--[[
MADE BY BCHEESE, 2021.

Control:
Arrow Keys - move
Key Z      - zoom in
Key X      - zoom out
--]]

local Window = require("window")
local win
local w, h
local scale
local pos
local mimg
local update
local gamepad

function sqr(v)
	return v * v
end

function vec(_x, _y)
	local v = {
		x = _x,
		y = _y
	}
	return v
end

function len(_vec)
	return math.sqrt(sqr(_vec.x) + sqr(_vec.y))
end

function mandelbrot(w, h, iter, offset, scale)
  update = false
  
	for y = 0, h - 1 do
		for x = 0, w - 1 do
			p = vec(x - offset.x, y - offset.y)
			p.x = p.x * scale
			p.y = p.y * scale
			
			z = vec(0, 0)
			
			i = 0
			while (i < iter and (sqr(z.x) + sqr(z.y)) < 4) do
        n = vec()
        n.x = sqr(z.x) - sqr(z.y) + p.x
        n.y = 2 * z.x * z.y + p.y
        
        z.x = n.x
        z.y = n.y
        
        i = i + 1
			end
			
      if (i == iter) then
        image.pixel(mimg, x * 2,     y, 1)
        image.pixel(mimg, x * 2 + 1, y, 1)
      else
        image.pixel(mimg, x * 2,     y, 1 + (i / iter) * 7)
        image.pixel(mimg, x * 2 + 1, y, 1 + (i / iter) * 7)
			end
		end
	end
end

function _init()
  w = 280
  h = 120

  win = Window:new("Mandelbrot", 144, 24, w, h)
  
  win.onclose = function()
    sys.exit()
  end

  mimg  = image.new(w, h, 8)
  scale = 30
  pos   = vec(w / 3.5, h / 2.25)
  mandelbrot(w, h, 16, pos, 1 / scale)
end

function _step(t)
  win:step(t)

  gamepad = input.gamepad(0)
  if gamepad & 1 > 0 then pos.x = pos.x - 5; update = true end
  if gamepad & 2 > 0 then pos.x = pos.x + 5; update = true end
  if gamepad & 4 > 0 then pos.y = pos.y + 5; update = true end
  if gamepad & 8 > 0 then pos.y = pos.y - 5; update = true end
  
  if gamepad & 64  > 0 then scale = scale - 5; update = true end
  if gamepad & 128 > 0 then scale = scale + 5; update = true end


  if update == true then
    mandelbrot(w, h, 16, pos, 1 / scale)
  end

  image.draw(mimg, 0, 0, 0, 0, w, h)
end