From 824b9aa08236d9a9aeb0ad640309c88dea345fe8 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Fri, 29 Jul 2016 14:37:41 +0200
Subject: [PATCH 01/19] Added support for Last-Modified and ETag

---
 src/CachePlugin.php | 110 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 103 insertions(+), 7 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index f0bdbd4..d1ef3ef 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -5,6 +5,7 @@
 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;
@@ -58,7 +59,6 @@ public function __construct(CacheItemPoolInterface $pool, StreamFactory $streamF
     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);
@@ -69,15 +69,42 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
         $cacheItem = $this->pool->getItem($key);
 
         if ($cacheItem->isHit()) {
-            // return cached response
             $data = $cacheItem->get();
-            $response = $data['response'];
-            $response = $response->withBody($this->streamFactory->createStream($data['body']));
+            if (isset($data['expiresAt']) && time() > $data['expiresAt']) {
+                // This item is still valid according to previous cache headers
+                return new FulfilledPromise($this->createResponseFromCacheItem($cacheItem));
+            }
+
+            // Add headers to ask the server if this cache is still valid
+            if ($modifiedAt = $this->getModifiedAt($cacheItem)) {
+                $modifiedAt = new \DateTime('@'.$modifiedAt);
+                $modifiedAt->setTimezone(new \DateTimeZone('GMT'));
+                $request = $request->withHeader(
+                    'If-Modified-Since',
+                    sprintf('%s GMT', $modifiedAt->format('l, d-M-y H:i:s'))
+                );
+            }
 
-            return new FulfilledPromise($response);
+            if ($etag = $this->getETag($cacheItem)) {
+                $request = $request->withHeader(
+                    'If-None-Match',
+                    $etag
+                );
+            }
         }
 
+
         return $next($request)->then(function (ResponseInterface $response) use ($cacheItem) {
+            if (304 === $response->getStatusCode()) {
+                // The cached response we have is still valid
+                $data = $cacheItem->get();
+                $data['expiresAt'] = time() + $this->getMaxAge($response);
+                $cacheItem->set($data)->expiresAfter($this->config['cache_lifetime']);
+                $this->pool->save($cacheItem);
+
+                return $this->createResponseFromCacheItem($cacheItem);
+            }
+
             if ($this->isCacheable($response)) {
                 $bodyStream = $response->getBody();
                 $body = $bodyStream->__toString();
@@ -87,8 +114,15 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                     $response = $response->withBody($this->streamFactory->createStream($body));
                 }
 
-                $cacheItem->set(['response' => $response, 'body' => $body])
-                    ->expiresAfter($this->getMaxAge($response));
+                $cacheItem
+                    ->expiresAfter($this->config['cache_lifetime'])
+                    ->set([
+                    'response' => $response,
+                    'body' => $body,
+                    'expiresAt' => time() + $this->getMaxAge($response),
+                    'createdAt' => time(),
+                    'etag' => $response->getHeader('ETag'),
+                ]);
                 $this->pool->save($cacheItem);
             }
 
@@ -195,13 +229,75 @@ private function getMaxAge(ResponseInterface $response)
     private function configureOptions(OptionsResolver $resolver)
     {
         $resolver->setDefaults([
+            'cache_lifetime' => 2592000, // 30 days
             'default_ttl' => null,
             'respect_cache_headers' => true,
             'hash_algo' => 'sha1',
         ]);
 
+        $resolver->setAllowedTypes('cache_lifetime', 'int');
         $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 timestamp when the cached response was stored.
+     *
+     * @param CacheItemInterface $cacheItem
+     *
+     * @return int|null
+     */
+    private function getModifiedAt(CacheItemInterface $cacheItem)
+    {
+        $data = $cacheItem->get();
+        if (!isset($data['createdAt'])) {
+            return null;
+        }
+
+        return $data['createdAt'];
+    }
+
+    /**
+     * Get the ETag from the cached response.
+     *
+     * @param CacheItemInterface $cacheItem
+     *
+     * @return string|null
+     */
+    private function getETag(CacheItemInterface $cacheItem)
+    {
+        $data = $cacheItem->get();
+        if (!isset($data['etag'])) {
+            return null;
+        }
+
+        if (is_array($data['etag'])) {
+            foreach($data['etag'] as $etag) {
+                if (!empty($etag)) {
+                    return $etag;
+                }
+            }
+
+            return null;
+        }
+
+        return $data['etag'];
+    }
 }

From 3b2f72094401e61193d48b8f75d676013e7e7f6c Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Fri, 29 Jul 2016 14:44:10 +0200
Subject: [PATCH 02/19] style fix

