CachePlugin::calculateResponseExpiresAt() - Code Metrics - Inspection of "Allow a cache item to be stored forever (#20)" - php-http/cache-plugin - Measure and Improve Code Quality continuously with Scrutinizer

Completed

Push — master ( a9dbc0...28d904 )

by David

created 2016-08-15 08:47 UTC

CachePlugin::calculateResponseExpiresAt() A

↳ Parent: CachePlugin

Complexity

Conditions	2
Paths	2

Size

Total Lines	8
Code Lines	4

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	3
CRAP Score	2.0625

Importance

Changes	1
Bugs	0	Features	0

Metric	Value
c	1
b	0
f	0
dl	0
loc	8
ccs	3
cts	4
cp	0.75
rs	9.4285
cc	2
eloc	4
nc	2
nop	1
crap	2.0625

<?php

namespace Http\Client\Common\Plugin;

use Http\Client\Common\Plugin;
use Http\Message\StreamFactory;
use Http\Promise\FulfilledPromise;
use Psr\Cache\CacheItemInterface;
use Psr\Cache\CacheItemPoolInterface;
use Psr\Http\Message\RequestInterface;
use Psr\Http\Message\ResponseInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;

/**
 * Allow for caching a response.
 *
 * @author Tobias Nyholm <[email protected]>
 */
final class CachePlugin implements Plugin
{
    /**
     * @var CacheItemPoolInterface
     */
    private $pool;

    /**
     * @var StreamFactory
     */
    private $streamFactory;

    /**
     * @var array
     */
    private $config;

    /**
     * @param CacheItemPoolInterface $pool
     * @param StreamFactory          $streamFactory
     * @param array                  $config        {
     *
     *     @var bool $respect_cache_headers Whether to look at the cache directives or ignore them
     *     @var int $default_ttl (seconds) If we do not respect cache headers or can't calculate a good ttl, use this
     *              value
     *     @var string $hash_algo The hashing algorithm to use when generating cache keys
     *     @var int $cache_lifetime (seconds) To support serving a previous stale response when the server answers 304
     *              we have to store the cache for a longer time than the server originally says it is valid for.
     *              We store a cache item for $cache_lifetime + max age of the response.
     * }
     */
    public function __construct(CacheItemPoolInterface $pool, StreamFactory $streamFactory, array $config = [])
    {
        $this->pool = $pool;
        $this->streamFactory = $streamFactory;

        $optionsResolver = new OptionsResolver();
        $this->configureOptions($optionsResolver);
        $this->config = $optionsResolver->resolve($config);
    }

    /**
     * {@inheritdoc}
     */
    public function handleRequest(RequestInterface $request, callable $next, callable $first)
    {
        $method = strtoupper($request->getMethod());
        // if the request not is cachable, move to $next
        if ($method !== 'GET' && $method !== 'HEAD') {
            return $next($request);
        }

        // If we can cache the request
        $key = $this->createCacheKey($request);
        $cacheItem = $this->pool->getItem($key);

        if ($cacheItem->isHit()) {
            $data = $cacheItem->get();
            // The array_key_exists() is to be removed in 2.0.
            if (array_key_exists('expiresAt', $data) && ($data['expiresAt'] === null || time() < $data['expiresAt'])) {
                // This item is still valid according to previous cache headers
                return new FulfilledPromise($this->createResponseFromCacheItem($cacheItem));
            }

            // Add headers to ask the server if this cache is still valid
            if ($modifiedSinceValue = $this->getModifiedSinceHeaderValue($cacheItem)) {
                $request = $request->withHeader('If-Modified-Since', $modifiedSinceValue);
            }

            if ($etag = $this->getETag($cacheItem)) {
                $request = $request->withHeader('If-None-Match', $etag);
            }
        }

        return $next($request)->then(function (ResponseInterface $response) use ($cacheItem) {
            if (304 === $response->getStatusCode()) {
                if (!$cacheItem->isHit()) {
                    /*
                     * We do not have the item in cache. This plugin did not add If-Modified-Since
                     * or If-None-Match headers. Return the response from server.
                     */
                    return $response;
                }

                // The cached response we have is still valid
                $data = $cacheItem->get();
                $maxAge = $this->getMaxAge($response);
                $data['expiresAt'] = $this->calculateResponseExpiresAt($maxAge);
                $cacheItem->set($data)->expiresAfter($this->calculateCacheItemExpiresAfter($maxAge));
                $this->pool->save($cacheItem);

                return $this->createResponseFromCacheItem($cacheItem);
            }

            if ($this->isCacheable($response)) {
                $bodyStream = $response->getBody();
                $body = $bodyStream->__toString();
                if ($bodyStream->isSeekable()) {
                    $bodyStream->rewind();
                } else {
                    $response = $response->withBody($this->streamFactory->createStream($body));
                }

