package main

import (
	"container/list"
	"context"
	"dndmusicbot/reisenstreamer"
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"sync"
	"time"

	"github.com/avast/retry-go/v4"
	"github.com/google/uuid"
	"github.com/gopxl/beep"
	"github.com/julienschmidt/httprouter"
	"github.com/kataras/go-events"
	ytdl "github.com/kkdai/youtube/v2"
)

var player *Player

func init() {
	player = new(Player)
	player.playlist = list.New()
}

type Player struct {
	sync.RWMutex

	current    *list.Element
	playlist   *list.List
	PlayList   *ytdl.Playlist
	PlaylistID uuid.UUID
	Playing    bool
	ctx        context.Context
	cancel     context.CancelFunc
}

type PlayerItem struct {
	Artist   string
	Title    string
	ID       string
	Uri      string
	Position time.Duration
	Duration time.Duration
	sr       beep.SampleRate
	streamer *reisenstreamer.Streamer
	fn       beep.StreamerFunc
	ctx      context.Context
	cancel   context.CancelFunc
	Loaded   bool
	Idx      int
}

func (i *PlayerItem) Load() error {
	if i.streamer != nil {
		return nil
	}

	i.ctx, i.cancel = context.WithCancel(context.Background())
	stream, err := retry.DoWithData(func() (*reisenstreamer.Streamer, error) {
		out := reisenstreamer.New(i.ctx, i.Uri)
		if i.ctx.Err() != nil {
			return nil, retry.Unrecoverable(i.ctx.Err())
		}
		if out == nil {
			return nil, errors.New("streamer is nil")
		}
		return out, nil
	})

	if err != nil {
		log.Println(err)
		return err
	}

	i.streamer = stream
	i.fn = stream.StreamerFunc()
	i.sr = beep.SampleRate(stream.SampleRate)
	i.Loaded = true

	return nil
}

func (i *PlayerItem) Unload() {
	i.Loaded = false
	i.Position = 0

	if i.cancel != nil {
		i.cancel()
	}

	if i.streamer != nil {
		i.streamer.Close()
	}

	i.fn = nil
	i.streamer = nil
}

// TODO use context here to cancel this if someone loads two lists..
func (p *Player) LoadPlaylist(id uuid.UUID, playlist *ytdl.Playlist) {
	if p.cancel != nil {
		p.cancel()
	}

	if p.Playing {
		p.Stop()
	}

	p.PlaylistID = id
	p.PlayList = playlist

	p.ctx, p.cancel = context.WithCancel(context.Background())
	for i, info := range playlist.Videos {
		select {
		case <-p.ctx.Done():
			log.Printf("LoadPlaylist cancelled: %v\n", p.ctx.Err())
			return
		default:
			item := new(PlayerItem)
			item.Artist = info.Author
			item.Title = info.Title
			item.Duration = info.Duration
			item.ID = info.ID
			item.Uri = "http://localhost:" + config.GetString("web.port") + "/youtube/" + info.ID
			item.Idx = i + 1
			p.playlist.PushBack(item)
		}
	}

	p.Next()
}

func (p *Player) Stop() {
	if !p.Playing {
		return
	}

	p.Playing = false
	p.PlaylistID = uuid.UUID{}
	app.events.Emit(events.EventName("player"))

	if p.current != nil {
		p.current.Value.(*PlayerItem).cancel()
		p.NextValue().Value.(*PlayerItem).cancel()
	}

	p.current = nil

	p.playlist = p.playlist.Init()
}

func (p *Player) Play(idx int) {
	var i int

	var e *list.Element

	for e = p.playlist.Front(); e != nil; e = e.Next() {
		if idx == i {
			break
		}
		i++
	}

	if e != nil {
		e.Value.(*PlayerItem).Load()
		cur := p.current
		next := p.NextValue()

		p.current = e
		p.NextValue().Value.(*PlayerItem).Load()

		app.events.Emit(events.EventName("player"))

		cur.Value.(*PlayerItem).Unload()
		next.Value.(*PlayerItem).Unload()
	}
}

func (p *Player) NextValue() *list.Element {
	switch {
	case p.current == nil:
		fallthrough
	case p.current.Next() == nil:
		return p.playlist.Front()
	default:
		return p.current.Next()
	}
}

func (p *Player) PrevValue() *list.Element {
	if p.current.Prev() != nil {
		return p.current.Prev()
	} else {
		return p.playlist.Back()
	}
}

func (p *Player) Next() {
	p.current = p.NextValue()
	p.PrevValue().Value.(*PlayerItem).Unload()

	p.Playing = true
	app.events.Emit(events.EventName("player"))

	item := p.current.Value.(*PlayerItem)
	err := item.Load()
	if err != nil {
		log.Println(err)
		return
	}

	// Preload next song.
	next := p.NextValue()
	err = next.Value.(*PlayerItem).Load()
	if err != nil {
		log.Println(err)
		return
	}
}

func (p *Player) Prev() {
	p.current = p.PrevValue()
	p.Playing = true
	app.events.Emit(events.EventName("player"))

	item := p.current.Value.(*PlayerItem)
	err := item.Load()
	if err != nil {
		log.Println(err)
		return
	}

	// Reload next song
	next := p.NextValue().Value.(*PlayerItem)
	next.Unload()
	next.Load()

	// Unload nextnext song.
	if p.NextValue().Next() == nil {
		p.playlist.Front().Value.(*PlayerItem).Unload()
	} else {
		p.NextValue().Next().Value.(*PlayerItem).Unload()
	}
}

func (p *Player) Stream(samples [][2]float64) (n int, ok bool) {
	if !p.Playing || p.current.Value.(*PlayerItem).streamer == nil || !p.current.Value.(*PlayerItem).streamer.Started {
		for i := 0; i < len(samples); i++ {
			samples[i] = [2]float64{}
		}
		return len(samples), true
	}

	item := p.current.Value.(*PlayerItem)
	n, ok = item.fn.Stream(samples)
	item.Position = item.sr.D(item.sr.N(item.Position) + n)

	if !ok {
		go p.Next()
		ok = true
		return
	}

	return
}

func (p *Player) Err() error {
	return nil
}

func CurrentPlaylist(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
	w.Header().Add("Content-Type", "application/json")

	if player.PlayList == nil {
		json.NewEncoder(w).Encode(nil)
		return
	}

	err := json.NewEncoder(w).Encode(player.PlayList.Videos)
	if err != nil {
		http.Error(w, "Unable to get playlist. "+err.Error(), http.StatusInternalServerError)
	}
}