1<?php
2
3namespace GuzzleHttp\Psr7;
4
5use Psr\Http\Message\UriInterface;
6
7/**
8 * Resolves a URI reference in the context of a base URI and the opposite way.
9 *
10 * @author Tobias Schultze
11 *
12 * @link https://tools.ietf.org/html/rfc3986#section-5
13 */
14final class UriResolver
15{
16    /**
17     * Removes dot segments from a path and returns the new path.
18     *
19     * @param string $path
20     *
21     * @return string
22     * @link http://tools.ietf.org/html/rfc3986#section-5.2.4
23     */
24    public static function removeDotSegments($path)
25    {
26        if ($path === '' || $path === '/') {
27            return $path;
28        }
29
30        $results = [];
31        $segments = explode('/', $path);
32        foreach ($segments as $segment) {
33            if ($segment === '..') {
34                array_pop($results);
35            } elseif ($segment !== '.') {
36                $results[] = $segment;
37            }
38        }
39
40        $newPath = implode('/', $results);
41
42        if ($path[0] === '/' && (!isset($newPath[0]) || $newPath[0] !== '/')) {
43            // Re-add the leading slash if necessary for cases like "/.."
44            $newPath = '/' . $newPath;
45        } elseif ($newPath !== '' && ($segment === '.' || $segment === '..')) {
46            // Add the trailing slash if necessary
47            // If newPath is not empty, then $segment must be set and is the last segment from the foreach
48            $newPath .= '/';
49        }
50
51        return $newPath;
52    }
53
54    /**
55     * Converts the relative URI into a new URI that is resolved against the base URI.
56     *
57     * @param UriInterface $base Base URI
58     * @param UriInterface $rel  Relative URI
59     *
60     * @return UriInterface
61     * @link http://tools.ietf.org/html/rfc3986#section-5.2
62     */
63    public static function resolve(UriInterface $base, UriInterface $rel)
64    {
65        if ((string) $rel === '') {
66            // we can simply return the same base URI instance for this same-document reference
67            return $base;
68        }
69
70        if ($rel->getScheme() != '') {
71            return $rel->withPath(self::removeDotSegments($rel->getPath()));
72        }
73
74        if ($rel->getAuthority() != '') {
75            $targetAuthority = $rel->getAuthority();
76            $targetPath = self::removeDotSegments($rel->getPath());
77            $targetQuery = $rel->getQuery();
78        } else {
79            $targetAuthority = $base->getAuthority();
80            if ($rel->getPath() === '') {
81                $targetPath = $base->getPath();
82                $targetQuery = $rel->getQuery() != '' ? $rel->getQuery() : $base->getQuery();
83            } else {
84                if ($rel->getPath()[0] === '/') {
85                    $targetPath = $rel->getPath();
86                } else {
87                    if ($targetAuthority != '' && $base->getPath() === '') {
88                        $targetPath = '/' . $rel->getPath();
89                    } else {
90                        $lastSlashPos = strrpos($base->getPath(), '/');
91                        if ($lastSlashPos === false) {
92                            $targetPath = $rel->getPath();
93                        } else {
94                            $targetPath = substr($base->getPath(), 0, $lastSlashPos + 1) . $rel->getPath();
95                        }
96                    }
97                }
98                $targetPath = self::removeDotSegments($targetPath);
99                $targetQuery = $rel->getQuery();
100            }
101        }
102
103        return new Uri(Uri::composeComponents(
104            $base->getScheme(),
105            $targetAuthority,
106            $targetPath,
107            $targetQuery,
108            $rel->getFragment()
109        ));
110    }
111
112    /**
113     * Returns the target URI as a relative reference from the base URI.
114     *
115     * This method is the counterpart to resolve():
116     *
117     *    (string) $target === (string) UriResolver::resolve($base, UriResolver::relativize($base, $target))
118     *
119     * One use-case is to use the current request URI as base URI and then generate relative links in your documents
120     * to reduce the document size or offer self-contained downloadable document archives.
121     *
122     *    $base = new Uri('http://example.com/a/b/');
123     *    echo UriResolver::relativize($base, new Uri('http://example.com/a/b/c'));  // prints 'c'.