                $maxAge = $this->getMaxAge($response);
                $cacheItem
                    ->expiresAfter($this->calculateCacheItemExpiresAfter($maxAge))
                    ->set([
                        'response' => $response,
                        'body' => $body,
                        'expiresAt' => $this->calculateResponseExpiresAt($maxAge),
                        'createdAt' => time(),
                        'etag' => $response->getHeader('ETag'),
                    ]);
                $this->pool->save($cacheItem);
            }

            return $response;
        });
    }

    /**
     * Calculate the timestamp when this cache item should be dropped from the cache. The lowest value that can be
     * returned is $maxAge.
     *
     * @param int|null $maxAge
     *
     * @return int|null Unix system time passed to the PSR-6 cache
     */
    private function calculateCacheItemExpiresAfter($maxAge)
    {
        if ($this->config['cache_lifetime'] === null && $maxAge === null) {
            return;
        }

        return $this->config['cache_lifetime'] + $maxAge;
    }

    /**
     * Calculate the timestamp when a response expires. After that timestamp, we need to send a
     * If-Modified-Since / If-None-Match request to validate the response.
     *
     * @param int|null $maxAge
     *
     * @return int|null Unix system time. A null value means that the response expires when the cache item expires
     */
    private function calculateResponseExpiresAt($maxAge)
    {
        if ($maxAge === null) {
            return;
        }

        return time() + $maxAge;
    }

    /**
     * Verify that we can cache this response.
     *
     * @param ResponseInterface $response
     *
     * @return bool
     */
    protected function isCacheable(ResponseInterface $response)
    {
        if (!in_array($response->getStatusCode(), [200, 203, 300, 301, 302, 404, 410])) {
            return false;
        }
        if (!$this->config['respect_cache_headers']) {
            return true;
        }
        if ($this->getCacheControlDirective($response, 'no-store') || $this->getCacheControlDirective($response, 'private')) {
            return false;
        }

        return true;
    }

    /**
     * Get the value of a parameter in the cache control header.
     *
     * @param ResponseInterface $response
     * @param string            $name     The field of Cache-Control to fetch
     *
     * @return bool|string The value of the directive, true if directive without value, false if directive not present
     */
    private function getCacheControlDirective(ResponseInterface $response, $name)
    {
        $headers = $response->getHeader('Cache-Control');
        foreach ($headers as $header) {
            if (preg_match(sprintf('|%s=?([0-9]+)?|i', $name), $header, $matches)) {

                // return the value for $name if it exists
                if (isset($matches[1])) {
                    return $matches[1];
                }

                return true;
            }
        }

        return false;
    }

    /**
     * @param RequestInterface $request
     *
     * @return string
     */
    private function createCacheKey(RequestInterface $request)
    {
        return hash($this->config['hash_algo'], $request->getMethod().' '.$request->getUri());
    }

    /**
     * Get a ttl in seconds. It could return null if we do not respect cache headers and got no defaultTtl.
     *
     * @param ResponseInterface $response
     *
     * @return int|null
     */
    private function getMaxAge(ResponseInterface $response)
    {
        if (!$this->config['respect_cache_headers']) {
            return $this->config['default_ttl'];
        }

        // check for max age in the Cache-Control header
        $maxAge = $this->getCacheControlDirective($response, 'max-age');
        if (!is_bool($maxAge)) {
            $ageHeaders = $response->getHeader('Age');
            foreach ($ageHeaders as $age) {
                return $maxAge - ((int) $age);
            }

            return (int) $maxAge;
        }

        // check for ttl in the Expires header
        $headers = $response->getHeader('Expires');
        foreach ($headers as $header) {
            return (new \DateTime($header))->getTimestamp() - (new \DateTime())->getTimestamp();
        }

        return $this->config['default_ttl'];
    }

    /**
     * Configure an options resolver.
     *
     * @param OptionsResolver $resolver
     */
    private function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'cache_lifetime' => 86400 * 30, // 30 days
            'default_ttl' => 0,
            'respect_cache_headers' => true,
            'hash_algo' => 'sha1',
        ]);

