fof-main.php

<?php
/*
 * This file is part of FEED ON FEEDS - http://feedonfeeds.com/
 *
 * fof-main.php - initializes FoF, and contains functions used from other scripts
 *
 *
 * Copyright (C) 2004-2007 Stephen Minutillo
 * steve@minutillo.com - http://minutillo.com/steve/
 *
 * Distributed under the GPL - see LICENSE
 *
 */

/*
globals controlling behavior:
$fof_no_login -- does not force auth redirect if true
$fof_installer -- forces auth to admin, changes log file

$fof_logall -- forces logging on
$fof_tracelog -- enables ridiculous logging for debugging
 */

defined('FEED_IMAGE_CACHE_REFRESH_SECS') || define('FEED_IMAGE_CACHE_REFRESH_SECS', (7 * 24 * 60 * 60));

/* quiet warnings, default to UTC */
date_default_timezone_set('UTC');

fof_repair_drain_bamage();

if ((@include_once ('fof-config.php')) === false) {
	echo "You will first need to create a fof-config.php file.  Please copy fof-config.php.dist to fof-config.php and then update the values to match your database settings.\n";
	die();
}

require_once 'fof-asset.php';
require_once 'fof-db.php';
require_once 'classes/fof-prefs.php';
require_once 'library/urljoin.php';

fof_db_connect(empty($fof_installer) ? false : $fof_installer);

if (empty($fof_installer)) {
	if (empty($fof_no_login)) {
		require_user();
	} else {
		$fof_user_id = 1;
	}

	$fof_prefs_obj = &FoF_Prefs::instance();

	ob_start();
	fof_init_plugins();
	ob_end_clean();
}

require_once 'autoloader.php';

function fof_set_content_type($type = 'text/html') {
	static $set;
	if (!$set) {
		header("Content-Type: $type; charset=utf-8");
		$set = true;
	}
}

function fof_log($message, $topic = 'debug') {
	global $fof_prefs_obj;
	global $fof_installer;
	global $fof_logall;
	static $log;

	if ((empty($fof_prefs_obj) || empty($fof_prefs_obj->admin_prefs['logging']))
		&& empty($fof_logall)
		&& empty($fof_installer)) {
		return;
	}

	if (!isset($log)) {
		$log_path = (defined('FOF_DATA_PATH') ? FOF_DATA_PATH : '.');
		$log_file = (empty($fof_installer) ? 'fof.log' : 'fof-install.log');
		$log_fullpath = implode(DIRECTORY_SEPARATOR, array($log_path, $log_file));
		$log = fopen($log_fullpath, 'a');

		if (!$log) {
			die("FATAL: couldn't open logfile $log_fullpath");
		}
	}

	// log topic restriction?
	if (!empty($fof_prefs_obj->admin_prefs['log_topics'])) {
		$topic_restriction = explode(' ', $fof_prefs_obj->admin_prefs['log_topics']);

		if (!in_array($topic, $topic_restriction)) {
			return;
		}

	}

	$message = str_replace("\n", "\\n", $message);
	$message = str_replace("\r", "\\r", $message);

	fwrite($log, date('r') . " [$topic] $message\n");
}

/** Assemble a shorthand trace of calls at current state.
 *For debugging purposes.
 */
function fof_stacktrace($skip_frames = 0, $include_args = true) {
	$trace = '';
	$opts = $include_args ? 0 : DEBUG_BACKTRACE_IGNORE_ARGS;
	$bt = array_reverse(array_slice(debug_backtrace($opts), 1 + $skip_frames));
	$prev_file = null;
	foreach ($bt as $frame) {
		$trace .= '>';
		$file = empty($frame['file']) ? '?' : basename($frame['file']);
		$line = empty($frame['line']) ? '?' : $frame['line'];
		$func = (empty($frame['class']) ? '' : $frame['class']) .
			(empty($frame['type']) ? '' : $frame['type']) .
			(empty($frame['function']) ? '?' : $frame['function']);
		if ($file != $prev_file) {
			$trace .= $file . ':';
			$prev_file = $file;
		}
		$trace .= $line . ':' . $func;
	}
	if ($include_args) {
		$last_frame = end($bt);
		$args = array();
		foreach ($last_frame['args'] as $k => $v) {
			$args[] = var_export($v, true);
		}

		$trace .= '(' . implode(', ', $args) . ')';
	} else {
		$trace .= '()';
	}

	return $trace;
}

/* deeper log, for debugging */
function fof_trace($message = NULL) {
	global $fof_tracelog;

	if (empty($fof_tracelog)) {
		return;
	}

	$trace = fof_stacktrace(1, true);

	if (!empty($message)) {
		$trace .= ': ' . $message;
	}

	fof_log($trace, 'trace');
}

function fof_authenticate($user_name, $user_password_hash) {
	global $fof_user_name;

	if (fof_db_authenticate_hash($user_name, $user_password_hash)) {
		$user_login_expire_time = time() + (60 * 60 * 24 * 365 * 10); /* 10 years */
		setcookie('user_name', $fof_user_name, $user_login_expire_time);
		setcookie('user_password_hash', $user_password_hash, $user_login_expire_time);
		return true;
	}

	return false;
}

function require_user() {
	global $fof_user_id, $fof_user_name, $fof_user_level;

	if (defined('FOF_AUTH_EXTERNAL') && !empty($_SERVER['REMOTE_USER'])) {
		$user_row = fof_db_get_user($_SERVER['REMOTE_USER']);
		if (empty($user_row)) {
			fof_log('user "' . $_SERVER['REMOTE_USER'] . '" not indexed', 'auth');

			if (defined('FOF_AUTH_EXTERNAL_ADD')) {
				fof_db_add_user($_SERVER['REMOTE_USER'], 'unused password' . $_SERVER['UNIQUE_ID']);
				$user_row = fof_db_get_user($_SERVER['REMOTE_USER']);
				fof_log('added new index for user "' . $_SERVER['REMOTE_USER'] . '"', 'auth');
			}
		}
		if (!empty($user_row)) {
			$fof_user_id = $user_row['user_id'];
			$fof_user_name = $user_row['user_name'];
			$fof_user_level = $user_row['user_level'];

			fof_log('user "' . $_SERVER['REMOTE_USER'] . '" established', 'auth');
			return true;
		}
		if (defined('FOF_AUTH_EXTERNAL_ONLY')) {
			return false;
		}

	}

	if (!isset($_COOKIE['user_name']) || !isset($_COOKIE['user_password_hash'])) {
		header('Location: login.php');
		exit();
	}

	$user_name = $_COOKIE['user_name'];
	$user_password_hash = $_COOKIE['user_password_hash'];

	if (!fof_authenticate($user_name, $user_password_hash)) {
		header('Location: login.php');
		exit();
	}
}

function fof_logout() {
	setcookie('user_name', '', time());
	setcookie('user_password_hash', '', time());
}

function fof_current_user() {
	global $fof_user_id;

	return $fof_user_id;
}

function fof_username() {
	global $fof_user_name;

	return $fof_user_name;
}

function fof_prefs() {
	$p = &FoF_Prefs::instance();
	return $p->prefs;
}

function fof_is_admin() {
	global $fof_user_level;

	return $fof_user_level == 'admin';
}

function fof_get_tags($user_id) {
	$tags = array();

	$counts = fof_db_get_tag_unread($user_id);
	$statement = fof_db_get_tags($user_id);
	while (($row = fof_db_get_row($statement)) !== false) {
		if (isset($counts[$row['tag_id']])) {
			$row['unread'] = $counts[$row['tag_id']];
		} else {
			$row['unread'] = 0;
		}

		$tags[] = $row;
	}

	return $tags;
}

function fof_get_item_tags($user_id, $item_id) {
	$result = fof_db_get_item_tags($user_id, $item_id);

