package playlist

import (
	"fmt"
	"log"
	"time"

	segmentpkg "segmento/internal/segment"
)

const DefaultPlaylistDuration = 20 * time.Second

type segment struct {
	segmentpkg.Segment
	seqId int
}

type PlaylistListener interface {
	OnUpdate(p Playlist)
}

type Playlist interface {
	Duration() time.Duration
	TargetDuration() time.Duration
	Render() string
	ReadSegments(chan *segmentpkg.Segment) error
	AddListener(l PlaylistListener)
}

type MediaPlaylist struct {
	Segments  []*segment
	Listeners []PlaylistListener

	seqId int
}

func NewMediaPlaylist() *MediaPlaylist {
	return &MediaPlaylist{
		Segments:  make([]*segment, 0, 10),
		Listeners: make([]PlaylistListener, 0),
	}
}

func (p *MediaPlaylist) nextSeqId() int {
	next := p.seqId
	p.seqId++
	return next
}

func (p *MediaPlaylist) Duration() time.Duration {
	return p.durationOf(p.Segments)
}

func (p *MediaPlaylist) TargetDuration() time.Duration {
	return DefaultPlaylistDuration
}

// pass by pointer or value here?
// I think value is better, the struct is tiny and only contains a pointer
// to the data buffer
func (p *MediaPlaylist) AddSegment(s *segmentpkg.Segment) error {
	nextId := p.nextSeqId()
	ss := segment{*s, nextId}
	p.Segments = append(p.Segments, &ss)

	if len(p.Segments) > 1 {
		for {
			if p.durationOf(p.Segments[1:]) > p.TargetDuration() {
				p.Segments = p.Segments[1:]
			}
			break
		}
	}

	p.updateListeners()

	return nil
}

func (p *MediaPlaylist) durationOf(ss []*segment) time.Duration {
	var t time.Duration
	for _, s := range ss {
		t += s.Duration()
	}
	return t
}

func (p *MediaPlaylist) Render() string {
	var r string
	r += "#EXTM3U\n"
	r += "#EXT-X-VERSION:3\n"
	r += "#EXT-X-TARGETDURATION:3\n" // TODO
	for _, s := range p.Segments {
		r += fmt.Sprintf("#EXTINF:%.05f\n", float32(s.Duration())/float32(time.Second))
		r += "http://www.example.com/x.mp3\n"
	}
	r += "#EXT-X-ENDLIST"
	return r
}

// Listeners

func (p *MediaPlaylist) AddListener(l PlaylistListener) {
	p.Listeners = append(p.Listeners, l)
}

func (p *MediaPlaylist) updateListeners() {
	for _, l := range p.Listeners {
		l.OnUpdate(p)
	}
}

func (p *MediaPlaylist) ReadSegments(segments chan *segmentpkg.Segment) error {
	for s := range segments {
		log.Println("got segment with duration", s.Duration(), "and len", s.Len(), "bytes")
		p.AddSegment(s)
	}
	log.Println("exiting ReadSegments")
	return nil
}