// 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

step2list = new Array();
step2list["ational"]="ate";
step2list["tional"]="tion";
step2list["enci"]="ence";
step2list["anci"]="ance";
step2list["izer"]="ize";
step2list["bli"]="ble";
step2list["alli"]="al";
step2list["entli"]="ent";
step2list["eli"]="e";
step2list["ousli"]="ous";
step2list["ization"]="ize";
step2list["ation"]="ate";
step2list["ator"]="ate";
step2list["alism"]="al";
step2list["iveness"]="ive";
step2list["fulness"]="ful";
step2list["ousness"]="ous";
step2list["aliti"]="al";
step2list["iviti"]="ive";
step2list["biliti"]="ble";
step2list["logi"]="log";

step3list = new Array();
step3list["icate"]="ic";
step3list["ative"]="";
step3list["alize"]="al";
step3list["iciti"]="ic";
step3list["ical"]="ic";
step3list["ful"]="";
step3list["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

function stemWord(w) {
	var stem;
	var suffix;
	var firstch;
	var origword = w;

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

   	var re;
   	var re2;
   	var re3;
   	var re4;

	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;

}