package main

import (
	"fmt"
	"image"
	"image/color"
	"image/draw"
	"log"

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

const (
	screenWidth  = 128
	screenHeight = 128
)

var (
	drawImage *image.RGBA
	gc        *gg.Context
)

func update(screen *ebiten.Image) error {

	if ebiten.IsRunningSlowly() {
		return nil
	}
	screen.ReplacePixels(drawImage.Pix)
	ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %f", ebiten.CurrentFPS()))
	return nil
}

func main() {
	drawImage = image.NewRGBA(image.Rect(0, 0, screenWidth, screenHeight))
	rect := image.Rect(0, 0, screenWidth, screenHeight)
  // 2 colour palette (black/red)
	palette := color.Palette{
		color.RGBA{0, 0, 0, 0},
		color.RGBA{255, 0, 0, 255},
	}
	paletteImage := image.NewPaletted(rect, palette)

	gc = gg.NewContextForImage(drawImage)
	gc.SetRGB(0, 0, 0)
	gc.SetRGBA(1, 0, 0, 1)
	gc.SetLineWidth(1)
	gc.DrawLine(20, 20, 80, 60)
	gc.Stroke()

	// draw onto palette
	draw.Draw(paletteImage, rect, gc.Image(), rect.Bounds().Min, draw.Over)
	// draw back again
	draw.Draw(drawImage, rect, paletteImage, rect.Bounds().Min, draw.Over)

	scale := float64(800 / screenWidth)

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