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

declare(strict_types=1);

namespace GuzzleHttp\Psr7;

use Psr\Http\Message\UriInterface;

/**
 * Provides methods to normalize and compare URIs.
 *
 * @author Tobias Schultze
 *
 * @link https://tools.ietf.org/html/rfc3986#section-6
 */
final class UriNormalizer
{
    /**
     * Default normalizations which only include the ones that preserve semantics.
     */
    public const PRESERVING_NORMALIZATIONS =
        self::CAPITALIZE_PERCENT_ENCODING |
        self::DECODE_UNRESERVED_CHARACTERS |
        self::CONVERT_EMPTY_PATH |
        self::REMOVE_DEFAULT_HOST |
        self::REMOVE_DEFAULT_PORT |
        self::REMOVE_DOT_SEGMENTS;

    /**
     * All letters within a percent-encoding triplet (e.g., &quot;%3A&quot;) are case-insensitive, and should be capitalized.
     *
     * Example: http://example.org/a%c2%b1b → http://example.org/a%C2%B1b
     */
    public const CAPITALIZE_PERCENT_ENCODING = 1;

    /**
     * Decodes percent-encoded octets of unreserved characters.
     *
     * For consistency, percent-encoded octets in the ranges of ALPHA (%41–%5A and %61–%7A), DIGIT (%30–%39),
     * hyphen (%2D), period (%2E), underscore (%5F), or tilde (%7E) should not be created by URI producers and,
     * when found in a URI, should be decoded to their corresponding unreserved characters by URI normalizers.
     *
     * Example: http://example.org/%7Eusern%61me/ → http://example.org/~username/
     */
    public const DECODE_UNRESERVED_CHARACTERS = 2;

    /**
     * Converts the empty path to &quot;/&quot; for http and https URIs.
     *
     * Example: http://example.org → http://example.org/
     */
    public const CONVERT_EMPTY_PATH = 4;

    /**
     * Removes the default host of the given URI scheme from the URI.
     *
     * Only the &quot;file&quot; scheme defines the default host &quot;localhost&quot;.
     * All of `file:/myfile`, `file:///myfile`, and `file://localhost/myfile`
     * are equivalent according to RFC 3986. The first format is not accepted
     * by PHPs stream functions and thus already normalized implicitly to the
     * second format in the Uri class. See `GuzzleHttp\Psr7\Uri::composeComponents`.
     *
     * Example: file://localhost/myfile → file:///myfile
     */
    public const REMOVE_DEFAULT_HOST = 8;

    /**
     * Removes the default port of the given URI scheme from the URI.
     *
     * Example: http://example.org:80/ → http://example.org/
     */
    public const REMOVE_DEFAULT_PORT = 16;

    /**
     * Removes unnecessary dot-segments.
     *
     * Dot-segments in relative-path references are not removed as it would
     * change the semantics of the URI reference.
     *
     * Example: http://example.org/../a/b/../c/./d.html → http://example.org/a/c/d.html
     */
    public const REMOVE_DOT_SEGMENTS = 32;

    /**
     * Paths which include two or more adjacent slashes are converted to one.
     *
     * Webservers usually ignore duplicate slashes and treat those URIs equivalent.
     * But in theory those URIs do not need to be equivalent. So this normalization
     * may change the semantics. Encoded slashes (%2F) are not removed.
     *
     * Example: http://example.org//foo///bar.html → http://example.org/foo/bar.html
     */
    public const REMOVE_DUPLICATE_SLASHES = 64;

    /**
     * Sort query parameters with their values in alphabetical order.
     *
     * However, the order of parameters in a URI may be significant (this is not defined by the standard).
     * So this normalization is not safe and may change the semantics of the URI.
     *
     * Example: ?lang=en&amp;article=fred → ?article=fred&amp;lang=en
     *
     * Note: The sorting is neither locale nor Unicode aware (the URI query does not get decoded at all) as the
     * purpose is to be able to compare URIs in a reproducible way, not to have the params sorted perfectly.
     */
    public const SORT_QUERY_PARAMETERS = 128;

