<?php
/*
	Question2Answer by Gideon Greenspan and contributors
	http://www.question2answer.org/

	File: qa-include/qa-feed.php
	Description: Handles all requests to RSS feeds, first checking if they should be available


	This program 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 2
	of the License, or (at your option) any later version.

	This program 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.

	More about this license: http://www.question2answer.org/license.php
*/

	if (!defined('QA_VERSION')) { // don't allow this page to be requested directly from browser
		header('Location: ../');
		exit;
	}

	@ini_set('display_errors', 0); // we don't want to show PHP errors to RSS readers

	qa_report_process_stage('init_feed');

	require_once QA_INCLUDE_DIR.'app/options.php';


//	Functions used within this file

	function qa_feed_db_fail_handler($type, $errno=null, $error=null, $query=null)
/*
	Database failure handler function for RSS feeds - outputs HTTP and text errors
*/

	{
		header('HTTP/1.1 500 Internal Server Error');
		echo qa_lang_html('main/general_error');
		qa_exit('error');
	}


	function qa_feed_not_found()
/*
	Common function called when a non-existent feed is requested - outputs HTTP and text errors
*/
	{
		header('HTTP/1.0 404 Not Found');
		echo qa_lang_html('misc/feed_not_found');
		qa_exit();
	}


	function qa_feed_load_ifcategory($categoryslugs, $allkey, $catkey, &$title,
		$questionselectspec1=null, $questionselectspec2=null, $questionselectspec3=null, $questionselectspec4=null)
/*
	Common function to load appropriate set of questions for requested feed, check category exists, and set up page title
*/
	{
		$countslugs=@count($categoryslugs);

		list($questions1, $questions2, $questions3, $questions4, $categories, $categoryid)=qa_db_select_with_pending(
			$questionselectspec1,
			$questionselectspec2,
			$questionselectspec3,
			$questionselectspec4,
			$countslugs ? qa_db_category_nav_selectspec($categoryslugs, false) : null,
			$countslugs ? qa_db_slugs_to_category_id_selectspec($categoryslugs) : null
		);

		if ($countslugs && !isset($categoryid))
			qa_feed_not_found();

		if (isset($allkey))
			$title=(isset($categoryid) && isset($catkey)) ? qa_lang_sub($catkey, $categories[$categoryid]['title']) : qa_lang($allkey);

		return array_merge(
			is_array($questions1) ? $questions1 : array(),
			is_array($questions2) ? $questions2 : array(),
			is_array($questions3) ? $questions3 : array(),
			is_array($questions4) ? $questions4 : array()
		);
	}


//	Connect to database and get the type of feed and category requested (in some cases these are overridden later)

	qa_db_connect('qa_feed_db_fail_handler');
	qa_preload_options();

	$requestlower=strtolower(qa_request());
	$foursuffix=substr($requestlower, -4);

	if ( ($foursuffix=='.rss') || ($foursuffix=='.xml') )
		$requestlower=substr($requestlower, 0, -4);

	$requestlowerparts=explode('/', $requestlower);

	$feedtype=@$requestlowerparts[1];
	$feedparams=array_slice($requestlowerparts, 2);


//	Choose which option needs to be checked to determine if this feed can be requested, and stop if no matches

	$feedoption=null;
	$categoryslugs=$feedparams;

	switch ($feedtype) {
		case 'questions':
			$feedoption='feed_for_questions';
			break;

		case 'hot':
			$feedoption='feed_for_hot';
			if (!QA_ALLOW_UNINDEXED_QUERIES)
				$categoryslugs=null;
			break;

		case 'unanswered':
			$feedoption='feed_for_unanswered';
			if (!QA_ALLOW_UNINDEXED_QUERIES)
				$categoryslugs=null;
			break;

		case 'answers':
		case 'comments':
		case 'activity':
			$feedoption='feed_for_activity';
			break;

		case 'qa':
			$feedoption='feed_for_qa';
			break;

		case 'tag':
			if (strlen(@$feedparams[0])) {
				$feedoption='feed_for_tag_qs';
				$categoryslugs=null;
			}
			break;

		case 'search':
			if (strlen(@$feedparams[0])) {
				$feedoption='feed_for_search';
				$categoryslugs=null;
			}
			break;
	}

	$countslugs=@count($categoryslugs);

	if (!isset($feedoption))
		qa_feed_not_found();


