COOLDOWN_FACTOR = 0.9998
FADE_FACTOR = 0.985

num_modules = 20
center_module = 10

-- maximum energy values for each band
maxRedEnergy = 1
maxGreenEnergy = 1
maxBlueEnergy = 1

-- output color buffers
red = {}
green = {}
blue = {}

tmpRed = {}
tmpGreen = {}
tmpBlue = {}

function periodic()
  local redEnergy = get_energy_in_band(0, 400);
  local greenEnergy = get_energy_in_band(400, 4000);
  local blueEnergy = get_energy_in_band(4000, 22000);
  local centerIndex = 2 * center_module + 1;

  maxRedEnergy = maxRedEnergy * COOLDOWN_FACTOR
  if redEnergy > maxRedEnergy then
    maxRedEnergy = redEnergy
  end

  maxGreenEnergy = maxGreenEnergy * COOLDOWN_FACTOR
  if greenEnergy > maxGreenEnergy then
    maxGreenEnergy = greenEnergy
  end

  maxBlueEnergy = maxBlueEnergy * COOLDOWN_FACTOR
  if blueEnergy > maxBlueEnergy then
    maxBlueEnergy = blueEnergy
  end

  -- move the color buffers on by one
  for i = num_modules-1,1,-1 do
    tmpRed[i+1]   = FADE_FACTOR * tmpRed[i]
    tmpGreen[i+1] = FADE_FACTOR * tmpGreen[i]
    tmpBlue[i+1]  = FADE_FACTOR * tmpBlue[i]
  end

  -- set the new value for the center module
  newRed = redEnergy / maxRedEnergy
  if newRed > tmpRed[num_modules] then
    tmpRed[1] = newRed
  else
    tmpRed[1] = tmpRed[num_modules]
  end

  newGreen = greenEnergy / maxGreenEnergy
  if newGreen > tmpGreen[num_modules] then
    tmpGreen[1] = newGreen
  else
    tmpGreen[1] = tmpGreen[num_modules]
  end

  newBlue = blueEnergy / maxBlueEnergy
  if newBlue > tmpBlue[num_modules] then
    tmpBlue[1] = newBlue
  else
    tmpBlue[1] = tmpBlue[num_modules]
  end

  for i = 1,num_modules do
    red[i] = tmpRed[i]
    green[i] = tmpGreen[i]
    blue[i] = tmpBlue[i]
  end

  -- return the 3 color arrays
  return red, green, blue
end

function init(nmod, cmod)
  num_modules = nmod
  center_module = cmod

  for i = 1,nmod do
    red[i] = 0
    green[i] = 0
    blue[i] = 0
  end

  for i = 1,nmod do
    tmpRed[i] = 0
    tmpGreen[i] = 0
    tmpBlue[i] = 0
  end

  -- don't use fading
  return 0
end