<?php
declare(strict_types=1);

if (class_exists('ParagonIE_Sodium_Core_Salsa20', false)) {
    return;
}

/**
 * Class ParagonIE_Sodium_Core_Salsa20
 */
abstract class ParagonIE_Sodium_Core_Salsa20 extends ParagonIE_Sodium_Core_Util
{
    const ROUNDS = 20;

    /**
     * Calculate an salsa20 hash of a single block
     *
     * @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 core_salsa20(
        string $in,
        #[SensitiveParameter]
        string $k,
        ?string $c = null
    ): string {
        if (self::strlen($k) < 32) {
            throw new RangeException('Key must be 32 bytes long');
        }
        if ($c === null) {
            $j0  = $x0  = 0x61707865;
            $j5  = $x5  = 0x3320646e;
            $j10 = $x10 = 0x79622d32;
            $j15 = $x15 = 0x6b206574;
        } else {
            $j0  = $x0  = self::load_4(self::substr($c, 0, 4));
            $j5  = $x5  = self::load_4(self::substr($c, 4, 4));
            $j10 = $x10 = self::load_4(self::substr($c, 8, 4));
            $j15 = $x15 = self::load_4(self::substr($c, 12, 4));
        }
        $j1  = $x1  = self::load_4(self::substr($k, 0, 4));
        $j2  = $x2  = self::load_4(self::substr($k, 4, 4));
        $j3  = $x3  = self::load_4(self::substr($k, 8, 4));
        $j4  = $x4  = self::load_4(self::substr($k, 12, 4));
        $j6  = $x6  = self::load_4(self::substr($in, 0, 4));
        $j7  = $x7  = self::load_4(self::substr($in, 4, 4));
        $j8  = $x8  = self::load_4(self::substr($in, 8, 4));
        $j9  = $x9  = self::load_4(self::substr($in, 12, 4));
        $j11 = $x11 = self::load_4(self::substr($k, 16, 4));
        $j12 = $x12 = self::load_4(self::substr($k, 20, 4));
        $j13 = $x13 = self::load_4(self::substr($k, 24, 4));
        $j14 = $x14 = self::load_4(self::substr($k, 28, 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);
        }

        $x0  += $j0;
        $x1  += $j1;
        $x2  += $j2;
        $x3  += $j3;
        $x4  += $j4;
        $x5  += $j5;
        $x6  += $j6;
        $x7  += $j7;
        $x8  += $j8;
        $x9  += $j9;
        $x10 += $j10;
        $x11 += $j11;
        $x12 += $j12;
        $x13 += $j13;
        $x14 += $j14;
        $x15 += $j15;

        return self::store32_le($x0) .
            self::store32_le($x1) .
            self::store32_le($x2) .
            self::store32_le($x3) .
            self::store32_le($x4) .
            self::store32_le($x5) .
            self::store32_le($x6) .
            self::store32_le($x7) .
            self::store32_le($x8) .
            self::store32_le($x9) .
            self::store32_le($x10) .
            self::store32_le($x11) .
            self::store32_le($x12) .
            self::store32_le($x13) .
            self::store32_le($x14) .
            self::store32_le($x15);
    }

    /**
     * @internal You should not use this directly from another application
     *
     * @param int $len
     * @param string $nonce
     * @param string $key
     * @return string
     * @throws SodiumException
     * @throws TypeError
     */
    public static function salsa20(
        int $len,
        string $nonce,
        #[SensitiveParameter]
        string $key
    ): string {
        if (self::strlen($key) !== 32) {
            throw new RangeException('Key must be 32 bytes long');
        }
        $kcopy = $key;
        $in = self::substr($nonce, 0, 8) . str_repeat("\0", 8);
        $c = '';
        while ($len >= 64) {
            $c .= self::core_salsa20($in, $kcopy);
            $u = 1;
            // Internal counter.
            for ($i = 8; $i < 16; ++$i) {
                $u += self::chrToInt($in[$i]);
                $in[$i] = self::intToChr($u & 0xff);
                $u >>= 8;
            }
            $len -= 64;
        }
        if ($len > 0) {
            $c .= self::substr(
                self::core_salsa20($in, $kcopy),
                0,
                $len
            );
        }
        try {
            ParagonIE_Sodium_Compat::memzero($kcopy);
        } catch (SodiumException) {
            $kcopy = null;
        }
        return $c;
    }

    /**
     * @internal You should not use this directly from another application
     *
     * @param string $m
     * @param string $n
     * @param int $ic
     * @param string $k
     * @return string
     * @throws SodiumException
     * @throws TypeError
     */
    public static function salsa20_xor_ic(
        #[SensitiveParameter]
        string $m,
        string $n,
        int $ic,
        #[SensitiveParameter]
        string $k
    ): string {
        $mlen = self::strlen($m);
        if ($mlen < 1) {
            return '';
        }
        $kcopy = self::substr($k, 0, 32);
        $in = self::substr($n, 0, 8);
        // Initialize the counter
        $in .= ParagonIE_Sodium_Core_Util::store64_le($ic);

        $c = '';
        while ($mlen >= 64) {
            $block = self::core_salsa20($in, $kcopy);
            $c .= self::xorStrings(
                self::substr($m, 0, 64),
                self::substr($block, 0, 64)
            );
            $u = 1;
            for ($i = 8; $i < 16; ++$i) {
                $u += self::chrToInt($in[$i]);
                $in[$i] = self::intToChr($u & 0xff);
                $u >>= 8;
            }

            $mlen -= 64;
            $m = self::substr($m, 64);
        }

        if ($mlen) {
            $block = self::core_salsa20($in, $kcopy);
            $c .= self::xorStrings(
                self::substr($m, 0, $mlen),
                self::substr($block, 0, $mlen)
            );
        }
        try {
            ParagonIE_Sodium_Compat::memzero($block);
            ParagonIE_Sodium_Compat::memzero($kcopy);
        } catch (SodiumException) {
            $block = null;
            $kcopy = null;
        }

        return $c;
    }

    /**
     * @internal You should not use this directly from another application
     *
     * @param string $message
     * @param string $nonce
     * @param string $key
     * @return string
     * @throws SodiumException
     * @throws TypeError
     */
    public static function salsa20_xor(
        #[SensitiveParameter]
        string $message,
        string $nonce,
        #[SensitiveParameter]
        string $key
    ): string {
        return self::xorStrings(
            $message,
            self::salsa20(
                self::strlen($message),
                $nonce,
                $key
            )
        );
    }

    /**
     * @internal You should not use this directly from another application
     *
     * @param int $u
     * @param int $c
     * @return int
     */
    public static function rotate(int $u, int $c): int
    {
        $u &= 0xffffffff;
        $c %= 32;
        return (0xffffffff & (
                ($u << $c)
                    |
                ($u >> (32 - $c))
            )
        );
    }
}