//	Check that all the appropriate options are in place to allow this feed to be retrieved

	if (!(
		(qa_opt($feedoption)) &&
		($countslugs ? (qa_using_categories() && qa_opt('feed_per_category')) : true)
	))
		qa_feed_not_found();


//	Retrieve the appropriate questions and other information for this feed

	require_once QA_INCLUDE_DIR.'db/selects.php';

	$sitetitle=qa_opt('site_title');
	$siteurl=qa_opt('site_url');
	$full=qa_opt('feed_full_text');
	$count=qa_opt('feed_number_items');
	$showurllinks=qa_opt('show_url_links');

	$linkrequest=$feedtype.($countslugs ? ('/'.implode('/', $categoryslugs)) : '');
	$linkparams=null;

	switch ($feedtype) {
		case 'questions':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/recent_qs_title', 'main/recent_qs_in_x', $title,
				qa_db_qs_selectspec(null, 'created', 0, $categoryslugs, null, false, $full, $count)
			);
			break;

		case 'hot':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/hot_qs_title', 'main/hot_qs_in_x', $title,
				qa_db_qs_selectspec(null, 'hotness', 0, $categoryslugs, null, false, $full, $count)
			);
			break;

		case 'unanswered':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/unanswered_qs_title', 'main/unanswered_qs_in_x', $title,
				qa_db_unanswered_qs_selectspec(null, null, 0, $categoryslugs, false, $full, $count)
			);
			break;

		case 'answers':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/recent_as_title', 'main/recent_as_in_x', $title,
				qa_db_recent_a_qs_selectspec(null, 0, $categoryslugs, null, false, $full, $count)
			);
			break;

		case 'comments':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/recent_cs_title', 'main/recent_cs_in_x', $title,
				qa_db_recent_c_qs_selectspec(null, 0, $categoryslugs, null, false, $full, $count)
			);
			break;

		case 'qa':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/recent_qs_as_title', 'main/recent_qs_as_in_x', $title,
				qa_db_qs_selectspec(null, 'created', 0, $categoryslugs, null, false, $full, $count),
				qa_db_recent_a_qs_selectspec(null, 0, $categoryslugs, null, false, $full, $count)
			);
			break;

		case 'activity':
			$questions=qa_feed_load_ifcategory($categoryslugs, 'main/recent_activity_title', 'main/recent_activity_in_x', $title,
				qa_db_qs_selectspec(null, 'created', 0, $categoryslugs, null, false, $full, $count),
				qa_db_recent_a_qs_selectspec(null, 0, $categoryslugs, null, false, $full, $count),
				qa_db_recent_c_qs_selectspec(null, 0, $categoryslugs, null, false, $full, $count),
				qa_db_recent_edit_qs_selectspec(null, 0, $categoryslugs, null, true, $full, $count)
			);
			break;

		case 'tag':
			$tag=$feedparams[0];

			$questions=qa_feed_load_ifcategory(null, null, null, $title,
				qa_db_tag_recent_qs_selectspec(null, $tag, 0, $full, $count)
			);

			$title=qa_lang_sub('main/questions_tagged_x', $tag);
			$linkrequest='tag/'.$tag;
			break;

		case 'search':
			require_once QA_INCLUDE_DIR.'app/search.php';

			$query=$feedparams[0];

			$results=qa_get_search_results($query, 0, $count, null, true, $full);

			$title=qa_lang_sub('main/results_for_x', $query);
			$linkrequest='search';
			$linkparams=array('q' => $query);

			$questions=array();

			foreach ($results as $result) {
				$setarray=array(
					'title' => $result['title'],
					'url' => $result['url'],
				);

				if (isset($result['question']))
					$questions[]=array_merge($result['question'], $setarray);
				elseif (isset($result['url']))
					$questions[]=$setarray;
			}
			break;
	}


//	Remove duplicate questions (perhaps referenced in an answer and a comment) and cut down to size

	require_once QA_INCLUDE_DIR.'app/format.php';
	require_once QA_INCLUDE_DIR.'app/updates.php';
	require_once QA_INCLUDE_DIR.'util/string.php';

	if ( ($feedtype!='search') && ($feedtype!='hot') ) // leave search results and hot questions sorted by relevance
		$questions=qa_any_sort_and_dedupe($questions);

	$questions=array_slice($questions, 0, $count);
	$blockwordspreg=qa_get_block_words_preg();


//	Prepare the XML output

	$lines=array();

	$lines[]='<?xml version="1.0" encoding="utf-8"?>';
	$lines[]='<rss version="2.0">';
	$lines[]='<channel>';

