OC-Donut: donut.c ported to OpenComputers

local component = require("component")
local event = require("event")
local term = require("term")
local math = require("math")
local computer = require("computer")
local gpu = component.gpu

local w, h = gpu.getResolution()
local buffer = {}
local showFPS, bouncingMode, running = false, false, true
local donuts = {}
local A, B = 0, 0
local z, b = {}, {}

local function sin(x) return math.sin(x) end
local function cos(x) return math.cos(x) end

local fpsCounter = {
  sampleWindow = 3,
  updateInterval = 0.5,
  frameTimeQueue = {},
  queueSize = 180,
  queueIndex = 1,
  queueSum = 0,
  lastUpdateTime = 0,
  currentFPS = 0,
  update = function(self, dt)
    if #self.frameTimeQueue == self.queueSize then
      self.queueSum = self.queueSum - self.frameTimeQueue[self.queueIndex]
    end
    self.frameTimeQueue[self.queueIndex] = dt
    self.queueSum = self.queueSum + dt
    self.queueIndex = self.queueIndex % self.queueSize + 1
    local numFrames = math.min(#self.frameTimeQueue, self.queueSize)
    local averageFrameTime = self.queueSum / numFrames
    local fps = 1 / averageFrameTime
    local currentTime = computer.uptime()
    if currentTime - self.lastUpdateTime >= self.updateInterval then
      self.currentFPS = math.floor(fps + 0.5)
      self.lastUpdateTime = currentTime
    end
  end,
  draw = function(self)
    if showFPS then
      gpu.set(1, 1, string.format("FPS: %d", self.currentFPS))
    end
  end
}

local function cls()
  for i = 1, w * h do buffer[i] = " " end
end

local function flush()
  local str = table.concat(buffer)
  gpu.copy(1, 1, w, h, 0, 1)
  gpu.set(1, h, str:sub(1 + (h-1)*w))
  for i = h-1, 1, -1 do
    gpu.set(1, i, str:sub(1 + (i-1)*w, i*w))
  end
end

local function createDonut()
  return {
    x = w / 2,
    y = h / 2,
    vx = math.random(1, 2) * (math.random() > 0.5 and 1 or -1),
    vy = math.random(1, 2) * (math.random() > 0.5 and 1 or -1),
    size = math.random(10, 15)
  }
end

local function drawMessage()
  local message = "OC-Donut (Press X to quit.) Based on the original donut.c by Andy Sloane <[email protected]> Ported by nonogamer9"
  local oldBg, oldFg = gpu.getBackground(), gpu.getForeground()
  gpu.setBackground(0x0000FF)
  gpu.setForeground(0xFFFFFF)
  gpu.fill(1, h, w, 1, " ")
  gpu.set(1, h, message)
  gpu.setBackground(oldBg)
  gpu.setForeground(oldFg)
end

local function drawBouncingMessage(time)
  local message = "Watch The Donuts Bounce!"
  local messageLength = #message
  local yPosition = h - 2
  local xPosition = math.floor(w/2 - messageLength/2 + sin(time) * (w/2 - messageLength/2))
  local oldBg, oldFg = gpu.getBackground(), gpu.getForeground()
  gpu.setBackground(0x000000)
  gpu.setForeground(0xFFFF00)
  gpu.fill(1, yPosition, w, 1, " ")
  gpu.set(xPosition, yPosition, message)
  gpu.setBackground(oldBg)
  gpu.setForeground(oldFg)
end

local function updateBouncingDonuts()
  for _, donut in ipairs(donuts) do
    donut.x = donut.x + donut.vx
    donut.y = donut.y + donut.vy
    if donut.x <= donut.size or donut.x >= w - donut.size then
      donut.vx = -donut.vx
    end
    if donut.y <= donut.size or donut.y >= h - donut.size then
      donut.vy = -donut.vy
    end
  end
end

event.listen("key_down", function(_, _, _, code)
  if code == 59 then
    showFPS = not showFPS
    if not showFPS then gpu.set(1, 1, string.rep(" ", 10)) end
  elseif code == 60 then
    bouncingMode = not bouncingMode
    if bouncingMode then donuts = {createDonut()} end
  elseif code == 18 and bouncingMode then
    table.insert(donuts, createDonut())
  elseif code == 16 and bouncingMode and #donuts > 1 then
    table.remove(donuts)
  elseif code == 45 then
    running = false
  end
end)

while running do
  local frameStartTime = computer.uptime()
  for i = 1, w * h do b[i], z[i] = " ", 0 end
  if bouncingMode then updateBouncingDonuts() end
  local renderDonuts = bouncingMode and donuts or {{x = w/2, y = h/2, size = 30}}
  for _, donut in ipairs(renderDonuts) do
    for j = 0, 6.28, 0.07 do
      for i = 0, 6.28, 0.02 do
        local sini, cosj = sin(i), cos(j)
        local sinA, sinj = sin(A), sin(j)
        local cosA, cosj2 = cos(A), cosj + 2
        local mess = 1 / (sini * cosj2 * sinA + sinj * cosA + 5)
        local cosi, cosB = cos(i), cos(B)
        local sinB = sin(B)
        local t = sini * cosj2 * cosA - sinj * sinA
        local x = math.floor(donut.x + donut.size * mess * (cosi * cosj2 * cosB - t * sinB))
        local y = math.floor(donut.y + donut.size/2 * mess * (cosi * cosj2 * sinB + t * cosB))
        local o = x + w * y
        local N = math.floor(8 * ((sinj * sinA - sini * cosj * cosA) * cosB - sini * cosj * sinA - sinj * cosA - cosi * cosj * sinB))
        if y > 0 and y <= h and x > 0 and x <= w and mess > z[o] then
          z[o] = mess
          b[o] = string.sub(".,-~:;=!*#$@", math.max(N, 1), math.max(N, 1))
        end
      end
    end
  end
  cls()
  for k = 1, w * h do buffer[k] = b[k] end
  flush()
  if bouncingMode then drawBouncingMessage(frameStartTime) else drawMessage() end
  A, B = A + 0.08, B + 0.06
  local frameEndTime = computer.uptime()
  fpsCounter:update(frameEndTime - frameStartTime)
  fpsCounter:draw()
  os.sleep(0.05)
end

term.clear()
print("Thank you for using OC-Donut!")