node-nlp/examples/microsoft-bot/node_modules/chrono-node/src/parsers/EN/ENMonthNameParser.js

Library for NLU (Natural Language Understanding) done in Node.js

/*
    
    The parser for parsing month name and year.
    
    EX. 
        - January
        - January 2012
        - January, 2012
*/

var moment = require('moment');

var Parser = require('../parser').Parser;
var ParsedResult = require('../../result').ParsedResult;
var util  = require('../../utils/EN');

var PATTERN = new RegExp('(^|\\D\\s+|[^\\w\\s])' +
    '(Jan\\.?|January|Feb\\.?|February|Mar\\.?|March|Apr\\.?|April|May\\.?|Jun\\.?|June|Jul\\.?|July|Aug\\.?|August|Sep\\.?|Sept\\.?|September|Oct\\.?|October|Nov\\.?|November|Dec\\.?|December)' + 
    '\\s*' +
    '(?:' +
        '[,-]?\\s*([0-9]{4})(\\s*BE|AD|BC)?' +
    ')?' +
    '(?=[^\\s\\w]|\\s+[^0-9]|\\s+$|$)', 'i');

var MONTH_NAME_GROUP = 2;
var YEAR_GROUP = 3;
var YEAR_BE_GROUP = 4;

exports.Parser = function ENMonthNameParser(){
    Parser.apply(this, arguments);

    this.pattern = function() { return PATTERN; }
    
    this.extract = function(text, ref, match, opt){
        var result = new ParsedResult({
            text: match[0].substr(match[1].length, match[0].length - match[1].length),
            index: match.index + match[1].length,
            ref: ref,
        });

        
        var month = match[MONTH_NAME_GROUP];
        month = util.MONTH_OFFSET[month.toLowerCase()];

        var day = 1;

        var year = null;
        if (match[YEAR_GROUP]) {
            year = match[YEAR_GROUP];
            year = parseInt(year);

            if(match[YEAR_BE_GROUP]){
                if (match[YEAR_BE_GROUP].match(/BE/)) {
                    // Buddhist Era
                    year = year - 543;
                } else if (match[YEAR_BE_GROUP].match(/BC/)) {
                    // Before Christ
                    year = -year;
                }

            } else if (year < 100){ 

                year = year + 2000;
            }
        }

        if(year){
            result.start.imply('day', day);
            result.start.assign('month', month);
            result.start.assign('year', year);
        } else {
            
            //Find the most appropriated year
            var refMoment = moment(ref);
            refMoment.month(month - 1);
            refMoment.date(day);

            var nextYear = refMoment.clone().add(1, 'y');
            var lastYear = refMoment.clone().add(-1, 'y');
            if( Math.abs(nextYear.diff(moment(ref))) < Math.abs(refMoment.diff(moment(ref))) ){  
                refMoment = nextYear;
            }
            else if( Math.abs(lastYear.diff(moment(ref))) < Math.abs(refMoment.diff(moment(ref))) ){ 
                refMoment = lastYear;
            }

            result.start.imply('day', day);
            result.start.assign('month', month);
            result.start.imply('year', refMoment.year());
        }

        result.tags['ENMonthNameParser'] = true;
        return result;
    }
}