Add conditional responses to mock client

Following discussions at #3 this adds
a on method taking a RequestMatcher and then either a Response, an Exception or a
callable.

This allows for mock clients to not depend on the order the responses/exceptions
are mocked.

It also allows for responses to depend on some content in the request, avoiding
duplication in some cases.

Author: adamquaile

spec/ClientSpec.php

@@ -2,6 +2,7 @@
 
 namespace spec\Http\Mock;
 
+use Http\Message\RequestMatcher;
 use Http\Message\ResponseFactory;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
@@ -73,4 +74,54 @@ function it_returns_the_last_request(RequestInterface $request)
 
         $this->getLastRequest()->shouldReturn($request);
     }
+
+    function it_returns_response_if_request_matcher_matches(
+        RequestMatcher $matcher,
+        RequestInterface $request,
+        ResponseInterface $response
+    ) {
+        $matcher->matches($request)->willReturn(true);
+        $this->on($matcher, $response);
+        $this->sendRequest($request)->shouldReturn($response);
+    }
+
+    function it_throws_exception_if_request_matcher_matches(
+        RequestMatcher $matcher,
+        RequestInterface $request
+    ) {
+        $matcher->matches($request)->willReturn(true);
+        $this->on($matcher, new \Exception());
+        $this->shouldThrow('Exception')->duringSendRequest($request);
+    }
+
+    function it_skips_conditional_response_if_matcher_returns_false(
+        RequestMatcher $matcher,
+        RequestInterface $request,
+        ResponseInterface $expectedResponse,
+        ResponseInterface $skippedResponse
+    )
+    {
+        $matcher->matches($request)->willReturn(false);
+        $this->on($matcher, $skippedResponse);
+        $this->addResponse($expectedResponse);
+        $this->sendRequest($request)->shouldReturn($expectedResponse);
+    }
+
+    function it_calls_callable_with_request_as_argument_when_matcher_returns_true(
+        RequestMatcher $matcher,
+        RequestInterface $request,
+        ResponseInterface $response
+    )
+    {
+        $matcher->matches($request)->willReturn(true);
+
+        $this->on(
+            $matcher,
+            function(RequestInterface $request) use ($response) {
+                return $response->getWrappedObject();
+            }
+        );
+
+        $this->sendRequest($request)->shouldReturn($response);
+    }
 }

src/Client.php

@@ -7,6 +7,7 @@
 use Http\Client\HttpAsyncClient;
 use Http\Client\HttpClient;
 use Http\Discovery\MessageFactoryDiscovery;
+use Http\Message\RequestMatcher;
 use Http\Message\ResponseFactory;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
@@ -29,6 +30,11 @@ class Client implements HttpClient, HttpAsyncClient
      */
     private $responseFactory;
 
+    /**
+     * @var array
+     */
+    private $conditionalResults = [];
+
     /**
      * @var RequestInterface[]
      */
@@ -69,6 +75,17 @@ public function sendRequest(RequestInterface $request)
     {
         $this->requests[] = $request;
 
+        foreach ($this->conditionalResults as ['matcher' => $matcher, 'callable' => $callable]) {
+
+            /**
+             * @var RequestMatcher $matcher
+             * @var ResponseInterface|Exception $result
+             */
+            if ($matcher->matches($request)) {
+                return $callable($request);
+            }
+        }
+
         if (count($this->exceptions) > 0) {
             throw array_shift($this->exceptions);
         }
@@ -89,6 +106,32 @@ public function sendRequest(RequestInterface $request)
         return $this->responseFactory->createResponse();
     }
 
+    /**
+     * @param RequestMatcher $requestMatcher
+     * @param ResponseInterface|\Exception|callable $result
+     */
+    public function on(RequestMatcher $requestMatcher, $result)
+    {
+        $callable = null;
+        switch (true) {
+            case is_callable($result):
+                $callable = $result;
+                break;
+            case $result instanceof ResponseInterface:
+                $callable = function () use ($result) { return $result; };
+                break;
+            case $result instanceof \Exception:
+                $callable = function () use ($result) { throw $result; };
+                break;
+            default:
+                throw new \InvalidArgumentException("Result must be either a response, an exception, or a callable");
+        }
+        $this->conditionalResults[] = [
+            'matcher'   => $requestMatcher,
+            'callable'  => $callable
+        ];
+    }
+
     /**
      * Adds an exception that will be thrown.
      *