<?php
/**
 * Copyright (c) 2014 Lukas Reschke <lukas@owncloud.com>
 * This file is licensed under the Affero General Public License version 3 or
 * later.
 * See the COPYING-README file.
 */

namespace OC;

class HTTPHelper {
	const USER_AGENT = 'ownCloud Server Crawler';

	/** @var \OC\AllConfig */
	private $config;

	/**
	 * @param \OC\AllConfig $config
	 */
	public function __construct(AllConfig $config) {
		$this->config = $config;
	}

	/**
	 * Returns the default context array
	 * @return array
	 */
	public function getDefaultContextArray() {
		return array(
			'http' => array(
				'header' => 'User-Agent: ' . self::USER_AGENT . "\r\n",
				'timeout' => 10,
				'follow_location' => false, // Do not follow the location since we can't limit the protocol
			),
			'ssl' => array(
				'disable_compression' => true
			)
		);
	}

	/**
	 * Get URL content
	 * @param string $url Url to get content
	 * @throws \Exception If the URL does not start with http:// or https://
	 * @return string of the response or false on error
	 * This function get the content of a page via curl, if curl is enabled.
	 * If not, file_get_contents is used.
	 */
	public function getUrlContent($url) {
		if (!$this->isHTTPURL($url)) {
			throw new \Exception('$url must start with https:// or http://', 1);
		}

		$proxy = $this->config->getSystemValue('proxy', null);
		$proxyUserPwd = $this->config->getSystemValue('proxyuserpwd', null);
		if (function_exists('curl_init')) {
			$curl = curl_init();
			$max_redirects = 10;

			curl_setopt($curl, CURLOPT_HEADER, 0);
			curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
			curl_setopt($curl, CURLOPT_CONNECTTIMEOUT, 10);
			curl_setopt($curl, CURLOPT_URL, $url);
			curl_setopt($curl, CURLOPT_PROTOCOLS,  CURLPROTO_HTTP | CURLPROTO_HTTPS);
			curl_setopt($curl, CURLOPT_REDIR_PROTOCOLS,  CURLPROTO_HTTP | CURLPROTO_HTTPS);

			curl_setopt($curl, CURLOPT_USERAGENT, self::USER_AGENT);
			if ($proxy !== null) {
				curl_setopt($curl, CURLOPT_PROXY, $proxy);
			}
			if ($proxyUserPwd !== null) {
				curl_setopt($curl, CURLOPT_PROXYUSERPWD, $proxyUserPwd);
			}

			if (ini_get('open_basedir') === '' && (ini_get('safe_mode') === false) || strtolower(ini_get('safe_mode')) === 'off') {
				curl_setopt($curl, CURLOPT_FOLLOWLOCATION, true);
				curl_setopt($curl, CURLOPT_MAXREDIRS, $max_redirects);
				$data = curl_exec($curl);
			} else {
				curl_setopt($curl, CURLOPT_FOLLOWLOCATION, false);
				$mr = $max_redirects;
				if ($mr > 0) {
					$newURL = curl_getinfo($curl, CURLINFO_EFFECTIVE_URL);
					$rcurl = curl_copy_handle($curl);
					curl_setopt($rcurl, CURLOPT_HEADER, true);
					curl_setopt($rcurl, CURLOPT_NOBODY, true);
					curl_setopt($rcurl, CURLOPT_FORBID_REUSE, false);
					curl_setopt($rcurl, CURLOPT_RETURNTRANSFER, true);
					curl_setopt($rcurl, CURLOPT_USERAGENT, self::USER_AGENT);
					do {
						curl_setopt($rcurl, CURLOPT_URL, $newURL);
						$header = curl_exec($rcurl);
						if (curl_errno($rcurl)) {
							$code = 0;
						} else {
							$code = curl_getinfo($rcurl, CURLINFO_HTTP_CODE);
							if ($code == 301 || $code == 302) {
								preg_match('/Location:(.*?)\n/', $header, $matches);
								$newURL = trim(array_pop($matches));
							} else {
								$code = 0;
							}
						}
					} while ($code && --$mr);
					curl_close($rcurl);
					if ($mr > 0) {
						curl_setopt($curl, CURLOPT_URL, $newURL);
					}
				}

				if ($mr == 0 && $max_redirects > 0) {
					$data = false;
				} else {
					$data = curl_exec($curl);
				}
			}
			curl_close($curl);
		} else {
			$url = $this->getFinalLocationOfURL($url);
			$contextArray = $this->getDefaultContextArray();

			if ($proxy !== null) {
				$contextArray['http']['proxy'] = $proxy;
			}

			$ctx = stream_context_create(
				$contextArray
			);
			$data = @file_get_contents($url, 0, $ctx);

		}
		return $data;
	}

	/**
	 * Returns the response headers of a HTTP URL without following redirects
	 * @param string $location Needs to be a HTTPS or HTTP URL
	 * @return array
	 */
	public function getHeaders($location) {
		stream_context_set_default($this->getDefaultContextArray());
		return get_headers($location, 1);
	}

	/**
	 * Checks whether the supplied URL begins with HTTPS:// or HTTP:// (case insensitive)
	 * @param string $url
	 * @return bool
	 */
	public function isHTTPURL($url) {
		return stripos($url, 'https://') === 0 || stripos($url, 'http://') === 0;
	}

	/**
	 * Returns the last HTTP or HTTPS site the request has been redirected too using the Location HTTP header
	 * This is a very ugly workaround about the missing functionality to restrict fopen() to protocols
	 * @param string $location Needs to be a HTTPS or HTTP URL
	 * @throws \Exception In case the initial URL is not a HTTP or HTTPS one
	 * @return string
	 */
	public function getFinalLocationOfURL($location) {
		if(!$this->isHTTPURL($location)) {
			throw new \Exception('URL must begin with HTTPS or HTTP.');
		}
		$headerArray = $this->getHeaders($location, 1);

		if($headerArray !== false && isset($headerArray['Location'])) {
			while($this->isHTTPURL($headerArray['Location'])) {
				$location = $headerArray['Location'];
				$headerArray = $this->getHeaders($location);
			}
		}

		return $location;
	}

}