package main

import (
	"fmt"
	"runtime"

	"github.com/go-gl/gl/v2.1/gl"
	"github.com/go-gl/glfw/v3.2/glfw"
)

// create on key thing which would be used to mutate the state

func onKey(w *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
	fmt.Println(key) // this would mutate state telling us what keys are being pressed
	fmt.Println(action)
	if key == glfw.KeyEscape && action == glfw.Press {
		w.SetShouldClose(true)
	}
}

func loop(w *glfw.Window) bool {
	if w.ShouldClose() {
		return true
	}

	// gl.ClearColor(2, 0.5, 2.0, 1.0)

	gl.Clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT)
	w.SwapBuffers()
	glfw.PollEvents()

	// logic get new state
	// do drawing

	return loop(w)
}

func openWindow() {

	runtime.LockOSThread()

	if err := glfw.Init(); err != nil {
		panic(fmt.Errorf("could not initialize glfw: %v", err))
	}

	glfw.WindowHint(glfw.ContextVersionMajor, 4)
	glfw.WindowHint(glfw.ContextVersionMinor, 1)
	glfw.WindowHint(glfw.Resizable, glfw.True)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)

	win, err := glfw.CreateWindow(800, 600, "Hello world", nil, nil)

	win.SetKeyCallback(onKey)

	if err != nil {
		panic(fmt.Errorf("could not create opengl renderer: %v", err))
	}

	win.MakeContextCurrent()

	if err := gl.Init(); err != nil {
		panic(err)
	}

	// recursive function which takes old state creates new and loops until w *glfw.Window is not true

	loop(win) // we would also pass through the initial state here to

}

func main() {
	openWindow()
}