package main

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/binary"
	"encoding/json"
	"errors"
	"io"
	"log"
	"math/big"
	"time"

	mrand "math/rand"

	"github.com/sosodev/duration"
	"google.golang.org/api/option"
	"google.golang.org/api/youtube/v3"
)

func init() {
	log.Println("youtube.go loading..")

	var err error

	apikey := config.GetString("youtube.apikey")

	app.youtube, err = youtube.NewService(context.Background(), option.WithAPIKey(apikey))
	if err != nil {
		log.Fatal(err)
	}
	log.Println("youtube.go done.")
}

func ShufflePlaylist(list []string) ([]string, error) {
	seedb := make([]byte, 32)
	_, err := rand.Read(seedb)
	if err != nil {
		return nil, err
	}
	seed := binary.BigEndian.Uint64(seedb)
	mrand.Seed(int64(seed))
	mrand.Shuffle(len(list), func(i, j int) { list[i], list[j] = list[j], list[i] })

	return list, nil
}

func (app *App) GetSong(list []string) string {
	return list[app.plidx]
}

func (app *App) GetNextSong(list []string) string {
	app.plidx++
	if app.plidx >= len(app.active) {
		app.plidx = 0
	}
	return list[app.plidx]
}

func (app *App) GetPrevSong(list []string) string {
	app.plidx--
	if app.plidx < 0 {
		app.plidx = len(list)
	}
	return list[app.plidx]
}

func GetRandomSong(list []string) string {
	if !(len(list) > 0) {
		return ""
	}

	idx, err := rand.Int(rand.Reader, big.NewInt(int64(len(list)-1)))
	if err != nil {
		log.Println("Failed to get random int, ", err)
		return ""
	}
	return list[idx.Int64()]
}

type VideoInfo struct {
	Title   string
	Channel string
	Len     time.Duration
	Uri     string
}

func (app App) Video(vid string) (out VideoInfo, err error) {
	_, r, err := app.cache.GetOrCreate(vid+".videoinfo", func() (io.ReadCloser, error) {
		call := app.youtube.Videos.List([]string{"snippet", "contentDetails"})
		call.MaxResults(1)
		call.Id(vid)
		resp, err := call.Do()
		if err != nil {
			return nil, err
		}

		if len(resp.Items) != 1 {
			return nil, errors.New("response contains not 1 item")
		}

		video := resp.Items[0]

		songdur, err := duration.Parse(video.ContentDetails.Duration)
		if err != nil {
			return nil, err
		}

		out := new(VideoInfo)
		out.Len = songdur.ToTimeDuration()
		out.Title = video.Snippet.Title
		out.Channel = video.Snippet.ChannelTitle
		out.Uri = vid

		var buf bytes.Buffer

		json.NewEncoder(&buf).Encode(out)

		return io.NopCloser(&buf), nil

	})
	if err != nil {
		return
	}
	json.NewDecoder(r).Decode(&out)

	return out, nil
}

func (app App) Playlist(playlist string) ([]string, error) {
	call := app.youtube.PlaylistItems.List([]string{"contentDetails"})
	pageToken := ""
	call = call.MaxResults(50)
	call = call.PlaylistId(playlist)
	if pageToken != "" {
		call = call.PageToken(pageToken)
	}

	var list []string
	for {
		response, err := call.Do()
		if err != nil {
			return nil, err
		}
		for _, item := range response.Items {
			list = append(list, item.ContentDetails.VideoId)
		}
		pageToken = response.NextPageToken
		if pageToken == "" {
			break
		}
		call.PageToken(pageToken)
	}
	return list, nil
}