---
 src/CachePlugin.php | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index d1ef3ef..0cdd066 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -99,7 +99,7 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                 // The cached response we have is still valid
                 $data = $cacheItem->get();
                 $data['expiresAt'] = time() + $this->getMaxAge($response);
-                $cacheItem->set($data)->expiresAfter($this->config['cache_lifetime']);
+                $cacheItem->set($data)->expiresAfter($this->config['cache_lifetime'] + $data['expiresAt']);
                 $this->pool->save($cacheItem);
 
                 return $this->createResponseFromCacheItem($cacheItem);
@@ -114,12 +114,13 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                     $response = $response->withBody($this->streamFactory->createStream($body));
                 }
 
+                $expiresAt = time() + $this->getMaxAge($response);
                 $cacheItem
-                    ->expiresAfter($this->config['cache_lifetime'])
+                    ->expiresAfter($this->config['cache_lifetime'] + $expiresAt)
                     ->set([
                     'response' => $response,
                     'body' => $body,
-                    'expiresAt' => time() + $this->getMaxAge($response),
+                    'expiresAt' => $expiresAt,
                     'createdAt' => time(),
                     'etag' => $response->getHeader('ETag'),
                 ]);
@@ -268,7 +269,7 @@ private function getModifiedAt(CacheItemInterface $cacheItem)
     {
         $data = $cacheItem->get();
         if (!isset($data['createdAt'])) {
-            return null;
+            return;
         }
 
         return $data['createdAt'];
@@ -285,17 +286,17 @@ private function getETag(CacheItemInterface $cacheItem)
     {
         $data = $cacheItem->get();
         if (!isset($data['etag'])) {
-            return null;
+            return;
         }
 
         if (is_array($data['etag'])) {
-            foreach($data['etag'] as $etag) {
+            foreach ($data['etag'] as $etag) {
                 if (!empty($etag)) {
                     return $etag;
                 }
             }
 
-            return null;
+            return;
         }
 
         return $data['etag'];

From 3f36fb52ee36e0072135a42d29812674b5db4ce0 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Fri, 29 Jul 2016 14:56:33 +0200
Subject: [PATCH 03/19] Return the 304 response if we do not have a response in
 cache

---
 src/CachePlugin.php | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 0cdd066..6e9238c 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -96,6 +96,11 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
 
         return $next($request)->then(function (ResponseInterface $response) use ($cacheItem) {
             if (304 === $response->getStatusCode()) {
+                if (!$cacheItem->isHit()) {
+                    // We do not have the item in cache. We can return the cached response.
+                    return $response;
+                }
+
                 // The cached response we have is still valid
                 $data = $cacheItem->get();
                 $data['expiresAt'] = time() + $this->getMaxAge($response);

From 39c0cfea4704b050a155515dcbc105a3d09378b4 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Fri, 29 Jul 2016 15:46:45 +0200
Subject: [PATCH 04/19] Bugfix and started on the tests

---
 spec/CachePluginSpec.php | 13 ++++++++++---
 src/CachePlugin.php      | 11 ++++++-----
 2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 808806d..2a4f5a4 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -15,7 +15,7 @@ class CachePluginSpec extends ObjectBehavior
 {
     function let(CacheItemPoolInterface $pool, StreamFactory $streamFactory)
     {
-        $this->beConstructedWith($pool, $streamFactory, ['default_ttl'=>60]);
+        $this->beConstructedWith($pool, $streamFactory, ['default_ttl'=>60, 'cache_lifetime'=>1000]);
     }
 
     function it_is_initializable(CacheItemPoolInterface $pool)
@@ -41,11 +41,12 @@ function it_caches_responses(CacheItemPoolInterface $pool, CacheItemInterface $i
         $response->getBody()->willReturn($stream);
         $response->getHeader('Cache-Control')->willReturn(array());
         $response->getHeader('Expires')->willReturn(array());
+        $response->getHeader('ETag')->willReturn(array());
 
         $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(false);
-        $item->set(['response' => $response, 'body' => $httpBody])->willReturn($item)->shouldBeCalled();
-        $item->expiresAfter(60)->willReturn($item)->shouldBeCalled();
+        $item->set()->willReturn($item)->shouldBeCalled();
+        $item->expiresAfter(1060)->willReturn($item)->shouldBeCalled();
         $pool->save($item)->shouldBeCalled();
 
         $next = function (RequestInterface $request) use ($response) {
@@ -53,6 +54,12 @@ function it_caches_responses(CacheItemPoolInterface $pool, CacheItemInterface $i
         };
 
         $this->handleRequest($request, $next, function () {});
+        $item->get()->shouldHaveKeyWithValue('response', $response);
+        $item->get()->shouldHaveKeyWithValue('body', $httpBody);
+        $item->get()->shouldHaveKey('expiresAt');
+        $item->get()->shouldHaveKey('createdAt');
+        $item->get()->shouldHaveKey('etag');
+
     }
 
     function it_doesnt_store_failed_responses(CacheItemPoolInterface $pool, CacheItemInterface $item, RequestInterface $request, ResponseInterface $response)
diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 6e9238c..b30c8a3 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -103,8 +103,9 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
 
