feat: kepub conversions

Working *.epub to *.kepub.epub file conversions when
using a Kobo reader. Updated docker file to include
`kepubify` to convert to kepub. If not available the
file is just sent without conversion.

convert/convert.go

@@ -0,0 +1,14 @@
+package convert
+
+const (
+	MOBI_MIME = "application/x-mobipocket-ebook"
+	EPUB_MIME = "application/epub+zip"
+)
+
+type Converter interface {
+	// Whether or not the converter is available
+	// Usually based on the availability of the underlying tool
+	Available() bool
+	// Convert the input file to the output file
+	Convert(input string, output string) error
+}

convert/kepub.go

@@ -0,0 +1,29 @@
+package convert
+
+import (
+	"os/exec"
+	"sync"
+)
+
+type KepubConverter struct {
+	mutex sync.Mutex
+}
+
+func (kc *KepubConverter) Available() bool {
+	path, err := exec.LookPath("kepubify")
+	if err != nil {
+		return false
+	}
+	return path != ""
+}
+
+func (kc *KepubConverter) Convert(input string, output string) error {
+	kc.mutex.Lock()
+	defer kc.mutex.Unlock()
+	cmd := exec.Command("kepubify", "-v", "-u", "-o", output, input)
+	if err := cmd.Run(); err != nil {
+		return err
+	}
+
+	return nil
+}

convert/mobi.go

@@ -0,0 +1,25 @@
+package convert
+
+import (
+	"os/exec"
+	"sync"
+)
+
+type MobiConverter struct {
+	mutex sync.Mutex
+}
+
+func (mc *MobiConverter) Available() bool {
+	path, err := exec.LookPath("kindlegen")
+	if err != nil {
+		return false
+	}
+	return path != ""
+}
+
+func (mc *MobiConverter) Convert(input string, output string) error {
+	mc.mutex.Lock()
+	defer mc.mutex.Unlock()
+
+	return nil
+}