        $resolver->setAllowedTypes('cache_lifetime', ['int', 'null']);
        $resolver->setAllowedTypes('default_ttl', ['int', 'null']);
        $resolver->setAllowedTypes('respect_cache_headers', 'bool');
        $resolver->setAllowedValues('hash_algo', hash_algos());
    }

    /**
     * @param CacheItemInterface $cacheItem
     *
     * @return ResponseInterface
     */
    private function createResponseFromCacheItem(CacheItemInterface $cacheItem)
    {
        $data = $cacheItem->get();

        /** @var ResponseInterface $response */
        $response = $data['response'];
        $response = $response->withBody($this->streamFactory->createStream($data['body']));

        return $response;
    }

    /**
     * Get the value of the "If-Modified-Since" header.
     *
     * @param CacheItemInterface $cacheItem
     *
     * @return string|null
     */
    private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
    {
        $data = $cacheItem->get();
        // The isset() is to be removed in 2.0.
        if (!isset($data['createdAt'])) {
            return;
        }

        $modified = new \DateTime('@'.$data['createdAt']);
        $modified->setTimezone(new \DateTimeZone('GMT'));

        return sprintf('%s GMT', $modified->format('l, d-M-y H:i:s'));
    }

    /**
     * Get the ETag from the cached response.
     *
     * @param CacheItemInterface $cacheItem
     *
     * @return string|null
     */
    private function getETag(CacheItemInterface $cacheItem)
    {
        $data = $cacheItem->get();
        // The isset() is to be removed in 2.0.
        if (!isset($data['etag'])) {
            return;
        }

        if (!is_array($data['etag'])) {
            return $data['etag'];
        }

        foreach ($data['etag'] as $etag) {
            if (!empty($etag)) {
                return $etag;
            }
        }
    }
}


