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()
}