From 5f4c2a7e1af0a4c51474b26fa045b6330997e38f Mon Sep 17 00:00:00 2001
From: icewing <icewing@36083f99-b078-4883-b0ff-0f9b5a30f544>
Date: Wed, 21 May 2008 14:55:44 +0000
Subject: Marcus Povey <marcus@dushka.co.uk> * Added tag cloud functions

git-svn-id: https://code.elgg.org/elgg/trunk@669 36083f99-b078-4883-b0ff-0f9b5a30f544
---
 engine/lib/tags.php | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 engine/lib/tags.php

diff --git a/engine/lib/tags.php b/engine/lib/tags.php
new file mode 100644
index 000000000..9b675c018
--- /dev/null
+++ b/engine/lib/tags.php
@@ -0,0 +1,68 @@
+<?php
+	/**
+	 * Elgg tags
+	 * Functions for managing tags and tag clouds.
+	 * 
+	 * @package Elgg
+	 * @subpackage Core
+	 * @license http://www.gnu.org/licenses/old-licenses/gpl-2.0.html GNU Public License version 2
+	 * @author Marcus Povey <marcus@dushka.co.uk>
+	 * @copyright Curverider Ltd 2008
+	 * @link http://elgg.org/
+	 */
+
+	
+	/** 
+	 * The algorithm working out the size of font based on the number of tags.
+	 * This is quick and dirty.
+	 */
+	function calculate_tag_size($min, $max, $number_of_tags)
+	{
+		$buckets = 6;
+
+		$delta =  (($max - $min) / $buckets);
+		$thresholds = array();
+
+		for ($n=1; $n <= $buckets; $n++) {
+			$thresholds[$n-1] = ($min + $n) * $delta;
+		}
+	
+		// Correction
+		if ($thresholds[$buckets-1]>$max) $thresholds[$buckets-1] = $max;
+
+		$size = 0;
+		for ($n = 0; $n < count($thresholds); $n++) {
+			if ($number_of_tags >= $thresholds[$n]) 
+				$size = $n;
+		}
+
+		return $size;
+	}
+	
+	/**
+	 * This function generates an array of tags with a weighting.
+	 *
+	 * @param array $tags The array of tags.
+	 * @return An associated array of tags with a weighting, this can then be mapped to a display class. 
+	 */
+	function generate_tag_cloud(array $tags)
+	{
+		$cloud = array();
+		
+		$min = 65535;
+		$max = 0;
+		
+		foreach ($tags as $tag)
+		{
+			$cloud[$tag]++;
+			
+			if ($cloud[$tag]>$max) $max = $cloud[$tag];
+			if ($cloud[$tag]<$min) $min = $cloud[$tag];
+		}
+		
+		foreach ($cloud as $k => $v)
+			$cloud[$k] = calculate_tag_size($min, $max, $v);
+		
+		return $cloud;
+	}
+?>
\ No newline at end of file
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