<?php

/**
 * AJAX Cross Domain (PHP) Proxy 0.8
 * Copyright (C) 2016 Iacovos Constantinou (https://github.com/softius)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * Enables or disables filtering for cross domain requests.
 * Recommended value: true
 */
define('CSAJAX_FILTERS', false);

/**
 * If set to true, $valid_requests should hold only domains i.e. a.example.com, b.example.com, usethisdomain.com
 * If set to false, $valid_requests should hold the whole URL ( without the parameters ) i.e. http://example.com/this/is/long/url/
 * Recommended value: false (for security reasons - do not forget that anyone can access your proxy)
 */
define('CSAJAX_FILTER_DOMAIN', true);

/**
 * Enables or disables Expect: 100-continue header. Some webservers don't 
 * handle this header correctly.
 * Recommended value: false
 */
define('CSAJAX_SUPPRESS_EXPECT', false);

/**
 * Set debugging to true to receive additional messages - really helpful on development
 */
define('CSAJAX_DEBUG', true);

/**
 * A set of valid cross domain requests
 */
$valid_requests = array(
  'http://185.65.245.44/',
);
//header('Access-Control-Allow-Origin: *');

/**
 * Set extra multiple options for cURL
 * Could be used to define CURLOPT_SSL_VERIFYPEER & CURLOPT_SSL_VERIFYHOST for HTTPS
 * Also to overwrite any other options without changing the code
 * See http://php.net/manual/en/function.curl-setopt-array.php
 */
$curl_options = array(
  // CURLOPT_SSL_VERIFYPEER => false,
  // CURLOPT_SSL_VERIFYHOST => 2,
);

/* * * STOP EDITING HERE UNLESS YOU KNOW WHAT YOU ARE DOING * * */

// identify request headers
$request_headers = array();
foreach ($_SERVER as $key => $value) {
  if (strpos($key, 'HTTP_') === 0  ||  strpos($key, 'CONTENT_') === 0) {
    $headername = str_replace('_', ' ', str_replace('HTTP_', '', $key));
    $headername = str_replace(' ', '-', ucwords(strtolower($headername)));
    if (!in_array($headername, array('Host', 'X-Proxy-Url'))) {
      $request_headers[] = "$headername: $value";
    }
  }
}

// identify request method, url and params
$request_method = $_SERVER['REQUEST_METHOD'];
if ('GET' == $request_method) {
  $request_params = $_GET;
} elseif ('POST' == $request_method) {
  $request_params = $_POST;
  if (empty($request_params)) {
    $data = file_get_contents('php://input');
    if (!empty($data)) {
      $request_params = $data;
    }
  }
} elseif ('PUT' == $request_method || 'DELETE' == $request_method) {
  $request_params = file_get_contents('php://input');
} else {
  $request_params = null;
}

// Get URL from `csurl` in GET or POST data, before falling back to X-Proxy-URL header.
if (isset($_REQUEST['csurl'])) {
  $request_url = urldecode($_REQUEST['csurl']);
} elseif (isset($_SERVER['HTTP_X_PROXY_URL'])) {
  $request_url = urldecode($_SERVER['HTTP_X_PROXY_URL']);
} else {
  header($_SERVER['SERVER_PROTOCOL'] . ' 404 Not Found');
  header('Status: 404 Not Found');
  $_SERVER['REDIRECT_STATUS'] = 404;
  exit;
}

$p_request_url = parse_url($request_url);

// csurl may exist in GET request methods
if (is_array($request_params) && array_key_exists('csurl', $request_params)) {
  unset($request_params['csurl']);
}

// ignore requests for proxy :)
if (preg_match('!' . $_SERVER['SCRIPT_NAME'] . '!', $request_url) || empty($request_url) || count($p_request_url) == 1) {
  csajax_debug_message('Invalid request - make sure that csurl variable is not empty');
  exit;
}

