improve error handling

internal/epub/epub.go

@@ -49,12 +49,7 @@ type epubPart struct {
 }
 
 func New(options *Options) *ePub {
-	uid, err := uuid.NewV4()
+	uid := uuid.Must(uuid.NewV4())
-	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
-
 	tmpl := template.New("parser")
 	tmpl.Funcs(template.FuncMap{
 		"mod":  func(i, j int) bool { return i%j == 0 },
@@ -71,20 +66,12 @@ func New(options *Options) *ePub {
 }
 
 func (e *ePub) render(templateString string, data any) string {
-	tmpl, err := e.templateProcessor.Parse(templateString)
+	var result strings.Builder
-	if err != nil {
+	tmpl := template.Must(e.templateProcessor.Parse(templateString))
-		fmt.Fprintln(os.Stderr, err)
+	if err := tmpl.Execute(&result, data); err != nil {
-		os.Exit(1)
+		panic(err)
 	}
-	result := &strings.Builder{}
+	return regexp.MustCompile("\n+").ReplaceAllString(result.String(), "\n")
-	if err := tmpl.Execute(result, data); err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
-
-	stripBlank := regexp.MustCompile("\n+")
-
-	return stripBlank.ReplaceAllString(result.String(), "\n")
 }
 
 func (e *ePub) writeImage(wz *epubzip.EpubZip, img *epubimage.Image) error {

internal/epub/imagedata/epub_image_data.go

@@ -21,30 +21,42 @@ func (img *ImageData) CompressedSize() uint64 {
 	return img.Header.CompressedSize64 + 30 + uint64(len(img.Header.Name))
 }
 
+func exitWithError(err error) {
+	fmt.Fprintln(os.Stderr, err)
+	os.Exit(1)
+}
+
 func New(id int, part int, img image.Image, quality int) *ImageData {
 	name := fmt.Sprintf("OEBPS/Images/%d_p%d.jpg", id, part)
 	return NewRaw(name, img, quality)
 }
 
 func NewRaw(name string, img image.Image, quality int) *ImageData {
-	data := bytes.NewBuffer([]byte{})
+	var (
-	if err := jpeg.Encode(data, img, &jpeg.Options{Quality: quality}); err != nil {
+		data, cdata bytes.Buffer
-		fmt.Fprintln(os.Stderr, err)
+		err         error
-		os.Exit(1)
+	)
+
+	err = jpeg.Encode(&data, img, &jpeg.Options{Quality: quality})
+	if err != nil {
+		exitWithError(err)
 	}
 
-	cdata := bytes.NewBuffer([]byte{})
+	wcdata, err := flate.NewWriter(&cdata, flate.BestCompression)
-	wcdata, err := flate.NewWriter(cdata, flate.BestCompression)
 	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
+		exitWithError(err)
-		os.Exit(1)
 	}
-	wcdata.Write(data.Bytes())
+
-	wcdata.Close()
+	_, err = wcdata.Write(data.Bytes())
 	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
+		exitWithError(err)
-		os.Exit(1)
 	}
+
+	err = wcdata.Close()
+	if err != nil {
+		exitWithError(err)
+	}
+
 	t := time.Now()
 	return &ImageData{
 		&zip.FileHeader{