package media

import (
	"sort"
	"strings"

	youtubev2 "github.com/kkdai/youtube/v2"
)

// sortAudio returns the provided formats ordered in descending preferred
// order. The ideal candidate is opus-encoded stereo audio in a webm container,
// with the lowest available bitrate.
func sortAudio(inFormats youtubev2.FormatList) youtubev2.FormatList {
	var formats youtubev2.FormatList
	for _, format := range inFormats {
		if format.FPS == 0 && format.AudioChannels > 0 {
			formats = append(formats, format)
		}
	}
	sort.SliceStable(formats, func(i, j int) bool {
		isOpusI := strings.Contains(formats[i].MimeType, "opus")
		isOpusJ := strings.Contains(formats[j].MimeType, "opus")
		if isOpusI && isOpusJ {
			isStereoI := formats[i].AudioChannels == 2
			isStereoJ := formats[j].AudioChannels == 2
			if isStereoI && isStereoJ {
				return formats[i].ContentLength < formats[j].ContentLength
			}
			return isStereoI
		}
		return isOpusI
	})
	return formats
}