                 // The cached response we have is still valid
                 $data = $cacheItem->get();
-                $data['expiresAt'] = time() + $this->getMaxAge($response);
-                $cacheItem->set($data)->expiresAfter($this->config['cache_lifetime'] + $data['expiresAt']);
+                $maxAge = $this->getMaxAge($response);
+                $data['expiresAt'] = time() + $maxAge;
+                $cacheItem->set($data)->expiresAfter($this->config['cache_lifetime'] + $maxAge);
                 $this->pool->save($cacheItem);
 
                 return $this->createResponseFromCacheItem($cacheItem);
@@ -119,13 +120,13 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                     $response = $response->withBody($this->streamFactory->createStream($body));
                 }
 
-                $expiresAt = time() + $this->getMaxAge($response);
+                $maxAge = $this->getMaxAge($response);
                 $cacheItem
-                    ->expiresAfter($this->config['cache_lifetime'] + $expiresAt)
+                    ->expiresAfter($this->config['cache_lifetime'] + $maxAge)
                     ->set([
                     'response' => $response,
                     'body' => $body,
-                    'expiresAt' => $expiresAt,
+                    'expiresAt' => time() + $maxAge,
                     'createdAt' => time(),
                     'etag' => $response->getHeader('ETag'),
                 ]);

From 33c6e1c6fb8a8418e9aa8030211490c852b29226 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Sun, 31 Jul 2016 15:37:43 +0200
Subject: [PATCH 05/19] Style fixes

---
 src/CachePlugin.php | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index b30c8a3..6de0f1d 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -76,24 +76,17 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
             }
 
             // Add headers to ask the server if this cache is still valid
-            if ($modifiedAt = $this->getModifiedAt($cacheItem)) {
-                $modifiedAt = new \DateTime('@'.$modifiedAt);
-                $modifiedAt->setTimezone(new \DateTimeZone('GMT'));
-                $request = $request->withHeader(
-                    'If-Modified-Since',
-                    sprintf('%s GMT', $modifiedAt->format('l, d-M-y H:i:s'))
-                );
+            if ($mod = $this->getModifiedAt($cacheItem)) {
+                $mod = new \DateTime('@'.$mod);
+                $mod->setTimezone(new \DateTimeZone('GMT'));
+                $request = $request->withHeader('If-Modified-Since', sprintf('%s GMT', $mod->format('l, d-M-y H:i:s')));
             }
 
             if ($etag = $this->getETag($cacheItem)) {
-                $request = $request->withHeader(
-                    'If-None-Match',
-                    $etag
-                );
+                $request = $request->withHeader('If-None-Match', $etag);
             }
         }
 
-
         return $next($request)->then(function (ResponseInterface $response) use ($cacheItem) {
             if (304 === $response->getStatusCode()) {
                 if (!$cacheItem->isHit()) {

From 83e22ce43935599b45221bedc73e7f6eb40f0ff4 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Sun, 31 Jul 2016 17:17:43 +0200
Subject: [PATCH 06/19] Tests are passing

---
 composer.json            |  5 ++++
 spec/CachePluginSpec.php | 59 ++++++++++++++++++++++++++++++----------
 2 files changed, 50 insertions(+), 14 deletions(-)

diff --git a/composer.json b/composer.json
index aa8bde7..52df585 100644
--- a/composer.json
+++ b/composer.json
@@ -26,6 +26,11 @@
             "Http\\Client\\Common\\Plugin\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "spec\\Http\\Client\\Common\\Plugin\\": "spec/"
+        }
+    },
     "scripts": {
         "test": "vendor/bin/phpspec run",
         "test-ci": "vendor/bin/phpspec run -c phpspec.ci.yml"
diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 2a4f5a4..503617c 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -2,6 +2,8 @@
 
 namespace spec\Http\Client\Common\Plugin;
 
+use Prophecy\Argument;
+use Prophecy\Comparator\Factory as ComparatorFactory;
 use Http\Message\StreamFactory;
 use Http\Promise\FulfilledPromise;
 use PhpSpec\ObjectBehavior;
@@ -39,27 +41,28 @@ function it_caches_responses(CacheItemPoolInterface $pool, CacheItemInterface $i
         $request->getUri()->willReturn('/');
         $response->getStatusCode()->willReturn(200);
         $response->getBody()->willReturn($stream);
-        $response->getHeader('Cache-Control')->willReturn(array());
-        $response->getHeader('Expires')->willReturn(array());
-        $response->getHeader('ETag')->willReturn(array());
+        $response->getHeader('Cache-Control')->willReturn(array())->shouldBeCalled();
+        $response->getHeader('Expires')->willReturn(array())->shouldBeCalled();
+        $response->getHeader('ETag')->willReturn(array())->shouldBeCalled();
 
