// Porter stemmer in Javascript. Few comments, but it's easy to follow against the rules in the original
// paper, in
//
//  Porter, 1980, An algorithm for suffix stripping, Program, Vol. 14,
//  no. 3, pp 130-137,
//
// see also http://www.tartarus.org/~martin/PorterStemmer

// Release 1 be 'andargor', Jul 2004
// Release 2 (substantially revised) by Christopher McKenzie, Aug 2009

// SPDX-FileCopyrightText: 2009  Christopher McKenzie
//
// SPDX-License-Identifier: CC0-1.0

window.stemmer = function(w) {
    var step2list = {
            "ational" : "ate",
            "tional" : "tion",
            "enci" : "ence",
            "anci" : "ance",
            "izer" : "ize",
            "bli" : "ble",
            "alli" : "al",
            "entli" : "ent",
            "eli" : "e",
            "ousli" : "ous",
            "ization" : "ize",
            "ation" : "ate",
            "ator" : "ate",
            "alism" : "al",
            "iveness" : "ive",
            "fulness" : "ful",
            "ousness" : "ous",
            "aliti" : "al",
            "iviti" : "ive",
            "biliti" : "ble",
            "logi" : "log"
        },
        step3list = {
            "icate" : "ic",
            "ative" : "",
            "alize" : "al",
            "iciti" : "ic",
            "ical" : "ic",
            "ful" : "",
            "ness" : ""
        },
        c = "[^aeiou]",          // consonant
        v = "[aeiouy]",          // vowel
        C = c + "[^aeiouy]*",    // consonant sequence
        V = v + "[aeiou]*",      // vowel sequence

        mgr0 = "^(" + C + ")?" + V + C,                     // [C]VC... is m>0
        meq1 = "^(" + C + ")?" + V + C + "(" + V + ")?$",   // [C]VC[V] is m=1
        mgr1 = "^(" + C + ")?" + V + C + V + C,             // [C]VCVC... is m>1
        s_v = "^(" + C + ")?" + v;                          // vowel in stem

    var stem,
        suffix,
        firstch,
        re,
        re2,
        re3,
        re4,
        origword = w;

    if (w.length < 3) { return w; }

    firstch = w.substr(0,1);
    if (firstch == "y") {
        w = firstch.toUpperCase() + w.substr(1);
    }

    // Step 1a
    re = /^(.+?)(ss|i)es$/;
    re2 = /^(.+?)([^s])s$/;

    if (re.test(w)) { w = w.replace(re,"$1$2"); }
    else if (re2.test(w)) {        w = w.replace(re2,"$1$2"); }

    // Step 1b
    re = /^(.+?)eed$/;
    re2 = /^(.+?)(ed|ing)$/;
    if (re.test(w)) {
            var fp = re.exec(w);
            re = new RegExp(mgr0);
            if (re.test(fp[1])) {
                    re = /.$/;
                    w = w.replace(re,"");
            }
    } else if (re2.test(w)) {
            var fp = re2.exec(w);
            stem = fp[1];
            re2 = new RegExp(s_v);
            if (re2.test(stem)) {
                    w = stem;
                    re2 = /(at|bl|iz)$/;
                    re3 = new RegExp("([^aeiouylsz])\\1$");
                    re4 = new RegExp("^" + C + v + "[^aeiouwxy]$");
                    if (re2.test(w)) {        w = w + "e"; }
                    else if (re3.test(w)) { re = /.$/; w = w.replace(re,""); }
                    else if (re4.test(w)) { w = w + "e"; }
            }
    }

    // Step 1c
    re = /^(.+?)y$/;
    if (re.test(w)) {
            var fp = re.exec(w);
            stem = fp[1];
            re = new RegExp(s_v);
            if (re.test(stem)) { w = stem + "i"; }
    }

    // Step 2
    re = /^(.+?)(ational|tional|enci|anci|izer|bli|alli|entli|eli|ousli|ization|ation|ator|alism|iveness|fulness|ousness|aliti|iviti|biliti|logi)$/;
    if (re.test(w)) {
            var fp = re.exec(w);
            stem = fp[1];
            suffix = fp[2];
            re = new RegExp(mgr0);
            if (re.test(stem)) {
                    w = stem + step2list[suffix];
            }
    }

    // Step 3
    re = /^(.+?)(icate|ative|alize|iciti|ical|ful|ness)$/;
    if (re.test(w)) {
            var fp = re.exec(w);
            stem = fp[1];
            suffix = fp[2];
            re = new RegExp(mgr0);
            if (re.test(stem)) {
                    w = stem + step3list[suffix];
            }
    }

    // Step 4
    re = /^(.+?)(al|ance|ence|er|ic|able|ible|ant|ement|ment|ent|ou|ism|ate|iti|ous|ive|ize)$/;
    re2 = /^(.+?)(s|t)(ion)$/;
    if (re.test(w)) {
            var fp = re.exec(w);
            stem = fp[1];
            re = new RegExp(mgr1);
            if (re.test(stem)) {
                    w = stem;
            }
    } else if (re2.test(w)) {
            var fp = re2.exec(w);
            stem = fp[1] + fp[2];
            re2 = new RegExp(mgr1);
            if (re2.test(stem)) {
                    w = stem;
            }
    }

    // Step 5
    re = /^(.+?)e$/;
    if (re.test(w)) {
            var fp = re.exec(w);
            stem = fp[1];
            re = new RegExp(mgr1);
            re2 = new RegExp(meq1);
            re3 = new RegExp("^" + C + v + "[^aeiouwxy]$");
            if (re.test(stem) || (re2.test(stem) && !(re3.test(stem)))) {
                    w = stem;
            }
    }

    re = /ll$/;
    re2 = new RegExp(mgr1);
    if (re.test(w) && re2.test(w)) {
            re = /.$/;
            w = w.replace(re,"");
    }

    // and turn initial Y back to y

    if (firstch == "y") {
            w = firstch.toLowerCase() + w.substr(1);
    }

    return w;
}
