COOLDOWN_FACTOR = 0.995

BALANCE_RED   = 7.0
BALANCE_GREEN = 2.0
BALANCE_BLUE  = 1.5

num_modules = 20
center_module = 10

-- maximum energy value
maxEnergy = 1

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

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

function weighted_avg(array, centerIndex)
  return 0.2 * array[centerIndex - 1] +
         0.6 * array[centerIndex] +
         0.2 * array[centerIndex + 1]
end

function periodic()
  local redEnergy = get_energy_in_band(0, 400) * BALANCE_RED
  local greenEnergy = get_energy_in_band(400, 5000) * BALANCE_GREEN
  local blueEnergy = get_energy_in_band(5000, 22000) * BALANCE_BLUE
  local centerIndex = 2 * center_module + 1;

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

  if greenEnergy > maxEnergy then
    maxEnergy = greenEnergy
  end

  if blueEnergy > maxEnergy then
    maxEnergy = blueEnergy
  end

  -- move the color buffers on by one in each direction
  for i = 2,centerIndex,1 do
    tmpRed[i-1]   = tmpRed[i]
    tmpGreen[i-1] = tmpGreen[i]
    tmpBlue[i-1]  = tmpBlue[i]
  end

  for i = #tmpRed-1,centerIndex,-1 do
    tmpRed[i+1]   = tmpRed[i]
    tmpGreen[i+1] = tmpGreen[i]
    tmpBlue[i+1]  = tmpBlue[i]
  end

  -- set the new value for the center module
  tmpRed[centerIndex] = redEnergy / maxEnergy
  tmpGreen[centerIndex] = greenEnergy / maxEnergy
  tmpBlue[centerIndex] = blueEnergy / maxEnergy

  for i = 1,num_modules do
    red[i] = weighted_avg(tmpRed, 2*i)
    green[i] = weighted_avg(tmpGreen, 2*i)
    blue[i] = weighted_avg(tmpBlue, 2*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 = 1,2*(nmod+1) do
    tmpRed[i] = 0
    tmpGreen[i] = 0
    tmpBlue[i] = 0
  end

  -- don't use fading
  return 0
end