<?php
/**
 * MultiCurl class provides a convenient way to execute parallel HTTP(S)
 * requests via PHP MULTI CURL extension with additional restrictions.
 * For example: start 100 downloads with 2 parallel sessions, and get only
 * first 100 Kb per session.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 3.0 of the License, or (at your option) any later version.
 *
 * This library 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 Lesser General Public License for more details.
 *
 * @author    Vadym Timofeyev <tvad@mail333.com> http://weblancer.net/users/tvv/
 * @copyright 2007-2010 Vadym Timofeyev
 * @license   http://www.gnu.org/licenses/lgpl-3.0.txt
 * @version   1.07
 * @since     PHP 5.0
 * @example   examples/example.php How to use MultiCurl class library.
 */
abstract class MultiCurl {
	/**
	 * Maximal number of CURL multi sessions. Default: 10 sessions.
	 *
	 * @var integer
	 */
	private $maxSessions = 10;

	/**
	 * Maximal size of downloaded content. Default: 10 Mb (10 * 1024 * 1024).
	 *
	 * @var integer
	 */
	private $maxSize = 10485760;

	/**
	 * Common CURL options (used for all requests).
	 *
	 * @var array
	 */
	private $curlOptions;

	/**
	 * Current CURL multi sessions.
	 *
	 * @var array
	 */
	private $sessions = array();

	/**
	 * Class constructor. Setup primary parameters.
	 *
	 * @param array $curlOptions Common CURL options.
	 */
	public function __construct($curlOptions = array()) {
		if(empty($curlOptions))
		{
			$header[] = "Accept: */*";
			$header[] = "Cache-Control: max-age=0";
			$header[] = "Accept-Charset: utf-8;q=0.7,*;q=0.7";
			$header[] = "Accept-Language: en-us,en;q=0.5";
			$header[] = "Pragma: ";

			$curlOptions=array(
					CURLOPT_HEADER     		=> true,
					CURLOPT_HTTPHEADER 		=> $header,
					CURLOPT_USERAGENT  		=> 'Googlebot/2.1 (+http://www.google.com/bot.html)',
					CURLOPT_CONNECTTIMEOUT 	=> 20,
					CURLOPT_TIMEOUT 		=> 10
			);
		}
		$this->setCurlOptions($curlOptions);
	}

	/**
	 * Class destructor. Close opened sessions.
	 */
	public function __destruct() {
		foreach ($this->sessions as $i => $sess) {
			$this->destroySession($i);
		}
	}

	/**
	 * Adds new URL to query.
	 *
	 * @param mixed $url URL for downloading.
	 * @param array $curlOptions CURL options for current request.
	 */
	public function addUrl($url, $extra_data = NULL, $curlOptions = array()) {
		// Check URL
		if (!$url) {
			throw new Exception('URL is empty!');
		}

		// Check array of URLs
		if (is_array($url)) {
			foreach ($url as $s) {
				$this->addUrl($s, $curlOptions);
			}
			return;
		}

		// Check query
		while (count($this->sessions) == $this->maxSessions) {
			$this->checkSessions();
		}

		// Init new CURL session
		$ch = curl_init($url);
		foreach ($this->curlOptions as $option => $value) {
			curl_setopt($ch, $option, $value);
		}
		foreach ($curlOptions as $option => $value) {
			curl_setopt($ch, $option, $value);
		}

		// Init new CURL multi session
		$mh = curl_multi_init();
		curl_multi_add_handle($mh, $ch);
		$this->sessions[] = array($mh, $ch, $url, $extra_data);
		$sessions_key = array_keys($this->sessions);
		$this->execSession(array_pop($sessions_key));
	}

	/**
	 * Waits CURL milti sessions.
	 */
	public function wait() {
		while (count($this->sessions)) {
			$this->checkSessions();
		}
	}

	/**
	 * Executes all active CURL multi sessions.
	 */
	protected function checkSessions() {
		foreach ($this->sessions as $i => $sess) {
			if ($this->multiSelect($sess[0]) != -1) {
				$this->execSession($i);
			}
			else {
				throw new Exception('Multicurl loop detected!');
			}
		}
	}