         $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(false);
-        $item->set()->willReturn($item)->shouldBeCalled();
         $item->expiresAfter(1060)->willReturn($item)->shouldBeCalled();
-        $pool->save($item)->shouldBeCalled();
+
+        $item->set(Argument::that($this->getCacheItemMatcher([
+            'response' => $response->getWrappedObject(),
+            'body' => $httpBody,
+            'expiresAt' => 0,
+            'createdAt' => 0,
+            'etag' => []
+        ])))->willReturn($item)->shouldBeCalled();
+        $pool->save(Argument::any())->shouldBeCalled();
 
         $next = function (RequestInterface $request) use ($response) {
             return new FulfilledPromise($response->getWrappedObject());
         };
 
         $this->handleRequest($request, $next, function () {});
-        $item->get()->shouldHaveKeyWithValue('response', $response);
-        $item->get()->shouldHaveKeyWithValue('body', $httpBody);
-        $item->get()->shouldHaveKey('expiresAt');
-        $item->get()->shouldHaveKey('createdAt');
-        $item->get()->shouldHaveKey('etag');
-
     }
 
     function it_doesnt_store_failed_responses(CacheItemPoolInterface $pool, CacheItemInterface $item, RequestInterface $request, ResponseInterface $response)
@@ -107,13 +110,20 @@ function it_calculate_age_from_response(CacheItemPoolInterface $pool, CacheItemI
         $response->getHeader('Cache-Control')->willReturn(array('max-age=40'));
         $response->getHeader('Age')->willReturn(array('15'));
         $response->getHeader('Expires')->willReturn(array());
+        $response->getHeader('ETag')->willReturn(array());
 
         $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(false);
 
-        // 40-15 should be 25
-        $item->set(['response' => $response, 'body' => $httpBody])->willReturn($item)->shouldBeCalled();
-        $item->expiresAfter(25)->willReturn($item)->shouldBeCalled();
+        $item->set(Argument::that($this->getCacheItemMatcher([
+                'response' => $response->getWrappedObject(),
+                'body' => $httpBody,
+                'expiresAt' => 0,
+                'createdAt' => 0,
+                'etag' => []
+            ])))->willReturn($item)->shouldBeCalled();
+        // 40-15 should be 25 + the default 1000
+        $item->expiresAfter(1025)->willReturn($item)->shouldBeCalled();
         $pool->save($item)->shouldBeCalled();
 
         $next = function (RequestInterface $request) use ($response) {
@@ -122,4 +132,25 @@ function it_calculate_age_from_response(CacheItemPoolInterface $pool, CacheItemI
 
         $this->handleRequest($request, $next, function () {});
     }
+
+    private function getCacheItemMatcher(array $expectedData)
+    {
+        return function(array $actualData) use ($expectedData) {
+            foreach ($expectedData as $key => $value) {
+                if (!isset($actualData[$key])) {
+                    return false;
+                }
+
+                if ($key === 'expiresAt' || $key === 'createdAt') {
+                    // We do not need to validate the value of these fields.
+                    continue;
+                }
+
+                if ($actualData[$key] !== $value) {
+                    return false;
+                }
+            }
+            return true;
+        };
+    }
 }

From 370b0a0c77dc4b38eabd84f09fc03413293ec960 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Sun, 31 Jul 2016 17:19:05 +0200
Subject: [PATCH 07/19] Style fix

---
 spec/CachePluginSpec.php | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 503617c..1b43a52 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -49,13 +49,13 @@ function it_caches_responses(CacheItemPoolInterface $pool, CacheItemInterface $i
         $item->isHit()->willReturn(false);
         $item->expiresAfter(1060)->willReturn($item)->shouldBeCalled();
 
-        $item->set(Argument::that($this->getCacheItemMatcher([
+        $item->set($this->getCacheItemMatcher([
             'response' => $response->getWrappedObject(),
             'body' => $httpBody,
             'expiresAt' => 0,
             'createdAt' => 0,
             'etag' => []
-        ])))->willReturn($item)->shouldBeCalled();
+        ]))->willReturn($item)->shouldBeCalled();
         $pool->save(Argument::any())->shouldBeCalled();
 
         $next = function (RequestInterface $request) use ($response) {
@@ -115,13 +115,13 @@ function it_calculate_age_from_response(CacheItemPoolInterface $pool, CacheItemI
         $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(false);
 
-        $item->set(Argument::that($this->getCacheItemMatcher([
+        $item->set($this->getCacheItemMatcher([
                 'response' => $response->getWrappedObject(),
                 'body' => $httpBody,
                 'expiresAt' => 0,
                 'createdAt' => 0,
                 'etag' => []
-            ])))->willReturn($item)->shouldBeCalled();
+            ]))->willReturn($item)->shouldBeCalled();
         // 40-15 should be 25 + the default 1000
         $item->expiresAfter(1025)->willReturn($item)->shouldBeCalled();
         $pool->save($item)->shouldBeCalled();
@@ -133,9 +133,17 @@ function it_calculate_age_from_response(CacheItemPoolInterface $pool, CacheItemI
         $this->handleRequest($request, $next, function () {});
     }
 
