local perlin
do
	--[[
	    Implemented as described here:
	    http://flafla2.github.io/2014/08/09/perlinnoise.html
	]]--

	perlin = {}
	perlin.p = {}

	-- Hash lookup table as defined by Ken Perlin
	-- This is a randomly arranged array of all numbers from 0-255 inclusive
	local permutation = {151,160,137,91,90,15,
	  131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
	  190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
	  88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
	  77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
	  102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
	  135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
	  5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
	  223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
	  129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
	  251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
	  49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
	  138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
	}

	-- p is used to hash unit cube coordinates to [0, 255]
	for i=0,255 do
	    -- Convert to 0 based index table
	    perlin.p[i] = permutation[i+1]
	    -- Repeat the array to avoid buffer overflow in hash function
	    perlin.p[i+256] = permutation[i+1]
	end

	-- Return range: [-1, 1]
	function perlin:noise(x, y, z)
	    y = y or 0
	    z = z or 0

	    -- Calculate the "unit cube" that the point asked will be located in
	    local xi = bit32.band(math.floor(x),255)
	    local yi = bit32.band(math.floor(y),255)
	    local zi = bit32.band(math.floor(z),255)

	    -- Next we calculate the location (from 0 to 1) in that cube
	    x = x - math.floor(x)
	    y = y - math.floor(y)
	    z = z - math.floor(z)

	    -- We also fade the location to smooth the result
	    local u = self.fade(x)
	    local v = self.fade(y)
	    local w = self.fade(z)

	    -- Hash all 8 unit cube coordinates surrounding input coordinate
	    local p = self.p
	    local A, AA, AB, AAA, ABA, AAB, ABB, B, BA, BB, BAA, BBA, BAB, BBB
	    A   = p[xi  ] + yi
	    AA  = p[A   ] + zi
	    AB  = p[A+1 ] + zi
	    AAA = p[ AA ]
	    ABA = p[ AB ]
	    AAB = p[ AA+1 ]
	    ABB = p[ AB+1 ]

	    B   = p[xi+1] + yi
	    BA  = p[B   ] + zi
	    BB  = p[B+1 ] + zi
	    BAA = p[ BA ]
	    BBA = p[ BB ]
	    BAB = p[ BA+1 ]
	    BBB = p[ BB+1 ]

	    -- Take the weighted average between all 8 unit cube coordinates
	    return self.lerp(w,
	        self.lerp(v,
	            self.lerp(u,
	                self:grad(AAA,x,y,z),
	                self:grad(BAA,x-1,y,z)
	            ),
	            self.lerp(u,
	                self:grad(ABA,x,y-1,z),
	                self:grad(BBA,x-1,y-1,z)
	            )
	        ),
	        self.lerp(v,
	            self.lerp(u,
	                self:grad(AAB,x,y,z-1), self:grad(BAB,x-1,y,z-1)
	            ),
	            self.lerp(u,
	                self:grad(ABB,x,y-1,z-1), self:grad(BBB,x-1,y-1,z-1)
	            )
	        )
	    )
	end

	-- Gradient function finds dot product between pseudorandom gradient vector
	-- and the vector from input coordinate to a unit cube vertex
	perlin.dot_product = {
	    [0x0]=function(x,y,z) return  x + y end,
	    [0x1]=function(x,y,z) return -x + y end,
	    [0x2]=function(x,y,z) return  x - y end,
	    [0x3]=function(x,y,z) return -x - y end,
	    [0x4]=function(x,y,z) return  x + z end,
	    [0x5]=function(x,y,z) return -x + z end,
	    [0x6]=function(x,y,z) return  x - z end,
	    [0x7]=function(x,y,z) return -x - z end,
	    [0x8]=function(x,y,z) return  y + z end,
	    [0x9]=function(x,y,z) return -y + z end,
	    [0xA]=function(x,y,z) return  y - z end,
	    [0xB]=function(x,y,z) return -y - z end,
	    [0xC]=function(x,y,z) return  y + x end,
	    [0xD]=function(x,y,z) return -y + z end,
	    [0xE]=function(x,y,z) return  y - x end,
	    [0xF]=function(x,y,z) return -y - z end
	}
	function perlin:grad(hash, x, y, z)
	    return self.dot_product[bit32.band(hash,0xF)](x,y,z)
	end

