Backend: Fallback to file extension for mime type detection

Signed-off-by: Michael Mayer <michael@liquidbytes.net>

pkg/fs/filetype.go

@@ -228,3 +228,12 @@ func (t FileType) FindFirst(fileName string, dirs []string, baseDir string, stri
 
 	return ""
 }
+
+// NormalizedExt returns the file extension without dot and in lowercase.
+func NormalizedExt(fileName string) string {
+	if dot := strings.LastIndex(fileName, "."); dot != -1 && len(fileName[dot+1:]) >= 1 {
+		return strings.ToLower(fileName[dot+1:])
+	}
+
+	return ""
+}

pkg/fs/filetype_test.go

@@ -133,3 +133,40 @@ func TestFileType_FindFirst(t *testing.T) {
 		assert.Equal(t, Abs("testdata/directory/example.bmp"), result)
 	})
 }
+
+func TestNormalizedExt(t *testing.T) {
+	t.Run("none", func(t *testing.T) {
+		result := NormalizedExt("testdata/test")
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("dot", func(t *testing.T) {
+		result := NormalizedExt("testdata/test.")
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("test.z", func(t *testing.T) {
+		result := NormalizedExt("testdata/test.z")
+		assert.Equal(t, "z", result)
+	})
+
+	t.Run("test.jpg", func(t *testing.T) {
+		result := NormalizedExt("testdata/test.jpg")
+		assert.Equal(t, "jpg", result)
+	})
+
+	t.Run("test.PNG", func(t *testing.T) {
+		result := NormalizedExt("testdata/test.PNG")
+		assert.Equal(t, "png", result)
+	})
+
+	t.Run("test.MOV", func(t *testing.T) {
+		result := NormalizedExt("testdata/test.MOV")
+		assert.Equal(t, "mov", result)
+	})
+
+	t.Run("test.xmp", func(t *testing.T) {
+		result := NormalizedExt("testdata/test.xMp")
+		assert.Equal(t, "xmp", result)
+	})
+}

pkg/fs/mime.go

@@ -30,9 +30,11 @@ func MimeType(filename string) string {
 
 	if _, err := handle.Read(buffer); err != nil {
 		return ""
-	} else if t, err := filetype.Get(buffer); err != nil {
+	} else if t, err := filetype.Get(buffer); err == nil && t != filetype.Unknown {
-		return ""
-	} else {
 		return t.MIME.Value
+	} else if t := filetype.GetType(NormalizedExt(filename)); t != filetype.Unknown {
+		return t.MIME.Value
+	} else {
+		return ""
 	}
 }