// check against valid requests
if (CSAJAX_FILTERS) {
  $parsed = $p_request_url;
  if (CSAJAX_FILTER_DOMAIN) {
  } else {
    $check_url = isset($parsed['scheme']) ? $parsed['scheme'] . '://' : '';
    $check_url .= isset($parsed['user']) ? $parsed['user'] . ($parsed['pass'] ? ':' . $parsed['pass'] : '') . '@' : '';
    $check_url .= isset($parsed['host']) ? $parsed['host'] : '';
    $check_url .= isset($parsed['port']) ? ':' . $parsed['port'] : '';
    $check_url .= isset($parsed['path']) ? $parsed['path'] : '';
    if (!in_array($check_url, $valid_requests)) {
      csajax_debug_message('Invalid domain - ' . $request_url . ' does not included in valid requests');
      exit;
    }
  }
}

// append query string for GET requests
if ($request_method == 'GET' && count($request_params) > 0 && (!array_key_exists('query', $p_request_url) || empty($p_request_url['query']))) {
  $request_url .= '?' . http_build_query($request_params);
}

// let the request begin
$ch = curl_init($request_url);

// Suppress Expect header
if (CSAJAX_SUPPRESS_EXPECT) {
  array_push($request_headers, 'Expect:');
}
curl_setopt($ch, CURLOPT_HTTPHEADER, $request_headers);   // (re-)send headers
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);     // return response
curl_setopt($ch, CURLOPT_HEADER, true);       // enabled response headers
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);       // enabled redirects
curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36');       // enabled response headers
// add data for POST, PUT or DELETE requests
if ('POST' == $request_method) {
  $post_data = is_array($request_params) ? http_build_query($request_params) : $request_params;
  curl_setopt($ch, CURLOPT_POST, true);
  curl_setopt($ch, CURLOPT_POSTFIELDS,  $post_data);
} elseif ('PUT' == $request_method || 'DELETE' == $request_method) {
  curl_setopt($ch, CURLOPT_CUSTOMREQUEST, $request_method);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $request_params);
}

// Set multiple options for curl according to configuration
if (is_array($curl_options) && 0 <= count($curl_options)) {
  curl_setopt_array($ch, $curl_options);
}

// retrieve response (headers and content)
$response = curl_exec($ch);

// Get header size and split response
$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
$response_headers = substr($response, 0, $header_size);
$response_content = substr($response, $header_size);

curl_close($ch);

// split response to header and content
//list($response_headers, $response_content) = preg_split('/(\r\n){2}/', $response, 2);

// (re-)send the headers
$response_headers = preg_split('/(\r\n){1}/', $response_headers);

$access_control_header_key = null;
foreach ($response_headers as $key => $response_header) {
  if (stripos($response_header, 'Access-Control-Allow-Origin:') !== false) {
    $access_control_header_key = $key;
    break;
  }
}

// If Access-Control-Allow-Origin header exists, check and modify if necessary
if ($access_control_header_key !== null) {
  $header_parts = explode(':', $response_headers[$access_control_header_key], 2);
  $header_value = trim($header_parts[1]);
  if ($header_value !== '*') {
    $response_headers[$access_control_header_key] = 'Access-Control-Allow-Origin: *';
  }
} else {
  // If header doesn't exist, add it with value *
  $response_headers[] = 'Access-Control-Allow-Origin: *';
}

// foreach ($response_headers as $key => $response_header) {
//   // Rewrite the `Location` header, so clients will also use the proxy for redirects.
//   if (preg_match('/^Location:/', $response_header)) {
//     list($header, $value) = preg_split('/: /', $response_header, 2);
//     $response_header = 'Location: ' . $_SERVER['REQUEST_URI'] . '?csurl=' . $value;
//   }
//   if (!preg_match('/^(Transfer-Encoding):/', $response_header)) {
//     header($response_header, false);
//   }
// }

//$response_content_utf8 = mb_convert_encoding($response_content, 'UTF-8', 'HTML-ENTITIES');

// Підготовка JSON-відповіді
header('Content-Type: application/json');
$responseJSON = [
  'data' => $response_content,
  //'headers' => $response_headers,
];

// Вивід JSON
echo json_encode($responseJSON, JSON_UNESCAPED_UNICODE);

function csajax_debug_message($message)
{
  if (true == CSAJAX_DEBUG) {
    print $message . PHP_EOL;
  }
}