1		<?php
2
3		namespace Http\Client\Common\Plugin;
4
5		use Http\Client\Common\Plugin;
6		use Http\Message\StreamFactory;
7		use Http\Promise\FulfilledPromise;
8		use Psr\Cache\CacheItemInterface;
9		use Psr\Cache\CacheItemPoolInterface;
10		use Psr\Http\Message\RequestInterface;
11		use Psr\Http\Message\ResponseInterface;
12		use Symfony\Component\OptionsResolver\OptionsResolver;
13
14		/**
15		* Allow for caching a response.
16		*
17		* @author Tobias Nyholm <[email protected]>
18		*/
19		final class CachePlugin implements Plugin
20		{
21		/**
22		* @var CacheItemPoolInterface
23		*/
24		private $pool;
25
26		/**
27		* @var StreamFactory
28		*/
29		private $streamFactory;
30
31		/**
32		* @var array
33		*/
34		private $config;
35
36		/**
37		* @param CacheItemPoolInterface $pool
38		* @param StreamFactory $streamFactory
39		* @param array $config {
40		*
41		* @var bool $respect_cache_headers Whether to look at the cache directives or ignore them
42		* @var int $default_ttl (seconds) If we do not respect cache headers or can't calculate a good ttl, use this
43		* value
44		* @var string $hash_algo The hashing algorithm to use when generating cache keys
45		* @var int $cache_lifetime (seconds) To support serving a previous stale response when the server answers 304
46		* we have to store the cache for a longer time than the server originally says it is valid for.
47		* We store a cache item for $cache_lifetime + max age of the response.
48		* }
49		*/
50	10	public function __construct(CacheItemPoolInterface $pool, StreamFactory $streamFactory, array $config = [])
51		{
52	10	$this->pool = $pool;
53	10	$this->streamFactory = $streamFactory;
54
55	10	$optionsResolver = new OptionsResolver();
56	10	$this->configureOptions($optionsResolver);
57	10	$this->config = $optionsResolver->resolve($config);
58	10	}
59
60		/**
61		* {@inheritdoc}
62		*/
63	8	public function handleRequest(RequestInterface $request, callable $next, callable $first)
64	1	{
65	8	$method = strtoupper($request->getMethod());
66		// if the request not is cachable, move to $next
67	8	if ($method !== 'GET' && $method !== 'HEAD') {
68	1	return $next($request);
69		}
70
71		// If we can cache the request
72	7	$key = $this->createCacheKey($request);
73	7	$cacheItem = $this->pool->getItem($key);
74
75	7	if ($cacheItem->isHit()) {
76	3	$data = $cacheItem->get();
77		// The array_key_exists() is to be removed in 2.0.
78	3	if (array_key_exists('expiresAt', $data) && ($data['expiresAt'] === null \|\| time() < $data['expiresAt'])) {
79		// This item is still valid according to previous cache headers
80	1	return new FulfilledPromise($this->createResponseFromCacheItem($cacheItem));
81		}
82
83		// Add headers to ask the server if this cache is still valid
84	2	if ($modifiedSinceValue = $this->getModifiedSinceHeaderValue($cacheItem)) {
85	2	$request = $request->withHeader('If-Modified-Since', $modifiedSinceValue);
86	2	}
87
88	2	if ($etag = $this->getETag($cacheItem)) {
89	2	$request = $request->withHeader('If-None-Match', $etag);
90	2	}
91	2	}
92
93	6	return $next($request)->then(function (ResponseInterface $response) use ($cacheItem) {
94	6	if (304 === $response->getStatusCode()) {
95	2	if (!$cacheItem->isHit()) {
96		/*
97		* We do not have the item in cache. This plugin did not add If-Modified-Since
98		* or If-None-Match headers. Return the response from server.
99		*/
100	1	return $response;
101		}
102
103		// The cached response we have is still valid
104	1	$data = $cacheItem->get();
105	1	$maxAge = $this->getMaxAge($response);
106	1	$data['expiresAt'] = $this->calculateResponseExpiresAt($maxAge);
107	1	$cacheItem->set($data)->expiresAfter($this->calculateCacheItemExpiresAfter($maxAge));
108	1	$this->pool->save($cacheItem);
109
110	1	return $this->createResponseFromCacheItem($cacheItem);
111		}
112
113	4	if ($this->isCacheable($response)) {
114	3	$bodyStream = $response->getBody();
115	3	$body = $bodyStream->__toString();
116	3	if ($bodyStream->isSeekable()) {
117	3	$bodyStream->rewind();
118	3	} else {
119		$response = $response->withBody($this->streamFactory->createStream($body));
120		}
121
122	3	$maxAge = $this->getMaxAge($response);
123		$cacheItem
124	3	->expiresAfter($this->calculateCacheItemExpiresAfter($maxAge))
125	3	->set([
126	3	'response' => $response,
127	3	'body' => $body,
128	3	'expiresAt' => $this->calculateResponseExpiresAt($maxAge),
129	3	'createdAt' => time(),
130	3	'etag' => $response->getHeader('ETag'),
131	3	]);
132	3	$this->pool->save($cacheItem);
133	3	}
134
135	4	return $response;
136	6	});
137		}
138
139		/**
140		* Calculate the timestamp when this cache item should be dropped from the cache. The lowest value that can be
141		* returned is $maxAge.
142		*
143		* @param int\|null $maxAge
144		*
145		* @return int\|null Unix system time passed to the PSR-6 cache
146		*/
147	4	private function calculateCacheItemExpiresAfter($maxAge)
148		{
149	4	if ($this->config['cache_lifetime'] === null && $maxAge === null) {
150		return;
151		}
152
153	4	return $this->config['cache_lifetime'] + $maxAge;
154		}
155
156		/**
157		* Calculate the timestamp when a response expires. After that timestamp, we need to send a
158		* If-Modified-Since / If-None-Match request to validate the response.
159		*
160		* @param int\|null $maxAge
