go

@@ -12,6 +12,10 @@ import (
 	"github.com/pkg/errors"
 )
 
+var (
+	ErrSetMuteInput = errors.New("setMuteSoapBuild input error. Was expecting 0 or 1.")
+)
+
 type playEnvelope struct {
 	XMLName  xml.Name `xml:"s:Envelope"`
 	Schema   string   `xml:"xmlns:s,attr"`
@@ -432,7 +436,7 @@ func pauseSoapBuild() ([]byte, error) {
 
 func setMuteSoapBuild(m string) ([]byte, error) {
 	if m != "0" && m != "1" {
-		return nil, errors.New("setMuteSoapBuild input error. Was expecting 0 or 1.")
+		return nil, ErrSetMuteInput
 	}
 
 	d := setMuteEnvelope{

soapcalls/soapcallers.go

@@ -25,7 +25,11 @@ type States struct {
 	ProcessStop   bool
 }
 
-var log zerolog.Logger
+var (
+	log                   zerolog.Logger
+	ErrNoMatchingFileType = errors.New("no matching file type")
+	ErrZombieCallbacks    = errors.New("zombie callbacks, we should ignore those")
+)
 
 // TVPayload this is the heart of Go2TV. We pass that type to the
 // webserver. We need to explicitly initialize it.
@@ -899,7 +903,7 @@ func (p *TVPayload) GetProcessStop(uuid string) (bool, error) {
 		return p.MediaRenderersStates[uuid].ProcessStop, nil
 	}
 
-	return true, errors.New("zombie callbacks, we should ignore those")
+	return true, ErrZombieCallbacks
 }
 
 func (p *TVPayload) Log() *zerolog.Logger {
@@ -945,5 +949,5 @@ func parseProtocolInfo(b []byte, mt string) error {
 		}
 	}
 
-	return errors.New("no matching file type")
+	return ErrNoMatchingFileType
 }

soapcalls/xmlparsers.go

@@ -11,6 +11,10 @@ import (
 	"github.com/pkg/errors"
 )
 
+var (
+	ErrWrongDMR = errors.New("something broke somewhere - wrong DMR URL?")
+)
+
 type rootNode struct {
 	XMLName xml.Name `xml:"root"`
 	Device  struct {
@@ -129,7 +133,7 @@ func DMRextractor(dmrurl string) (*DMRextracted, error) {
 		return ex, nil
 	}
 
-	return nil, errors.New("something broke somewhere - wrong DMR URL?")
+	return nil, ErrWrongDMR
 }
 
 // EventNotifyParser parses the Notify messages from the DMR device.

utils/dlnatools.go

@@ -41,6 +41,8 @@ var (
 		"image/jpeg":              "JPEG_LRG",
 		"image/png":               "PNG_LRG",
 	}
+
+	ErrInvalidSeekFlag = errors.New("invalid seek flag")
 )
 
 func defaultStreamingFlags() string {
@@ -76,7 +78,7 @@ func BuildContentFeatures(mediaType string, seek string, transcode bool) (string
 	case "11":
 		cf.WriteString("DLNA.ORG_OP=11;")
 	default:
-		return "", errors.New("invalid seek flag")
+		return "", ErrInvalidSeekFlag
 	}
 
 	switch transcode {

utils/transcode.go

@@ -9,6 +9,10 @@ import (
 	"os/exec"
 )
 
+var (
+	ErrInvalidInput = errors.New("invalid ffmpeg input")
+)
+
 // ServeTranscodedStream passes an input file or io.Reader to ffmpeg and writes the output directly
 // to our io.Writer.
 func ServeTranscodedStream(w io.Writer, input interface{}, ff *exec.Cmd) error {
@@ -22,7 +26,7 @@ func ServeTranscodedStream(w io.Writer, input interface{}, ff *exec.Cmd) error {
 	case io.Reader:
 		in = "pipe:0"
 	default:
-		return errors.New("invalid ffmpeg input")
+		return ErrInvalidInput
 	}
 
 	if ff != nil && ff.Process != nil {

utils/transcode_windows.go

@@ -7,6 +7,10 @@ import (
 	"syscall"
 )
 
+var (
+	ErrInvalidInput = errors.New("invalid ffmpeg input")
+)
+
 // ServeTranscodedStream passes an input file or io.Reader to ffmpeg and writes the output directly
 // to our io.Writer.
 func ServeTranscodedStream(w io.Writer, input interface{}, ff *exec.Cmd) error {
@@ -20,7 +24,7 @@ func ServeTranscodedStream(w io.Writer, input interface{}, ff *exec.Cmd) error {
 	case io.Reader:
 		in = "pipe:0"
 	default:
-		return errors.New("invalid ffmpeg input")
+		return ErrInvalidInput
 	}
 
 	if ff != nil && ff.Process != nil {

utils/urlstreamer.go

@@ -9,6 +9,10 @@ import (
 	"net/url"
 )
 
+var (
+	ErrBadStatus = errors.New("streamURL bad status code")
+)
+
 // StreamURL returns the response body for the input media URL.
 func StreamURL(ctx context.Context, s string) (io.ReadCloser, error) {
 	_, err := url.ParseRequestURI(s)
@@ -28,7 +32,7 @@ func StreamURL(ctx context.Context, s string) (io.ReadCloser, error) {
 	}
 
 	if resp.StatusCode >= 400 {
-		return nil, errors.New("streamURL bad status code: " + resp.Status)
+		return nil, ErrBadStatus
 	}
 
 	body := resp.Body