<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle 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.
//
// Moodle 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 Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * A block which displays Remote feeds
 *
 * @package   block_rss_client
 * @copyright  Daryl Hawes
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL
 */

 class block_rss_client extends block_base {
    /** The maximum time in seconds that cron will wait between attempts to retry failing RSS feeds. */
    const CLIENT_MAX_SKIPTIME = 43200; // 60 * 60 * 12 seconds.

    function init() {
        $this->title = get_string('pluginname', 'block_rss_client');
    }

    function applicable_formats() {
        return array('all' => true, 'tag' => false);   // Needs work to make it work on tags MDL-11960
    }

    function specialization() {
        // After the block has been loaded we customize the block's title display
        if (!empty($this->config) && !empty($this->config->title)) {
            // There is a customized block title, display it
            $this->title = $this->config->title;
        } else {
            // No customized block title, use localized remote news feed string
            $this->title = get_string('remotenewsfeed', 'block_rss_client');
        }
    }

    function get_content() {
        global $CFG, $DB;

        if ($this->content !== NULL) {
            return $this->content;
        }

        // initalise block content object
        $this->content = new stdClass;
        $this->content->text   = '';
        $this->content->footer = '';

        if (empty($this->instance)) {
            return $this->content;
        }

        if (!isset($this->config)) {
            // The block has yet to be configured - just display configure message in
            // the block if user has permission to configure it

            if (has_capability('block/rss_client:manageanyfeeds', $this->context)) {
                $this->content->text = get_string('feedsconfigurenewinstance2', 'block_rss_client');
            }

            return $this->content;
        }

        // How many feed items should we display?
        $maxentries = 5;
        if ( !empty($this->config->shownumentries) ) {
            $maxentries = intval($this->config->shownumentries);
        }elseif( isset($CFG->block_rss_client_num_entries) ) {
            $maxentries = intval($CFG->block_rss_client_num_entries);
        }


        /* ---------------------------------
         * Begin Normal Display of Block Content
         * --------------------------------- */

        $output = '';


        if (!empty($this->config->rssid)) {
            list($rss_ids_sql, $params) = $DB->get_in_or_equal($this->config->rssid);

            $rss_feeds = $DB->get_records_select('block_rss_client', "id $rss_ids_sql", $params);

            $showtitle = false;
            if (count($rss_feeds) > 1) {
                // when many feeds show the title for each feed
                $showtitle = true;
            }

            foreach($rss_feeds as $feed){
                $output.= $this->get_feed_html($feed, $maxentries, $showtitle);
            }
        }

        $this->content->text = $output;

        return $this->content;
    }


    function instance_allow_multiple() {
        return true;
    }

    function has_config() {
        return true;
    }

    function instance_allow_config() {
        return true;
    }

    /**
     * Returns the html of a feed to be displaed in the block
     *
     * @param mixed feedrecord The feed record from the database
     * @param int maxentries The maximum number of entries to be displayed
     * @param boolean showtitle Should the feed title be displayed in html
     * @return string html representing the rss feed content
     */
    function get_feed_html($feedrecord, $maxentries, $showtitle){
        global $CFG;
        require_once($CFG->libdir.'/simplepie/moodle_simplepie.php');

        $feed = new moodle_simplepie($feedrecord->url);

        if(isset($CFG->block_rss_client_timeout)){
            $feed->set_cache_duration($CFG->block_rss_client_timeout*60);
        }

        if ($CFG->debugdeveloper && $feed->error()) {
            return '<p>'. $feedrecord->url .' Failed with code: '.$feed->error().'</p>';
        }

        $r = ''; // return string

        if($this->config->block_rss_client_show_channel_image){
            if($image = $feed->get_image_url()){
                $imagetitle = s($feed->get_image_title());
                $imagelink  = $feed->get_image_link();

                $r.='<div class="image" title="'.$imagetitle.'">'."\n";
                if($imagelink){
                    $r.='<a href="'.$imagelink.'">';
                }
                $r.='<img src="'.$image.'" alt="'.$imagetitle.'" />'."\n";
                if($imagelink){
                    $r.='</a>';
                }
                $r.= '</div>';
            }
        }

        if(empty($feedrecord->preferredtitle)){
            $feedtitle = $this->format_title($feed->get_title());
        }else{
            $feedtitle = $this->format_title($feedrecord->preferredtitle);
        }

        if($showtitle){
            $r.='<div class="title">'.$feedtitle.'</div>';
        }


        $r.='<ul class="list no-overflow">'."\n";

        $feeditems = $feed->get_items(0, $maxentries);
        foreach($feeditems as $item){
            $r.= $this->get_item_html($item);
        }

        $r.='</ul>';


        if ($this->config->block_rss_client_show_channel_link) {

            $channellink = $feed->get_link();

            if (!empty($channellink)){
                //NOTE: this means the 'last feed' display wins the block title - but
                //this is exiting behaviour..
                $this->content->footer = '<a href="'.htmlspecialchars(clean_param($channellink,PARAM_URL)).'">'. get_string('clientchannellink', 'block_rss_client') .'</a>';
            }
        }

        if (empty($this->config->title)){
            //NOTE: this means the 'last feed' displayed wins the block title - but
            //this is exiting behaviour..
            $this->title = strip_tags($feedtitle);
        }

        return $r;
    }


    /**
     * Returns the html list item of a feed item
     *
     * @param mixed item simplepie_item representing the feed item
     * @return string html li representing the rss feed item
     */
    function get_item_html($item){

