Adds API version verification (#28)

* Adds API version verification

Adds a check to the package middleware to ensure that the request
and response version are defined in the configuration.

* Keep ability to pass no versions in the request

src/RequestMigrationsMiddleware.php

@@ -6,6 +6,7 @@
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Config;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\HttpException;
 
 class RequestMigrationsMiddleware
 {
@@ -17,6 +18,14 @@ class RequestMigrationsMiddleware
      */
     public function handle(Request $request, Closure $next) : Response
     {
+        if ($this->requestVersion($request) && ! in_array($this->requestVersion($request), $this->versions())) {
+            throw new HttpException(400, 'The request version is invalid');
+        }
+
+        if ($this->responseVersion($request) && ! in_array($this->responseVersion($request), $this->versions())) {
+            throw new HttpException(400, 'The response version is invalid');
+        }
+
         $migrator = new Migrator($request, Config::get('request-migrations'));
 
         $migrator->processResponseMigrations(
@@ -27,4 +36,38 @@ public function handle(Request $request, Closure $next) : Response
 
         return $migrator->getResponse();
     }
+
+    /**
+     * Get all the available versions.
+     *
+     * @return array
+     */
+    private function versions() : array
+    {
+        return array_keys(Config::get('request-migrations.versions'));
+    }
+
+    /**
+     * Get the request version from the request.
+     *
+     * @param \Illuminate\Http\Request $request
+     *
+     * @return string
+     */
+    private function requestVersion(Request $request) : string
+    {
+        return $request->header(Config::get('request-migrations.headers.request-version'), '');
+    }
+
+    /**
+     * Get the response version from the request.
+     *
+     * @param \Illuminate\Http\Request $request
+     *
+     * @return string
+     */
+    private function responseVersion(Request $request) : string
+    {
+        return $request->header(Config::get('request-migrations.headers.response-version'), '');
+    }
 }