-- based on
-- https://github.com/healeYcodes/virtual-ants/blob/main/index.html

require("util")

local function round2even(num)
  return 2 * math.floor(num / 2)
end

local function rotate(direction, clockwise)
  local match
  if clockwise then
    match = {
      u = "r",
      r = "d",
      d = "l",
      l = "u",
    }
  else
    match = {
      u = "l",
      l = "d",
      d = "r",
      r = "u"
    }
  end
  return match[direction]
end

local function initColors(rules)
  rules = rules:lower()
  local colorbrewer = require("colorbrewer")
  local scheme = colorbrewer.random()
  local variant = scheme[#rules]
  COLORS = {}
  for i = 1, #rules do
    COLORS[i] = {
      clockwise = rules:sub(i, i) == "r",
      rgba = variant[i]
    }
  end
end

local function initScreen(width, height)
  love.window.setMode(width, height, { highdpi = true })
  WIDTH, HEIGHT = round2even(width), round2even(height)
  CANVAS = love.graphics.newCanvas(WIDTH, HEIGHT)
  CANVAS:renderTo(function()
    local color = COLORS[1].rgba
    color[4] = 0.9
    love.graphics.setColor(color)
    love.graphics.rectangle("fill", 0, 0, WIDTH, HEIGHT)
  end)
  UNITS = 8
end

local function initAnt()
  ANT = {
    x = (WIDTH / 2) - ((WIDTH / 2) % UNITS),
    y = (HEIGHT / 2) - ((HEIGHT / 2) % UNITS),
    direction = "u",
  }
end

local function initGrid()
  GRID = {}
  GRID.mt = {}
  setmetatable(GRID, GRID.mt)
  GRID.mt.__index = function(table, key)
    table[key] = {}
    table[key].mt = {}
    setmetatable(table[key], table[key].mt)
    table[key].mt.__index = function(innerTable, innerKey)
      innerTable[innerKey] = 1
      return innerTable[innerKey]
    end
    return table[key]
  end
end

function love.load(args)
  local width = args[1] or 800
  local height = args[2] or 600
  local rules = args[3] or "RL"
  initColors(rules)
  initScreen(width, height)
  initAnt()
  initGrid()
end

local function color(x, y)
  return GRID[x][y]
end

local function current()
  return color(ANT.x, ANT.y)
end

local function setCurrent(index)
  GRID[ANT.x][ANT.y] = index
end

local function updateCurrent()
  local val = current()
  if val == #COLORS then
    val = 1
  else
    val = val + 1
  end
  setCurrent(val)
end

local function nextColor()
  local c = COLORS[current()]
  updateCurrent()
  return c
end

function love.update()
  require("lurker").update()
  local c = nextColor()
  ANT.direction = rotate(ANT.direction, c.clockwise)
  CANVAS:renderTo(function()
    love.graphics.setBlendMode("alpha")
    love.graphics.setColor(c.rgba)
    love.graphics.rectangle("fill", ANT.x, ANT.y, UNITS, UNITS)
  end)
  if ANT.direction == "u" then
    ANT.y = ANT.y - UNITS
  elseif ANT.direction == "r" then
    ANT.x = ANT.x + UNITS
  elseif ANT.direction == "d" then
    ANT.y = ANT.y + UNITS
  else
    ANT.x = ANT.x - UNITS
  end

  if ANT.x >= WIDTH then
    ANT.x = 0
  elseif ANT.x < 0 then
    ANT.x = (WIDTH - 1) - ((WIDTH - 1) % UNITS)
  end
  if ANT.y >= HEIGHT then
    ANT.y = 0
  elseif ANT.y < 0 then
    ANT.y = (HEIGHT - 1) - ((HEIGHT - 1) % UNITS)
  end
end

function love.draw()
  love.graphics.setBlendMode("screen", "premultiplied")
  love.graphics.setColor(COLORS[1].rgba)
  love.graphics.draw(CANVAS, 0, 0)
end