<?php

if (class_exists('ParagonIE_Sodium_Core32_HChaCha20', false)) {
    return;
}

/**
 * Class ParagonIE_Sodium_Core_HChaCha20
 */
class ParagonIE_Sodium_Core32_HChaCha20 extends ParagonIE_Sodium_Core32_ChaCha20
{
    /**
     * @param string $in
     * @param string $key
     * @param string|null $c
     * @return string
     */
    public static function hChaCha20($in = '', $key = '', $c = null)
    {
        $ctx = array();

        if ($c === null) {
            $ctx[0] = new ParagonIE_Sodium_Core32_Int32(array(0x6170, 0x7865));
            $ctx[1] = new ParagonIE_Sodium_Core32_Int32(array(0x3320, 0x646e));
            $ctx[2] = new ParagonIE_Sodium_Core32_Int32(array(0x7962, 0x2d32));
            $ctx[3] = new ParagonIE_Sodium_Core32_Int32(array(0x6b20, 0x6574));
        } else {
            $ctx[0] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($c, 0, 4));
            $ctx[1] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($c, 4, 4));
            $ctx[2] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($c, 8, 4));
            $ctx[3] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($c, 12, 4));
        }
        $ctx[4]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 0, 4));
        $ctx[5]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 4, 4));
        $ctx[6]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 8, 4));
        $ctx[7]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 12, 4));
        $ctx[8]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 16, 4));
        $ctx[9]  = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 20, 4));
        $ctx[10] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 24, 4));
        $ctx[11] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($key, 28, 4));
        $ctx[12] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($in, 0, 4));
        $ctx[13] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($in, 4, 4));
        $ctx[14] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($in, 8, 4));
        $ctx[15] = ParagonIE_Sodium_Core32_Int32::fromReverseString(self::substr($in, 12, 4));

        return self::hChaCha20Bytes($ctx);
    }

    /**
     * @param array $ctx
     * @return string
     */
    protected static function hChaCha20Bytes(array $ctx)
    {
        /**
         * @var ParagonIE_Sodium_Core32_Int32 $x0
         * @var ParagonIE_Sodium_Core32_Int32 $x1
         * @var ParagonIE_Sodium_Core32_Int32 $x2
         * @var ParagonIE_Sodium_Core32_Int32 $x3
         * @var ParagonIE_Sodium_Core32_Int32 $x12
         * @var ParagonIE_Sodium_Core32_Int32 $x13
         * @var ParagonIE_Sodium_Core32_Int32 $x14
         * @var ParagonIE_Sodium_Core32_Int32 $x15
         */
        $x0  = $ctx[0];
        $x1  = $ctx[1];
        $x2  = $ctx[2];
        $x3  = $ctx[3];
        $x4  = $ctx[4];
        $x5  = $ctx[5];
        $x6  = $ctx[6];
        $x7  = $ctx[7];
        $x8  = $ctx[8];
        $x9  = $ctx[9];
        $x10 = $ctx[10];
        $x11 = $ctx[11];
        $x12 = $ctx[12];
        $x13 = $ctx[13];
        $x14 = $ctx[14];
        $x15 = $ctx[15];

        for ($i = 0; $i < 10; ++$i) {
            # QUARTERROUND( x0,  x4,  x8,  x12)
            list($x0, $x4, $x8, $x12) = self::quarterRound($x0, $x4, $x8, $x12);

            # QUARTERROUND( x1,  x5,  x9,  x13)
            list($x1, $x5, $x9, $x13) = self::quarterRound($x1, $x5, $x9, $x13);

            # QUARTERROUND( x2,  x6,  x10,  x14)
            list($x2, $x6, $x10, $x14) = self::quarterRound($x2, $x6, $x10, $x14);

            # QUARTERROUND( x3,  x7,  x11,  x15)
            list($x3, $x7, $x11, $x15) = self::quarterRound($x3, $x7, $x11, $x15);

            # QUARTERROUND( x0,  x5,  x10,  x15)
            list($x0, $x5, $x10, $x15) = self::quarterRound($x0, $x5, $x10, $x15);

            # QUARTERROUND( x1,  x6,  x11,  x12)
            list($x1, $x6, $x11, $x12) = self::quarterRound($x1, $x6, $x11, $x12);

            # QUARTERROUND( x2,  x7,  x8,  x13)
            list($x2, $x7, $x8, $x13) = self::quarterRound($x2, $x7, $x8, $x13);

            # QUARTERROUND( x3,  x4,  x9,  x14)
            list($x3, $x4, $x9, $x14) = self::quarterRound($x3, $x4, $x9, $x14);
        }

        return $x0->toReverseString() .
            $x1->toReverseString() .
            $x2->toReverseString() .
            $x3->toReverseString() .
            $x12->toReverseString() .
            $x13->toReverseString() .
            $x14->toReverseString() .
            $x15->toReverseString();
    }
}
