<?php

/**

* Check spelling of searches

*

* Dictionary adapted from code by Vincenzo Russo, Ian Barber

* http://neminis.org/blog/research/text-mining/spelling-correction-with-soundex/

* 

* @package    VideoGallery

* @subpackage Spell

* @copyright  Copyright (c) 2011 Andrew Weeks http://meloncholy.com

* @license    MIT licence. See licence.txt for details.

* @version    0.1

*/



class Spell extends CI_Model

{

	// Dictionary

	var $dic;

	// Dictionary minus single letter words

	var $dic_edit;

	

	function __construct()

	{

		parent::__construct();

		$this->load->database();



		$this->dic = $this->load_dic('dic');

		$this->dic_edit = $this->load_dic('dicedit');

	}

	

	function check($word)

	{

		return isset($this->dic[strtolower($word)]);

	}



	// $match == how close to correct spelling word is, roughly

	function correct($word, &$match = 0.0)

	{

		$joined_words = array();

		$edits1 = $edits2 = array();



		$word = strtolower($word);



		if(isset($this->dic[$word]))

		{

			$match = 1.0;

			return $word;

		}

		elseif (strlen($word) == 1)

		{

			$match = 0.0;

			return $word;

		}

		

		foreach($this->dic_edit as $dic_word => $count)

		{

			$dist = levenshtein($word, $dic_word);

			

			if($dist == 1) 

			{	

				$edits1[$dic_word] = $count;

			} 

			elseif($dist == 2)

			{

				$edits2[$dic_word] = $count;

			}

		}



		if(count($edits1)) 

		{

			$match = 0.6;

			arsort($edits1);

			return key($edits1);

		}

		elseif(count($edits2)) 

		{

			$match = 0.3;

			arsort($edits2);

			return key($edits2);

		}



		// Nothing better

		$match = 0.0;

		return $word;

	}

	

	/**

	 * Store a new dictionary of words in the database. Only needed to update the list. 

	 * 

	 * @param string $file List of words or phrases to learn (one per line)

	 */

	

	function train($file)

	{

		$dic = array();

		$dic_edit = array();



		$contents = file_get_contents($file);

		// get all strings of word letters

		preg_match_all('/\w+/', $contents, $matches);

		unset($contents);

		

		foreach($matches[0] as $word) 

		{

			$word = strtolower($word);

			

			if(!isset($dic[$word])) 

			{

				$dic[$word] = 0;

			}

			$dic[$word] += 1;

		}

		

		unset($matches);

		

		foreach ($dic as $word => $matches)

		{

			if (strlen($word) > 1) $dic_edit[$word] = $matches;

		}

		

		$this->dic = $dic;

		$this->dic_edit = $dic_edit;

		

		$this->save_dic($dic, 'dic');

		$this->save_dic($dic_edit, 'dicedit');

		echo "Updated dictionaries from $file.";

	}

	

	/**
	 * Store the new dictionary in the database (called by train)
	 *
	 * @param array $dic New dictionary
	 * @param string $table Target table
	 */	

	private function save_dic($dic, $table)

	{

		// Why can't I execute 2 of these at once through CodeIgniter?

		$this->db->query("DELETE FROM $table");

		

		$sql = "INSERT INTO $table (word, freq) VALUES ";

		

		foreach ($dic as $word => $freq)

		{

			$sql .= "\n('$word', $freq), ";

		}

		

		// Cut ', '

		$sql = substr($sql, 0, strlen($sql) - 2);

		$this->db->query($sql);

	}

	

	/**

	 * Load dictionary from database

	 * 

	 * @param string $table Table to load

	 * 

	 */

	private function load_dic($table)

	{

		$dic = array();

		$query = $this->db->query("SELECT * FROM $table");

		

		foreach ($query->result() as $row)

		{

			$dic[$row->word] = $row->freq;

		}

			

		return $dic;

	}

	

	/**

	 * Join words together to try in dictionary

	 *

	 * @param array $words Search string to check as array of words

	 * @param array $joined_words Array of joined words (internal; passed by ref)

	 * @param int $pos_start Current position in array (internal)

	 * @param array $comb_start Array of joined words current building (internal)

	 * @return array Array of joined words

	 */

	function join($words, &$joined_words = array(), $pos_start = 0, $comb_start = array())

	{

		$count = count($words);

		$len = $count - $pos_start;

		$comb = $comb_start;



		for ( ; $len > 0; $len--)

		{

			$pos = $pos_start;

			$word = implode(array_slice($words, $pos, $len));

			

			if ($len == 1 || $this->check($word))

			{

				if ($pos + $len <= $count)

				{

					array_push($comb, $word);

					if ($pos + $len < $count) $this->join($words, $joined_words, $pos + $len, $comb);

				}

				

				if ($pos + $len == $count) array_push($joined_words, $comb);

			}

			$comb = $comb_start;

		}

		

		return $joined_words;

	}

	

	/**

	 * Split compound words for spell check

	 *

	 * @param string $word Word to split

	 * @return array Array of split words

	 */

	function split($word)

	{

		$new_words = array();

		return $this->split_r(str_split($word), $new_words);

	}



	private function split_r($letters, &$new_words, $pos_start = 0, $len = false, $comb_start = array())

	{

		$count = count($letters);

		$len = $count - $pos_start;

		$comb = $comb_start;

		$unknown = 0;



		for ( ; $len > 0; $len--)

		{

			$pos = $pos_start;

			$word = implode(array_slice($letters, $pos, $len));

						

			if ($pos + $len <= $count)

			{

				array_push($comb, $word);

				if ($pos + $len < $count) $this->split_r($letters, $new_words, $pos + $len, $len, $comb);

			}

				

			if ($pos + $len == $count)

			{

				for ($w = 0; $w < count($comb); $w++)

				{

					if (strlen($comb[$w]) > 1 && $this->check($comb[$w])) 

					{

						$unknown = 0;

					}

					else

					{

						$unknown++;

					}

					if ($unknown == 2) break;

				}

					

				if ($unknown < 2) array_push($new_words, $comb);

			}

			$comb = $comb_start;

		}

		return $new_words;

	}

	

	function join_alts($split_words_sets)

	{

		$split_words_list = array();

		$this->join_alts_r($split_words_sets, $split_words_list);

		return $split_words_list;

	}

	

	private function join_alts_r($split_words_sets, &$split_words_list, $set_idx = 0, $cur_split_words = array())

	{

		

		foreach ($split_words_sets[$set_idx] as $split_word)

		{

			$new_split_words = array_merge($cur_split_words, $split_word);



			if ($set_idx == count($split_words_sets) - 1)

			{

				array_push($split_words_list, $new_split_words);

			}

			else

			{

				$this->join_alts_r($split_words_sets, $split_words_list, $set_idx + 1, $new_split_words);

			}

		}

	}

}