<?php
/*
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace Google\Http;

use Google\Auth\HttpHandler\HttpHandlerFactory;
use Google\Client;
use Google\Task\Runner;
use Google\Service\Exception as GoogleServiceException;
use GuzzleHttp\ClientInterface;
use GuzzleHttp\Exception\RequestException;
use GuzzleHttp\Psr7\Response;
use Psr\Http\Message\RequestInterface;
use Psr\Http\Message\ResponseInterface;

/**
 * This class implements the RESTful transport of apiServiceRequest()'s
 */
class REST
{
  /**
   * Executes a Psr\Http\Message\RequestInterface and (if applicable) automatically retries
   * when errors occur.
   *
   * @param Client $client
   * @param RequestInterface $req
   * @param string $expectedClass
   * @param array $config
   * @param array $retryMap
   * @return mixed decoded result
   * @throws \Google\Service\Exception on server side error (ie: not authenticated,
   *  invalid or malformed post body, invalid url)
   */
  public static function execute(
      ClientInterface $client,
      RequestInterface $request,
      $expectedClass = null,
      $config = array(),
      $retryMap = null
  ) {
    $runner = new Runner(
        $config,
        sprintf('%s %s', $request->getMethod(), (string) $request->getUri()),
        array(get_class(), 'doExecute'),
        array($client, $request, $expectedClass)
    );

    if (null !== $retryMap) {
      $runner->setRetryMap($retryMap);
    }

    return $runner->run();
  }

  /**
   * Executes a Psr\Http\Message\RequestInterface
   *
   * @param Client $client
   * @param RequestInterface $request
   * @param string $expectedClass
   * @return array decoded result
   * @throws \Google\Service\Exception on server side error (ie: not authenticated,
   *  invalid or malformed post body, invalid url)
   */
  public static function doExecute(ClientInterface $client, RequestInterface $request, $expectedClass = null)
  {
    try {
      $httpHandler = HttpHandlerFactory::build($client);
      $response = $httpHandler($request);
    } catch (RequestException $e) {
      // if Guzzle throws an exception, catch it and handle the response
      if (!$e->hasResponse()) {
        throw $e;
      }

      $response = $e->getResponse();
      // specific checking for Guzzle 5: convert to PSR7 response
      if ($response instanceof \GuzzleHttp\Message\ResponseInterface) {
        $response = new Response(
            $response->getStatusCode(),
            $response->getHeaders() ?: [],
            $response->getBody(),
            $response->getProtocolVersion(),
            $response->getReasonPhrase()
        );
      }
    }

    return self::decodeHttpResponse($response, $request, $expectedClass);
  }

  /**
   * Decode an HTTP Response.
   * @static
   * @throws \Google\Service\Exception
   * @param RequestInterface $response The http response to be decoded.
   * @param ResponseInterface $response
   * @param string $expectedClass
   * @return mixed|null
   */
  public static function decodeHttpResponse(
      ResponseInterface $response,
      RequestInterface $request = null,
      $expectedClass = null
  ) {
    $code = $response->getStatusCode();

    // retry strategy
    if (intVal($code) >= 400) {
      // if we errored out, it should be safe to grab the response body
      $body = (string) $response->getBody();

      // Check if we received errors, and add those to the Exception for convenience
      throw new GoogleServiceException($body, $code, null, self::getResponseErrors($body));
    }

    // Ensure we only pull the entire body into memory if the request is not
    // of media type
    $body = self::decodeBody($response, $request);

    if ($expectedClass = self::determineExpectedClass($expectedClass, $request)) {
      $json = json_decode($body, true);

      return new $expectedClass($json);
    }

    return $response;
  }

  private static function decodeBody(ResponseInterface $response, RequestInterface $request = null)
  {
    if (self::isAltMedia($request)) {
      // don't decode the body, it's probably a really long string
      return '';
    }

    return (string) $response->getBody();
  }

  private static function determineExpectedClass($expectedClass, RequestInterface $request = null)
  {
    // "false" is used to explicitly prevent an expected class from being returned
    if (false === $expectedClass) {
      return null;
    }

    // if we don't have a request, we just use what's passed in
    if (null === $request) {
      return $expectedClass;
    }

    // return what we have in the request header if one was not supplied
    return $expectedClass ?: $request->getHeaderLine('X-Php-Expected-Class');
  }

  private static function getResponseErrors($body)
  {
    $json = json_decode($body, true);

    if (isset($json['error']['errors'])) {
      return $json['error']['errors'];
    }

    return null;
  }

  private static function isAltMedia(RequestInterface $request = null)
  {
    if ($request && $qs = $request->getUri()->getQuery()) {
      parse_str($qs, $query);
      if (isset($query['alt']) && $query['alt'] == 'media') {
        return true;
      }
    }

    return false;
  }
}