require("lockbox").insecure();

local Bit = require("lockbox.util.bit");
local String = require("string");
local Math = require("math");
local Queue = require("lockbox.util.queue");

local SHIFT = {	7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,  7, 12, 17, 22,
				5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,  5,  9, 14, 20,
				4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,  4, 11, 16, 23,
				6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21,  6, 10, 15, 21 };

local CONSTANTS = {	0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
					0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
					0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
					0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
					0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
					0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
					0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
					0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
					0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
					0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
					0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
					0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
					0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
					0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
					0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
					0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391};

local AND = Bit.band;
local OR  = Bit.bor;
local NOT = Bit.bnot;
local XOR = Bit.bxor;
local LROT = Bit.lrotate;
local RROT = Bit.rrotate;
local LSHIFT = Bit.lshift;
local RSHIFT = Bit.rshift;

--MD5 is little-endian
local bytes2word = function(b0,b1,b2,b3)
	local i = b3; i = LSHIFT(i,8);
	i = OR(i,b2); i = LSHIFT(i,8);
	i = OR(i,b1); i = LSHIFT(i,8);
	i = OR(i,b0);
	return i;
end

local word2bytes = function(word)
	local b0,b1,b2,b3;
	b0 = AND(word,0xFF); word = RSHIFT(word,8);
	b1 = AND(word,0xFF); word = RSHIFT(word,8);
	b2 = AND(word,0xFF); word = RSHIFT(word,8);
	b3 = AND(word,0xFF);
	return b0,b1,b2,b3;
end

local bytes2dword = function(b0,b1,b2,b3,b4,b5,b6,b7)
	local i = bytes2word(b0,b1,b2,b3);
	local j = bytes2word(b4,b5,b6,b7);
	return (j*0x100000000)+i;
end

local dword2bytes = function(i)
	local b4,b5,b6,b7 = word2bytes(Math.floor(i/0x100000000));
	local b0,b1,b2,b3 = word2bytes(i);
	return b0,b1,b2,b3,b4,b5,b6,b7;
end

local F = function(x,y,z) return OR(AND(x,y),AND(NOT(x),z)); end
local G = function(x,y,z) return OR(AND(x,z),AND(y,NOT(z))); end
local H = function(x,y,z) return XOR(x,XOR(y,z)); end
local I = function(x,y,z) return XOR(y,OR(x,NOT(z))); end

local MD5 = function()

	local queue = Queue();

	local A = 0x67452301;
	local B = 0xefcdab89;
	local C = 0x98badcfe;
	local D = 0x10325476;
	local public = {};

	local processBlock = function()
		local a = A;
		local b = B;
		local c = C;
		local d = D;

		local X = {};

		for i=1,16 do
			X[i] = bytes2word(queue.pop(),queue.pop(),queue.pop(),queue.pop());
		end

		for i=0,63 do
			local f,g,temp;

			if (0 <= i) and (i <= 15) then
				f = F(b,c,d);
				g = i;
			elseif (16 <= i) and (i <= 31) then
				f = G(b,c,d);
				g = (5*i + 1) % 16;
			elseif (32 <= i) and (i <= 47) then
				f = H(b,c,d);
				g = (3*i + 5) % 16;
			elseif (48 <= i) and (i <= 63) then
				f = I(b,c,d);
				g = (7*i) % 16;
			end
			temp = d;
			d = c;
			c = b;
			b = b + LROT((a + f + CONSTANTS[i+1] + X[g+1]), SHIFT[i+1]);
			a = temp;
		end

		A = AND(A + a, 0xFFFFFFFF);
		B = AND(B + b, 0xFFFFFFFF);
		C = AND(C + c, 0xFFFFFFFF);
		D = AND(D + d, 0xFFFFFFFF);
	end

	public.init = function()
		queue.reset();

		A = 0x67452301;
		B = 0xefcdab89;
		C = 0x98badcfe;
		D = 0x10325476;

		return public;
	end

	public.update = function(bytes)
		for b in bytes do
			queue.push(b);
			if(queue.size() >= 64) then processBlock(); end
		end

		return public;
	end

	public.finish = function()
		local bits = queue.getHead() * 8;

		queue.push(0x80);
		while ((queue.size()+7) % 64) < 63 do
			queue.push(0x00);
		end

		local b0,b1,b2,b3,b4,b5,b6,b7 = dword2bytes(bits);

		queue.push(b0);
		queue.push(b1);
		queue.push(b2);
		queue.push(b3);
		queue.push(b4);
		queue.push(b5);
		queue.push(b6);
		queue.push(b7);

		while queue.size() > 0 do
			processBlock();
		end

		return public;
	end

	public.asBytes = function()
		local  b0, b1, b2, b3 = word2bytes(A);
		local  b4, b5, b6, b7 = word2bytes(B);
		local  b8, b9,b10,b11 = word2bytes(C);
		local b12,b13,b14,b15 = word2bytes(D);

		return {b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15};
	end

	public.asHex = function()
		local  b0, b1, b2, b3 = word2bytes(A);
		local  b4, b5, b6, b7 = word2bytes(B);
		local  b8, b9,b10,b11 = word2bytes(C);
		local b12,b13,b14,b15 = word2bytes(D);

		return String.format("%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
				b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,b10,b11,b12,b13,b14,b15);
	end

	return public;

end

return MD5;