<?php

if (!defined('SODIUM_COMPAT_AEGIS_C0')) {

    define('SODIUM_COMPAT_AEGIS_C0', "\x00\x01\x01\x02\x03\x05\x08\x0d\x15\x22\x37\x59\x90\xe9\x79\x62");

}

if (!defined('SODIUM_COMPAT_AEGIS_C1')) {

    define('SODIUM_COMPAT_AEGIS_C1', "\xdb\x3d\x18\x55\x6d\xc2\x2f\xf1\x20\x11\x31\x42\x73\xb5\x28\xdd");

}

class ParagonIE_Sodium_Core_AEGIS256 extends ParagonIE_Sodium_Core_AES

{

    /**

     * @param string $ct

     * @param string $tag

     * @param string $ad

     * @param string $key

     * @param string $nonce

     * @return string

     * @throws SodiumException

     */

    public static function decrypt($ct, $tag, $ad, $key, $nonce)

    {

        $state = self::init($key, $nonce);

        // ad_blocks = Split(ZeroPad(ad, 128), 128)

        $ad_blocks = (self::strlen($ad) + 15) >> 4;

        // for ai in ad_blocks:

        //     Absorb(ai)

        for ($i = 0; $i < $ad_blocks; ++$i) {

            $ai = self::substr($ad, $i << 4, 16);

            if (self::strlen($ai) < 16) {

                $ai = str_pad($ai, 16, "\0", STR_PAD_RIGHT);

            }

            $state->absorb($ai);

        }

        $msg = '';

        $cn = self::strlen($ct) & 15;

        $ct_blocks = self::strlen($ct) >> 4;

        // ct_blocks = Split(ZeroPad(ct, 128), 128)

        // cn = Tail(ct, |ct| mod 128)

        for ($i = 0; $i < $ct_blocks; ++$i) {

            $msg .= $state->dec(self::substr($ct, $i << 4, 16));

        }

        // if cn is not empty:

        //   msg = msg || DecPartial(cn)

        if ($cn) {

            $start = $ct_blocks << 4;

            $msg .= $state->decPartial(self::substr($ct, $start, $cn));

        }

        $expected_tag = $state->finalize(

            self::strlen($ad) << 3,

            self::strlen($msg) << 3

        );

        if (!self::hashEquals($expected_tag, $tag)) {

            try {

                // The RFC says to erase msg, so we shall try:

                ParagonIE_Sodium_Compat::memzero($msg);

            } catch (SodiumException $ex) {

                // Do nothing if we cannot memzero

            }

            throw new SodiumException('verification failed');

        }

        return $msg;

    }

    /**

     * @param string $msg

     * @param string $ad

     * @param string $key

     * @param string $nonce

     * @return array

     * @throws SodiumException

     */

    public static function encrypt($msg, $ad, $key, $nonce)

    {

        $state = self::init($key, $nonce);

        $ad_len = self::strlen($ad);

        $msg_len = self::strlen($msg);

        $ad_blocks = ($ad_len + 15) >> 4;

        for ($i = 0; $i < $ad_blocks; ++$i) {

            $ai = self::substr($ad, $i << 4, 16);

            if (self::strlen($ai) < 16) {

                $ai = str_pad($ai, 16, "\0", STR_PAD_RIGHT);

            }

            $state->absorb($ai);

        }

        $ct = '';

        $msg_blocks = ($msg_len + 15) >> 4;

        for ($i = 0; $i < $msg_blocks; ++$i) {

            $xi = self::substr($msg, $i << 4, 16);

            if (self::strlen($xi) < 16) {

                $xi = str_pad($xi, 16, "\0", STR_PAD_RIGHT);

            }

            $ct .= $state->enc($xi);

        }

        $tag = $state->finalize(

            $ad_len << 3,

            $msg_len << 3

        );

        return array(

            self::substr($ct, 0, $msg_len),

            $tag

        );

    }

    /**

     * @param string $key

     * @param string $nonce

     * @return ParagonIE_Sodium_Core_AEGIS_State256

     */

    public static function init($key, $nonce)

    {

        return ParagonIE_Sodium_Core_AEGIS_State256::init($key, $nonce);

    }

}