require("lockbox").insecure();

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

local SUBST = {
  0x29, 0x2E, 0x43, 0xC9, 0xA2, 0xD8, 0x7C, 0x01, 0x3D, 0x36, 0x54, 0xA1, 0xEC, 0xF0, 0x06, 0x13,
  0x62, 0xA7, 0x05, 0xF3, 0xC0, 0xC7, 0x73, 0x8C, 0x98, 0x93, 0x2B, 0xD9, 0xBC, 0x4C, 0x82, 0xCA,
  0x1E, 0x9B, 0x57, 0x3C, 0xFD, 0xD4, 0xE0, 0x16, 0x67, 0x42, 0x6F, 0x18, 0x8A, 0x17, 0xE5, 0x12,
  0xBE, 0x4E, 0xC4, 0xD6, 0xDA, 0x9E, 0xDE, 0x49, 0xA0, 0xFB, 0xF5, 0x8E, 0xBB, 0x2F, 0xEE, 0x7A,
  0xA9, 0x68, 0x79, 0x91, 0x15, 0xB2, 0x07, 0x3F, 0x94, 0xC2, 0x10, 0x89, 0x0B, 0x22, 0x5F, 0x21,
  0x80, 0x7F, 0x5D, 0x9A, 0x5A, 0x90, 0x32, 0x27, 0x35, 0x3E, 0xCC, 0xE7, 0xBF, 0xF7, 0x97, 0x03,
  0xFF, 0x19, 0x30, 0xB3, 0x48, 0xA5, 0xB5, 0xD1, 0xD7, 0x5E, 0x92, 0x2A, 0xAC, 0x56, 0xAA, 0xC6,
  0x4F, 0xB8, 0x38, 0xD2, 0x96, 0xA4, 0x7D, 0xB6, 0x76, 0xFC, 0x6B, 0xE2, 0x9C, 0x74, 0x04, 0xF1,
  0x45, 0x9D, 0x70, 0x59, 0x64, 0x71, 0x87, 0x20, 0x86, 0x5B, 0xCF, 0x65, 0xE6, 0x2D, 0xA8, 0x02,
  0x1B, 0x60, 0x25, 0xAD, 0xAE, 0xB0, 0xB9, 0xF6, 0x1C, 0x46, 0x61, 0x69, 0x34, 0x40, 0x7E, 0x0F,
  0x55, 0x47, 0xA3, 0x23, 0xDD, 0x51, 0xAF, 0x3A, 0xC3, 0x5C, 0xF9, 0xCE, 0xBA, 0xC5, 0xEA, 0x26,
  0x2C, 0x53, 0x0D, 0x6E, 0x85, 0x28, 0x84, 0x09, 0xD3, 0xDF, 0xCD, 0xF4, 0x41, 0x81, 0x4D, 0x52,
  0x6A, 0xDC, 0x37, 0xC8, 0x6C, 0xC1, 0xAB, 0xFA, 0x24, 0xE1, 0x7B, 0x08, 0x0C, 0xBD, 0xB1, 0x4A,
  0x78, 0x88, 0x95, 0x8B, 0xE3, 0x63, 0xE8, 0x6D, 0xE9, 0xCB, 0xD5, 0xFE, 0x3B, 0x00, 0x1D, 0x39,
  0xF2, 0xEF, 0xB7, 0x0E, 0x66, 0x58, 0xD0, 0xE4, 0xA6, 0x77, 0x72, 0xF8, 0xEB, 0x75, 0x4B, 0x0A,
  0x31, 0x44, 0x50, 0xB4, 0x8F, 0xED, 0x1F, 0x1A, 0xDB, 0x99, 0x8D, 0x33, 0x9F, 0x11, 0x83, 0x14 };

local XOR = Bit.bxor;

local MD2 = function()

    local queue = Queue();

    local X = {};
    for i = 0, 47 do
        X[i] = 0x00;
    end

    local C = {};
    for i = 0, 15 do
        C[i] = 0x00;
    end

    local public = {};

    local processBlock = function()
        local block = {};

        for i = 0, 15 do
            block[i] = queue.pop();
        end

        for i = 0, 15 do
            X[i + 16] = block[i];
            X[i + 32] = XOR(X[i], block[i]); --mix
        end

        local t;

        --update block
        t = 0;
        for i = 0, 17 do
            for j = 0, 47 do
                X[j] = XOR(X[j], SUBST[t + 1]);
                t = X[j];
            end
            t = (t + i) % 256;
        end

        --update checksum
        t = C[15];
        for i = 0, 15 do
            C[i] = XOR(C[i], SUBST[XOR(block[i], t) + 1]);
            t = C[i];
        end

    end

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

        X = {};
        for i = 0, 47 do
            X[i] = 0x00;
        end

        C = {};
        for i = 0, 15 do
            C[i] = 0x00;
        end

        return public;
    end

    public.update = function(stream)
        for b in stream do
            queue.push(b);
            if(queue.size() >= 16) then processBlock(); end
        end

        return public;
    end

    public.finish = function()
        local i = 16 - queue.size();

        while queue.size() < 16 do
            queue.push(i);
        end

        processBlock();

        queue.push(C[ 0]); queue.push(C[ 1]); queue.push(C[ 2]); queue.push(C[ 3]);
        queue.push(C[ 4]); queue.push(C[ 5]); queue.push(C[ 6]); queue.push(C[ 7]);
        queue.push(C[ 8]); queue.push(C[ 9]); queue.push(C[10]); queue.push(C[11]);
        queue.push(C[12]); queue.push(C[13]); queue.push(C[14]); queue.push(C[15]);

        processBlock();

        return public;
    end

    public.asBytes = function()
        return {X[ 0], X[ 1], X[ 2], X[ 3], X[ 4], X[ 5], X[ 6], X[ 7],
                X[ 8], X[ 9], X[10], X[11], X[12], X[13], X[14], X[15]};
    end

    public.asHex = function()
        return String.format("%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
                X[ 0], X[ 1], X[ 2], X[ 3], X[ 4], X[ 5], X[ 6], X[ 7],
                X[ 8], X[ 9], X[10], X[11], X[12], X[13], X[14], X[15]);
    end

    public.asString = function()
        return string.pack(string.rep('B', 16),
                X[ 0], X[ 1], X[ 2], X[ 3], X[ 4], X[ 5], X[ 6], X[ 7],
                X[ 8], X[ 9], X[10], X[11], X[12], X[13], X[14], X[15]);
    end

    return public;

end

return MD2;