    /**
     * Returns a normalized URI.
     *
     * The scheme and host component are already normalized to lowercase per PSR-7 UriInterface.
     * This methods adds additional normalizations that can be configured with the $flags parameter.
     *
     * PSR-7 UriInterface cannot distinguish between an empty component and a missing component as
     * getQuery(), getFragment() etc. always return a string. This means the URIs &quot;/?#&quot; and &quot;/&quot; are
     * treated equivalent which is not necessarily true according to RFC 3986. But that difference
     * is highly uncommon in reality. So this potential normalization is implied in PSR-7 as well.
     *
     * @param UriInterface $uri   The URI to normalize
     * @param int          $flags A bitmask of normalizations to apply, see constants
     *
     * @link https://tools.ietf.org/html/rfc3986#section-6.2
     */
    public static function normalize(UriInterface $uri, int $flags = self::PRESERVING_NORMALIZATIONS): UriInterface
    {
        if ($flags &amp; self::CAPITALIZE_PERCENT_ENCODING) {
            $uri = self::capitalizePercentEncoding($uri);
        }

        if ($flags &amp; self::DECODE_UNRESERVED_CHARACTERS) {
            $uri = self::decodeUnreservedCharacters($uri);
        }

        if ($flags &amp; self::CONVERT_EMPTY_PATH &amp;&amp; $uri-&gt;getPath() === '' &amp;&amp;
            ($uri-&gt;getScheme() === 'http' || $uri-&gt;getScheme() === 'https')
        ) {
            $uri = $uri-&gt;withPath('/');
        }

        if ($flags &amp; self::REMOVE_DEFAULT_HOST &amp;&amp; $uri-&gt;getScheme() === 'file' &amp;&amp; $uri-&gt;getHost() === 'localhost') {
            $uri = $uri-&gt;withHost('');
        }

        if ($flags &amp; self::REMOVE_DEFAULT_PORT &amp;&amp; $uri-&gt;getPort() !== null &amp;&amp; Uri::isDefaultPort($uri)) {
            $uri = $uri-&gt;withPort(null);
        }

        if ($flags &amp; self::REMOVE_DOT_SEGMENTS &amp;&amp; !Uri::isRelativePathReference($uri)) {
            $uri = $uri-&gt;withPath(UriResolver::removeDotSegments($uri-&gt;getPath()));
        }

        if ($flags &amp; self::REMOVE_DUPLICATE_SLASHES) {
            $uri = $uri-&gt;withPath(preg_replace('#//++#', '/', $uri-&gt;getPath()));
        }

        if ($flags &amp; self::SORT_QUERY_PARAMETERS &amp;&amp; $uri-&gt;getQuery() !== '') {
            $queryKeyValues = explode('&amp;', $uri-&gt;getQuery());
            sort($queryKeyValues);
            $uri = $uri-&gt;withQuery(implode('&amp;', $queryKeyValues));
        }

        return $uri;
    }

    /**
     * Whether two URIs can be considered equivalent.
     *
     * Both URIs are normalized automatically before comparison with the given $normalizations bitmask. The method also
     * accepts relative URI references and returns true when they are equivalent. This of course assumes they will be
     * resolved against the same base URI. If this is not the case, determination of equivalence or difference of
     * relative references does not mean anything.
     *
     * @param UriInterface $uri1           An URI to compare
     * @param UriInterface $uri2           An URI to compare
     * @param int          $normalizations A bitmask of normalizations to apply, see constants
     *
     * @link https://tools.ietf.org/html/rfc3986#section-6.1
     */
    public static function isEquivalent(UriInterface $uri1, UriInterface $uri2, int $normalizations = self::PRESERVING_NORMALIZATIONS): bool
    {
        return (string) self::normalize($uri1, $normalizations) === (string) self::normalize($uri2, $normalizations);
    }

    private static function capitalizePercentEncoding(UriInterface $uri): UriInterface
    {
        $regex = '/(?:%[A-Fa-f0-9]{2})++/';

        $callback = function (array $match) {
            return strtoupper($match[0]);
        };

        return
            $uri-&gt;withPath(
                preg_replace_callback($regex, $callback, $uri-&gt;getPath())
            )-&gt;withQuery(
                preg_replace_callback($regex, $callback, $uri-&gt;getQuery())
            );
    }

    private static function decodeUnreservedCharacters(UriInterface $uri): UriInterface
    {
        $regex = '/%(?:2D|2E|5F|7E|3[0-9]|[46][1-9A-F]|[57][0-9A])/i';

        $callback = function (array $match) {
            return rawurldecode($match[0]);
        };

        return
            $uri-&gt;withPath(
                preg_replace_callback($regex, $callback, $uri-&gt;getPath())
            )-&gt;withQuery(
                preg_replace_callback($regex, $callback, $uri-&gt;getQuery())
            );
    }

    private function __construct()
    {
        // cannot be instantiated
    }
}
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