<?php
declare(strict_types=1);

if (class_exists('ParagonIE_Sodium_Core_HSalsa20', false)) {
    return;
}

/**
 * Class ParagonIE_Sodium_Core_HSalsa20
 */
abstract class ParagonIE_Sodium_Core_HSalsa20 extends ParagonIE_Sodium_Core_Salsa20
{
    /**
     * Calculate an hsalsa20 hash of a single block
     *
     * HSalsa20 doesn't have a counter and will never be used for more than
     * one block (used to derive a subkey for xsalsa20).
     *
     * @internal You should not use this directly from another application
     *
     * @param string $in
     * @param string $k
     * @param string|null $c
     * @return string
     * @throws TypeError
     */
    public static function hsalsa20(
        string $in,
        #[SensitiveParameter]
        string $k,
        ?string $c = null
    ): string {
        if ($c === null) {
            $x0  = 0x61707865;
            $x5  = 0x3320646e;
            $x10 = 0x79622d32;
            $x15 = 0x6b206574;
        } else {
            $x0  = self::load_4(self::substr($c, 0, 4));
            $x5  = self::load_4(self::substr($c, 4, 4));
            $x10 = self::load_4(self::substr($c, 8, 4));
            $x15 = self::load_4(self::substr($c, 12, 4));
        }
        $x1  = self::load_4(self::substr($k, 0, 4));
        $x2  = self::load_4(self::substr($k, 4, 4));
        $x3  = self::load_4(self::substr($k, 8, 4));
        $x4  = self::load_4(self::substr($k, 12, 4));
        $x11 = self::load_4(self::substr($k, 16, 4));
        $x12 = self::load_4(self::substr($k, 20, 4));
        $x13 = self::load_4(self::substr($k, 24, 4));
        $x14 = self::load_4(self::substr($k, 28, 4));
        $x6  = self::load_4(self::substr($in, 0, 4));
        $x7  = self::load_4(self::substr($in, 4, 4));
        $x8  = self::load_4(self::substr($in, 8, 4));
        $x9  = self::load_4(self::substr($in, 12, 4));

        for ($i = self::ROUNDS; $i > 0; $i -= 2) {
            $x4 ^= self::rotate($x0 + $x12, 7);
            $x8 ^= self::rotate($x4 + $x0, 9);
            $x12 ^= self::rotate($x8 + $x4, 13);
            $x0 ^= self::rotate($x12 + $x8, 18);
            $x9 ^= self::rotate($x5 + $x1, 7);
            $x13 ^= self::rotate($x9 + $x5, 9);
            $x1 ^= self::rotate($x13 + $x9, 13);
            $x5 ^= self::rotate($x1 + $x13, 18);
            $x14 ^= self::rotate($x10 + $x6, 7);
            $x2 ^= self::rotate($x14 + $x10, 9);
            $x6 ^= self::rotate($x2 + $x14, 13);
            $x10 ^= self::rotate($x6 + $x2, 18);
            $x3 ^= self::rotate($x15 + $x11, 7);
            $x7 ^= self::rotate($x3 + $x15, 9);
            $x11 ^= self::rotate($x7 + $x3, 13);
            $x15 ^= self::rotate($x11 + $x7, 18);
            $x1 ^= self::rotate($x0 + $x3, 7);
            $x2 ^= self::rotate($x1 + $x0, 9);
            $x3 ^= self::rotate($x2 + $x1, 13);
            $x0 ^= self::rotate($x3 + $x2, 18);
            $x6 ^= self::rotate($x5 + $x4, 7);
            $x7 ^= self::rotate($x6 + $x5, 9);
            $x4 ^= self::rotate($x7 + $x6, 13);
            $x5 ^= self::rotate($x4 + $x7, 18);
            $x11 ^= self::rotate($x10 + $x9, 7);
            $x8 ^= self::rotate($x11 + $x10, 9);
            $x9 ^= self::rotate($x8 + $x11, 13);
            $x10 ^= self::rotate($x9 + $x8, 18);
            $x12 ^= self::rotate($x15 + $x14, 7);
            $x13 ^= self::rotate($x12 + $x15, 9);
            $x14 ^= self::rotate($x13 + $x12, 13);
            $x15 ^= self::rotate($x14 + $x13, 18);
        }

        return self::store32_le($x0) .
            self::store32_le($x5) .
            self::store32_le($x10) .
            self::store32_le($x15) .
            self::store32_le($x6) .
            self::store32_le($x7) .
            self::store32_le($x8) .
            self::store32_le($x9);
    }
}
