<?php
	class Lingua_Stem_Ru
	{
		public $VERSION = "0.02";
		public $Stem_Caching = 1;
		public $Stem_Cache = array();
		public $VOWEL = '/аеиоуыэюя/';
		public $PERFECTIVEGROUND = '/((ив|ивши|ившись|ыв|ывши|ывшись)|((?<=[ая])(в|вши|вшись)))$/';
		public $REFLEXIVE = '/(с[яь])$/';
		public $ADJECTIVE = '/(ее|ие|ые|ое|ими|ыми|ей|ий|ый|ой|ем|им|ым|ом|его|ого|ему|ому|их|ых|ую|юю|ая|яя|ою|ею)$/';
		public $PARTICIPLE = '/((ивш|ывш|ующ)|((?<=[ая])(ем|нн|вш|ющ|щ)))$/';
		public $VERB = '/((ила|ыла|ена|ейте|уйте|ите|или|ыли|ей|уй|ил|ыл|им|ым|ен|ило|ыло|ено|ят|ует|уют|ит|ыт|ены|ить|ыть|ишь|ую|ю)|((?<=[ая])(ла|на|ете|йте|ли|й|л|ем|н|ло|но|ет|ют|ны|ть|ешь|нно)))$/';
		public $NOUN = '/(а|ев|ов|ие|ье|е|иями|ями|ами|еи|ии|и|ией|ей|ой|ий|й|иям|ям|ием|ем|ам|ом|о|у|ах|иях|ях|ы|ь|ию|ью|ю|ия|ья|я)$/';
		public $RVRE = '/^(.*?[аеиоуыэюя])(.*)$/';
		public $DERIVATIONAL = '/[^аеиоуыэюя][аеиоуыэюя]+[^аеиоуыэюя]+[аеиоуыэюя].*(?<=о)сть?$/';

		function s(&$s, $re, $to)
		{
			$orig = $s;
			$s = preg_replace($re, $to, $s);
			return $orig !== $s;
		}

		function m($s, $re)
		{
			return preg_match($re, $s);
		}

		function stem_word($word)
		{
			$word = mb_strtolower($word);
			//$word = strtr($word, 'ё', 'е');
			# Check against cache of stemmed words
			if ($this->Stem_Caching && isset($this->Stem_Cache[$word]))
			{
				return $this->Stem_Cache[$word];
			}

			$stem = $word;

			do
			{
				if (! preg_match($this->RVRE, $word, $p))
					break;

				$start = $p[1];
				$RV = $p[2];

				if (!$RV)
					break;

				# Step 1
				if (! $this->s($RV, $this->PERFECTIVEGROUND, ''))
				{
					$this->s($RV, $this->REFLEXIVE, '');

					if ($this->s($RV, $this->ADJECTIVE, ''))
					{
						$this->s($RV, $this->PARTICIPLE, '');
					}
					else
					{
						if (! $this->s($RV, $this->VERB, ''))
							$this->s($RV, $this->NOUN, '');
					}
				}

				# Step 2
				$this->s($RV, '/и$/', '');

				# Step 3
				if ($this->m($RV, $this->DERIVATIONAL))
					$this->s($RV, '/ость?$/', '');

				# Step 4
				if (!$this->s($RV, '/ь$/', ''))
				{
					$this->s($RV, '/ейше?/', '');
					$this->s($RV, '/нн$/', 'н');
				}

				$stem = $start.$RV;
			}
			while(false);

			if ($this->Stem_Caching)
				$this->Stem_Cache[$word] = $stem;

			return $stem;
		}

		function stem_caching($parm_ref)
		{
		  $caching_level = @$parm_ref['-level'];
		  if ($caching_level) {
		      if (!$this->m($caching_level, '/^[012]$/')) {
		          die(__CLASS__ . "::stem_caching() - Legal values are '0','1' or '2'. '$caching_level' is not a legal value");
		      }
		      $this->Stem_Caching = $caching_level;
		  }
		  return $this->Stem_Caching;
		}

		function clear_stem_cache()
		{
		  $this->Stem_Cache = array();
		}
	}
?>