package syncer

import (
	"os"
	"path/filepath"
	"testing"
)

func writeFile(t *testing.T, dir, name, content string) string {
	t.Helper()
	p := filepath.Join(dir, name)
	if err := os.WriteFile(p, []byte(content), 0o644); err != nil {
		t.Fatal(err)
	}
	return p
}

func TestListLocalTracksUsesM3UOrderWhenPresent(t *testing.T) {
	dir := t.TempDir()
	writeFile(t, dir, "b-track.mp3", "data")
	writeFile(t, dir, "a-track.mp3", "data")
	writeFile(t, dir, "c-track.mp3", "data")
	writeFile(t, dir, "playlist.m3u", "#EXTM3U\nb-track.mp3\nc-track.mp3\na-track.mp3\n")

	tracks, err := ListLocalTracks(dir)
	if err != nil {
		t.Fatal(err)
	}
	got := titles(tracks)
	want := []string{"b-track", "c-track", "a-track"}
	if !equalStrings(got, want) {
		t.Fatalf("expected order %v, got %v", want, got)
	}
}

func TestListLocalTracksAppendsUnreferencedTracksAfterPlaylist(t *testing.T) {
	dir := t.TempDir()
	writeFile(t, dir, "a-track.mp3", "data")
	writeFile(t, dir, "b-track.mp3", "data")
	writeFile(t, dir, "z-new-track.mp3", "data")
	// Playlist doesn't mention the newly added track yet.
	writeFile(t, dir, "playlist.m3u", "b-track.mp3\na-track.mp3\n")

	tracks, err := ListLocalTracks(dir)
	if err != nil {
		t.Fatal(err)
	}
	got := titles(tracks)
	want := []string{"b-track", "a-track", "z-new-track"}
	if !equalStrings(got, want) {
		t.Fatalf("expected order %v, got %v", want, got)
	}
}

func TestListLocalTracksIgnoresMissingPlaylistEntries(t *testing.T) {
	dir := t.TempDir()
	writeFile(t, dir, "a-track.mp3", "data")
	writeFile(t, dir, "playlist.m3u", "does-not-exist.mp3\na-track.mp3\n")

	tracks, err := ListLocalTracks(dir)
	if err != nil {
		t.Fatal(err)
	}
	got := titles(tracks)
	want := []string{"a-track"}
	if !equalStrings(got, want) {
		t.Fatalf("expected order %v, got %v", want, got)
	}
}

func TestListLocalTracksFallsBackToAlphabeticalWithoutPlaylist(t *testing.T) {
	dir := t.TempDir()
	writeFile(t, dir, "b-track.mp3", "data")
	writeFile(t, dir, "a-track.mp3", "data")

	tracks, err := ListLocalTracks(dir)
	if err != nil {
		t.Fatal(err)
	}
	got := titles(tracks)
	want := []string{"a-track", "b-track"}
	if !equalStrings(got, want) {
		t.Fatalf("expected order %v, got %v", want, got)
	}
}

func TestListLocalTracksErrorsOnMultiplePlaylists(t *testing.T) {
	dir := t.TempDir()
	writeFile(t, dir, "a-track.mp3", "data")
	writeFile(t, dir, "one.m3u", "a-track.mp3\n")
	writeFile(t, dir, "two.m3u8", "a-track.mp3\n")

	if _, err := ListLocalTracks(dir); err == nil {
		t.Fatal("expected error when multiple playlist files are present")
	}
}

func titles(tracks []Track) []string {
	titles := make([]string, len(tracks))
	for i, t := range tracks {
		titles[i] = t.Title
	}
	return titles
}