	$tags = array();

	while (($row = fof_db_get_row($result)) !== false) {
		$tags[] = $row['tag_name'];
	}

	return $tags;
}

function fof_tag_feed($user_id, $feed_id, $tag) {
	$tag_id = fof_db_get_tag_by_name($tag);
	if ($tag_id == NULL) {
		$tag_id = fof_db_create_tag($tag);
	}

	$result = fof_db_get_items($user_id, $feed_id, $what = 'all', NULL, NULL);

	$items = array();
	foreach ($result as $r) {
		$items[] = $r['item_id'];
	}

	fof_db_tag_items($user_id, $tag_id, $items);

	fof_db_subscription_tag_add($user_id, $feed_id, $tag_id);
}

function fof_untag_feed($user_id, $feed_id, $tag) {
	$tag_id = fof_db_get_tag_by_name($tag);
	if ($tag_id == NULL) {
		$tag_id = fof_db_create_tag($tag);
	}

	$result = fof_db_get_items($user_id, $feed_id, $what = "all", NULL, NULL);

	$items = array();
	foreach ($result as $r) {
		$items[] = $r['item_id'];
	}

	fof_db_untag_items($user_id, $tag_id, $items);

	fof_db_subscription_tag_remove($user_id, $feed_id, $tag_id);
}

function fof_tag_item($user_id, $item_id, $tag) {
	$tags = is_array($tag) ? $tag : array($tag);

	foreach ($tags as $tag) {
		// remove tag, if it starts with '-'
		if ($tag[0] == '-') {
			fof_untag_item($user_id, $item_id, substr($tag, 1));
			continue;
		}

		$tag_id = fof_db_get_tag_by_name($tag);
		if ($tag_id == NULL) {
			$tag_id = fof_db_create_tag($tag);
		}

		fof_db_tag_items($user_id, $tag_id, $item_id);
	}
}

function fof_untag_item($user_id, $item_id, $tag) {
	$tag_id = fof_db_get_tag_by_name($tag);
	fof_db_untag_items($user_id, $tag_id, $item_id);
}

// remove all occurences of $tag from all items for $user_id
function fof_untag($user_id, $tag) {
	$tag_ids = fof_db_get_tag_name_map(array($tag));
	if (empty($tag_ids)) {
		fof_log('non-existent tag "' . $tag . '"');
		return false;
	}

	return fof_db_untag_user_all($user_id, $tag_ids);
}

function fof_nice_time_stamp($age) {
	$age = time() - $age;

	if ($age == 0) {
		return array(
			'never',
			'&infin;',
		);
	}

	$days = floor($age / 60 / 60 / 24);
	if ($days > 365) {
		return array(
			floor($days / 365) . ' year' . (floor($days / 365) == 1 ? '' : 's') . ' ago',
			floor($days / 365) . 'y',
		);
	} else if ($days > 7) {
		return array(
			floor($days / 7) . ' week' . (floor($days / 7) == 1 ? '' : 's') . ' ago',
			floor($days / 7) . 'w',
		);
	} else if ($days) {
		return array(
			$days . ' day' . ($days == 1 ? '' : 's') . ' ago',
			$days . 'd',
		);
	}

	$hours = round($age / 60 / 60) % 24;
	if ($hours) {
		return array(
			$hours . ' hour' . ($hours == 1 ? '' : 's') . ' ago',
			$hours . 'h',
		);
	}

	$minutes = round($age / 60) % 60;
	if ($minutes) {
		return array(
			$minutes . ' minute' . ($minutes == 1 ? '' : 's') . ' ago',
			$minutes . 'm',
		);
	}

	$seconds = $age % 60;
	if ($seconds) {
		return array(
			$seconds . ' second' . ($seconds == 1 ? '' : 's') . ' ago',
			$seconds . 's',
		);
	}

	return array(
		'never',
		'&infin;',
	);
}

/* returns an array representing a user's view of a feed */
function fof_get_feed($user_id, $feed_id) {
	$feed = fof_db_subscription_feed_get($user_id, $feed_id);

	/* turn array of tag ids from prefs into array of tag names */
	$feed['tags'] = array();
	$tagmap = fof_db_get_tag_id_map();
	foreach ($feed['subscription_prefs']['tags'] as $tagid) {
		$feed['tags'][] = $tagmap[$tagid];
	}

	/* fetch counts, and pick the ones we're interested in */
	list($feed['feed_items'], $feed['feed_tagged'], $counts) = fof_db_feed_counts($user_id, $feed_id);
	$feed['feed_unread'] = $counts['unread'];
	$feed['feed_read'] = $feed['feed_items'] - $feed['feed_unread'];
	$feed['feed_starred'] = $counts['star']; // note not same!

	$feed['feed_age'] = $feed['feed_cache_date'];
	list($feed['agestr'], $feed['agestrabbr']) = fof_nice_time_stamp($feed['feed_cache_date']);

	$feed['max_date'] = 0;
	$feed['lateststr'] = '';
	$feed['lateststrabbr'] = '';
	$statement = fof_db_get_latest_item_age($user_id, $feed_id);
	$feed['max_date'] = fof_db_get_row($statement, 'max_date', TRUE);
	list($feed['lateststr'], $feed['lateststrabbr']) = fof_nice_time_stamp($feed['max_date']);

	return $feed;
}

function fof_get_feeds($user_id, $order = 'feed_title', $direction = 'asc') {
	$feeds = array();

	$tagmap = fof_db_get_tag_id_map();

	$result = fof_db_get_subscriptions($user_id);

	$i = 0;
	$feeds_index = array();
	while (($row = fof_db_get_row($result)) !== false) {
		/* remember where we are */
		$feeds_index[$row['feed_id']] = $i;

		/* fix user prefs */
		fof_db_subscription_feed_fix($row);

		/* initialize some values.. these will be populated later */
		$row['feed_items'] = 0;
		$row['feed_read'] = 0;
		$row['feed_unread'] = 0;
		$row['feed_starred'] = 0;
		$row['feed_tagged'] = 0;
		$row['max_date'] = 0;
		$row['lateststr'] = '';
		$row['lateststrabbr'] = '';

		/* alternative titles replace original ones */
		if (!empty ($row['alt_title']))
		    $row['feed_title'] = $row['alt_title'];

		/* we can set these now, though */
		$row['feed_age'] = $row['feed_cache_date'];
		list($row['agestr'], $row['agestrabbr']) = fof_nice_time_stamp($row['feed_cache_date']);

		$row['tags'] = array();
		foreach ($row['subscription_prefs']['tags'] as $tagid) {
			$row['tags'][] = $tagmap[$tagid];
		}

		$feeds[$i] = $row;

		$i++;
	}

	/* tally up all items */
	$result = fof_db_get_item_count($user_id);
	while (($row = fof_db_get_row($result)) !== false) {
		$i = $feeds_index[$row['feed_id']];
		$feeds[$i]['feed_items'] += $row['count'];
		$feeds[$i]['feed_read'] += $row['count'];
	}

	/* tally up unread items */
	$result = fof_db_get_item_count($user_id, 'unread');
	while (($row = fof_db_get_row($result)) !== false) {
		$i = $feeds_index[$row['feed_id']];
		$feeds[$i]['feed_unread'] += $row['count'];
		$feeds[$i]['feed_read'] -= $row['count'];
	}

	/* tally up starred items */
	$result = fof_db_get_item_count($user_id, 'starred');
	while (($row = fof_db_get_row($result)) !== false) {
		$i = $feeds_index[$row['feed_id']];
		$feeds[$i]['feed_starred'] += $row['count'];
	}