124     *    echo UriResolver::relativize($base, new Uri('http://example.com/a/x/y'));  // prints '../x/y'.
125     *    echo UriResolver::relativize($base, new Uri('http://example.com/a/b/?q')); // prints '?q'.
126     *    echo UriResolver::relativize($base, new Uri('http://example.org/a/b/'));   // prints '//example.org/a/b/'.
127     *
128     * This method also accepts a target that is already relative and will try to relativize it further. Only a
129     * relative-path reference will be returned as-is.
130     *
131     *    echo UriResolver::relativize($base, new Uri('/a/b/c'));  // prints 'c' as well
132     *
133     * @param UriInterface $base   Base URI
134     * @param UriInterface $target Target URI
135     *
136     * @return UriInterface The relative URI reference
137     */
138    public static function relativize(UriInterface $base, UriInterface $target)
139    {
140        if ($target->getScheme() !== '' &&
141            ($base->getScheme() !== $target->getScheme() || $target->getAuthority() === '' && $base->getAuthority() !== '')
142        ) {
143            return $target;
144        }
145
146        if (Uri::isRelativePathReference($target)) {
147            // As the target is already highly relative we return it as-is. It would be possible to resolve
148            // the target with `$target = self::resolve($base, $target);` and then try make it more relative
149            // by removing a duplicate query. But let's not do that automatically.
150            return $target;
151        }
152
153        if ($target->getAuthority() !== '' && $base->getAuthority() !== $target->getAuthority()) {
154            return $target->withScheme('');
155        }
156
157        // We must remove the path before removing the authority because if the path starts with two slashes, the URI
158        // would turn invalid. And we also cannot set a relative path before removing the authority, as that is also
159        // invalid.
160        $emptyPathUri = $target->withScheme('')->withPath('')->withUserInfo('')->withPort(null)->withHost('');
161
162        if ($base->getPath() !== $target->getPath()) {
163            return $emptyPathUri->withPath(self::getRelativePath($base, $target));
164        }
165
166        if ($base->getQuery() === $target->getQuery()) {
167            // Only the target fragment is left. And it must be returned even if base and target fragment are the same.
168            return $emptyPathUri->withQuery('');
169        }
170
171        // If the base URI has a query but the target has none, we cannot return an empty path reference as it would
172        // inherit the base query component when resolving.
173        if ($target->getQuery() === '') {
174            $segments = explode('/', $target->getPath());
175            $lastSegment = end($segments);
176
177            return $emptyPathUri->withPath($lastSegment === '' ? './' : $lastSegment);
178        }
179
180        return $emptyPathUri;
181    }
182
183    private static function getRelativePath(UriInterface $base, UriInterface $target)
184    {
185        $sourceSegments = explode('/', $base->getPath());
186        $targetSegments = explode('/', $target->getPath());
187        array_pop($sourceSegments);
188        $targetLastSegment = array_pop($targetSegments);
189        foreach ($sourceSegments as $i => $segment) {
190            if (isset($targetSegments[$i]) && $segment === $targetSegments[$i]) {
191                unset($sourceSegments[$i], $targetSegments[$i]);
192            } else {
193                break;
194            }
195        }
196        $targetSegments[] = $targetLastSegment;
197        $relativePath = str_repeat('../', count($sourceSegments)) . implode('/', $targetSegments);
198
199        // A reference to am empty last segment or an empty first sub-segment must be prefixed with "./".
200        // This also applies to a segment with a colon character (e.g., "file:colon") that cannot be used
201        // as the first segment of a relative-path reference, as it would be mistaken for a scheme name.
202        if ('' === $relativePath || false !== strpos(explode('/', $relativePath, 2)[0], ':')) {
203            $relativePath = "./$relativePath";
204        } elseif ('/' === $relativePath[0]) {
205            if ($base->getAuthority() != '' && $base->getPath() === '') {
206                // In this case an extra slash is added by resolve() automatically. So we must not add one here.
207                $relativePath = ".$relativePath";
208            } else {
209                $relativePath = "./$relativePath";
210            }
211        }
212
213        return $relativePath;
214    }
215
216    private function __construct()
217    {
218        // cannot be instantiated
219    }
220}
221