local Screen = require("screen")
local scrn, map1, map2, width, height

function _init()
  local c
  scrn = Screen:new("Life!", 10, 4)
  makepointer()
  scrn:palette(1, 0, 0, 3)
  scrn:palette(2, 0, 3, 0)
  scrn:palette(3, 0, 3, 3)
  scrn:palette(4, 3, 0, 0)
  scrn:palette(5, 3, 0, 3)
  scrn:palette(6, 3, 3, 0)
  scrn:palette(7, 3, 3, 3)
  scrn:palette(8, 0, 0, 15)
  scrn:palette(9, 0, 15, 0)
  scrn:palette(10, 0, 15, 15)
  scrn:palette(11, 15, 0, 0)
  scrn:palette(12, 15, 0, 15)
  scrn:palette(13, 15, 15, 0)
  scrn:palette(14, 15, 15, 15)
  scrn:autocolor()
  width, height = scrn:size()
  map1 = {}
  map2 = {}
  sys.stepinterval(0)
  for y = 0, height - 1 do
    for x = 0, width - 1 do
      c = math.floor(math.random(1024)) % 15
      map1[xy(x, y)] = c
    end
  end
end

function _step(t)
  local map, live, neis
  scrn:step(t)
  if input.hotkey() == "q" then
    sys.exit(0)
  end
  for y = 0, height - 1 do
    for x = 0, width - 1 do
      live = map1[xy(x, y)]
      neis = nei(x, y)
      if live > 7 then
        if (neis < 2) or (neis > 3) then
          set(x, y, live - 7)
        else
          set(x, y, live)
        end
      else
        if neis == 3 then
          set(x, y, procreate(x, y))
        else
          set(x, y, live)
        end
      end
    end
  end
  local mx, my, mb = input.mouse()
  if mb == 1 then
    local c = (map2[xy(mx, my)] % 8) + 7
    set(mx - 1, my - 1, c)
    set(mx + 1, my + 0, c)
    set(mx - 1, my + 1, c)
    set(mx + 0, my + 1, c)
    set(mx + 0, my + 0, c)
  end
  map = map1
  map1 = map2
  map2 = map
end

function xy(x, y)
  return (y * width + x) % (width * height)
end

function nei(x, y)
  local lives = 0
  for _y = -1, 1 do
    for _x = -1, 1 do
      if (map1[xy(x + _x, y + _y)] or 0) > 7 then
        lives = lives + 1
      end
    end
  end
  if map1[xy(x, y)] > 7 then
    lives = lives - 1
  end
  return lives
end

function procreate(x, y)
  local r, g, b = 0, 0, 0
  for _y = -1, 1 do
    for _x = -1, 1 do
      if (map1[xy(x + _x, y + _y)] or 0) > 7 then
        local c = map1[xy(x + _x, y + _y)] - 7
        r = r + (c & 4) / 4
        g = g + (c & 2) / 2
        b = b + (c & 1)
      end
    end
  end
  local child = 0
  if r > 1 then
    child = child + 4
  end
  if g > 1 then
    child = child + 2
  end
  if b > 1 then
    child = child + 1
  end
  if child == 0 then
    child = 1 + (math.floor(math.random(128)) % 7)
  end
  return child + 7
end

function set(x, y, alive)
  if map1[xy(x, y)] ~= alive or map2[xy(x, y)] ~= alive then
    map2[xy(x, y)] = alive
    gfx.pixel(x, y, map2[xy(x, y)] or 0)
  end
end

function makepointer()
  gfx.fgcolor(2)
  gfx.line(0, 5, 10, 5)
  gfx.line(5, 0, 5, 10)
  gfx.fgcolor(0)
  gfx.plot(5, 5)
  local pimg = image.new(11, 11, 2)
  image.copy(pimg, 0, 0, 0, 0, 11, 11)
  image.pointer(pimg, 5, 5)
end