	/* tally up tags which aren't system-tags */
	$result = fof_db_get_item_count($user_id, 'tagged');
	while (($row = fof_db_get_row($result)) !== false) {
		$i = $feeds_index[$row['feed_id']];
		$feeds[$i]['feed_tagged'] += $row['count'];
	}

	/* find most recent item for each feed */
	$result = fof_db_get_latest_item_age($user_id);
	while (($row = fof_db_get_row($result)) !== false) {
		$i = $feeds_index[$row['feed_id']];
		$feeds[$i]['max_date'] = $row['max_date'];
		list($feeds[$i]['lateststr'], $feeds[$i]['lateststrabbr']) = fof_nice_time_stamp($row['max_date']);
	}

	return fof_multi_sort($feeds, $order, $direction != 'asc');
}

/* describe what is being displayed */
function fof_view_title($feed = NULL, $what = 'unread', $when = NULL, $start = NULL, $limit = NULL, $search = NULL, $itemcount = 0) {
	$prefs = fof_prefs();
	$title = 'feed on feeds - showing';

	if ($itemcount) {
		if (is_numeric($start)) {
			if (!is_numeric($limit)) {
				$limit = $prefs['howmany'];
			}

			if ($start || $limit < $itemcount) {
				$end = $start + $limit;
				if ($end > $itemcount) {
					$end = $itemcount;
				}

				$start += 1;
				if ($start != $end) {
					$title .= " $start to $end of ";
				}

			}
		}

		$title .= " $itemcount";
	}
	$title .= ' item' . ($itemcount != 1 ? 's' : '');

	if (!empty($feed)) {
		/* we only need this one thing here, so try to minimize activity by shirking the full fix function call */
		$feed = fof_db_subscription_feed_get(fof_current_user(), $feed);
		$feed['display_title'] = empty($feed['subscription_prefs']['alt_title']) ? $feed['feed_title'] : $feed['subscription_prefs']['alt_title'];
		$title .= ' in \'' . htmlentities($feed['display_title']) . '\'';
	}

	if (empty($what)) {
		$what = 'unread';
	}

	if ($what != 'all') {
		$tags = explode(' ', $what);
		$last_tag = array_pop($tags);
		if (!empty($last_tag)) {
			$title .= ' tagged';
			if (!empty($tags)) {
				$title .= ' ' . implode(', ', $tags) . (count($tags) > 1 ? ',' : '') . ' and';
			}
			$title .= ' ' . $last_tag;
		}
	}

	if (!empty($when)) {
		$title .= ' from ' . $when;
	}

	if (isset($search)) {
		$title .= ' <a href="#" title="Toggle highlights" onclick="toggle_highlight(); return false;">matching <mark class="fof-highlight"><em>' . $search . '</em></mark></a>';
	}

	return $title;
}

function fof_get_items($user_id, $feed = NULL, $what = "unread", $when = NULL, $start = NULL, $limit = NULL, $order = "desc", $search = NULL) {
	global $fof_item_filters;

	$items = fof_db_get_items($user_id, $feed, $what, $when, $start, $limit, $order, $search);

	for ($i = 0; $i < count($items); $i++) {
		foreach ($fof_item_filters as $filter) {
			$items[$i]['item_content'] = $filter($items[$i]['item_content']);
		}
	}

	return $items;
}

function fof_get_item($user_id, $item_id, $run_filters = true) {
	global $fof_item_filters;

	$item = fof_db_get_item($user_id, $item_id);

	if ($run_filters) {
		foreach ($fof_item_filters as $filter) {
			$item['item_content'] = $filter($item['item_content']);
		}
	}

	return $item;
}

function fof_delete_subscription($user_id, $feed_id) {
	fof_db_delete_subscription($user_id, $feed_id);

	if (fof_db_get_subscribed_users_count($feed_id) == 0) {
		fof_db_delete_feed($feed_id);
	}
}

/* simple wrapper to construct a safe GET-style URL from location and variables */
function fof_url($path = '.', $query_variables = array(), $fragment = NULL) {
	$url = $path;
	$qv = array();
	foreach ($query_variables as $k => $v) {
		if (!empty($v)) {
			$qv[] = urlencode($k) . '=' . urlencode($v);
		}
	}

	if (!empty($qv)) {
		$url .= '?' . implode('&amp;', $qv);
	}

	if (!empty($fragment)) {
		$url .= '#' . urlencode($fragment);
	}

	return $url;
}

function fof_get_nav_links($feed = NULL, $what = 'new', $when = NULL, $start = NULL, $limit = NULL, $search = NULL, $itemcount = 9999) {
	$prefs = fof_prefs();
	$navlinks = '';

	$qv = array('feed' => $feed,
		'what' => $what,
		'when' => $when,
		'search' => $search,
		'howmany' => $limit);

	if (!empty($when)) {
		$begin = strtotime(($when == 'today') ? fof_todays_date() : $when);

		$tomorrow = date("Y/m/d", $begin + (24 * 60 * 60));
		$yesterday = date("Y/m/d", $begin - (24 * 60 * 60));

		$navlinks .= '<a href="' . fof_url('.', array_merge($qv, array('when' => $yesterday))) . '">[&laquo; ' . $yesterday . ']</a>';

		if ($when != "today") {
			$navlinks .= ' <a href="' . fof_url('.', array_merge($qv, array('when' => 'today'))) . '">[today]</a>';
			$navlinks .= ' <a href="' . fof_url('.', array_merge($qv, array('when' => 'tomorrow'))) . '">[' . $tomorrow . '&raquo;]</a>';
		}
	}

	if (is_numeric($start)) {
		if (!is_numeric($limit)) {
			$limit = isset($prefs['howmany']) ? $prefs['howmany'] : NULL;
			$qv['howmany'] = $limit;
		}

		if ($itemcount <= $limit) {
			return '';
		}

		$earlier = $start + $limit;
		$later = $start - $limit;

		$qv['how'] = 'paged';

		if ($itemcount > $earlier) {
			$navlinks .= ' <a href="' . fof_url('.', array_merge($qv, array('which' => $earlier))) . '">[&laquo; previous ' . $limit . ']</a>';
			$navlinks .= ' <a href="' . fof_url('.', array_merge($qv, array('how' => 'unpaged'))) . '">[all-at-once]</a>';
		}

		if ($later >= 0) {
			$navlinks .= ' <a href="' . fof_url('.', array_merge($qv, array('which' => $start))) . '">[current items]</a>';
			$navlinks .= ' <a href="' . fof_url('.', array_merge($qv, array('which' => $later))) . '">[next ' . $limit . ' &raquo;]</a>';
		}
	}

	return $navlinks;
}

function fof_render_feed_link($row) {
	$p = &FoF_Prefs::instance();

	$link = $row['feed_link'];
	$description = htmlentities($row['feed_description']);
	$title = htmlentities(isset($row['display_title']) ? $row['display_title'] : $row['feed_title']);
	$url = $row['feed_url'];

	if ($title == "[no title]") {
		$title = $link;
	}

	if ($title == "[no link]") {
		$title = $url;
	}

	$s = "<b><a href=\"$link\" title=\"$description\"";
	if ($p->get('item_target')) {
		$s .= " target=\"_blank\"";
	}

	$s .= ">$title</a></b> ";
	$s .= "<a href=\"$url\">(rss)</a>";

	return $s;
}

function fof_opml_to_array($opml) {
	$ret = Array();
	$reader = new XMLReader();
	if (!$reader->xml($opml)) {
		die("Could not parse OPML file");
	}
	while ($reader->read()) {
		if ($reader->name === 'outline') {
			$feed = $reader->getAttribute('xmlUrl');
			if ($feed) {
				$ret[] = $feed;
			}
		}
	}
	return $ret;
}

function fof_prepare_url($url) {
	if (substr($url, 0, 7) == 'feed://') {
		$url = substr($url, 7);
	}

	if (substr($url, 0, 7) != 'http://'
		&& substr($url, 0, 8) != 'https://') {
		$url = 'http://' . $url;
	}

	return $url;
}

function fof_subscribe($user_id, $url, $unread = 'today') {
	fof_trace();

