Add common go types

internal/common/sort.go

@@ -0,0 +1,89 @@
+package common
+
+import "sort"
+
+type albumLessFunc func(p1, p2 *Album) bool
+
+type albumSorter struct {
+	albums []*Album
+	less   []albumLessFunc
+}
+
+func (s *albumSorter) Len() int {
+	return len(s.albums)
+}
+
+func (s *albumSorter) Swap(i, j int) {
+	s.albums[i], s.albums[j] = s.albums[j], s.albums[i]
+}
+
+func (s *albumSorter) Less(i, j int) bool {
+	p, q := s.albums[i], s.albums[j]
+
+	var k int
+	for k = 0; k < len(s.less)-1; k++ {
+		less := s.less[k]
+		switch {
+		case less(p, q):
+			return true
+		case less(q, p):
+			return false
+		}
+	}
+
+	return s.less[k](p, q)
+}
+
+func (s *albumSorter) Sort(albums []*Album) {
+	s.albums = albums
+	sort.Sort(s)
+}
+
+func OrderAlbumBy(less ...albumLessFunc) *albumSorter {
+	return &albumSorter{
+		less: less,
+	}
+}
+
+func SortAlbums(album []*Album, field string) {
+	title := orderAlbumByTitle
+	artists := orderAlbumByArtists
+	years := orderAlbumByYears
+	modified := orderAlbumByModified
+
+	var sorter *albumSorter
+	switch field {
+	case "artist":
+		sorter = OrderAlbumBy(artists, title, years, modified)
+	case "year":
+		sorter = OrderAlbumBy(years, title, artists, modified)
+	case "modified":
+		sorter = OrderAlbumBy(modified, title, artists, years)
+	default:
+		sorter = OrderAlbumBy(title, artists, years, modified)
+	}
+
+	sorter.Sort(album)
+}
+
+func orderAlbumByTitle(c1, c2 *Album) bool {
+	return c1.Title() < c2.Title()
+}
+
+func orderAlbumByArtists(left, right *Album) bool {
+	if len(left.Artists()) > 0 && len(right.Artists()) > 0 {
+		return left.Artists()[0] < right.Artists()[0]
+	}
+	return false
+}
+
+func orderAlbumByYears(c1, c2 *Album) bool {
+	if len(c1.Dates()) > 0 && len(c2.Dates()) > 0 {
+		return c1.Dates()[0] < c2.Dates()[0]
+	}
+	return false
+}
+
+func orderAlbumByModified(c1, c2 *Album) bool {
+	return c1.LastModified().Before(c2.LastModified())
+}