// +build example jsgo

package main

import (
        "bytes"
        "image"
        "image/color"
        _ "image/png"
        "log"

        "github.com/hajimehoshi/ebiten"
        "github.com/hajimehoshi/ebiten/examples/resources/images"
)

const (
        screenWidth  = 320
        screenHeight = 240
)

var (
        count       int
        ebitenImage *ebiten.Image
)

func update(screen *ebiten.Image) error {
        count++
        count %= ebiten.FPS * 10
        diff := float64(count) * 0.2
        switch {
        case 480 < count:
                diff = 0
        case 240 < count:
                diff = float64(480-count) * 0.2
        }

        if ebiten.IsRunningSlowly() {
                return nil
        }

        screen.Fill(color.NRGBA{0x00, 0x00, 0x80, 0xff})

        // Draw 100 Ebitens
        op := &ebiten.DrawImageOptions{}
        op.ColorM.Scale(1.0, 1.0, 1.0, 0.5)
        for i := 0; i < 10*10; i++ {
                op.GeoM.Reset()
                x := float64(i%10)*diff + 15
                y := float64(i/10)*diff + 20
                op.GeoM.Translate(x, y)
                screen.DrawImage(ebitenImage, op)
        }
        return nil
}

func main() {
        // Decode image from a byte slice instead of a file so that
        // this example works in any working directory.
        // If you want to use a file, there are some options:
        // 1) Use os.Open and pass the file to the image decoder.
        //    This is a very regular way, but doesn't work on browsers.
        // 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
        //    This works even on browsers.
        // 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
        //    This also works on browsers.
        img, _, err := image.Decode(bytes.NewReader(images.Ebiten_png))
        if err != nil {
                log.Fatal(err)
        }
        ebitenImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)

        if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Alpha Blending (Ebiten Demo)"); err != nil {
                log.Fatal(err)
        }
}