	$url = trim($url);
	if (empty($url)) {
		return "<span style=\"color:red\">Error: <b>cannot subscribe to nothing</b> (empty url?)</span><br>\n";
	}

	/* ensure url at least has a reasonable protocol */
	$url = fof_prepare_url($url);

	$feed = fof_db_get_feed_by_url($url);
	if (empty($feed)) {
		/* raw url does not exist, try cooking it with simplepie */
		if (($rss = fof_parse($url)) === false
			|| $rss->error()) {
			$rss_error = (isset($rss) && $rss->error()) ? $rss->error() : '';
			return "<span style=\"color:red\">Error: <b>Failed to subscribe to '$url'</b>"
				. (!empty($rss_error) ? ": $rss_error</span> <span><a href=\"http://feedvalidator.org/check?url=" . urlencode($url) . "\">try to validate it?</a>" : "")
				. "</span><br>\n";
		}

		$self = $rss->get_link(0, 'self');
		if ($self && $self != $url) {
			// rel="self" URL differs from subscription URL, try to redirect
			$self_rss = fof_parse($self);
			if ($self_rss === false || $self_rss->error()) {
				fof_log("Feed at $url declared $self as its self, which returned error " . ($self_rss ? $self_rss->error() : '(unknown'));
				$self_rss = null;
				$url = $rss->subscribe_url();
			} else {
				fof_log("Feed at $url has canonical URL at $self");
				$url = $self;
			}
		}

		$feed = fof_db_get_feed_by_url($url);
		if (empty($feed)) {
			/* cooked url does not exist, add it */
			$new_feed_id = fof_db_add_feed($url, $rss->get_title(), $rss->get_link(), $rss->get_description());
			if (empty($new_feed_id)) {
				return "<span style=\"color:red\">Error: <b>Failed to subscribe to '$url'</b></span<br>\n";
			}

			$feed = fof_db_get_feed_by_id($new_feed_id);
			/* assert(!empty($feed)) */
		}
	}

	if (fof_db_is_subscribed($user_id, $url)) {
		return "<span>You are already subscribed to '" . fof_render_feed_link($feed) . "'.</span><br>\n";
	}

	/* subscribe to the feed */
	fof_db_add_subscription($user_id, $feed['feed_id']);

	/* update the feed */
	list(, $err) = fof_update_feed($new_feed_id);
	if (!empty($err)) {
		return "<span style=\"color:red\">$err</span><br>\n";
	}

	/* set requested existing items unread */
	if ($unread != 'no') {
		fof_db_mark_feed_unread($user_id, $feed['feed_id'], $unread);
	}

	/* set tags for user on any existing items */
	fof_apply_plugin_tags($feed['feed_id'], NULL, $user_id);

	return "<span style=\"color:green\"><b>Subscribed to '" . fof_render_feed_link($feed) . "'.</b></span><br>\n";
}

function fof_mark_item_unread($feed_id, $id) {
	$result = fof_db_get_subscribed_users($feed_id);
	$users = array();
	while (($user_id = fof_db_get_row($result, 'user_id')) !== false) {
		$users[] = $user_id;
	}
	fof_db_mark_item_unread($users, $id);
}

function fof_new_parser($useragent='FoF '.SIMPLEPIE_USERAGENT) {
	$p = &FoF_Prefs::instance();
	$admin_prefs = $p->admin_prefs;

	$pie = new SimplePie();
	$pie->set_cache_location(dirname(__FILE__) . '/cache');
	$pie->set_cache_duration($admin_prefs["manualtimeout"] * 60);

	if (defined('FOF_USER_AGENT'))
		$pie->set_useragent(FOF_USER_AGENT);
	else
		$pie->set_useragent($useragent);

	// we allow iframe (for YouTube embeds etc.), the rest is SimplePie's default
	$striptags = $pie->strip_htmltags;
	if (($key = array_search('iframe', $striptags)) !== false) {
		unset($striptags[$key]);
	}
	$pie->strip_htmltags($striptags);

	return $pie;
}

/** Let SimplePie process a feed URL.
 */
function fof_parse($url, $body = null)
{
	if (empty($url)) {
		fof_log("got empty url");
		return false;
	}

	$p =& FoF_Prefs::instance();

	$pie = fof_new_parser();
	if ($body) {
		$pie->set_raw_data($body);
	} else {
		$pie->set_feed_url($url);
	}

	// do we have a cookie file?
	if ( is_readable ( $cookiestxt = (defined('FOF_DATA_PATH') ? FOF_DATA_PATH : dirname(__FILE__)) . '/cookies.txt' ) ) {
		$pie->set_curl_options(array(
			CURLOPT_COOKIEFILE => $cookiestxt,
			CURLOPT_COOKIEJAR => $cookiestxt
		) );
	}

	$pie->init();

	/* A feed might contain data before the <?xml declaration, which will cause
	 * SimplePie to fail to parse it.
	 * In case of an error in parsing, retry after trying to fetch and scrub the
	 * feed data.
	 * XXX: What error does this case report?  Could probably check for that,
	 * and only try the scrubbing when it makes sense.
	 */
	if ($pie->error()) {
		fof_log('failed to parse feed url ' . $url . ': ' . $pie->error());

		if ( ($data = file_get_contents($url)) === false) {
			fof_log("failed to fetch '$url'");
			return $pie;
		}

		$data = preg_replace ( '~.*<\?xml~sim', '<?xml', $data );

		unset($pie);

		$pie = fof_new_parser();
		$pie->set_raw_data($data);
		$pie->init();
	}

	return $pie;
}

/* XXX: why is fof_subscription_to_tags a global? */
function fof_apply_tags($feed_id, $item_id) {
	global $fof_subscription_to_tags;

	if (!isset($fof_subscription_to_tags)) {
		$fof_subscription_to_tags = fof_db_get_subscription_to_tags();
	}

	fof_trace("subs_to_tags:" . var_export($fof_subscription_to_tags, TRUE));

	if (isset($fof_subscription_to_tags[$feed_id])) {
		$feed_subs = $fof_subscription_to_tags[$feed_id];
		if (is_array($feed_subs)) {
			foreach ($feed_subs as $user_id => $tags) {
				if (is_array($tags)) {
					// we check tag names, because '-<name>' means untag
					$tag_names = fof_db_get_tag_id_map($tags);

					fof_tag_item($user_id, $item_id, $tag_names);
				}
			}
		}
	}
}

/* returns array of number of items added, and status message to display */
function fof_update_feed($id, $body = null) {
	global $fof_item_prefilters;
	static $blacklist = null;
	static $admin_prefs = null;

	fof_log("fof_update_feed($id)");
	$now = time();

	if ($blacklist === null) {
		$p = &FoF_Prefs::instance();
		$admin_prefs = $p->admin_prefs;
		$blacklist = preg_split('/(\r\n|\r|\n)/', isset($admin_prefs['blacklist']) ? $admin_prefs['blacklist'] : NULL, -1, PREG_SPLIT_NO_EMPTY);
	}

	if (empty($id)) {
		fof_log("Empty feed ID", "update");
		return array(0, '');
	}

	$feed = fof_db_get_feed_by_id($id);
	if (empty($feed)) {
		fof_log("no such feed '$id'", "update");
		return array(0, "Error: <b>no such feed '$id'</b>");
	}

	fof_log("updating feed_id:$id url:'" . $feed['feed_url'] . "'", "update");

	fof_db_feed_mark_attempted_cache($id);

