<?php
/*
**	$Id$
**
**	Relog Internet Tools 3 Library ("ITOOLS3")     
**
**	it_urlcache.class - Interface to URL content cache in DB
**
**	This class relies on a DB table with the following scheme:
**	url		CHAR(255)	NOT NULL,
**	updateinterval	INT		NOT NULL,
**	lastupdate	INT		NOT NULL,
**	nextupdate	INT		NOT NULL,
**	contentmd5	CHAR(32)	NOT NULL,
**	content		TEXT		NOT NULL,
**	PRIMARY KEY	(url),
**	KEY		(nextupdate)
*/

/* PRIVATE */
define("_IT_URLCACHE_DEFAULT_INTERVAL", 300);
define("_IT_URLCACHE_MAX_CONNECTIONS", 30);

class it_urlcache extends it_db_record
{
	/* PRIVATE */
	var $default_interval = _IT_URLCACHE_DEFAULT_INTERVAL;
	var $max_connections = _IT_URLCACHE_MAX_CONNECTIONS;

function set_default_interval($default_interval)
{
	$this->default_interval = $default_interval;
}


function set_max_connections($max_connections)
{
	$this->max_connections = $max_connections;
}


/*
 * Register an URL to be fetched by background process.
 * Note: get() will return an empty string until the url is fetched for the
 * first time
 */
function register($url)
{
	if (!$this->read($url))
	{
		$tags = array("url" => $url, "updateinterval" => $this->default_interval);
		$this->create($tags);
	}
}


/*
 * Removes the url from the cache. It won't be fetched again until register()
 * is called again.
 */
function unregister($url)
{
	if ($this->read($url))
		$this->delete();
}


/*
 * Get content of url. Returns empty string if it was never successfully
 * fetched.
 */
function get_content($url)
{
	$this->read($url);
	return $this->data['content'];
}


/*
 * Try to refetch all URLs in the database.
 * Note: This is intented for background process use only as it may take
 * a while to finish...
 */
function update_cache()
{
	$now = time();
	$pages = array();

	$result = $this->table->safe_sql_select("WHERE nextupdate < $now", "url");

	while (list($url) = $this->table->db->fetch_array($result))
		$pages[] = $url;

	$this->table->db->free($result);

	$this->_fetch_urls($pages, $now);
}


/* PRIVATE */
function _update_cache($url, $content, $now)
{
	$contentmd5 = md5($content);

	if ($this->read($url))
	{
		$interval = $this->data['updateinterval'];
		$age = $now - $this->data['lastupdate'];

		if ($this->data['contentmd5'] == $contentmd5)
		{
			if ($age > ($interval * 2))
				$interval = $interval * 1.5;

			$tags = array("updateinterval" => $interval, "nextupdate" => $now + $interval);
		}
		else
		{
			if ($age < ($interval / 2))
				$interval = $interval / 1.5;

			if ($interval < $this->default_interval)
				$interval = $this->default_interval;

			$tags = array("updateinterval" => $interval, "lastupdate" => $now, "nextupdate" => $now + $interval, "contentmd5" => $contentmd5, "content" => $content);
		}

		$this->update($tags);
	}
	else
	{
		$tags = array("url" => $url, "updateinterval" => $this->default_interval, "lastupdate" => $now, "nextupdate" => $now + $this->default_interval, "contentmd5" => $contentmd5, "content" => $content);
		$this->create($tags);
	}
}


/*
 * PRIVATE
 * Fetch URL in array $urls and store update cache database accordingly
 */
function _fetch_urls($pages, $now)
{
	$pos = 0;
	$fds = array();
	$urls = array();
	$content = array();
	$count = 0;

	for ($pos = 0; ($pos < count($pages)) && ($pos < $this->max_connections); $pos++)
	{
		debug("Opening $pages[$pos]", 10);

		if ($fd = fopen($pages[$pos], "r"))
		{
			socket_set_blocking($fd, false);
			$fds[] = $fd;
			$urls[] = $pages[$pos];
			$content[] = "";
			$count++;
			debug("Opened $pages[$pos]", 10);
		}
	}

	while ($count > 0)
	{
		$read = 0;

		for ($i = 0; $i < count($fds); $i++)
		{
			if ($fds[$i])
			{
				if (!feof($fds[$i]))
				{
					$data = fread($fds[$i], 4096);
					$content[$i] .= $data;
					$read += strlen($data);
					debug("Read " . strlen($data) . " from $urls[$i]", 10);
				}

				if (feof($fds[$i]))
				{
					fclose($fds[$i]);
					$fds[$i] = 0;
					$count--;
					$this->_update_cache($urls[$i], $content[$i], $now);
					debug("Finished $urls[$i]: " . strlen($content[$i]) . " bytes", 10);

					/* Schedule next url for retrieval */
					if ($pos < count($pages))
					{
						if ($fd = fopen($pages[$pos], "r"))
						{
							socket_set_blocking($fd, false);
							$fds[$i] = $fd;
							$urls[$i] = $pages[$pos];
							$content[$i] = "";
							$count++;
							debug("Opened $pages[$pos]", 10);
						}

						$pos++;
					}
				}
			}
		}

		/* We are in non-blocking mode, be nice */
		if (($count > 0) && ($read == 0))
		{
			sleep(1);
			debug("Sleeping...", 10);
		}
	}
}

} /* End class it_urlcache */