<?php     
/*
Plugin Name: Ambient Information
Plugin URI: http://0blog.com/ambinfo-wp-plugin.php
Description: Adds ability to embed ambient information into web pages.
Version: 0.02 alpha
Author: Toivo Lainevool
Author URI: http://0blog.com/
*/ 
/**
 * ambinfo.php
 * This plugin is used to add ambient information into Wordpress.
 * Currently the only type of information available is changing color based
 * on the age of the post.
 
 * To use this plugin, first change the $ambinfo_stale_time, $ambinfo_fresh_color,
 *  and $ambinfo_stale_color to your desired setting.
 * Then all you have to do is call ambinfo_echo_age_color() or ambinfo_get_age_color()
 *  to retrive a color based on the age of a post.
 *
 * For questions, comment, support and encouraging words use: ambinfo-wp-plugin@0blog.com
 *
 * This work is licensed under the Creative Commons Attribution License. To view a copy 
 * of this license, visit http://creativecommons.org/licenses/by/2.0/ or send a letter 
 * to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.   
 */


//Change this to reflect what you want to consider a 'stale' post.
$ambinfo_stale_time = 60 * 60 * 24 * 4;//four days

//This is the color returned when things are freshest
$ambinfo_fresh_color = '#90a090';

//This is the color returned when $ambinfo_stale_time is reached
$ambinfo_stale_color = '#000000';


/**
  * Use this function to echo the aged color of a post. 
  *
  * @param post_id the id of the post to get the aged color for,
  *   if it is blank, the aged color for the newest post will be used
  */
function ambinfo_echo_age_color($post_id = '') {
	print ambinfo_get_age_color($post_id);
}

/**
  * Use this function to get the aged color of a post. 
  *
  * @param post_id the id of the post to get the aged color for,
  *   if it is blank, the aged color for the newest post will be used
  */
function ambinfo_get_age_color($post_id = '') {
	global $ambinfo_stale_time, $ambinfo_fresh_color, $ambinfo_stale_color;
	$newest = _ambinfo_get_newest_post_time($post_id);
	$age_in_millis = (time() - $newest);
	if ($age_in_millis >= $ambinfo_stale_time) {
		$color = $ambinfo_stale_color;
	} else {
		if ($age_in_millis == 0) {
			$div = 1;
		} else {
			$div = $ambinfo_stale_time / ($ambinfo_stale_time - $age_in_millis);
		}
		$red = _get_aged_color_part('red', $div);
		$green = _get_aged_color_part('green', $div);
		$blue = _get_aged_color_part('blue', $div);
		
		$color = strtoupper("#"._ambinfo_to_hex($red)._ambinfo_to_hex($green)._ambinfo_to_hex($blue));
	}
	return $color;
}

/**
  * private function, get a single value for an rgb part
  */
function _get_aged_color_part( $color_part, $div ) {
	global $ambinfo_fresh_color, $ambinfo_stale_color;
	$fresh = _ambinfo_get_color_part( $color_part, $ambinfo_fresh_color );
	$stale = _ambinfo_get_color_part( $color_part, $ambinfo_stale_color );
	return  abs($fresh - (abs($fresh - $stale) - (abs($fresh - $stale) / $div)));
}	
/**
  *Take in a decimal number and return a 2 digit hex number.
  */
function _ambinfo_to_hex( $color ) {
	$result = dechex($color);
	if( strlen($result) == 1) {
		$result = "0" . $result;
	}
	return $result;
}

/** 
  * Gets the RGB part of the given color.  Format can be '#rrggbb', 'rrggbb', '#rgb', 'rgb'
  */
function _ambinfo_get_color_part($rgb, $color) {
	if( preg_match("/#.*/", $color)) {
		$color = substr( $color, 1 );
	}
	if( strlen($color) == 3 ) {
		$color = preg_replace( "/(.)(.)(.)/", "$1$1$2$2$3$3", $color);
	}
	switch ($rgb) {
		case 'red':
		    $hex = substr($color, 0, 2);
		    break;
		case 'green':
		    $hex = substr($color, 2, 2);
		    break;
		case 'blue':
		    $hex = substr($color, 4, 2);
		    break;
		default:
		    $hex = "ff";
		    break;
	}
	return hexdec($hex);
}

/**
  * Get the post id for the post with the atest time.
  */
function _ambinfo_get_newest_post_time($post_id) {
	global $wpdb, $tableposts;
	if( $post_id == "") {
		return $wpdb->get_var("SELECT UNIX_TIMESTAMP(post_modified) FROM $tableposts ORDER BY post_date DESC LIMIT 1");
	} else {
		return $wpdb->get_var("SELECT UNIX_TIMESTAMP(post_modified) FROM $tableposts WHERE ID = $post_id");
	}
}


?>