package main

import (
	"fmt"
	"image"
	"math"
	"os"
	"time"

	_ "image/png"

	"gitbutter.pw/zolfite/project-rpg/gameobjects"
	"github.com/faiface/pixel"
	"github.com/faiface/pixel/pixelgl"
	"golang.org/x/image/colornames"
)

func loadPicture(path string) (pixel.Picture, error) {
	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer file.Close()
	img, _, err := image.Decode(file)
	if err != nil {
		return nil, err
	}
	return pixel.PictureDataFromImage(img), nil
}

func run() {
	cfg := pixelgl.WindowConfig{
		Title:  "Project RPG",
		Bounds: pixel.R(0, 0, 1024, 768),
		VSync:  true,
	}
	win, err := pixelgl.NewWindow(cfg)
	if err != nil {
		panic(err)
	}

	spritesheet, err := loadPicture("sprites.png")
	if err != nil {
		panic(err)
	}
	//batch := pixel.NewBatch(&pixel.TrianglesData{}, spritesheet)

	background, err := loadPicture("background.png")

	if err != nil {
		panic(err)
	}
	bg := pixel.NewSprite(background, background.Bounds())
	//batch := pixel.NewBatch(&pixel.TrianglesData{}, spritesheet)

	var (
		camPos       = pixel.ZV
		camZoom      = 0.3
		camZoomSpeed = 1.2
	)

	var (
		frames = 0
		second = time.Tick(time.Second)
	)
	player := gameobjects.NewPlayer(win, spritesheet)

	var fps int64 = 60
	timePerFrame := 1000000000 / fps
	var lastTime int64 = time.Now().UnixNano()
	var now int64
	var dt int64

	// Game Loop
	for !win.Closed() {
		now = time.Now().UnixNano()
		dt += (now - lastTime)
		lastTime = time.Now().UnixNano()

		//Execute a frame.
		if dt >= timePerFrame {

			// *** Update begins *** //

			cam := pixel.IM.Scaled(camPos, camZoom).Moved(win.Bounds().Center().Sub(camPos))

			win.SetMatrix(cam)

			player.Update(win, dt)

			camPos.X = player.PlayerVec.X
			camPos.Y = player.PlayerVec.Y
			camZoom *= math.Pow(camZoomSpeed, win.MouseScroll().Y)

			// *** Update Ends *** //

			// *** Render begin *** //
			win.Clear(colornames.Forestgreen)
			bg.Draw(win, pixel.IM.Moved(win.Bounds().Center()))
			player.Render(win)

			//batch.Draw(win)
			win.Update()

			// *** Render End *** //
			dt = 0
			frames++
			select {
			case <-second:
				win.SetTitle(fmt.Sprintf("%s | FPS: %d", cfg.Title, frames))
				frames = 0
			default:
			}
		}
	}
}

func main() {
	pixelgl.Run(run)
}