	$rss = fof_parse($feed['feed_url'], $body);

	if ($rss === false || $rss->error()) {
		if ($rss !== false) {
			$rss_error = $rss->error();
		}

		if (empty($rss_error)) {
			$rss_error = 'unknown error';
		}

		fof_db_feed_update_attempt_status($id, $rss_error);
		fof_log("feed update failed feed_id:$id url:'" . $feed['feed_url'] . "': " . $rss_error, "update");
		return array(0, "Error: <b>failed to parse feed '" . $feed['feed_url'] . "'</b>: $rss_error");
	}
	fof_db_feed_update_attempt_status($id, NULL);

	$feed_image = $feed['feed_image'];
	$feed_image_cache_date = $feed['feed_image_cache_date'];

	/* periodically update the feed's image */
	/* or if cached image file does not exist */
	if (($feed['feed_image_cache_date'] + FEED_IMAGE_CACHE_REFRESH_SECS) < time()
		|| (!empty($feed_image) && !file_exists($feed_image))) {
		/*
			Feed images tend to be larger and less-square than favicons, but
			are more likely to be directly related to the feed, so are being
			given the first chance at representing the feed.
			Perhaps the prioritization should be configurable by preference,
			or check the dimensions and prefer a favicon if feedimage is over
			some size?
		*/
		$feed_image_url = $rss->get_image_url();
		if (!empty($feed_image_url)
			&& ($new_feed_image = fof_cache_image_url($feed_image_url)) !== false) {
			/* Use the image specified by the feed, if we can get it. */
			$feed_image = $new_feed_image;
			$feed_image_cache_date = time();
		} else if (($new_feed_image = fof_get_favicon($feed['feed_link'])) !== false) {
			/* Use the feed site's favicon, if we can. */
			$feed_image = $new_feed_image;
			$feed_image_cache_date = time();
		}
	}

	$feed_title = $rss->get_title();
	$feed_link = $rss->get_link();
	$feed_description = $rss->get_description();

	// If the feed URL updates, follow it (but only if it's good)
	$feed_url = $feed['feed_url'];
	$self_url = urljoin($feed_url, $rss->get_link(0, 'self'));
	if ($feed_url != $feed_url) {
		$new_rss = fof_parse($feed_url);
		if ($new_rss === false || $new_rss->error()) {
			fof_log("Feed $id redirected to bad URL $feed_url; ignoring");
		} else {
			fof_log("Feed $id redirected to new URL $self_url");
			$feed_url = $self_url;
		}
	}

	if (!$body) {
		/* set the feed's current information */
		fof_db_feed_update_metadata($id, $feed_title, $feed_link,
			$feed_url,
			$feed_description,
			$feed_image, $feed_image_cache_date);
	}

	$feed_id = $feed['feed_id'];
	$n = 0;

	// Set up the dynamic updates here, so we can include would-be-purged items
	$purgedUpdTimes = array();
	$count_Added = 0;

	$items_in_feed = 0;
	if ($rss->get_items()) {
		foreach ($rss->get_items() as $item) {
			$items_in_feed++;

			$title = $item->get_title();
			foreach ($blacklist as $bl) {
				if (stristr($title, $bl) !== false) {
					fof_log($feed_id . ": Item title \"$title\" contained blacklisted term \"$bl\"", 'update');
					continue 2;
				}
			}
			if (empty($title)) {
				fof_log($feed_id . ': Item had no title', 'update');
				$title = '[no title]';
			}

			$link = $item->get_permalink();
			if (empty($link)) {
				// Some feeds don't furnish an item link...
				fof_log($feed_id . ': Item had no link; synthesizing', 'update');
				$link = $feed['feed_link'];
			}

			$content = $item->get_content();
			if (!$content) {
				fof_log($feed_id . ': Item has no content', 'update');
				$content = '';
			}

			$enclosures = $item->get_enclosures();
			foreach ($enclosures as $enclosure) {
			    if ($enclosure->get_type() == 'image/jpeg')
			        $content = '<img src="' . $enclosure->get_link() . '" alt=""/>' . $content;
            }


			$authors = $item->get_authors();
			$author = '';
			if (!empty($authors) && is_array($authors)) {
				foreach ($authors as $aobj) {
					$author .= " " . $aobj->get_name() . " " . $aobj->get_email();
				}
			}

			// don't fetch entries older than the purge limit
			$date = $item->get_date('U');
			if (!$date || $date > time()) {
				// Item either didn't come with a date or it was nonsensical (to be fair, RFC822 is terrible), so use the current time instead
				$date = time();
				fof_log($feed_id . ": item $link had no date; synthesizing", 'update');
			} elseif (!empty($admin_prefs['purge'])
				&& $date <= (time() - $admin_prefs['purge'] * 24 * 3600)) {
				fof_log($feed_id . ": item $link is older than cutoff", 'update');
				$purgedUpdTimes[] = $date;
				continue;
			}

			foreach ($fof_item_prefilters as $filter) {
				list($link, $title, $content) = $filter($item, $link, $title, $content);
			}

			/* check if item already known */
			$item_id = $item->get_id();
			$found = fof_db_find_item($feed_id, $item_id);

			$id = fof_db_add_item($found, $feed_id, $item_id, $link, $title, $content, time(), $date, $author);
			if ($found == NULL || !fof_db_item_get_complete($id)) {
				// item is new, or wasn't finished being added, so let's add subscriptions
				$n++;
				$count_Added++;

				fof_mark_item_unread($feed_id, $id);
				fof_apply_tags($feed_id, $id);
				fof_apply_plugin_tags($feed_id, $id, NULL);

				fof_db_item_set_complete($id);
			}
		}
	}

	// Update WebSub subscriptions
	$feed_websub_hub = $rss->get_link(0, 'hub');
	if ($feed_websub_hub && ($feed_websub_hub != $feed['feed_websub_hub']
		|| $feed['feed_websub_lease'] < $now)) {
		// Either the hub has changed, or the lease is expiring. Update the subscription.
		fof_log("Updating WebSub subscription for $feed_url ($feed_id)");
		fof_subscribe_websub($feed_id, $feed_url, $feed_websub_hub, $feed['feed_websub_secret']);
	}

	unset($rss);

	if (!empty($admin_prefs['dynupdates'])) {
		// Determine the average time between items, to determine the next update time

		$count = 0;
		$lastTime = 0;
		$totalDelta = 0.0;
		$totalDeltaSquare = 0.0;

		// Accumulate the times for the pre-purged items
		sort($purgedUpdTimes, SORT_NUMERIC);
		foreach ($purgedUpdTimes as $time) {
			if ($count > 0) {
				$delta = $time - $lastTime;
				$totalDelta += $delta;
				$totalDeltaSquare += $delta * $delta;
			}
			$lastTime = $time;
			$count++;
		}

		// Accumulate the times for the stored items
		$result = fof_db_items_updated_list($feed_id);
		while ($row = fof_db_get_row($result)) {
			if ($count > 0) {
				$delta = (float) ($row['item_updated'] - $lastTime);
				$totalDelta += $delta;
				$totalDeltaSquare += $delta * $delta;
			}
			$count++;
			$lastTime = $row['item_updated'];
		}

		// If there were no new items, use the time since the last one to grow the window
		if (!$count_Added) {
			$delta = time() - $lastTime;
			if ($delta > 0 && $count > 0) {
				$totalDelta += $delta;
				$totalDeltaSquare += $delta * $delta;
				$count++;
			}
		}

		$stdev = 0;
		if ($count > 0) {
			$mean = $totalDelta / $count;
			if ($count > 1) {
				$stdev = sqrt(($count * $totalDeltaSquare - $totalDelta * $totalDelta)
					/ ($count * ($count - 1)));
			}
		} else {
			// We don't have any items to go on, so let's just say it's a day
			$mean = 86400;
		}