+
+    /**
+     * Private function to match requests
+     *
+     * @param array $expectedData
+     *
+     * @return \Closure
+     */
     private function getCacheItemMatcher(array $expectedData)
     {
-        return function(array $actualData) use ($expectedData) {
+        return Argument::that(function(array $actualData) use ($expectedData) {
             foreach ($expectedData as $key => $value) {
                 if (!isset($actualData[$key])) {
                     return false;
@@ -151,6 +159,6 @@ private function getCacheItemMatcher(array $expectedData)
                 }
             }
             return true;
-        };
+        });
     }
 }

From d89d2336907ccdb8fce64132beba96a8162d5a5c Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Sun, 31 Jul 2016 17:50:56 +0200
Subject: [PATCH 08/19] Added tests

---
 spec/CachePluginSpec.php | 141 ++++++++++++++++++++++++++++++++++++++-
 src/CachePlugin.php      |   2 +-
 2 files changed, 140 insertions(+), 3 deletions(-)

diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 1b43a52..8515ee3 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -3,7 +3,6 @@
 namespace spec\Http\Client\Common\Plugin;
 
 use Prophecy\Argument;
-use Prophecy\Comparator\Factory as ComparatorFactory;
 use Http\Message\StreamFactory;
 use Http\Promise\FulfilledPromise;
 use PhpSpec\ObjectBehavior;
@@ -133,9 +132,147 @@ function it_calculate_age_from_response(CacheItemPoolInterface $pool, CacheItemI
         $this->handleRequest($request, $next, function () {});
     }
 
+    function it_saves_etag(CacheItemPoolInterface $pool, CacheItemInterface $item, RequestInterface $request, ResponseInterface $response, StreamInterface $stream)
+    {
+        $httpBody = 'body';
+        $stream->__toString()->willReturn($httpBody);
+        $stream->isSeekable()->willReturn(true);
+        $stream->rewind()->shouldBeCalled();
+
+        $request->getMethod()->willReturn('GET');
+        $request->getUri()->willReturn('/');
+        $response->getStatusCode()->willReturn(200);
+        $response->getBody()->willReturn($stream);
+        $response->getHeader('Cache-Control')->willReturn(array());
+        $response->getHeader('Expires')->willReturn(array());
+        $response->getHeader('ETag')->willReturn(array('foo_etag'));
+
+        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $item->isHit()->willReturn(false);
+        $item->expiresAfter(1060)->willReturn($item);
+
+        $item->set($this->getCacheItemMatcher([
+            'response' => $response->getWrappedObject(),
+            'body' => $httpBody,
+            'expiresAt' => 0,
+            'createdAt' => 0,
+            'etag' => ['foo_etag']
+        ]))->willReturn($item)->shouldBeCalled();
+        $pool->save(Argument::any())->shouldBeCalled();
+
+        $next = function (RequestInterface $request) use ($response) {
+            return new FulfilledPromise($response->getWrappedObject());
+        };
+
+        $this->handleRequest($request, $next, function () {});
+    }
+
+    function it_adds_etag_and_modfied_since_to_request(CacheItemPoolInterface $pool, CacheItemInterface $item, RequestInterface $request, ResponseInterface $response, StreamInterface $stream)
+    {
+        $httpBody = 'body';
+
+        $request->getMethod()->willReturn('GET');
+        $request->getUri()->willReturn('/');
+
+        $request->withHeader('If-Modified-Since', 'Thursday, 01-Jan-70 01:18:31 GMT')->shouldBeCalled()->willReturn($request);
+        $request->withHeader('If-None-Match', 'foo_etag')->shouldBeCalled()->willReturn($request);
+
+        $response->getStatusCode()->willReturn(304);
+
+        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $item->isHit()->willReturn(true, false);
+        $item->get()->willReturn([
+            'response' => $response,
+            'body' => $httpBody,
+            'expiresAt' => 0,
+            'createdAt' => 4711,
+            'etag' => ['foo_etag']
+        ])->shouldBeCalled();
+
+        $next = function (RequestInterface $request) use ($response) {
+            return new FulfilledPromise($response->getWrappedObject());
+        };
+
+        $this->handleRequest($request, $next, function () {});
+    }
+
+    function it_servces_a_cached_response(CacheItemPoolInterface $pool, CacheItemInterface $item, RequestInterface $request, ResponseInterface $response, StreamInterface $stream, StreamFactory $streamFactory)
+    {
+        $httpBody = 'body';
+
+        $request->getMethod()->willReturn('GET');
+        $request->getUri()->willReturn('/');
+
+        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $item->isHit()->willReturn(true);
+        $item->get()->willReturn([
+            'response' => $response,
+            'body' => $httpBody,
+            'expiresAt' => time()+1000000, //It is in the future
+            'createdAt' => 4711,
+            'etag' => []
+        ])->shouldBeCalled();
+
+        // Make sure we add back the body
+        $response->withBody($stream)->willReturn($response)->shouldBeCalled();
+        $streamFactory->createStream($httpBody)->shouldBeCalled()->willReturn($stream);
+
+        $next = function (RequestInterface $request) use ($response) {
+            return new FulfilledPromise($response->getWrappedObject());
+        };
+
+        $this->handleRequest($request, $next, function () {});
+    }
+
+    function it_serves_and_resaved_expired_response(CacheItemPoolInterface $pool, CacheItemInterface $item, RequestInterface $request, ResponseInterface $response, StreamInterface $stream, StreamFactory $streamFactory)
+    {
+        $httpBody = 'body';
+
+        $request->getMethod()->willReturn('GET');
+        $request->getUri()->willReturn('/');
+
+        $request->withHeader(Argument::any(), Argument::any())->willReturn($request);
+        $request->withHeader(Argument::any(), Argument::any())->willReturn($request);
+
+        $response->getStatusCode()->willReturn(304);
+        $response->getHeader('Cache-Control')->willReturn(array());
+        $response->getHeader('Expires')->willReturn(array())->shouldBeCalled();
+
+        // Make sure we add back the body
+        $response->withBody($stream)->willReturn($response)->shouldBeCalled();
+
+        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $item->isHit()->willReturn(true, true);
+        $item->expiresAfter(1060)->willReturn($item)->shouldBeCalled();
+        $item->get()->willReturn([
+            'response' => $response,
+            'body' => $httpBody,
+            'expiresAt' => 0,
+            'createdAt' => 4711,
+            'etag' => ['foo_etag']
+        ])->shouldBeCalled();
+
+        $item->set($this->getCacheItemMatcher([
+            'response' => $response->getWrappedObject(),
+            'body' => $httpBody,
+            'expiresAt' => 0,
+            'createdAt' => 0,
+            'etag' => ['foo_etag']
+        ]))->willReturn($item)->shouldBeCalled();
+        $pool->save(Argument::any())->shouldBeCalled();
+
+        $streamFactory->createStream($httpBody)->shouldBeCalled()->willReturn($stream);
+
+        $next = function (RequestInterface $request) use ($response) {
+            return new FulfilledPromise($response->getWrappedObject());
+        };
+
+        $this->handleRequest($request, $next, function () {});
+    }
+
 