	-- Fade function is used to smooth final output
	function perlin.fade(t)
	    return t * t * t * (t * (t * 6 - 15) + 10)
	end

	function perlin.lerp(t, a, b)
	    return a + t * (b - a)
	end
end

local tint = {
  2,
  0.7,
  0.1,
}

local setTintedPalette = function()
	for i = 0, 255 do
	    term.setPaletteColor(i,
	        i/ (255 / tint[1]),
	        i/ (255 / tint[2]),
	        i/ (255 / tint[3])
	    )
	end
end

local scr_x, scr_y = term.getSize()
scr_x = scr_x * 6 - 1
scr_y = scr_y * 9


local stringchar = string.char
local tableconcat = table.concat

local screen = {}
local genScreen = function(x, y)
	for yy = y, y + scr_y do
		screen[yy] = screen[yy] or {}
		for xx = x, x + scr_x do
			screen[yy][xx] = screen[yy][xx] or stringchar((perlin:noise(
				0.2 * xx,
				0.2 * yy,
				0.3
			) * 64) + 64)
		end
	end
end

local render = function(x, y, xPos, yPos, width, height)
	genScreen(x + xPos, y + yPos)
	local buffer = {}
    for yy = 1, height do
		buffer[yy] = tableconcat(
			screen[yy + y + yPos], nil,
			x + xPos,
			x + width + xPos
		)
    end
	term.drawPixels(xPos, yPos, buffer)
end

local getTintFromFile = function()
	local file = fs.open("/.noisegen_tint", "r")
	if file then
		tint = textutils.unserialize(file.readAll())
		file.close()
	else
		file = fs.open("/.noisegen_tint", "w")
		file.write(textutils.serialize(tint))
		file.close()
	end
	setTintedPalette()
end

local main = function()
	local i, ii, x, y = 1, 1, 1, 1
	local iLimit = 1000
	local evt, e1, e2, e3
	local t_tick = os.startTimer(0)
	local t_getTint = os.startTimer(2)
	local t_screenwipe = os.startTimer(1)

	term.setGraphicsMode(2)
	--getTintFromFile()

	local randTable = {}
	for a = 1, iLimit do
		randTable[a] = math.random(-2, 2)
	end
	local width = math.random(20, 100)
	local height = math.random(20, 100)
	local xPos = math.random(1, scr_x - width - 1)
	local yPos = math.random(1, scr_y - height - 1)

	term.setBackgroundColor(colors.black)
	term.clear()

	while true do
		evt, e1, e2, e3 = os.pullEvent()
		if i == iLimit then
			width = math.random(20, 100)
			height = math.random(20, 100)
			xPos = math.random(1, scr_x - width - 1)
			yPos = math.random(1, scr_y - height - 1)
			i = 1
		end
		if evt == "timer" then
			if e1 == t_tick then

				x = i + math.sin(math.rad(i * 2)) * 3
				y = math.cos(i / 50) * 10

				x, y = math.floor(x), math.floor(y)

			    render(x, y, xPos, yPos, width, height)
				i = i + 1
				ii = ii + 1
				t_tick = os.startTimer(0)

				tint = {
					math.sin(100 + ii / 200) / 2 + 1.2,
					math.sin(200 + ii / 300) / 2 + 1.2,
					math.sin(300 + ii / 600) / 2 + 1.2,
				}
				setTintedPalette()

			elseif e1 == t_getTint then
				--getTintFromFile()
				t_getTint = os.startTimer(2)

			end
		end
	end
end

local status, message = pcall(main)

term.setGraphicsMode(0)
for i = 0, 15 do
    term.setPaletteColor(2^i, term.nativePaletteColor(2^i))
end
term.setCursorPos(1, 1)

if not status then
	error(message)
end
