package main

import (
	"image"
	"image/png"
	"log"
	"os"
	"time"
	"unsafe"

	"github.com/veandco/go-sdl2/sdl"
)

func main() {
	sdl.Init(sdl.INIT_EVERYTHING)
	window, render, err := sdl.CreateWindowAndRenderer(1024, 768, sdl.WINDOW_SHOWN)
	if err != nil {
		log.Fatal(err)
	}
	f, err := os.Open("rocket.png")
	if err != nil {
		log.Fatal(err)
	}
	img, err := png.Decode(f)
	if err != nil {
		log.Fatal(err)
	}
	ir, ok := img.(*image.RGBA)
	if !ok {
		log.Fatal("Not RGBA")
	}
	width := int32(ir.Bounds().Dx())
	height := int32(ir.Bounds().Dy())
	surf, err := sdl.CreateRGBSurfaceWithFormatFrom(
		unsafe.Pointer(&ir.Pix[0]),
		width,
		height,
		32,
		int32(ir.Bounds().Dx()*4),
		// this has confused me in the past, must be ABGR, at least on Intel 64 bit
		sdl.PIXELFORMAT_ABGR8888,
	)
	if err != nil {
		log.Fatal(err)
	}
	tex, err := render.CreateTextureFromSurface(surf)
	if err != nil {
		log.Fatal(err)
	}
	t := time.Tick(16 * time.Millisecond)
	window.Show()
	y := 768 - height/2
	for {
		<-t
		render.Copy(
			tex,
			&sdl.Rect{0, 0, width, height},
			&sdl.Rect{1024/2, y, width/2, height/2},
		)
		y = y - 5
		if y <= 0-height/2 {
			return
		}
		render.Present()
	}

}