		$nextInterval = 0;
		$lastInterval = $now - $lastTime;

		// This algorithm is rife with fiddling, and I really need to generate metrics to test the efficacy
		$nextInterval = max($lastTime + $nextInterval, $now);
		if ($count_Added > 1) {
			// We missed an update, so make the interval shorter by how much we missed it by
			$nextInterval -= $lastInterval;
		}
		// fudge factor
		$nextInterval += $stdev / ($count_Added + 1);

		// Always check at least twice a day
		$nextTime = min($nextInterval, $now + 86400 / 2);

		fof_log($feed['feed_title'] . ": Next feed update in "
			. ($nextTime - $now) . " seconds;"
			. " count=$count t=$totalDelta t2=$totalDeltaSquare"
			. " mean=$mean stdev=$stdev");
		if ($count_Added > 0) {
			// In a perfect world, we want both of these numbers to be low
			fof_log("DYNUPDATE_ADD $feed_id count $count_Added overstep $lastInterval");
		} else {
			fof_log("DYNUPDATE_NONE $feed_id since $lastInterval");
		}
		fof_db_feed_cache_set($feed_id, (int) round($nextTime));
	}

	$delete = array();

	/*  If 'purge' preference is set, we delete any items that are not tagged by
		by anything other than 'folded', are older than 'purge' days, and are
		not one of the most recent 'purge_grace' items in the feed.

		FIXME: behavior question: should auto-tagged feeds purge items with
		their auto-tags set?
	*/
	if (!empty($admin_prefs['purge'])) {
		/*  Always keep at least as many items as feed provides, or as set by
			preferences.
		*/
		$grace = $items_in_feed;
		if (!empty($admin_prefs['purge_grace'])) {
			$grace = $admin_prefs['purge_grace'];
		}

		/* It's okay to purge 'folded' items. */
		$ignore_tags = array('folded');

		fof_log('purge is ' . $admin_prefs['purge']);

		$result = fof_db_items_purge_list($feed_id, $admin_prefs['purge'], $grace, $ignore_tags);

		while (($row = fof_db_get_row($result)) !== false) {
			$delete[] = $row['item_id'];
		}
	}

	/*  If 'match_similarity' preference is set, we delete any items with
		matching titles and similar content.
	*/
	if (!empty($admin_prefs['match_similarity'])) {
		$threshold = $admin_prefs['match_similarity'];

		$result = fof_db_items_duplicate_list();

		while ($row = fof_db_get_row($result)) {
			$similarity = 0;

			similar_text($row['c1'], $row['c2'], $similarity);

			if ($similarity > $threshold) {
				$delete[] = $row['item_id'];
			}

		}
	}

	fof_db_items_delete($delete);

	fof_db_feed_mark_cached($feed_id);

	$log = "feed update complete, $n new items, " . count($delete) . " items purged";
	if (empty($admin_prefs['purge'])) {
		$log .= " (purging disabled)";
	}
	fof_log($log, "update");

	return array($n, "");
}

/* Update a WebSub subscription */
function fof_subscribe_websub($feed_id, $feed_url, $hub, $secret) {
	// If we don't have a secret, generate one
	if (!$secret) {
		if (function_exists('openssl_random_pseudo_bytes')) {
			$secret = bin2hex(openssl_random_pseudo_bytes(8));
		} else {
			$secret = '' . mt_rand();
		}
		fof_log("Generated new secret");
	} else {
		fof_log("Reused existing secret");
	}

	fof_db_feed_update_websub($feed_id, $hub, $secret);

	fof_log("base URL is " . fof_base_url());
	$callback = urljoin(fof_base_url(), "websub.php/$feed_id/$secret");
	fof_log("Callback URL is $callback");

	// send the callback subscription to the hub
	$curl = curl_init();
	$fields = [
		'hub.callback' => $callback,
		'hub.mode' => 'subscribe',
		'hub.topic' => $feed_url
	];
	curl_setopt_array($curl, [
		CURLOPT_URL => $hub,
		CURLOPT_POST => count($fields),
		CURLOPT_POSTFIELDS => http_build_query($fields),
		CURLOPT_RETURNTRANSFER => true]);
	curl_exec($curl);
	fof_log("WebSub subscription to $feed_id ($feed_url) returned HTTP code "
		. curl_getinfo($curl, CURLINFO_HTTP_CODE));
	curl_close($curl);
}

/*  for all users subscribed to feed_id (or the specified user_id)
and for all items in feed_id (or the specified item_id)
and for each plugin active for each user
run the plugin filter on the item data
and set the resulting tags for the user and item
 */
function fof_apply_plugin_tags($feed_id, $item_id = NULL, $user_id = NULL) {
	$users = array();

	if ($user_id) {
		$users[] = $user_id;
	} else {
		$result = fof_db_get_subscribed_users($feed_id);
		while (($row = fof_db_get_row($result)) !== false) {
			$users[] = $row['user_id'];
		}
	}

	$items = array();
	if ($item_id) {
		$items[] = fof_db_get_item($user_id, $item_id);
	} else {
		$result = fof_db_get_items($user_id, $feed_id, $what = "all", NULL, NULL);

		foreach ($result as $r) {
			$items[] = $r;
		}
	}

	foreach ($users as $user) {
		fof_log("tagging for $user");

		global $fof_tag_prefilters;
		foreach ($fof_tag_prefilters as $plugin => $filter) {
			fof_log("considering $plugin $filter");

			foreach ($items as $item) {
				$tags = $filter($item['item_link'], $item['item_title'], $item['item_content'], $item);
				fof_tag_item($user, $item['item_id'], $tags);
			}
		}
	}
}

/* Return an associative array with plugin names as keys, mapped to array with
the following values:
code => path to php plugin file, suitable for including
meta => optionally-loaded contents of plugin ini file
*/
function fof_list_plugins($wantmeta = false, $dir = FOF_DIR . DIRECTORY_SEPARATOR . 'plugins') {
	$plugins = array();
	$dirlist = opendir($dir);
	while (($file = readdir($dirlist)) !== false) {
		$info = pathinfo($file);
		if (empty($info['filename']) || $info['filename'][0] === '.') {
			continue;
		}
		$filepath = $dir . DIRECTORY_SEPARATOR . $file;
		if ($info['extension'] === 'php') {
			$plugins[$info['filename']]['code'] = $filepath;
		} elseif ($info['extension'] === 'ini') {
			$plugins[$info['filename']]['meta'] = $wantmeta ? parse_ini_file($filepath) : null;
		}
	}
	closedir($dirlist);

	return $plugins;
}

function fof_init_plugins() {
	global $fof_item_filters,
		$fof_item_prefilters,
		$fof_tag_prefilters,
		$fof_plugin_prefs,
		$fof_domitem_filters,
		$fof_render_filters;

	$fof_item_filters = array();
	$fof_item_prefilters = array();
	$fof_plugin_prefs = array();
	$fof_tag_prefilters = array();
	$fof_domitem_filters = array();
	$fof_render_filters = array();

	$p = &FoF_Prefs::instance();

	$plugins = fof_list_plugins();
	$active_plugins = array();
	foreach ($plugins as $plugin => $data) {
		if (!empty($data['code'])) {
			if ($p->get('plugin_' . $plugin) == false) {
				$active_plugins[] = $plugin;
				include $data['code'];
			}
		}
	}
	fof_log('included plugins: ' . implode(', ', $active_plugins));
}

function fof_add_tag_prefilter($plugin, $function) {
	global $fof_tag_prefilters;

