Added VaryGenerator

spec/Cache/Generator/HeaderCacheKeyGeneratorSpec.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace spec\Http\Client\Common\Plugin\Cache\Generator;
+
+use PhpSpec\ObjectBehavior;
+use Psr\Http\Message\RequestInterface;
+
+class HeaderCacheKeyGeneratorSpec extends ObjectBehavior
+{
+    public function let()
+    {
+        $this->beConstructedWith(['Authorization', 'Content-Type']);
+    }
+
+    public function it_is_initializable()
+    {
+        $this->shouldHaveType('Http\Client\Common\Plugin\Cache\Generator\HeaderCacheKeyGenerator');
+    }
+
+    public function it_is_a_key_generator()
+    {
+        $this->shouldImplement('Http\Client\Common\Plugin\Cache\Generator\CacheKeyGenerator');
+    }
+
+    public function it_generates_cache_from_request(RequestInterface $request)
+    {
+        $request->getMethod()->shouldBeCalled()->willReturn('GET');
+        $request->getUri()->shouldBeCalled()->willReturn('http://example.com/foo');
+        $request->getHeaderLine('Authorization')->shouldBeCalled()->willReturn('bar');
+        $request->getHeaderLine('Content-Type')->shouldBeCalled()->willReturn('application/baz');
+
+        $this->generate($request)->shouldReturn('GET http://example.com/foo Authorization:"bar" Content-Type:"application/baz"');
+    }
+}

src/Cache/Generator/HeaderCacheKeyGenerator.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace Http\Client\Common\Plugin\Cache\Generator;
+
+use Psr\Http\Message\RequestInterface;
+
+/**
+ * Generate a cache key by specify what headers you want to vary on.
+ *
+ * @author Tobias Nyholm <[email protected]>
+ */
+class HeaderCacheKeyGenerator implements CacheKeyGenerator
+{
+    /**
+     * The header names we should take into account when creating the cache key.
+     *
+     * @var array
+     */
+    private $headerNames;
+
+    /**
+     * @param $headerNames
+     */
+    public function __construct(array $headerNames)
+    {
+        $this->headerNames = $headerNames;
+    }
+
+    public function generate(RequestInterface $request)
+    {
+        $concatenatedHeaders = [];
+        foreach ($this->headerNames as $headerName) {
+            $concatenatedHeaders[] = sprintf(' %s:"%s"', $headerName, $request->getHeaderLine($headerName));
+        }
+
+        return $request->getMethod().' '.$request->getUri().implode('', $concatenatedHeaders);
+    }
+}