Make sure we support PSR-18 (#16)

* Make sure we support PSR-18

* Added file header

* Update HttpClientTrait.php

StyleCI fix

Author: Nyholm

composer.json

@@ -16,8 +16,7 @@
     "require":     {
         "php": "^7.1",
         "phpunit/phpunit": "^7.5",
-        "psr/http-message-implementation": "^1.0",
-        "php-http/mock-client": "^1.1",
+        "php-http/mock-client": "^1.2",
         "nyholm/psr7": "^1.0.0"
     },
     "require-dev": {

src/CachedResponseClient.php

@@ -22,6 +22,8 @@
  */
 class CachedResponseClient implements HttpClient
 {
+    use HttpClientTrait;
+
     /**
      * @var HttpClient
      */
@@ -59,7 +61,7 @@ public function __construct(HttpClient $delegate, $cacheDir, $apiKey = null, $ap
     /**
      * {@inheritdoc}
      */
-    public function sendRequest(RequestInterface $request)
+    protected function doSendRequest(RequestInterface $request)
     {
         $host = (string) $request->getUri()->getHost();
         $cacheKey = (string) $request->getUri();

src/HttpClientTrait.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the Geocoder package.
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @license    MIT License
+ */
+
+namespace Geocoder\IntegrationTest;
+
+use Psr\Http\Client\ClientInterface;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+
+/*
+ * This test is not 100% perfect. You may have installed HTTPlug:1.x and PSR-18.
+ */
+if (\interface_exists(ClientInterface::class)) {
+    /**
+     * @internal code for php-http/httplug:2.x
+     */
+    trait HttpClientTrait
+    {
+        abstract protected function doSendRequest(RequestInterface $request);
+
+        public function sendRequest(RequestInterface $request): ResponseInterface
+        {
+            return $this->doSendRequest($request);
+        }
+    }
+} else {
+    /**
+     * @internal code for php-http/httplug:1.x
+     */
+    trait HttpClientTrait
+    {
+        abstract protected function doSendRequest(RequestInterface $request);
+
+        public function sendRequest(RequestInterface $request)
+        {
+            return $this->doSendRequest($request);
+        }
+    }
+}