// +build example jsgo

// This is an example to implement an audio player.
// See examples/wav for a simpler example to play a sound file.

package main

import (
        "fmt"
        "image/color"
        "io/ioutil"
        "log"
        "time"

        "github.com/hajimehoshi/ebiten"
        "github.com/hajimehoshi/ebiten/audio"
        "github.com/hajimehoshi/ebiten/audio/mp3"
        "github.com/hajimehoshi/ebiten/audio/wav"
        "github.com/hajimehoshi/ebiten/ebitenutil"
        raudio "github.com/hajimehoshi/ebiten/examples/resources/audio"
        "github.com/hajimehoshi/ebiten/inpututil"
)

const (
        screenWidth  = 320
        screenHeight = 240

        // This sample rate doesn't match with wav/mp3's sample rate,
        // but decoders adjust them.
        sampleRate = 48000
)

var (
        playerBarColor     = color.RGBA{0x80, 0x80, 0x80, 0xff}
        playerCurrentColor = color.RGBA{0xff, 0xff, 0xff, 0xff}
)

// Player represents the current audio state.
type Player struct {
        audioContext *audio.Context
        audioPlayer  *audio.Player
        current      time.Duration
        total        time.Duration
        seBytes      []byte
        seCh         chan []byte
        volume128    int
}

func playerBarRect() (x, y, w, h int) {
        w, h = 300, 4
        x = (screenWidth - w) / 2
        y = screenHeight - h - 16
        return
}

func NewPlayer(audioContext *audio.Context) (*Player, error) {
        const bytesPerSample = 4 // TODO: This should be defined in audio package
        s, err := mp3.Decode(audioContext, audio.BytesReadSeekCloser(raudio.Classic_mp3))
        if err != nil {
                return nil, err
        }
        p, err := audio.NewPlayer(audioContext, s)
        if err != nil {
                return nil, err
        }
        player := &Player{
                audioContext: audioContext,
                audioPlayer:  p,
                total:        time.Second * time.Duration(s.Length()) / bytesPerSample / sampleRate,
                volume128:    128,
                seCh:         make(chan []byte),
        }
        if player.total == 0 {
                player.total = 1
        }
        player.audioPlayer.Play()
        go func() {
                s, err := wav.Decode(audioContext, audio.BytesReadSeekCloser(raudio.Jab_wav))
                if err != nil {
                        log.Fatal(err)
                        return
                }
                b, err := ioutil.ReadAll(s)
                if err != nil {
                        log.Fatal(err)
                        return
                }
                player.seCh <- b
        }()
        return player, nil
}

func (p *Player) update() error {
        select {
        case p.seBytes = <-p.seCh:
                close(p.seCh)
                p.seCh = nil
        default:
        }

        if p.audioPlayer.IsPlaying() {
                p.current = p.audioPlayer.Current()
        }
        p.seekBarIfNeeded()
        p.switchPlayStateIfNeeded()
        p.playSEIfNeeded()
        p.updateVolumeIfNeeded()

        if inpututil.IsKeyJustPressed(ebiten.KeyB) {
                b := ebiten.IsRunnableInBackground()
                ebiten.SetRunnableInBackground(!b)
        }
        return nil
}

func (p *Player) playSEIfNeeded() {
        if p.seBytes == nil {
                // Bytes for the SE is not loaded yet.
                return
        }

        if !inpututil.IsKeyJustPressed(ebiten.KeyP) {
                return
        }
        sePlayer, _ := audio.NewPlayerFromBytes(p.audioContext, p.seBytes)
        sePlayer.Play()
}

func (p *Player) updateVolumeIfNeeded() {
        if ebiten.IsKeyPressed(ebiten.KeyZ) {
                p.volume128--
        }
        if ebiten.IsKeyPressed(ebiten.KeyX) {
                p.volume128++
        }
        if p.volume128 < 0 {
                p.volume128 = 0
        }
        if 128 < p.volume128 {
                p.volume128 = 128
        }
        p.audioPlayer.SetVolume(float64(p.volume128) / 128)
}

func (p *Player) switchPlayStateIfNeeded() {
        if !inpututil.IsKeyJustPressed(ebiten.KeyS) {
                return
        }
        if p.audioPlayer.IsPlaying() {
                p.audioPlayer.Pause()
                return
        }
        p.audioPlayer.Play()
}

func (p *Player) seekBarIfNeeded() {
        if !inpututil.IsMouseButtonJustPressed(ebiten.MouseButtonLeft) {
                return
        }

        // Calculate the next seeking position from the current cursor position.
        x, y := ebiten.CursorPosition()
        bx, by, bw, bh := playerBarRect()
        const padding = 4
        if y < by-padding || by+bh+padding <= y {
                return
        }
        if x < bx || bx+bw <= x {
                return
        }
        pos := time.Duration(x-bx) * p.total / time.Duration(bw)
        p.current = pos
        p.audioPlayer.Seek(pos)
}

func (p *Player) close() error {
        return p.audioPlayer.Close()
}

func (p *Player) draw(screen *ebiten.Image) {
        // Draw the bar.
        x, y, w, h := playerBarRect()
        ebitenutil.DrawRect(screen, float64(x), float64(y), float64(w), float64(h), playerBarColor)

        // Draw the cursor on the bar.
        c := p.current
        cw, ch := 4, 10
        cx := int(time.Duration(w)*c/p.total) + x - cw/2
        cy := y - (ch-h)/2
        ebitenutil.DrawRect(screen, float64(cx), float64(cy), float64(cw), float64(ch), playerCurrentColor)

        // Compose the curren time text.
        m := (c / time.Minute) % 100
        s := (c / time.Second) % 60
        currentTimeStr := fmt.Sprintf("%02d:%02d", m, s)

        // Draw the debug message.
        msg := fmt.Sprintf(`FPS: %0.2f
Press S to toggle Play/Pause
Press P to play SE
Press Z or X to change volume of the music
Press B to switch the run-in-background state
Current Time: %s`, ebiten.CurrentFPS(), currentTimeStr)
        ebitenutil.DebugPrint(screen, msg)
}

var (
        musicPlayer *Player
)

func update(screen *ebiten.Image) error {
        if err := musicPlayer.update(); err != nil {
                return err
        }

        if ebiten.IsRunningSlowly() {
                return nil
        }

        musicPlayer.draw(screen)
        return nil
}

func main() {
        audioContext, err := audio.NewContext(sampleRate)
        if err != nil {
                log.Fatal(err)
        }

        musicPlayer, err = NewPlayer(audioContext)
        if err != nil {
                log.Fatal(err)
        }
        if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Audio (Ebiten Demo)"); err != nil {
                log.Fatal(err)
        }
        if err := musicPlayer.close(); err != nil {
                log.Fatal(err)
        }
}