new helper class Http\ApiConnection communicating with an OIDC server and API server

src/Http/ApiConnection.php

+<?php
+
+declare(strict_types=1);
+
+namespace Dbp\Relay\CoreBundle\Http;
+
+use Dbp\Relay\CoreBundle\Helpers\Tools;
+use Psr\Cache\CacheItemPoolInterface;
+use Psr\Http\Message\ResponseInterface;
+use Psr\Log\LoggerInterface;
+
+class ApiConnection
+{
+    public const API_URL_CONFIG_PARAMETER = 'api_url';
+
+    public const KEYCLOAK_SERVER_URL_CONFIG_PARAMETER = 'keycloak_server_url';
+    public const KEYCLOAK_REALM_CONFIG_PARAMETER = 'keycloak_realm';
+    public const CLIENT_ID_CONFIG_PARAMETER = 'client_id';
+    public const CLIENT_SECRET_CONFIG_PARAMETER = 'client_secret';
+
+    /** @var Connection */
+    private $connection;
+
+    /** @var array */
+    private $config;
+
+    /** @var object|null */
+    private $clientHandler;
+
+    /** @var CacheItemPoolInterface|null */
+    private $cachePool;
+
+    /** @var int */
+    private $cacheTTL;
+
+    /** @var LoggerInterface|null */
+    private $logger;
+
+    /** @var string */
+    private $accessToken;
+
+    public function __construct()
+    {
+        $this->config = [];
+    }
+
+    public function setCache(?CacheItemPoolInterface $cachePool, int $ttl): void
+    {
+        $this->cachePool = $cachePool;
+        $this->cacheTTL = $ttl;
+        if ($this->connection !== null) {
+            $this->connection->setCache($cachePool, $ttl);
+        }
+    }
+
+    public function setConfig(array $config): void
+    {
+        $this->config = $config;
+    }
+
+    /*
+     * Used to mock up server for unit testing.
+     */
+    public function setClientHandler(?object $handler): void
+    {
+        $this->clientHandler = $handler;
+        if ($this->connection !== null) {
+            $this->connection->setClientHandler($handler);
+        }
+    }
+
+    public function setLogger(LoggerInterface $logger): void
+    {
+        $this->logger = $logger;
+        if ($this->connection !== null) {
+            $this->connection->setLogger($logger);
+        }
+    }
+
+    /**
+     * @throws ConnectionException
+     */
+    public function get(string $uri, array $options): ResponseInterface
+    {
+        $requestOptions = [
+            Connection::REQUEST_OPTION_HEADERS => [
+                'Authorization' => 'Bearer '.$this->getAccessToken(),
+            ],
+        ];
+
+        return $this->getApiConnection()->get($uri, $options, $requestOptions);
+    }
+
+    /**
+     * @throws ConnectionException
+     */
+    private function getAccessToken(): string
+    {
+        if ($this->accessToken === null) {
+            $idServerUrl = $this->config[self::KEYCLOAK_SERVER_URL_CONFIG_PARAMETER];
+            $idServerRealm = $this->config[self::KEYCLOAK_REALM_CONFIG_PARAMETER];
+            $clientId = $this->config[self::CLIENT_ID_CONFIG_PARAMETER];
+            $clientSecret = $this->config[self::CLIENT_SECRET_CONFIG_PARAMETER];
+
+            $tokenUrl = $idServerUrl.'/realms/'.$idServerRealm.'/protocol/openid-connect/token';
+            $response = $this->getIdServerConnection()->postForm($tokenUrl, [
+                'client_id' => $clientId,
+                'client_secret' => $clientSecret,
+                'grant_type' => 'client_credentials',
+            ]);
+
+            $responseData = $response->getBody()->getContents();
+
+            try {
+                $token = Tools::decodeJSON($responseData, true);
+            } catch (\JsonException $exception) {
+                throw new ConnectionException(sprintf('Failed to JSON decode access token: '.$exception->getMessage()), ConnectionException::JSON_EXCEPTION);
+            }
+
+            $this->accessToken = $token['access_token'];
+        }
+
+        return $this->accessToken;
+    }
+
+    private function getApiConnection(): Connection
+    {
+        if ($this->connection === null) {
+            $connection = new Connection($this->config[self::API_URL_CONFIG_PARAMETER]);
+
+            if ($this->cachePool !== null) {
+                $connection->setCache($this->cachePool, $this->cacheTTL);
+            }
+            if ($this->clientHandler !== null) {
+                $connection->setClientHandler($this->clientHandler);
+            }
+            if ($this->logger !== null) {
+                $connection->setLogger($this->logger);
+            }
+
+            $this->connection = $connection;
+        }
+
+        return $this->connection;
+    }
+
+    private function getIdServerConnection(): Connection
+    {
+        $idServerConnection = new Connection();
+
+        if ($this->clientHandler !== null) {
+            $idServerConnection->setClientHandler($this->clientHandler);
+        }
+
+        return $idServerConnection;
+    }
+}

src/Http/ConnectionException.php

@@ -10,6 +10,7 @@ use Psr\Http\Message\ResponseInterface;
 class ConnectionException extends \RuntimeException
 {
     public const REQUEST_EXCEPTION = 1;
+    public const JSON_EXCEPTION = 2;
 
     /** @var RequestInterface|null */
     private $request;