     /**
-     * Private function to match requests
+     * Private function to match cache item data.
      *
      * @param array $expectedData
      *
diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 6de0f1d..76bd9d6 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -70,7 +70,7 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
 
         if ($cacheItem->isHit()) {
             $data = $cacheItem->get();
-            if (isset($data['expiresAt']) && time() > $data['expiresAt']) {
+            if (isset($data['expiresAt']) && time() < $data['expiresAt']) {
                 // This item is still valid according to previous cache headers
                 return new FulfilledPromise($this->createResponseFromCacheItem($cacheItem));
             }

From 23d0cd4ba11015b4e3ef628157f1511b703e29ad Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Mon, 1 Aug 2016 12:47:23 +0200
Subject: [PATCH 09/19] Updated comment

---
 src/CachePlugin.php | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 76bd9d6..50685e9 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -90,7 +90,10 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
         return $next($request)->then(function (ResponseInterface $response) use ($cacheItem) {
             if (304 === $response->getStatusCode()) {
                 if (!$cacheItem->isHit()) {
-                    // We do not have the item in cache. We can return the cached response.
+                    /* 
+                     * 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;
                 }
 

From bf2e511347adb2aedcd623bb7a1549cad7b150a0 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Mon, 1 Aug 2016 06:47:28 -0400
Subject: [PATCH 10/19] Applied fixes from StyleCI

[ci skip] [skip ci]
---
 src/CachePlugin.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 50685e9..eba2bbd 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -90,8 +90,8 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
         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 
+                    /*
+                     * 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;

From eb2cd5816f6b44d95a8a1992fc05438a768f66d5 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 11:26:45 +0200
Subject: [PATCH 11/19] Made the code easier to read

---
 src/CachePlugin.php | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index eba2bbd..1c04712 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -76,10 +76,8 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
             }
 
             // Add headers to ask the server if this cache is still valid
-            if ($mod = $this->getModifiedAt($cacheItem)) {
-                $mod = new \DateTime('@'.$mod);
-                $mod->setTimezone(new \DateTimeZone('GMT'));
-                $request = $request->withHeader('If-Modified-Since', sprintf('%s GMT', $mod->format('l, d-M-y H:i:s')));
+            if ($modifiedSinceValue = $this->getModifiedSinceHeaderValue($cacheItem)) {
+                $request = $request->withHeader('If-Modified-Since', $modifiedSinceValue);
             }
 
             if ($etag = $this->getETag($cacheItem)) {
@@ -117,13 +115,14 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                 }
 