	$fof_tag_prefilters[$plugin] = $function;
}

function fof_add_item_filter($function, $order = null) {
	global $fof_item_filters;

	if (is_int($order)) {
		$fof_item_filters[$order] = $function;
	} else {
		$fof_item_filters[] = $function;
	}

	ksort($fof_item_filters);
}

function fof_add_domitem_filter($function, $order = null) {
	global $fof_domitem_filters;

	if (is_int($order)) {
		$fof_domitem_filters[$order] = $function;
		ksort($fof_domitem_filters);
	} else {
		$fof_domitem_filters[] = $function;
	}
}

function fof_add_render_filter($function, $order = null) {
	global $fof_render_filters;

	if (is_int($order)) {
		$fof_render_filters[$order] = $function;
	} else {
		$fof_render_filters[] = $function;
	}

	ksort($fof_render_filters);
}

function fof_add_item_prefilter($function) {
	global $fof_item_prefilters;

	$fof_item_prefilters[] = $function;
}

function fof_add_pref($name, $key, $type = "string") {
	global $fof_plugin_prefs;

	$fof_plugin_prefs[] = array($name, $key, $type);
}

function fof_add_item_widget($function) {
	global $fof_item_widgets;

	$fof_item_widgets[] = $function;
}

function fof_get_widgets($item) {
	global $fof_item_widgets;

	$widgets = array();

	if (is_array($fof_item_widgets)) {
		foreach ($fof_item_widgets as $widget) {
			$w = $widget($item);
			if ($w) {
				$widgets[] = $w;
			}

		}
	}

	return $widgets;
}

function fof_get_plugin_prefs() {
	global $fof_plugin_prefs;

	return $fof_plugin_prefs;
}

function fof_multi_sort($tab, $key, $rev) {
	usort($tab, function($a, $b) use($key, $rev) {
		$la = strtolower($a[$key]);
		$lb = strtolower($b[$key]);
		if ($la == $lb)
			return 0;
		elseif ($rev)
			return $la > $lb ? -1 : 1;
		else
			return $la < $lb ? -1 : 1;
	});

	return $tab;
}

function fof_todays_date() {
	$prefs = fof_prefs();
	$offset = isset($prefs['tzoffset']) ? $prefs['tzoffset'] : 0;

	return gmdate("Y/m/d", time() + ($offset * 60 * 60));
}

function fof_repair_drain_bamage() {
	if (ini_get('register_globals')) {
		foreach ($_REQUEST as $k => $v) {unset($GLOBALS[$k]);}
	}
}

/** Fetch the specified image, cache it, and return its cached name.
 */
function fof_cache_image_url($url) {
	$pie_file = new SimplePie_File($url);

	/* did something go wrong */
	if ($pie_file->success !== true) {
		fof_log('failed to retrieve image url:' . $url . ' error:' . $pie_file->error);
		return false;
	}

	/* did we get any response other than a success */
	if ($pie_file->status_code !== 200) {
		fof_log('failed to retrieve image url:' . $url . ' status_code:' . $pie_file->status_code);
		return false;
	}

	/* did we get nothing */
	if (empty($pie_file->body)) {
		fof_log('got empty content from url:' . $url);
		return false;
	}

	return fof_cache_image_data($url, $pie_file->headers['content-type'], $pie_file->body);
}

/** Store an image in our cache, returning the filename where the data now resides.
A nicer solution here would be to store the content-type bound to the data,
but there's no real server-agnostic way of doing that.
 */
function fof_cache_image_data($url, $content_type, $data) {
	/* First, verify that the resource is actually an image.. */

	if (empty($data) || empty($url)) {
		fof_log('will not cache emptiness');
		return false;
	}

	/* we don't care about the encoding, just the type */
	@list($media_type) = explode(';', $content_type, 2);
	@list($type, $subtype) = explode('/', $media_type, 2);
	if (strcasecmp($type, 'image') !== 0) {
		fof_log('did not get an image from url:' . $url . ' content-type:' . $media_type);
		return false;
	}

	/* Now determine what sort of image it is, so we can use the correct
		filename extension when we save it locally.
	*/
	/* strip fragments and queries off the url to reveal the path */
	@list($url) = explode('#', $url, 2);
	@list($url) = explode('?', $url, 2);
	/* and hope there is an extension to extract */
	$ext = pathinfo($url, PATHINFO_EXTENSION);

	/* FIXME:
		Ought to verify that the extension actually maps back onto an image
		type, so that we don't end up saving, say, '.php' images.
		I don't know of a lightweight nor portable means of accomplishing that,
		though, so let's just blacklist some simple ones.
	*/
	if (in_array(strtolower($ext), array('php', 'cgi', 'asp', 'aspx'))) {
		$ext = null;
	}

	if (empty($ext)) {
		/* no extension?  try to improvise one from the content-type */
		@list($ext) = explode('+', $subtype, 2);
		if (empty($ext)) {
			$ext = 'image';
		}
	}

	/* where to cache image data */
	$filename_parts = array(dirname(__FILE__), 'cache', (md5($data) . '.' . $ext));

	/* FIXME: detect and handle hugely-improbable collisions.. */

	if (file_put_contents(implode(DIRECTORY_SEPARATOR, $filename_parts), $data) === false) {
		fof_log('failed to write to ' . implode(DIRECTORY_SEPARATOR, $filename_parts));
		return false;
	}

	/* remove the absolute path before returning the filename we cached info */
	array_shift($filename_parts);

	fof_log('cached image ' . $url . ' as ' . implode(DIRECTORY_SEPARATOR, $filename_parts));

	return implode(DIRECTORY_SEPARATOR, $filename_parts);
}

/** Wrap FavIcon notices into fof_log.
 */
function fof_favicon_log($errno, $errstr) {
	if ($errno === E_USER_NOTICE) {
		fof_log($errstr, 'favicon');
		return true;
	}

	/* Anything else gets passed along. */
	return false;
}
/** Fetch the favicon for a url, cache it, and return its cached name.
 */
function fof_get_favicon($url) {
	include_once 'classes/favicon.php';

	/* gather up notices from favicon and reroute to fof log */
	set_error_handler('fof_favicon_log');
	$favicon = new FavIcon($url);
	$favicon = $favicon->getIcon();
	restore_error_handler();

	if (empty($favicon)) {
		fof_log('FavIcon resolution failed for ' . $url);
		return false;
	}

	return fof_cache_image_data($favicon['href'], $favicon['type'], $favicon['data']);
}

/* generate the contents of a tr element from a feed db row*/
function fof_render_feed_row($f, $error = false) {
	global $fof_asset;
	global $fof_prefs_obj;

	$out = '';

	/* provide some reasonable fallbacks when things aren't set */
	$link = $f['feed_link'] == '[no link]' ? $f['feed_url'] : $f['feed_link'];
	$title = empty($f['display_title']) ? $f['feed_title'] : $f['display_title'];
	if (empty($title) || $title == '[no title]') {
		$title = $link;
	}

	$title_json = htmlentities(json_encode($title), ENT_QUOTES);

	/* show desired feed icon, if any at all */
	if ($fof_prefs_obj->get('favicons')) {
		$image = empty($f['display_image']) ? $f['feed_image'] : $f['display_image'];
	}

	/* otherwise show default */
	if (empty($image)) {
		$image = $fof_asset['feed_icon'];
	}

	/* however, if a feed failed to update, show an alert */
	if (!empty($f['feed_cache_last_attempt_status'])) {
		$image = $fof_asset['alert_icon'];
	}

	if ($error) {
        $image_html = '<img class="feed-icon" src="' . $fof_asset['alert_icon'] . '" title="' . htmlentities($error, ENT_QUOTES) . '" />';
    } else {
	    $image_html = '<img class="feed-icon" src="' . htmlentities($image, ENT_QUOTES) . '"' . (empty($f['feed_cache_last_attempt_status']) ? '' : (' title="Last update attempt was not successful." alt="' . htmlentities($f['feed_cache_last_attempt_status'], ENT_QUOTES) . '"')) . '>';
    }