161		*
162		* @return int\|null Unix system time. A null value means that the response expires when the cache item expires
163		*/
164	4	private function calculateResponseExpiresAt($maxAge)
165		{
166	4	if ($maxAge === null) {
167		return;
168		}
169
170	4	return time() + $maxAge;
171		}
172
173		/**
174		* Verify that we can cache this response.
175		*
176		* @param ResponseInterface $response
177		*
178		* @return bool
179		*/
180	4	protected function isCacheable(ResponseInterface $response)
181		{
182	4	if (!in_array($response->getStatusCode(), [200, 203, 300, 301, 302, 404, 410])) {
183	1	return false;
184		}
185	3	if (!$this->config['respect_cache_headers']) {
186		return true;
187		}
188	3	if ($this->getCacheControlDirective($response, 'no-store') \|\| $this->getCacheControlDirective($response, 'private')) {
189		return false;
190		}
191
192	3	return true;
193		}
194
195		/**
196		* Get the value of a parameter in the cache control header.
197		*
198		* @param ResponseInterface $response
199		* @param string $name The field of Cache-Control to fetch
200		*
201		* @return bool\|string The value of the directive, true if directive without value, false if directive not present
202		*/
203	4	private function getCacheControlDirective(ResponseInterface $response, $name)
204		{
205	4	$headers = $response->getHeader('Cache-Control');
206	4	foreach ($headers as $header) {
207	1	if (preg_match(sprintf('\|%s=?([0-9]+)?\|i', $name), $header, $matches)) {
208
209		// return the value for $name if it exists
210	1	if (isset($matches[1])) {
211	1	return $matches[1];
212		}
213
214		return true;
215		}
216	4	}
217
218	4	return false;
219		}
220
221		/**
222		* @param RequestInterface $request
223		*
224		* @return string
225		*/
226	7	private function createCacheKey(RequestInterface $request)
227		{
228	7	return hash($this->config['hash_algo'], $request->getMethod().' '.$request->getUri());
229		}
230
231		/**
232		* Get a ttl in seconds. It could return null if we do not respect cache headers and got no defaultTtl.
233		*
234		* @param ResponseInterface $response
235		*
236		* @return int\|null
237		*/
238	4	private function getMaxAge(ResponseInterface $response)
239		{
240	4	if (!$this->config['respect_cache_headers']) {
241		return $this->config['default_ttl'];
242		}
243
244		// check for max age in the Cache-Control header
245	4	$maxAge = $this->getCacheControlDirective($response, 'max-age');
246	4	if (!is_bool($maxAge)) {
247	1	$ageHeaders = $response->getHeader('Age');
248	1	foreach ($ageHeaders as $age) {
249	1	return $maxAge - ((int) $age);
250		}
251
252		return (int) $maxAge;
253		}
254
255		// check for ttl in the Expires header
256	3	$headers = $response->getHeader('Expires');
257	3	foreach ($headers as $header) {
258		return (new \DateTime($header))->getTimestamp() - (new \DateTime())->getTimestamp();
259	3	}
260
261	3	return $this->config['default_ttl'];
262		}
263
264		/**
265		* Configure an options resolver.
266		*
267		* @param OptionsResolver $resolver
268		*/
269	10	private function configureOptions(OptionsResolver $resolver)
270		{
271	10	$resolver->setDefaults([
272	10	'cache_lifetime' => 86400 * 30, // 30 days
273	10	'default_ttl' => 0,
274	10	'respect_cache_headers' => true,
275	10	'hash_algo' => 'sha1',
276	10	]);
277
278	10	$resolver->setAllowedTypes('cache_lifetime', ['int', 'null']);
279	10	$resolver->setAllowedTypes('default_ttl', ['int', 'null']);
280	10	$resolver->setAllowedTypes('respect_cache_headers', 'bool');
281	10	$resolver->setAllowedValues('hash_algo', hash_algos());
282	10	}
283
284		/**
285		* @param CacheItemInterface $cacheItem
286		*
287		* @return ResponseInterface
288		*/
289	2	private function createResponseFromCacheItem(CacheItemInterface $cacheItem)
290		{
291	2	$data = $cacheItem->get();
292
293		/** @var ResponseInterface $response */
294	2	$response = $data['response'];
295	2	$response = $response->withBody($this->streamFactory->createStream($data['body']));
296
297	2	return $response;
298		}
299
300		/**
301		* Get the value of the "If-Modified-Since" header.
302		*
303		* @param CacheItemInterface $cacheItem
304		*
305		* @return string\|null
306		*/
307	2	private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
308		{
309	2	$data = $cacheItem->get();
310		// The isset() is to be removed in 2.0.
311	2	if (!isset($data['createdAt'])) {
312		return;
313		}
314
315	2	$modified = new \DateTime('@'.$data['createdAt']);
316	2	$modified->setTimezone(new \DateTimeZone('GMT'));
317
318	2	return sprintf('%s GMT', $modified->format('l, d-M-y H:i:s'));
319		}
320
321		/**
322		* Get the ETag from the cached response.
323		*
324		* @param CacheItemInterface $cacheItem
325		*
326		* @return string\|null
327		*/
328	2	private function getETag(CacheItemInterface $cacheItem)
329		{
330	2	$data = $cacheItem->get();
331		// The isset() is to be removed in 2.0.
332	2	if (!isset($data['etag'])) {
333		return;
334		}
335
336	2	if (!is_array($data['etag'])) {
337		return $data['etag'];
338		}
339
340	2	foreach ($data['etag'] as $etag) {
341	2	if (!empty($etag)) {
342	2	return $etag;
343		}
344		}
345		}
346		}
347

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CachePlugin::calculateResponseExpiresAt() A

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