// +build example

package main

import (
        "fmt"
        "image"
        _ "image/jpeg"
        "log"
        "net/http"

        "github.com/hajimehoshi/ebiten"
        "github.com/hajimehoshi/ebiten/ebitenutil"
)

var (
        count          int
        highDPIImage   *ebiten.Image
        highDPIImageCh = make(chan *ebiten.Image)
)

func init() {
        // Licensed under Public Domain
        // https://commons.wikimedia.org/wiki/File:As08-16-2593.jpg
        const url = "https://upload.wikimedia.org/wikipedia/commons/1/1f/As08-16-2593.jpg"

        // Load the image asynchronously.
        go func() {
                res, err := http.Get(url)
                if err != nil {
                        log.Fatal(err)
                }
                defer res.Body.Close()

                img, _, err := image.Decode(res.Body)
                if err != nil {
                        log.Fatal(err)
                }

                eimg, err := ebiten.NewImageFromImage(img, ebiten.FilterLinear)
                if err != nil {
                        log.Fatal(err)
                }

                highDPIImageCh <- eimg
                close(highDPIImageCh)
        }()
}

func update(screen *ebiten.Image) error {
        if highDPIImage == nil {
                // Use select and 'default' clause for non-blocking receiving.
                select {
                case img := <-highDPIImageCh:
                        highDPIImage = img
                default:
                }
        }

        if ebiten.IsRunningSlowly() {
                return nil
        }

        if highDPIImage == nil {
                ebitenutil.DebugPrint(screen, "Loading the image...")
                return nil
        }

        scale := ebiten.DeviceScaleFactor()
        sw, sh := screen.Size()

        w, h := highDPIImage.Size()
        op := &ebiten.DrawImageOptions{}

        // Move the images's center to the upper left corner.
        op.GeoM.Translate(float64(-w)/2, float64(-h)/2)

        // The image is just too big. Adjust the scale.
        op.GeoM.Scale(0.25, 0.25)

        // Scale the image by the device ratio so that the rendering result can be same
        // on various (diffrent-DPI) environments.
        op.GeoM.Scale(scale, scale)

        // Move the image's center to the screen's center.
        op.GeoM.Translate(float64(sw)/2, float64(sh)/2)
        screen.DrawImage(highDPIImage, op)

        ebitenutil.DebugPrint(screen, fmt.Sprintf("Device Scale Ratio: %0.2f", scale))
        return nil
}

func main() {
        const (
                screenWidth  = 640
                screenHeight = 480
        )

        // Pass the invert of scale so that Ebiten's auto scaling by device scale is disabled.
        s := ebiten.DeviceScaleFactor()
        if err := ebiten.Run(update, int(screenWidth*s), int(screenHeight*s), 1/s, "High DPI (Ebiten Demo)"); err != nil {
                log.Fatal(err)
        }
}