changed genre scanning to parse multiple genres, updated db to accommodate.

backend/metadata/genre.go

@@ -0,0 +1,48 @@
+// Package metadata provides audio file metadata extraction utilities.
+package metadata
+
+import (
+	"strings"
+
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+// genreSeparators defines the characters treated as genre delimiters.
+const genreSeparators = ",;"
+
+// ParseGenres splits a raw genre string on commas and semicolons,
+// trims whitespace, normalizes each entry to title case, removes
+// duplicates, and returns the unique genre names.  An empty or
+// whitespace-only input returns nil.
+func ParseGenres(raw string) []string {
+	parts := strings.FieldsFunc(
+		raw, func(r rune) bool {
+			return strings.ContainsRune(genreSeparators, r)
+		},
+	)
+
+	caser := cases.Title(language.English)
+	seen := make(map[string]struct{}, len(parts))
+
+	var genres []string
+
+	for _, p := range parts {
+		name := strings.TrimSpace(p)
+		if name == "" {
+			continue
+		}
+
+		name = caser.String(name)
+
+		if _, ok := seen[name]; ok {
+			continue
+		}
+
+		seen[name] = struct{}{}
+
+		genres = append(genres, name)
+	}
+
+	return genres
+}