                 $maxAge = $this->getMaxAge($response);
+                $currentTime = time();
                 $cacheItem
                     ->expiresAfter($this->config['cache_lifetime'] + $maxAge)
                     ->set([
                     'response' => $response,
                     'body' => $body,
-                    'expiresAt' => time() + $maxAge,
-                    'createdAt' => time(),
+                    'expiresAt' => $currentTime + $maxAge,
+                    'createdAt' => $currentTime,
                     'etag' => $response->getHeader('ETag'),
                 ]);
                 $this->pool->save($cacheItem);
@@ -232,7 +231,7 @@ private function getMaxAge(ResponseInterface $response)
     private function configureOptions(OptionsResolver $resolver)
     {
         $resolver->setDefaults([
-            'cache_lifetime' => 2592000, // 30 days
+            'cache_lifetime' => 86400 * 30, // 30 days
             'default_ttl' => null,
             'respect_cache_headers' => true,
             'hash_algo' => 'sha1',
@@ -261,20 +260,23 @@ private function createResponseFromCacheItem(CacheItemInterface $cacheItem)
     }
 
     /**
-     * Get the timestamp when the cached response was stored.
+     * Get the value of the "If-Modified-Since" header.
      *
      * @param CacheItemInterface $cacheItem
      *
-     * @return int|null
+     * @return string|null
      */
-    private function getModifiedAt(CacheItemInterface $cacheItem)
+    private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
     {
         $data = $cacheItem->get();
         if (!isset($data['createdAt'])) {
             return;
         }
 
-        return $data['createdAt'];
+        $modified = new \DateTime('@'.$data['createdAt']);
+        $modified->setTimezone(new \DateTimeZone('GMT'));
+
+        return sprintf('%s GMT', $modified->format('l, d-M-y H:i:s'));
     }
 
     /**

From 0e6792af1433931f1135ac519e1e880589728d1e Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 11:39:35 +0200
Subject: [PATCH 12/19] Updated hash

---
 spec/CachePluginSpec.php | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 8515ee3..07472d2 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -147,7 +147,7 @@ function it_saves_etag(CacheItemPoolInterface $pool, CacheItemInterface $item, R
         $response->getHeader('Expires')->willReturn(array());
         $response->getHeader('ETag')->willReturn(array('foo_etag'));
 
-        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(false);
         $item->expiresAfter(1060)->willReturn($item);
 
@@ -179,7 +179,7 @@ function it_adds_etag_and_modfied_since_to_request(CacheItemPoolInterface $pool,
 
         $response->getStatusCode()->willReturn(304);
 
-        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(true, false);
         $item->get()->willReturn([
             'response' => $response,
@@ -203,7 +203,7 @@ function it_servces_a_cached_response(CacheItemPoolInterface $pool, CacheItemInt
         $request->getMethod()->willReturn('GET');
         $request->getUri()->willReturn('/');
 
-        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(true);
         $item->get()->willReturn([
             'response' => $response,
@@ -241,7 +241,7 @@ function it_serves_and_resaved_expired_response(CacheItemPoolInterface $pool, Ca
         // Make sure we add back the body
         $response->withBody($stream)->willReturn($response)->shouldBeCalled();
 
-        $pool->getItem('e3b717d5883a45ef9493d009741f7c64')->shouldBeCalled()->willReturn($item);
+        $pool->getItem('d20f64acc6e70b6079845f2fe357732929550ae1')->shouldBeCalled()->willReturn($item);
         $item->isHit()->willReturn(true, true);
         $item->expiresAfter(1060)->willReturn($item)->shouldBeCalled();
         $item->get()->willReturn([

From 8c5047f8416d0102f3d0a140d4c13a5f53b37dab Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 12:54:31 +0200
Subject: [PATCH 13/19] Minor

---
 spec/CachePluginSpec.php |  5 ++++-
 src/CachePlugin.php      | 16 ++++++++--------
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 07472d2..355c989 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -16,7 +16,10 @@ class CachePluginSpec extends ObjectBehavior
 {
     function let(CacheItemPoolInterface $pool, StreamFactory $streamFactory)
     {
-        $this->beConstructedWith($pool, $streamFactory, ['default_ttl'=>60, 'cache_lifetime'=>1000]);
+        $this->beConstructedWith($pool, $streamFactory, [
+            'default_ttl' => 60,
+            'cache_lifetime'=>1000
+        ]);
     }
 
     function it_is_initializable(CacheItemPoolInterface $pool)
diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 1c04712..796e836 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -293,16 +293,16 @@ private function getETag(CacheItemInterface $cacheItem)
             return;
         }
 