        $link        = $item->get_link();
        $title       = $item->get_title();
        $description = $item->get_description();


        if(empty($title)){
            // no title present, use portion of description
            $title = core_text::substr(strip_tags($description), 0, 20) . '...';
        }else{
            $title = break_up_long_words($title, 30);
        }

        if(empty($link)){
            $link = $item->get_id();
        } else {
            try {
                // URLs in our RSS cache will be escaped (correctly as theyre store in XML)
                // html_writer::link() will re-escape them. To prevent double escaping unescape here.
                // This can by done using htmlspecialchars_decode() but moodle_url also has that effect.
                $link = new moodle_url($link);
            } catch (moodle_exception $e) {
                // Catching the exception to prevent the whole site to crash in case of malformed RSS feed
                $link = '';
            }
        }

        $r = html_writer::start_tag('li');
            $r.= html_writer::start_tag('div',array('class'=>'link'));
                $r.= html_writer::link($link, s($title), array('onclick'=>'this.target="_blank"'));
            $r.= html_writer::end_tag('div');

            if($this->config->display_description && !empty($description)){

                $formatoptions = new stdClass();
                $formatoptions->para = false;

                $r.= html_writer::start_tag('div',array('class'=>'description'));
                    $description = format_text($description, FORMAT_HTML, $formatoptions, $this->page->course->id);
                    $description = break_up_long_words($description, 30);
                    $r.= $description;
                $r.= html_writer::end_tag('div');
            }
        $r.= html_writer::end_tag('li');

        return $r;
    }

    /**
     * Strips a large title to size and adds ... if title too long
     *
     * @param string title to shorten
     * @param int max character length of title
     * @return string title s() quoted and shortened if necessary
     */
    function format_title($title,$max=64) {

        if (core_text::strlen($title) <= $max) {
            return s($title);
        } else {
            return s(core_text::substr($title,0,$max-3).'...');
        }
    }

    /**
     * cron - goes through all the feeds. If the feed has a skipuntil value
     * that is less than the current time cron will attempt to retrieve it
     * with the cache duration set to 0 in order to force the retrieval of
     * the item and refresh the cache.
     *
     * If a feed fails then the skipuntil time of that feed is set to be
     * later than the next expected cron time. The amount of time will
     * increase each time the fetch fails until the maximum is reached.
     *
     * If a feed that has been failing is successfully retrieved it will
     * go back to being handled as though it had never failed.
     *
     * CRON should therefor process requests for permanently broken RSS
     * feeds infrequently, and temporarily unavailable feeds will be tried
     * less often until they become available again.
     *
     * @return boolean Always returns true
     */
    function cron() {
        global $CFG, $DB;
        require_once($CFG->libdir.'/simplepie/moodle_simplepie.php');

        // Get the legacy cron time, strangely the cron property of block_base
        // does not seem to get set. This means we must retrive it here.
        $this->cron = $DB->get_field('block', 'cron', array('name' => 'rss_client'));

        // We are going to measure execution times
        $starttime =  microtime();
        $starttimesec = time();

        // Fetch all site feeds.
        $rs = $DB->get_recordset('block_rss_client');
        $counter = 0;
        mtrace('');
        foreach ($rs as $rec) {
            mtrace('    ' . $rec->url . ' ', '');

            // Skip feed if it failed recently.
            if ($starttimesec < $rec->skipuntil) {
                mtrace('skipping until ' . userdate($rec->skipuntil));
                continue;
            }

            // Fetch the rss feed, using standard simplepie caching
            // so feeds will be renewed only if cache has expired
            core_php_time_limit::raise(60);

            $feed =  new moodle_simplepie();
            // set timeout for longer than normal to be agressive at
            // fetching feeds if possible..
            $feed->set_timeout(40);
            $feed->set_cache_duration(0);
            $feed->set_feed_url($rec->url);
            $feed->init();

            if ($feed->error()) {
                // Skip this feed (for an ever-increasing time if it keeps failing).
                $rec->skiptime = $this->calculate_skiptime($rec->skiptime);
                $rec->skipuntil = time() + $rec->skiptime;
                $DB->update_record('block_rss_client', $rec);
                mtrace("Error: could not load/find the RSS feed - skipping for {$rec->skiptime} seconds.");
            } else {
                mtrace ('ok');
                // It worked this time, so reset the skiptime.
                if ($rec->skiptime > 0) {
                    $rec->skiptime = 0;
                    $rec->skipuntil = 0;
                    $DB->update_record('block_rss_client', $rec);
                }
                // Only increase the counter when a feed is sucesfully refreshed.
                $counter ++;
            }
        }
        $rs->close();

        // Show times
        mtrace($counter . ' feeds refreshed (took ' . microtime_diff($starttime, microtime()) . ' seconds)');

        return true;
    }

    /**
     * Calculates a new skip time for a record based on the current skip time.
     *
     * @param int $currentskip The curreent skip time of a record.
     * @return int A new skip time that should be set.
     */
    protected function calculate_skiptime($currentskip) {
        // The default time to skiptime.
        $newskiptime = $this->cron * 1.1;
        if ($currentskip > 0) {
            // Double the last time.
            $newskiptime = $currentskip * 2;
        }
        if ($newskiptime > self::CLIENT_MAX_SKIPTIME) {
            // Do not allow the skip time to increase indefinatly.
            $newskiptime = self::CLIENT_MAX_SKIPTIME;
        }
        return $newskiptime;
    }
}