package main

import (
	"fmt"
	"github.com/hajimehoshi/ebiten/v2"
	"github.com/hajimehoshi/ebiten/v2/ebitenutil"
	"github.com/micosilent/go_chip8/emulator"
	"image/color"
	"log"
	"os"
	"time"
)

const (
	screenWidth  = 640
	screenHeight = 320
	gridWidth    = 64
	gridHeight   = 32
)

type Game struct {
	counter       int
	lastFrameTime time.Time
	debugText     string
	emulator      *emulator.CHIP8
	screenImage   *ebiten.Image
}

func (g *Game) Update() error {

	// We need the emulator to process around 700 instructions per second
	for i := 0; i < 1; i++ {
		g.emulator.EmulateCycle()
		if g.emulator.DrawFlag {
			g.screenImage = g.DrawPixels()
			g.emulator.DrawFlag = false
		}
	}
	return nil
}

func (g *Game) DrawPixels() *ebiten.Image {
	img := ebiten.NewImage(gridWidth, gridHeight)
	white := color.White
	black := color.Black

	// Draw the boolean array to the image
	for x := 0; x < gridWidth; x++ {
		for y := 0; y < gridHeight; y++ {
			if g.emulator.GetPixelAtCoordinate(x, y) {
				img.Set(x, y, white)
			} else {
				img.Set(x, y, black)
			}
		}
	}

	return img
}

func newGame() *Game {
	return &Game{
		counter:       1,
		lastFrameTime: time.Now(),
		debugText:     "",
		emulator:      emulator.NewChip8(),
	}
}

func check(err error) {
	if err != nil {
		log.Fatal(err)
	}
}

func (g *Game) Draw(screen *ebiten.Image) {
	deltaTime := time.Since(g.lastFrameTime)
	fps := int(1 / deltaTime.Seconds())
	g.debugText = fmt.Sprintf("Counter: %d, fps: %d", g.counter, fps)
	ebitenutil.DebugPrint(screen, g.debugText)
	g.counter++
	g.lastFrameTime = time.Now()

	scaleX := float64(screenWidth) / float64(gridWidth)
	scaleY := float64(screenHeight) / float64(gridHeight)

	op := &ebiten.DrawImageOptions{}
	op.GeoM.Scale(scaleX, scaleY)
	screen.DrawImage(g.screenImage, op)
}

func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {
	return screenWidth, screenHeight
}

func (g *Game) LoadROM(path string) {
	dat, err := os.ReadFile(path)
	check(err)

	err = g.emulator.LoadROMIntoMemory(dat)
	check(err)
}

func main() {
	game := newGame()
	game.LoadROM("roms/ibm_logo.ch8")
	ebiten.SetWindowSize(screenWidth, screenHeight)
	ebiten.SetWindowTitle("Go CHIP8 Emulator")

	err := ebiten.RunGame(game)
	check(err)
}