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

	File: qa-include/qa-db-hotness.php
	Description: Functions for dealing with question hotness in the database


	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;
	}


	function qa_db_hotness_update($firstpostid, $lastpostid=null, $viewincrement=false)
/*
	Recalculate the hotness in the database for posts $firstpostid to $lastpostid (if specified)
	If $viewincrement is true, also increment the views counter for the post (if different IP from last view),
	and include that in the hotness calculation
*/
	{
		if (qa_to_override(__FUNCTION__)) { $args=func_get_args(); return qa_call_override(__FUNCTION__, $args); }

		if (qa_should_update_counts()) {
			if (!isset($lastpostid))
				$lastpostid=$firstpostid;

			$query=	"UPDATE ^posts AS x, (SELECT parents.postid, parents.created AS qcreated, COALESCE(MAX(children.created), parents.created) as acreated, COUNT(children.postid) AS acount, parents.netvotes, parents.views FROM ^posts AS parents LEFT JOIN ^posts AS children ON parents.postid=children.parentid AND children.type='A' WHERE parents.postid>=# AND parents.postid<=# AND LEFT(parents.type, 1)='Q' GROUP BY postid) AS a SET x.hotness=(".
				'((TO_DAYS(a.qcreated)-734138)*86400.0+TIME_TO_SEC(a.qcreated))*# + '. // zero-point is Jan 1, 2010
				'((TO_DAYS(a.acreated)-734138)*86400.0+TIME_TO_SEC(a.acreated))*# + '.
				'(a.acount+0.0)*# + '.
				'(a.netvotes+0.0)*# + '.
				'(a.views+0.0+#)*#'.
			')'.($viewincrement ? ', x.views=x.views+1, x.lastviewip=$' : '').
			' WHERE x.postid=a.postid'.($viewincrement ? ' AND (x.lastviewip IS NULL OR x.lastviewip!=$)' : '');

			//	Additional multiples based on empirical analysis of activity on Q2A meta site to give approx equal influence for all factors

			$arguments=array(
				$firstpostid,
				$lastpostid,
				qa_opt('hot_weight_q_age'),
				qa_opt('hot_weight_a_age'),
				qa_opt('hot_weight_answers')*160000,
				qa_opt('hot_weight_votes')*160000,
				$viewincrement ? 1 : 0,
				qa_opt('hot_weight_views')*4000,
			);

			if ($viewincrement) {
				$ipbin = @inet_pton(qa_remote_ip_address());
				array_push($arguments, $ipbin, $ipbin);
			}

			 qa_db_query_raw(qa_db_apply_sub($query, $arguments));
		}
	}


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