add internal/infra/m3u.go

internal/infra/m3u.go

@@ -0,0 +1,29 @@
+package infra
+
+import (
+	"fmt"
+	"strings"
+
+	"radio-go/internal/domain"
+)
+
+// sanitize flattens a string so it can't break or forge an m3u line:
+// newlines become spaces and "#EXT" sequences are stripped so a song title
+// can never inject a fake #EXTINF entry.
+func sanitize(s string) string {
+	return strings.ReplaceAll(
+		strings.NewReplacer("\r", " ", "\n", " ").Replace(s),
+		"#EXT", "")
+}
+
+// WriteM3U renders an extended M3U playlist (relative mp3 names).
+func WriteM3U(station string, pl []domain.Track) string {
+	var b strings.Builder
+	b.WriteString("#EXTM3U\n")
+	for _, t := range pl {
+		dur := int(t.Duration)
+		title := sanitize(fmt.Sprintf("%s - %s", station, t.DisplayTitle()))
+		fmt.Fprintf(&b, "#EXTINF:%d,%s\n%s.mp3\n", dur, title, t.ID)
+	}
+	return b.String()
+}