feat(api): add conversion helpers for library DTOs

internal/api/convert.go

@@ -0,0 +1,67 @@
+package api
+
+import (
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+// uuidToString renders a pgtype.UUID as a canonical hyphenated string.
+// Returns "" when the UUID is invalid (unset). Duplicated from the subsonic
+// package intentionally — the two packages must not depend on each other.
+func uuidToString(u pgtype.UUID) string {
+	if !u.Valid {
+		return ""
+	}
+	b := u.Bytes
+	const hex = "0123456789abcdef"
+	out := make([]byte, 36)
+	j := 0
+	for i, x := range b {
+		if i == 4 || i == 6 || i == 8 || i == 10 {
+			out[j] = '-'
+			j++
+		}
+		out[j] = hex[x>>4]
+		out[j+1] = hex[x&0x0f]
+		j += 2
+	}
+	return string(out)
+}
+
+// parseUUID accepts the canonical hyphenated form produced by uuidToString.
+// Returns ok=false on any malformed input so handlers can 400 cleanly.
+func parseUUID(s string) (pgtype.UUID, bool) {
+	var u pgtype.UUID
+	if err := u.Scan(s); err != nil {
+		return pgtype.UUID{}, false
+	}
+	return u, u.Valid
+}
+
+// yearFromDate returns the 4-digit year from a pgtype.Date, or 0 when the
+// date is unset. Album release years are optional at scan time.
+func yearFromDate(d pgtype.Date) int {
+	if !d.Valid {
+		return 0
+	}
+	return d.Time.Year()
+}
+
+// durationMsToSec converts millisecond durations (as stored in tracks.duration_ms)
+// to seconds, rounding to nearest. Callers display seconds; sub-second precision
+// is not useful in UI.
+func durationMsToSec(ms int32) int {
+	return int((ms + 500) / 1000)
+}
+
+// coverURL returns the /api relative URL for an album's cover art. The
+// endpoint ships in Plan 3; until then it 404s, and the SPA does not wire
+// <img src> to it.
+func coverURL(albumID pgtype.UUID) string {
+	return "/api/albums/" + uuidToString(albumID) + "/cover"
+}
+
+// streamURL returns the /api relative URL for a track's audio stream. The
+// endpoint ships in Plan 3.
+func streamURL(trackID pgtype.UUID) string {
+	return "/api/tracks/" + uuidToString(trackID) + "/stream"
+}