MAPG-69 add Google OAuth handler

src/OAuth/GoogleOAuth.php

@@ -0,0 +1,41 @@
+<?php namespace MapGuesser\OAuth;
+
+use MapGuesser\Http\Request;
+
+class GoogleOAuth
+{
+    private static $dialogUrlBase = 'https://accounts.google.com/o/oauth2/v2/auth';
+
+    private static $tokenUrlBase = 'https://oauth2.googleapis.com/token';
+
+    public function getDialogUrl(string $state, string $redirectUrl): string
+    {
+        $oauthParams = [
+            'response_type' => 'code',
+            'client_id' => $_ENV['GOOGLE_OAUTH_CLIENT_ID'],
+            'scope' => 'openid email',
+            'redirect_uri' => $redirectUrl,
+            'state' => $state,
+            'nonce' => hash('sha256', random_bytes(10) . microtime()),
+        ];
+
+        return self::$dialogUrlBase . '?' . http_build_query($oauthParams);
+    }
+
+    public function getToken(string $code, string $redirectUrl)
+    {
+        $tokenParams = [
+            'code' => $code,
+            'client_id' => $_ENV['GOOGLE_OAUTH_CLIENT_ID'],
+            'client_secret' => $_ENV['GOOGLE_OAUTH_CLIENT_SECRET'],
+            'redirect_uri' => $redirectUrl,
+            'grant_type' => 'authorization_code',
+        ];
+
+        $request = new Request(self::$tokenUrlBase, Request::HTTP_POST);
+        $request->setQuery($tokenParams);
+        $response = $request->send();
+
+        return json_decode($response->getBody(), true);
+    }
+}