local Bit = require("lockbox.util.bit");
local String = require("string");
local Array = require("lockbox.util.array");
local Stream = require("lockbox.util.stream");
local Math = require("math");

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;

--PBKDF2 is big-endian
local bytes2word = function(b0,b1,b2,b3)
	local i = b0; i = LSHIFT(i,8);
	i = OR(i,b1); i = LSHIFT(i,8);
	i = OR(i,b2); i = LSHIFT(i,8);
	i = OR(i,b3);
	return i;
end

local word2bytes = function(word)
	local b0,b1,b2,b3;
	b3 = AND(word,0xFF); word = RSHIFT(word,8);
	b2 = AND(word,0xFF); word = RSHIFT(word,8);
	b1 = AND(word,0xFF); word = RSHIFT(word,8);
	b0 = 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 (i*0x100000000)+j;
end

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



local PBKDF2 = function()

	local public = {};
	
	local blockLen = 16;
	local dKeyLen = 256;
	local iterations = 4096;

	local salt;
	local password;
	

	local PRF;

	local dKey;


	public.setBlockLen = function(len)
		blockLen = len;
		return public;
	end

	public.setDKeyLen = function(len)
		dKeyLen = len
		return public;
	end

	public.setIterations = function(iter)
		iterations = iter;
		return public;
	end

	public.setSalt = function(saltBytes)
		salt = saltBytes;
		return public;
	end

	public.setPassword = function(passwordBytes)
		password = passwordBytes;
		return public;
	end

	public.setPRF = function(prf)
		PRF = prf;
		return public;
	end

	local buildBlock = function(i)
		local b0,b1,b2,b3 = word2bytes(i);
		local ii = {b0,b1,b2,b3};
		local s = Array.concat(salt,ii);

		local out = {};

		PRF.setKey(password);
		for c = 1,iterations do
			PRF.init()
				.update(Stream.fromArray(s));

			s = PRF.finish().asBytes();
			if(c > 1) then
				out = Array.XOR(out,s);
			else
				out = s;
			end
		end

		return out;		
	end

	public.finish = function()
		local blocks = Math.ceil(dKeyLen / blockLen);

		dKey = {};

		for b = 1, blocks do
			local block = buildBlock(b);
			dKey = Array.concat(dKey,block);
		end

		if(Array.size(dKey) > dKeyLen) then dKey = Array.truncate(dKey,dKeyLen); end

		return public;
	end
	
	public.asBytes = function()
		return dKey;
	end

	public.asHex = function()
		return Array.toHex(dKey);
	end

	return public;
end

return PBKDF2;