-        if (is_array($data['etag'])) {
-            foreach ($data['etag'] as $etag) {
-                if (!empty($etag)) {
-                    return $etag;
-                }
-            }
+        if (!is_array($data['etag'])) {
+            return $data['etag'];
+        }
 
-            return;
+        foreach ($data['etag'] as $etag) {
+            if (!empty($etag)) {
+                return $etag;
+            }
         }
 
-        return $data['etag'];
+        return;
     }
 }

From 68edac29b850e11ddb5c50ae583787e2cf199bdd Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 13:05:14 +0200
Subject: [PATCH 14/19] cs

---
 spec/CachePluginSpec.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/spec/CachePluginSpec.php b/spec/CachePluginSpec.php
index 355c989..97afd55 100644
--- a/spec/CachePluginSpec.php
+++ b/spec/CachePluginSpec.php
@@ -18,7 +18,7 @@ function let(CacheItemPoolInterface $pool, StreamFactory $streamFactory)
     {
         $this->beConstructedWith($pool, $streamFactory, [
             'default_ttl' => 60,
-            'cache_lifetime'=>1000
+            'cache_lifetime' => 1000
         ]);
     }
 

From 4ffc484f2399ad3c895ed674ca9b2f4e6fb7b47e Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 13:09:01 +0200
Subject: [PATCH 15/19] Removed return statement

---
 src/CachePlugin.php | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 796e836..51b27b7 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -302,7 +302,5 @@ private function getETag(CacheItemInterface $cacheItem)
                 return $etag;
             }
         }
-
-        return;
     }
 }

From 91a031a11c8327c5133ce85fbe497c2ca6a8ace0 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 13:18:04 +0200
Subject: [PATCH 16/19] cs

---
 src/CachePlugin.php | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 51b27b7..c9bf429 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -119,12 +119,12 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
                 $cacheItem
                     ->expiresAfter($this->config['cache_lifetime'] + $maxAge)
                     ->set([
-                    'response' => $response,
-                    'body' => $body,
-                    'expiresAt' => $currentTime + $maxAge,
-                    'createdAt' => $currentTime,
-                    'etag' => $response->getHeader('ETag'),
-                ]);
+                        'response' => $response,
+                        'body' => $body,
+                        'expiresAt' => $currentTime + $maxAge,
+                        'createdAt' => $currentTime,
+                        'etag' => $response->getHeader('ETag'),
+                    ]);
                 $this->pool->save($cacheItem);
             }
 

From 75db148ffa4631cadeb327e6b000471061c89384 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 15:45:00 +0200
Subject: [PATCH 17/19] Added comment

---
 src/CachePlugin.php | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index c9bf429..7bc7f4d 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -39,8 +39,12 @@ final class CachePlugin implements Plugin
      * @param array                  $config        {
      *
      *     @var bool $respect_cache_headers Whether to look at the cache directives or ignore them
-     *     @var int $default_ttl If we do not respect cache headers or can't calculate a good ttl, use this value
+     *     @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 that 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 = [])

From dfa5f178f7343bf064e583dd40d7a069d5744698 Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 15:46:03 +0200
Subject: [PATCH 18/19] Removed period

---
 src/CachePlugin.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 7bc7f4d..5f50b57 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -41,7 +41,7 @@ final class CachePlugin implements Plugin
      *     @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 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 that the server originally says it is valid for.
      *              We store a cache item for $cache_lifetime + max age of the response.

From cc8ac7578a5a895b948b9de12e42460270d10abc Mon Sep 17 00:00:00 2001
From: Tobias Nyholm <tobias.nyholm@gmail.com>
Date: Tue, 2 Aug 2016 17:58:25 +0200
Subject: [PATCH 19/19] Added docs about isset

---
 src/CachePlugin.php | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/CachePlugin.php b/src/CachePlugin.php
index 5f50b57..c4fb6af 100644
--- a/src/CachePlugin.php
+++ b/src/CachePlugin.php
@@ -74,6 +74,7 @@ public function handleRequest(RequestInterface $request, callable $next, callabl
 
         if ($cacheItem->isHit()) {
             $data = $cacheItem->get();
+            // The isset() is to be removed in 2.0.
             if (isset($data['expiresAt']) && time() < $data['expiresAt']) {
                 // This item is still valid according to previous cache headers
                 return new FulfilledPromise($this->createResponseFromCacheItem($cacheItem));
@@ -273,6 +274,7 @@ private function createResponseFromCacheItem(CacheItemInterface $cacheItem)
     private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
     {
         $data = $cacheItem->get();
+        // The isset() is to be removed in 2.0.
         if (!isset($data['createdAt'])) {
             return;
         }
@@ -293,6 +295,7 @@ private function getModifiedSinceHeaderValue(CacheItemInterface $cacheItem)
     private function getETag(CacheItemInterface $cacheItem)
     {
         $data = $cacheItem->get();
+        // The isset() is to be removed in 2.0.
         if (!isset($data['etag'])) {
             return;
         }