	/**
	 * Executes CURL multi session, check session status and downloaded size.
	 *
	 * @param integer $i A session id.
	 */
	protected function execSession($i) {
		list($mh, $ch) = $this->sessions[$i];
		if ($mh) {
			do {
				$mrc = curl_multi_exec($mh, $act);
			} while ($act > 0);
			if (!$act || $mrc !== CURLM_OK || curl_getinfo($ch, CURLINFO_SIZE_DOWNLOAD) >= $this->maxSize) {
				$this->closeSession($i);
			}
		}
	}

	/**
	 * Replace curl_multi_select.
	 *
	 * @see http://php.net/manual/en/function.curl-multi-select.php#110869
	 * @param resource $mh A cURL multi handle returned by curl_multi_init().
	 * @param float $timeout Time, in seconds, to wait for a response.
	 */
	protected function multiSelect($mh, $timeout = 1.0) {
		$ts = microtime(true);

		do {
			$mrc = curl_multi_exec($mh, $act);
			$ct = microtime(true);
			$t = $ct - $ts;
			if ($t >= $timeout) {
				return CURLM_CALL_MULTI_PERFORM;
			}
		} while ($mrc == CURLM_CALL_MULTI_PERFORM);
	}

	/**
	 * Closes session.
	 *
	 * @param integer $i A session id.
	 */
	protected function closeSession($i) {
		list(, $ch, $url, $extra_data) = $this->sessions[$i];

		$content = !curl_error($ch) ? curl_multi_getcontent($ch) : null;
		$info = curl_getinfo($ch);
		$this->destroySession($i);
		$this->onLoad($url, $content, $info, $extra_data);
	}

	/**
	 * Destroys session.
	 *
	 * @param integer $i A session id.
	 */
	protected function destroySession($i) {
		list($mh, $ch,) = $this->sessions[$i];

		curl_multi_remove_handle($mh, $ch);
		curl_close($ch);
		curl_multi_close($mh);

		unset($this->sessions[$i]);
	}

	/**
	 * Gets maximal number of CURL multi sessions.
	 *
	 * @return integer Maximal number of CURL multi sessions.
	 */
	public function getMaxSessions() {
		return $this->maxSessions;
	}

	/**
	 * Sets maximal number of CURL multi sessions.
	 *
	 * @param integer $maxSessions Maximal number of CURL multi sessions.
	 */
	public function setMaxSessions($maxSessions) {
		if ((int)$maxSessions <= 0) {
			throw new Exception('Max sessions number must be bigger then zero!');
		}

		$this->maxSessions = (int)$maxSessions;
	}

	/**
	 * Gets maximal size limit for downloaded content.
	 *
	 * @return integer Maximal size limit for downloaded content.
	 */
	public function getMaxSize() {
		return $this->maxSize;
	}

	/**
	 * Sets maximal size limit for downloaded content.
	 *
	 * @param integer $maxSize Maximal size limit for downloaded content.
	 */
	public function setMaxSize($maxSize) {
		if ((int)$maxSize <= 0) {
			throw new Exception('Max size limit must be bigger then zero!');
		}

		$this->maxSize = (int)$maxSize;
	}

	/**
	 * Gets CURL options for all requests.
	 *
	 * @return array CURL options.
	 */
	public function getCurlOptions() {
		return $this->curlOptions;
	}

	/**
	 * Sets CURL options for all requests.
	 *
	 * @param array $curlOptions CURL options.
	 */
	public function setCurlOptions($curlOptions) {
		if (!array_key_exists(CURLOPT_FOLLOWLOCATION, $curlOptions)) {
			$curlOptions[CURLOPT_FOLLOWLOCATION] = 1;
		}
		$curlOptions[CURLOPT_RETURNTRANSFER] = 1;
		$this->curlOptions = $curlOptions;
	}

	/**
	 * OnLoad callback event.
	 *
	 * @param string $url URL for downloading.
	 * @param string $content Downloaded content.
	 * @param array $info CURL session information.
	 */
	protected abstract function onLoad($url, $content, $info, $extra_data);

	/**
	 * Checks CURL extension, etc.
	 */
	public static function checkEnvironment() {
		if (!extension_loaded('curl')) {
			throw new Exception('CURL extension not loaded');
		}
	}
}