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    <h3>Editing: TimestampFirstCombCodec.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/**
 * This file is part of the ramsey/uuid library
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 *
 * @copyright Copyright (c) Ben Ramsey &lt;ben@benramsey.com&gt;
 * @license http://opensource.org/licenses/MIT MIT
 */

declare(strict_types=1);

namespace Ramsey\Uuid\Codec;

use Ramsey\Uuid\Exception\InvalidUuidStringException;
use Ramsey\Uuid\UuidInterface;

use function bin2hex;
use function sprintf;
use function substr;
use function substr_replace;

/**
 * TimestampFirstCombCodec encodes and decodes COMBs, with the timestamp as the
 * first 48 bits
 *
 * In contrast with the TimestampLastCombCodec, the TimestampFirstCombCodec
 * adds the timestamp to the first 48 bits of the COMB. To generate a
 * timestamp-first COMB, set the TimestampFirstCombCodec as the codec, along
 * with the CombGenerator as the random generator.
 *
 * ``` php
 * $factory = new UuidFactory();
 *
 * $factory-&gt;setCodec(new TimestampFirstCombCodec($factory-&gt;getUuidBuilder()));
 *
 * $factory-&gt;setRandomGenerator(new CombGenerator(
 *     $factory-&gt;getRandomGenerator(),
 *     $factory-&gt;getNumberConverter()
 * ));
 *
 * $timestampFirstComb = $factory-&gt;uuid4();
 * ```
 *
 * @link https://www.informit.com/articles/printerfriendly/25862 The Cost of GUIDs as Primary Keys
 *
 * @psalm-immutable
 */
class TimestampFirstCombCodec extends StringCodec
{
    /**
     * @psalm-return non-empty-string
     * @psalm-suppress MoreSpecificReturnType we know that the retrieved `string` is never empty
     * @psalm-suppress LessSpecificReturnStatement we know that the retrieved `string` is never empty
     */
    public function encode(UuidInterface $uuid): string
    {
        $bytes = $this-&gt;swapBytes($uuid-&gt;getFields()-&gt;getBytes());

        return sprintf(
            '%08s-%04s-%04s-%04s-%012s',
            bin2hex(substr($bytes, 0, 4)),
            bin2hex(substr($bytes, 4, 2)),
            bin2hex(substr($bytes, 6, 2)),
            bin2hex(substr($bytes, 8, 2)),
            bin2hex(substr($bytes, 10))
        );
    }

    /**
     * @psalm-return non-empty-string
     * @psalm-suppress MoreSpecificReturnType we know that the retrieved `string` is never empty
     * @psalm-suppress LessSpecificReturnStatement we know that the retrieved `string` is never empty
     */
    public function encodeBinary(UuidInterface $uuid): string
    {
        /** @phpstan-ignore-next-line PHPStan complains that this is not a non-empty-string. */
        return $this-&gt;swapBytes($uuid-&gt;getFields()-&gt;getBytes());
    }

    /**
     * @throws InvalidUuidStringException
     *
     * @inheritDoc
     */
    public function decode(string $encodedUuid): UuidInterface
    {
        $bytes = $this-&gt;getBytes($encodedUuid);

        return $this-&gt;getBuilder()-&gt;build($this, $this-&gt;swapBytes($bytes));
    }

    public function decodeBytes(string $bytes): UuidInterface
    {
        return $this-&gt;getBuilder()-&gt;build($this, $this-&gt;swapBytes($bytes));
    }

    /**
     * Swaps bytes according to the timestamp-first COMB rules
     */
    private function swapBytes(string $bytes): string
    {
        $first48Bits = substr($bytes, 0, 6);
        $last48Bits = substr($bytes, -6);

        $bytes = substr_replace($bytes, $last48Bits, 0, 6);
        $bytes = substr_replace($bytes, $first48Bits, -6);

        return $bytes;
    }
}
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