<?php

/*
*
* implements a Paice/Husk Stemmer written in PHP by Alexis Ulrich (http://alx2002.free.fr)
*
* This code is in the public domain.
*
*/


// the rule patterns include all accented forms for a given language
$rule_pattern_en = "/^([a-z]*)(\*){0,1}(\d)([a-z]*)([.|>])/" ;
$rule_pattern_fr = "/^([a-zàâèéêëîïôûùç]*)(\*){0,1}(\d)([a-zàâèéêëîïôûùç]*)([.|>])/" ;


// returns the number of the first rule from the rule number $rule_number
// that can be applied to the given reversed form
// returns -1 if no rule can be applied, ie the stem has been found
function getFirstRule ( $reversed_form , $rule_number , $language = 'en' ) {
    require( 'PaiceHuskStemRules_' . $language . '.php' );
    eval( "global \$rule_pattern_$language;" );
    eval( "\$PaiceHuskStemmerRules = \$PaiceHuskStemmerRules_$language;" );
    $nb_rules = sizeOf ( $PaiceHuskStemmerRules );
    for ( $i = $rule_number ; $i < $nb_rules ; $i ++) {
         // gets the letters from the current rule
         $rule = $PaiceHuskStemmerRules [ $i ];
        eval( " \$rule = preg_replace( \$rule_pattern_$language, \"\\\\ 1 \" , \$rule);" );
        if ( strncasecmp ( utf8_decode ( $rule ), $reversed_form , strlen ( utf8_decode ( $rule ))) == 0 ) return $i ;
    }
    return - 1 ;
}


/*
* Check the acceptability of a stem for a given language
*
* $reversed_stem:    the stem to check in reverse form
* $language:        text language (default: French)
*/
function checkAcceptability ( $reversed_stem , $language = 'en' ) {
    switch ( $language ) {
        case 'en' : # English
             if ( preg_match ( "/ [ aeiouy ]$ /" , utf8_encode ( $reversed_stem ))) {
                 // if the form starts with a vowel then at least two letters must remain after stemming (e.g., "owed"/"owing" --> "ow", but not "ear" --> "e")
                 return ( strlen ( $reversed_stem ) >= 2 );
            }
            else {
                 // if the form starts with a consonant then at least three letters must remain after stemming
                 if ( strlen ( $reversed_stem ) < 3 ) return False ;
                 // and at least one of these must be a vowel or "y" (e.g., "saying" --> "say" and "crying" --> "cry", but not "string" --> "str", "meant" --> "me" or "cement" --> "ce")
                 return ( preg_match ( "/[aeiouy]/" , utf8_encode ( $reversed_stem )));
            }
            break;
        case 'fr' : # French
             if ( preg_match ( "/ [ a??e????i??o?u??y ]$ /" , utf8_encode ( $reversed_stem ))) {
                 // if the form starts with a vowel then at least two letters must remain after stemming (e.g.: "?taient" --> "?t")
                 return ( strlen ( $reversed_stem ) > 2 );
            }
            else {
                 // if the form starts with a consonant then at least two letters must remain after stemming
                 if ( strlen ( $reversed_stem ) <= 2 ) {
                    return False ;
                }
                 // and at least one of these must be a vowel or "y"
                 return ( preg_match ( "/[a??e????i??o?u??y]/" , utf8_encode ( $reversed_stem )));
            }
            break;
            break;
        default:
            die( "Error in checkAcceptability function: the language <i>$language</i> is not supported." );
    }
}


/*
* the actual Paice/Husk stemmer
* which returns a stem for the given form
*
* $form:        the word for which we want the stem
* $language:    the word language (default: French)
*/
function PaiceHuskStemmer ( $form , $language = 'en' ) {
    require( 'PaiceHuskStemRules_' . $language . '.php' );
    eval( "global \$rule_pattern_$language;" );
    eval( "\$PaiceHuskStemmerRules = \$PaiceHuskStemmerRules_$language;" );
     $intact = True ;
     $stem_found = False ;
     $reversed_form = strrev ( utf8_decode ( $form ));
     $rule_number = 0 ;
     // that loop goes through the rules' array until it finds an ending one (ending by '.') or the last one ('end0.')
     while ( True ) {
         $rule_number = getFirstRule ( $reversed_form , $rule_number , $language );
        if ( $rule_number == - 1 ) {
             // no other rule can be applied => the stem has been found
             break;
        }
         $rule = $PaiceHuskStemmerRules [ $rule_number ];
        eval( "preg_match( \$rule_pattern_$language, \$rule, \$matches);" );
        if (( $matches [ 2 ] != '*' ) || ( $intact )) {
             $reversed_stem = utf8_decode ( $matches [ 4 ]) . substr ( $reversed_form , $matches [ 3 ], strlen ( $reversed_form )- $matches [ 3 ]);
            if ( checkAcceptability ( $reversed_stem , $language )) {
                 $reversed_form = $reversed_stem ;
                if ( $matches [ 5 ] == '.' ) break;
            }
            else {
                 // go to another rule
                 $rule_number ++;
            }
        }
        else {
             // go to another rule
             $rule_number ++;
        }
    }
    
    return utf8_encode ( strrev ( $reversed_form ));

}

?>