COOLDOWN_FACTOR = 0.9998
MAX_ENERGY_PROPAGATION = 0.5
EXPONENT=1.0
W_EXPONENT=1.0
OVERDRIVE=1

num_modules = 1
num_strips = 1

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

-- array storing the flame’s energy for each pixel
fireRedEnergy = {}
fireGreenEnergy = {}
fireBlueEnergy = {}
fireWhiteEnergy = {}

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

function limit(val)
	if val > 1 then
		return 1
	elseif val < 0 then
		return 0
	else
		return val
	end
end

function updateFire(newEnergy, energyArray)
	avgEnergyPerStrip = newEnergy * 2 / num_strips

	for s = 1,num_strips do
		-- Add new energy in the bottom row
		i = idx(s, 1)
		energyArray[i] = energyArray[i] + math.random() * avgEnergyPerStrip

		-- remove energy at the top
		i = idx(s, num_modules)
		energyArray[i] = energyArray[i] * (1.0 - math.random() * MAX_ENERGY_PROPAGATION)

		-- move energy upwards
		for m_out = num_modules,2,-1 do
			i_out = idx(s, m_out)
			i_in  = idx(s, m_out - 1)

			energyMoved = energyArray[i_in] * math.random() * MAX_ENERGY_PROPAGATION

			energyArray[i_in]  = energyArray[i_in]  - energyMoved
			energyArray[i_out] = energyArray[i_out] + energyMoved
		end
	end
end

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, 12000);
	local whiteEnergy = get_energy_in_band(12000, 22000);

	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

	maxWhiteEnergy = maxWhiteEnergy * COOLDOWN_FACTOR
	if whiteEnergy > maxWhiteEnergy then
		maxWhiteEnergy = whiteEnergy
	end

	updateFire(redEnergy / maxRedEnergy, fireRedEnergy)
	updateFire(greenEnergy / maxGreenEnergy, fireGreenEnergy)
	updateFire(blueEnergy / maxBlueEnergy, fireBlueEnergy)
	updateFire(whiteEnergy / maxWhiteEnergy, fireWhiteEnergy)

	-- make colors more exciting + remove the first (flickering) mass
	-- TODO: update
	for m = 1,num_modules do
		for s = 1,num_strips do
			i = idx(s, m)

			rval = limit(OVERDRIVE * fireRedEnergy[i]^EXPONENT)
			gval = limit(OVERDRIVE * fireGreenEnergy[i]^EXPONENT)
			bval = limit(OVERDRIVE * fireBlueEnergy[i]^EXPONENT)
			wval = limit(OVERDRIVE * fireWhiteEnergy[i]^W_EXPONENT)

			red[i] = rval
			green[i] = gval
			blue[i] = bval
			white[i] = wval
		end
	end

	-- return the 4 color arrays
	return red, green, blue, white
end

function init(nstrip, nmod, cmod)
	num_strips = nstrip
	num_modules = nmod

	for i = 1,(nmod*nstrip) do
		red[i] = 0
		green[i] = 0
		blue[i] = 0
		white[i] = 0

		fireRedEnergy[i] = 0
		fireGreenEnergy[i] = 0
		fireBlueEnergy[i] = 0
		fireWhiteEnergy[i] = 0
	end

	-- don't use fading
	return 0
end