<?php
/*
Plugin Name: Fun with Evolving posts
Plugin URI: [insert the plugin uri here]
Description: Provides a way to order posts according to visitor selection
Author: Andrew Rickmann
Version: 0.1
Author URI: http://www.wp-fun.co.uk
Generated At: www.funwithwizards.com;
*/
class fun_with_evo_posts
{

	private $boost_for_most_recent = 10;

	private $listed_posts = array();

	/**
	* Constructor - PHP5 only
	*/
	public function __construct(){
		add_filter('query_vars', array($this,'queryvars') );
		add_filter('post_link', array($this,'add_evo_click_vars'), 10 , 2 );
		add_action('template_redirect', array($this,'calc_evo_click'));
	}

	/**
	* Adds new variables to the query
	*/
	function queryvars( $qvars ){

		$qvars[] = 'evp';
		return $qvars;
	}


	/**
	 * Figure out if an evo click has been requested
	 */
	function calc_evo_click(){
		global $wp_query;
		//by this points we should have a post selected
		global $post;
		
		$evp = $wp_query->get('evp');
		
		if ( is_numeric($evp) && $evp == $post->ID ){
			$evp_m = (int) get_post_meta($evp, 'evo_click', true);
			$evp_m++;
			if (!update_post_meta($evp, 'evo_click', $evp_m)){
				add_post_meta($evp, 'evo_click', $evp_m, true);
			}
		}
	}

	/**
	 * Add the variable to identify the clicked link
	 * Note: assumes using pretty permalinks
	 * @param String $link the permalink
	 * @param Object $post post item
	 * @return String altered permalink 
	 */
	function add_evo_click_vars($link , $post){
		$link .= '?evp='.$post->ID;
		return $link;
	}


	function return_posts(){




		$post_num = get_option('posts_per_page');

		//get double the number of posts asked for
		//get them in a random order
		$post_limit = $post_num * 2;
		$the_posts = get_posts('numberposts='.$post_limit.'&orderby=date');

		//loop through the posts to get their weightings
		$weight_array = array();
		$id_array = array();

		//get the ID and thr weighting for each post
		$pcount = 1;
		foreach( $the_posts as $post ){
			 //get the number of clicks
			 $weight = (int) get_post_meta($post->ID, 'evo_click', true);
			 if ($pcount==1){
				 $weight = $weight + $this->boost_for_most_recent;
			 }
			 //reduce according to date order, to give date precedence
			 $diminish_by_date_order = 0.02 * $pcount;
			 $weight = $weight * $diminish_by_date_order;
			 //add weight to the array
			 $weight_array[$post->ID] = $weight;
			 $pcount++;
		}

//if no clicks yet there is no point in randomising
		if (array_sum($weight_array) > 0 ){
			//create a weighted array of values
			$weight_array2 = array();
			foreach($weight_array as $key => $val) {
			  $percent_of_total = round($val / array_sum($weight_array) * 100);
			  for ($x = 0; $x < $percent_of_total; $x++){
				$weight_array2[] = $key;
				}
			}

			//select 1000 random items from the weighted array
			//count each
			//return an array of IDs and weights
			$weighted_sort_order_array = array();
			for ($x = 0; $x < $post_num; $x++){
			  $rand_key = rand(0, count($weight_array2)-1);
			  $weighted_sort_order_array[$weight_array2[$rand_key]]++;
			}

			$this->weighted_order_array  = $weighted_sort_order_array;

		} else {
			$this->weighted_order_array  = $weight_array;
		}
		
		
		

		usort($the_posts,array($this,'sort_posts'));
		
		//remove half the posts
		array_splice($the_posts, $post_num);
		
		//add the remainder to the post list
		foreach($the_posts as $post){
			$this->listed_posts[] = $post->ID;
		}
		
		//return what is left
		return $the_posts;

	}

	function sort_posts($a,$b){

		$a_val = $this->weighted_order_array[$a->ID];
		$b_val = $this->weighted_order_array[$b->ID];

		if ($a_vale == $b_val) {
			return 0;
		}
		return ($a_val > $b_val) ? -1 : 1;
	}

}
$fun_with_evo_posts = new fun_with_evo_posts();
?>