	$lines[]='<title>'.qa_xml($sitetitle.' - '.$title).'</title>';
	$lines[]='<link>'.qa_xml(qa_path($linkrequest, $linkparams, $siteurl)).'</link>';
	$lines[]='<description>Powered by Question2Answer</description>';

	foreach ($questions as $question) {

	//	Determine whether this is a question, answer or comment, and act accordingly

		$options=array('blockwordspreg' => @$blockwordspreg, 'showurllinks' => $showurllinks);

		$time=null;
		$htmlcontent=null;

		if (isset($question['opostid'])) {
			$time=$question['otime'];

			if ($full)
				$htmlcontent=qa_viewer_html($question['ocontent'], $question['oformat'], $options);

		} elseif (isset($question['postid'])) {
			$time=$question['created'];

			if ($full)
				$htmlcontent=qa_viewer_html($question['content'], $question['format'], $options);
		}

		if ($feedtype=='search') {
			$titleprefix='';
			$urlxml=qa_xml($question['url']);

		} else {
			switch (@$question['obasetype'].'-'.@$question['oupdatetype']) {
				case 'Q-':
				case '-':
					$langstring=null;
					break;

				case 'Q-'.QA_UPDATE_VISIBLE:
					$langstring=$question['hidden'] ? 'misc/feed_hidden_prefix' : 'misc/feed_reshown_prefix';
					break;

				case 'Q-'.QA_UPDATE_CLOSED:
					$langstring=isset($question['closedbyid']) ? 'misc/feed_closed_prefix' : 'misc/feed_reopened_prefix';
					break;

				case 'Q-'.QA_UPDATE_TAGS:
					$langstring='misc/feed_retagged_prefix';
					break;

				case 'Q-'.QA_UPDATE_CATEGORY:
					$langstring='misc/feed_recategorized_prefix';
					break;

				case 'A-':
					$langstring='misc/feed_a_prefix';
					break;

				case 'A-'.QA_UPDATE_SELECTED:
					$langstring='misc/feed_a_selected_prefix';
					break;

				case 'A-'.QA_UPDATE_VISIBLE:
					$langstring=$question['ohidden'] ? 'misc/feed_hidden_prefix' : 'misc/feed_a_reshown_prefix';
					break;

				case 'A-'.QA_UPDATE_CONTENT:
					$langstring='misc/feed_a_edited_prefix';
					break;

				case 'C-':
					$langstring='misc/feed_c_prefix';
					break;

				case 'C-'.QA_UPDATE_TYPE:
					$langstring='misc/feed_c_moved_prefix';
					break;

				case 'C-'.QA_UPDATE_VISIBLE:
					$langstring=$question['ohidden'] ? 'misc/feed_hidden_prefix' : 'misc/feed_c_reshown_prefix';
					break;

				case 'C-'.QA_UPDATE_CONTENT:
					$langstring='misc/feed_c_edited_prefix';
					break;

				case 'Q-'.QA_UPDATE_CONTENT:
				default:
					$langstring='misc/feed_edited_prefix';
					break;

			}

			$titleprefix=isset($langstring) ? qa_lang($langstring) : '';

			$urlxml=qa_xml(qa_q_path($question['postid'], $question['title'], true, @$question['obasetype'], @$question['opostid']));
		}

		if (isset($blockwordspreg))
			$question['title']=qa_block_words_replace($question['title'], $blockwordspreg);

	//	Build the inner XML structure for each item

		$lines[]='<item>';
		$lines[]='<title>'.qa_xml($titleprefix.$question['title']).'</title>';
		$lines[]='<link>'.$urlxml.'</link>';

		if (isset($htmlcontent))
			$lines[]='<description>'.qa_xml($htmlcontent).'</description>';

		if (isset($question['categoryname']))
			$lines[]='<category>'.qa_xml($question['categoryname']).'</category>';

		$lines[]='<guid isPermaLink="true">'.$urlxml.'</guid>';

		if (isset($time))
			$lines[]='<pubDate>'.qa_xml(gmdate('r', $time)).'</pubDate>';

		$lines[]='</item>';
	}

	$lines[]='</channel>';
	$lines[]='</rss>';


//	Disconnect here, once all output is ready to go

	qa_db_disconnect();


//	Output the XML - and we're done!

	header('Content-type: text/xml; charset=utf-8');
	echo implode("\n", $lines);


/*
	Omit PHP closing tag to help avoid accidental output
*/