chrono-node/src/parsers/EN/ENWeekdayParser.js

A natural language date parser in Javascript

/*


*/
var moment = require('moment');
var Parser = require('../parser').Parser;
var ParsedResult = require('../../result').ParsedResult;

var DAYS_OFFSET = { 'sunday': 0, 'sun': 0, 'monday': 1, 'mon': 1,'tuesday': 2, 'tues':2, 'tue':2, 'wednesday': 3, 'wed': 3,
    'thursday': 4, 'thurs':4, 'thur': 4, 'thu': 4,'friday': 5, 'fri': 5,'saturday': 6, 'sat': 6};

var PATTERN = new RegExp('(\\W|^)' +
    '(?:(?:\\,|\\(|\\（)\\s*)?' +
    '(?:(this|last|next)\\s*)?' +
    '(' + Object.keys(DAYS_OFFSET).join('|') + ')' +
    '(?:\\s*(?:\\,|\\)|\\）))?' +
    '(?:\\s*(this|last|next)\\s*week)?' +
    '(?=\\W|$)', 'i');

var PREFIX_GROUP = 2;
var WEEKDAY_GROUP = 3;
var POSTFIX_GROUP = 4;

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

    this.pattern = function() { return PATTERN; };

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

        var dayOfWeek = match[WEEKDAY_GROUP].toLowerCase();
        var offset = DAYS_OFFSET[dayOfWeek];
        if(offset === undefined) return null;

        var startMoment = moment(ref);
        var prefix = match[PREFIX_GROUP];
        var postfix = match[POSTFIX_GROUP];

        if (prefix || postfix) {
            var norm = prefix || postfix;
            norm = norm.toLowerCase();

            if(norm == 'last')
                startMoment.day(offset - 7);
            else if(norm == 'next')
                startMoment.day(offset + 7);
            else if(norm== 'this')
                startMoment.day(offset);
        } else{
            var refOffset = startMoment.day();
            if ( opt.forwardDatesOnly && refOffset > offset ) {
              startMoment.day(offset + 7);
            } else if (!opt.forwardDatesOnly && Math.abs(offset - 7 - refOffset) < Math.abs(offset - refOffset)) {
              startMoment.day(offset - 7);
            } else if (!opt.forwardDatesOnly && Math.abs(offset + 7 - refOffset) < Math.abs(offset - refOffset)) {
              startMoment.day(offset + 7);
            } else {
              startMoment.day(offset);
            }
        }

        result.start.assign('weekday', offset);
        result.start.imply('day', startMoment.date());
        result.start.imply('month', startMoment.month() + 1);
        result.start.imply('year', startMoment.year());
        return result;
    }
};