Discard duplicated tags

scanner/metadata/metadata.go

@@ -57,6 +57,9 @@ func Extract(files ...string) (map[string]Tags, error) {
 }
 
 func NewTag(filePath string, fileInfo os.FileInfo, tags ParsedTags) Tags {
+	for t, values := range tags {
+		tags[t] = removeDuplicates(values)
+	}
 	return Tags{
 		filePath: filePath,
 		fileInfo: fileInfo,
@@ -64,6 +67,19 @@ func NewTag(filePath string, fileInfo os.FileInfo, tags ParsedTags) Tags {
 	}
 }
 
+func removeDuplicates(values []string) []string {
+	encountered := map[string]struct{}{}
+	var result []string
+	for _, v := range values {
+		if _, ok := encountered[v]; ok {
+			continue
+		}
+		encountered[v] = struct{}{}
+		result = append(result, v)
+	}
+	return result
+}
+
 type ParsedTags map[string][]string
 
 func (p ParsedTags) Map(customMappings ParsedTags) ParsedTags {

scanner/metadata/metadata_internal_test.go

@@ -68,6 +68,19 @@ var _ = Describe("Tags", func() {
 		})
 	})
 
+	Describe("removeDuplicates", func() {
+		It("removes duplicates", func() {
+			md := NewTag("/music/artist/album01/Song.mp3", nil, ParsedTags{
+				"genre": []string{"pop", "rock", "pop"},
+				"date":  []string{"2023-03-01", "2023-03-01"},
+				"mood":  []string{"happy", "sad"},
+			})
+			Expect(md.tags).To(HaveKeyWithValue("genre", []string{"pop", "rock"}))
+			Expect(md.tags).To(HaveKeyWithValue("date", []string{"2023-03-01"}))
+			Expect(md.tags).To(HaveKeyWithValue("mood", []string{"happy", "sad"}))
+		})
+	})
+
 	Describe("Bpm", func() {
 		var t *Tags
 		BeforeEach(func() {