local hashes = require "util.hashes"

local xor = require "bit".bxor

module "hmac"

local function arraystr(array)

    t = {}

    for i = 1,table.getn(array) do

        table.insert(t, string.char(array[i]))

    end

    return table.concat(t)

end

--[[

key

    the key to use in the hash

message

    the message to hash

hash

    the hash function

blocksize

    the blocksize for the hash function in bytes

hex

  return raw hash or hexadecimal string

--]]

function hmac(key, message, hash, blocksize, hex)

    local opad = {}

    local ipad = {}

    for i = 1,blocksize do

        opad[i] = 0x5c

        ipad[i] = 0x36

    end

    if #key > blocksize then

        key = hash(key)

    end

    for i = 1,#key do

        ipad[i] = xor(ipad[i],key:sub(i,i):byte())

        opad[i] = xor(opad[i],key:sub(i,i):byte())

    end

    opad = arraystr(opad)

    ipad = arraystr(ipad)

    if hex then

        return hash(opad..hash(ipad..message), true)

    else

        return hash(opad..hash(ipad..message))

    end

end

function md5(key, message, hex)

    return hmac(key, message, hashes.md5, 64, hex)

end

function sha1(key, message, hex)

    return hmac(key, message, hashes.sha1, 64, hex)

end

function sha256(key, message, hex)

    return hmac(key, message, hashes.sha256, 64, hex)

end

return _M