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<?php

namespace Aws\Crypto\Polyfill;

/**

 * Class ByteArray

 * @package Aws\Crypto\Polyfill

 */

class ByteArray extends \SplFixedArray

{

    use NeedsTrait;

    /**

     * ByteArray constructor.

     *

     * @param int|string|int[] $size

     *     If you pass in an integer, it creates a ByteArray of that size.

     *     If you pass in a string or array, it converts it to an array of

     *       integers between 0 and 255.

     * @throws \InvalidArgumentException

     */

    public function __construct($size = 0)

    {

        $arr = null;

        // Integer? This behaves just like SplFixedArray.

        if (\is_array($size)) {

            // Array? We need to pass the count to parent::__construct() then populate

            $arr = $size;

            $size = \count($arr);

        } elseif (\is_string($size)) {

            // We need to avoid mbstring.func_overload

            if (\is_callable('\\mb_str_split')) {

                $tmp = \mb_str_split($size, 1, '8bit');

            } else {

                $tmp = \str_split($size, 1);

            }

            // Let's convert each character to an 8-bit integer and store in $arr

            $arr = [];

            if (!empty($tmp)) {

                foreach ($tmp as $t) {

                    if (strlen($t) < 1) {

                        continue;

                    }

                    $arr []= \unpack('C', $t)[1] & 0xff;

                }

            }

            $size = \count($arr);

        } elseif ($size instanceof ByteArray) {

            $arr = $size->toArray();

            $size = $size->count();

        } elseif (!\is_int($size)) {

            throw new \InvalidArgumentException(

                'Argument must be an integer, string, or array of integers.'

            );

        }

        parent::__construct($size);

        if (!empty($arr)) {

            // Populate this object with values from constructor argument

            foreach ($arr as $i => $v) {

                $this->offsetSet($i, $v);

            }

        } else {

            // Initialize to zero.

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

                $this->offsetSet($i, 0);

            }

        }

    }

    /**

     * Encode an integer into a byte array. 32-bit (unsigned), big endian byte order.

     *

     * @param int $num

     * @return self

     */

    public static function enc32be($num)

    {

        return new ByteArray(\pack('N', $num));

    }

    /**

     * @param ByteArray $other

     * @return bool

     */

    public function equals(ByteArray $other)

    {

        if ($this->count() !== $other->count()) {

            return false;

        }

        $d = 0;

        for ($i = $this->count() - 1; $i >= 0; --$i) {

            $d |= $this[$i] ^ $other[$i];

        }

        return $d === 0;

    }

    /**

     * @param ByteArray $array

     * @return ByteArray

     */

    public function exclusiveOr(ByteArray $array)

    {

        self::needs(

            $this->count() === $array->count(),

            'Both ByteArrays must be equal size for exclusiveOr()'

        );

        $out = clone $this;

        for ($i = 0; $i < $this->count(); ++$i) {

            $out[$i] = $array[$i] ^ $out[$i];

        }

        return $out;

    }

    /**

     * Returns a new ByteArray incremented by 1 (big endian byte order).

     *

     * @param int $increase

     * @return self

     */

    public function getIncremented($increase = 1)

    {

        $clone = clone $this;

        $index = $clone->count();

        while ($index > 0) {

            --$index;

            $tmp = ($clone[$index] + $increase) & PHP_INT_MAX;

            $clone[$index] = $tmp & 0xff;

            $increase = $tmp >> 8;

        }

        return $clone;

    }

    /**

     * Sets a value. See SplFixedArray for more.

     *

     * @param int $index

     * @param int $newval

     * @return void

     */

    public function offsetSet($index, $newval)

    {

        parent::offsetSet($index, $newval & 0xff);

    }

    /**

     * Return a copy of this ByteArray, bitshifted to the right by 1.

     * Used in Gmac.

     *

     * @return self

     */

    public function rshift()

    {

        $out = clone $this;

        for ($j = $this->count() - 1; $j > 0; --$j) {

            $out[$j] = (($out[$j - 1] & 1) << 7) | ($out[$j] >> 1);

        }

        $out[0] >>= 1;

        return $out;

    }

    /**

     * Constant-time conditional select. This is meant to read like a ternary operator.

     *

     * $z = ByteArray::select(1, $x, $y); // $z is equal to $x

     * $z = ByteArray::select(0, $x, $y); // $z is equal to $y

     *

     * @param int $select

     * @param ByteArray $left

     * @param ByteArray $right

     * @return ByteArray

     */

    public static function select($select, ByteArray $left, ByteArray $right)

    {

        self::needs(

            $left->count() === $right->count(),

            'Both ByteArrays must be equal size for select()'

        );

        $rightLength = $right->count();

        $out = clone $right;

        $mask = (-($select & 1)) & 0xff;

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

            $out[$i] = $out[$i] ^ (($left[$i] ^ $right[$i]) & $mask);

        }

        return $out;

    }

    /**

     * Overwrite values of this ByteArray based on a separate ByteArray, with

     * a given starting offset and length.

     *

     * See JavaScript's Uint8Array.set() for more information.

     *

     * @param ByteArray $input

     * @param int $offset

     * @param int|null $length

     * @return self

     */

    public function set(ByteArray $input, $offset = 0, $length = null)

    {

        self::needs(

            is_int($offset) && $offset >= 0,

            'Offset must be a positive integer or zero'

        );

        if (is_null($length)) {

            $length = $input->count();

        }

        $i = 0; $j = $offset;

        while ($i < $length && $j < $this->count()) {

            $this[$j] = $input[$i];

            ++$i;

            ++$j;

        }

        return $this;

    }

    /**

     * Returns a slice of this ByteArray.

     *

     * @param int $start

     * @param null $length

     * @return self

     */

    public function slice($start = 0, $length = null)

    {

        return new ByteArray(\array_slice($this->toArray(), $start, $length));

    }

    /**

     * Mutates the current state and sets all values to zero.

     *

     * @return void

     */

    public function zeroize()

    {

        for ($i = $this->count() - 1; $i >= 0; --$i) {

            $this->offsetSet($i, 0);

        }

    }

    /**

     * Converts the ByteArray to a raw binary string.

     *

     * @return string

     */

    public function toString()

    {

        $count = $this->count();

        if ($count === 0) {

            return '';

        }

        $args = $this->toArray();

        \array_unshift($args, \str_repeat('C', $count));

        // constant-time, PHP <5.6 equivalent to pack('C*', ...$args);

        return \call_user_func_array('\\pack', $args);

    }

}