	$unread = empty($f['feed_unread']) ? 0 : $f['feed_unread'];
	$items = empty($f['feed_items']) ? 0 : $f['feed_items'];
	$starred = empty($f['feed_starred']) ? 0 : $f['feed_starred'];
	$tagged = empty($f['feed_tagged']) ? 0 : $f['feed_tagged'];
	$feed_view_unread_url = fof_url('.', array('feed' => $f['feed_id'], 'how' => 'paged'));
	$feed_view_all_url = fof_url('.', array('feed' => $f['feed_id'], 'how' => 'paged', 'what' => 'all'));
	$feed_unsubscribe_url = fof_url('delete.php', array('feed' => $f['feed_id']));
	$feed_update_url = fof_url('update.php', array('feed' => $f['feed_id']));

	switch ($fof_prefs_obj->get('sidebar_style')) {
		case 'simple': /* feed_url feed_unread feed_title */
			$out .= '	<td class="source"><a href="' . $f['feed_url'] . '" title="feed">' . $image_html . '</a></td>' . "\n";

			$out .= '	<td class="unread">' . (empty($unread) ? '' : $unread) . '</td>';

			$out .= '	<td class="title"><a href="' . ($unread ? $feed_view_unread_url : $feed_view_all_url) . '">' . $title . '</a></td>' . "\n";

			/* controls */
			$out .= '	<td class="controls hide-on-mobile"><a href="' . $feed_unsubscribe_url . '" title="delete" onclick="return sb_unsub_conf(' . $title_json . ');">[x]</a></td>' . "\n";
			break;

		case 'fancy': /* feed_url max_date feed_unread feed_title */
			$out .= '	<td class="source"><a href="' . $link . '" ' . ($fof_prefs_obj->get('item_target') ? ' target="_blank"' : '') . '>' . $image_html . '</a></td>' . "\n";

			$out .= '	<td class="latest"><span title="' . $f['lateststr'] . '" id="' . $f['feed_id'] . '-lateststr">' . $f['lateststrabbr'] . '</span></td>' . "\n";

			$out .= '	<td class="unread"><span class="nowrap" id="' . $f['feed_id'] . '-items">';
			if ($unread) {
				$out .= '<a class="unread" title="' . $unread . ' unread items" href="' . $feed_view_unread_url . '">' . $unread . '</a>';
			}

			$out .= '</span></td>' . "\n";

			$out .= '	<td class="title"><a href="' . ($unread ? $feed_view_unread_url : $feed_view_all_url) . '" title="' . ($unread ? ($unread . ' new of ') : '') . $items . ' total items">' . $title . '</a></td>' . "\n";

			/* controls */
			$out .= '	<td class="controls hide-on-mobile">';
			$out .= '<ul class="feedmenu">';
			$out .= '<li>';
			$out .= '<a href="#" title="feed controls">≡</a>';
			$out .= '<ul>';
			$out .= '<li><a href="#" title="last update ' . $f['agestr'] . '" onclick="return sb_update_feed(' . $f['feed_id'] . ');">Update Feed</a></li>';
			$out .= '<li><a href="#" title="mark all as read" onclick="return sb_readall_feed(' . $f['feed_id'] . ')">Mark all items as read</a></li>';
			$out .= '<li><a href="' . $feed_view_all_url . '" title="' . $items . ' total items">View all items</a></li>';
			$out .= '<li><a href="' . fof_url('feed-detail.php', array('feed' => $f['feed_id'])) . '">Feed details</a></li>';
			$out .= '<li><a href="' . $link . '" title="home page"' . ($fof_prefs_obj->get('item_target') ? ' target="_blank"' : '') . '>Feed Source Site</a></li>';
			$out .= '<li><a href="' . $feed_unsubscribe_url . '" title="unsubscribe" onclick="return sb_unsub_conf(' . $title_json . ');">Unsubscribe from feed</a></li>';
			$out .= '</ul>';
			$out .= '</li>';
			$out .= '</ul>';
			$out .= '</td>' . "\n";
			break;

		default: /* feed_age max_date feed_unread feed_url feed_title */
			$out .= '	<td class="updated hide-on-mobile"><span title="' . $f['agestr'] . '" id="' . $f['feed_id'] . '-agestr">' . $f['agestrabbr'] . '</span></td>' . "\n";

			$out .= '	<td class="latest"><span title="' . $f['lateststr'] . '" id="' . $f['feed_id'] . '-lateststr">' . $f['lateststrabbr'] . '</span></td>' . "\n";

			$out .= '	<td style="unread" class="nowrap" id="' . $f['feed_id'] . '-items">';
			if ($unread) {
				$out .= '<a class="unread" title="new items" href="' . $feed_view_unread_url . '">' . $unread . '</a>/';
			}

			$out .= '<a href="' . $feed_view_all_url . '" title="all items, ' . $starred . ' starred, ' . $tagged . ' tagged">' . $items . '</a>';
			$out .= '</td>' . "\n";

			$out .= '	<td class="source"><a href="' . $f['feed_url'] . '">' . $image_html . '</a>' . "\n";

			$out .= '	<td class="title"><a href="' . $link . '" title="home page"' . ($fof_prefs_obj->get('item_target') ? ' target="_blank"' : '') . '><b>' . $title . '</b></a></td>' . "\n";

			/* controls */
			$out .= '	<td class="controls hide-on-mobile"><span class="nowrap">';
			$out .= ' <a href="' . $feed_update_url . '" title="update">u</a>';
			$out .= ' <a href="#" title="mark all read" onclick="return sb_read_conf(' . $title_json . ', ' . $f['feed_id'] . ');">m</a>';
			$out .= ' <a href="' . $feed_unsubscribe_url . '" title="delete" onclick="return sb_unsub_conf(' . $title_json . ');">d</a>';
			$out .= '</span></td>' . "\n";
			break;
	}

	return $out;
}

class DOMDocumentWithErrContext extends DOMDocument {
	public $old_xml_err;
	public function __construct() {
		parent::__construct();
		$this->old_xml_err = libxml_use_internal_errors(true);
	}
}

// Helper function for plugins - extract a DOMdocument from a content string
function fof_content_to_dom($content) {
	$dom = new DOMDocumentWithErrContext();
	if (!$content) {
		return $dom;
	}

	$dom->loadHtml(mb_convert_encoding($content, 'HTML-ENTITIES', "UTF-8"));

	return $dom;
}

// Helper function for plugins - convert a DOMdocument back to a content string
function fof_dom_to_content($dom) {
	foreach (libxml_get_errors() as $error) {
		/* just ignore warnings */
		if ($error->level === LIBXML_ERR_WARNING) {
			continue;
		}
		fof_log(__FUNCTION__ . ': ' . $error->message);
	}
	libxml_clear_errors();
	libxml_use_internal_errors($dom->old_xml_err);

	return preg_replace('~<(?:!DOCTYPE|/?(?:html|body))[^>]*>\s*~i', '', $dom->saveHTML());
}

// Helper function to get the base URL of the current page
function fof_base_url() {
	// once again, why the heck isn't this a builtin function...
	$pageURL = 'http';
	if ($_SERVER['HTTPS'] == 'on') {
		$pageURL .= 's';
		$defaultPort = '443';
	} else {
		$defaultPort = '80';
	}
	$pageURL .= '://' . $_SERVER['SERVER_NAME'];
	if ($_SERVER["SERVER_PORT"] != $defaultPort) {
		$pageURL .= ':' . $_SERVER["SERVER_PORT"];
	}
	$pageURL .= $_SERVER['SCRIPT_NAME'];
	return $pageURL;
}
?>