Refactors Cover's Extension cleaning in Album

album.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+	"path"
 	"regexp"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -101,3 +103,14 @@ func (a *Album) String() string {
 	}
 	return res + a.Title
 }
+
+var rxExt = regexp.MustCompile(`\.([0-9]+)([a-zA-Z]+)\z`)
+
+func (a *Album) CoverExt() string {
+	ext := path.Ext(a.CoverURL)
+	m := rxExt.FindStringSubmatch(ext)
+	if m != nil {
+		ext = "." + m[2]
+	}
+	return strings.ToLower(ext)
+}

album_test.go

@@ -38,3 +38,22 @@ func (s *AlbumSuite) TestAuthors(c *C) {
 	}
 
 }
+
+func (s *AlbumSuite) TestExt(c *C) {
+	type TestData struct {
+		A   *Album
+		Res string
+	}
+	data := []TestData{
+		{&Album{CoverURL: "foo/bar/test.jpg"}, ".jpg"},
+		{&Album{CoverURL: "foo/bar/foo.JPG"}, ".jpg"},
+		{&Album{CoverURL: "foo/bar/foo.JPEG"}, ".jpeg"},
+		{&Album{CoverURL: "foo/bar/foo.023879jpg"}, ".jpg"},
+		{&Album{CoverURL: "foo/bar/foo.PNG"}, ".png"},
+		{&Album{CoverURL: "foo/bar/foo.gif"}, ".gif"},
+	}
+
+	for _, d := range data {
+		c.Check(d.A.CoverExt(), Equals, d.Res, Commentf("With URL %s", d.A.CoverURL))
+	}
+}

router.go

@@ -8,9 +8,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
-	"regexp"
 	"strconv"
-	"strings"
 
 	"ponyo.epfl.ch/gitlab/alexandre.tuleu/narco"
 
@@ -20,8 +18,6 @@ import (
 	"golang.org/x/net/context"
 )
 
-var rxExt = regexp.MustCompile(`[0-9]+`)
-
 func (a *appData) buildRouter() http.Handler {
 	router := httprouter.New()
 
@@ -79,9 +75,7 @@ func (a *appData) buildRouter() http.Handler {
 			}
 
 			album := *albumUnsafe
-			ext := path.Ext(album.CoverURL)
-			ext = strings.ToLower(rxExt.ReplaceAllString(ext, ""))
-			album.CoverURL = fmt.Sprintf("/covers/%d%s", album.ID, ext)
+			album.CoverURL = fmt.Sprintf("/covers/%d%s", album.ID, album.CoverExt())
 
 			enc := json.NewEncoder(w)
 			if err := enc.Encode(album); err != nil {