/**
 * Date utilities
 */

define(function () {
    'use strict';

    var DateHelper = {
        isValid: function(dateStr, format){
            if(!format) {
                format = 'DMY';
            }
            format = format.toUpperCase();
            if(format.length != 3) {
                if(format==='DDMMMYYYY'){
                    var d = this.format(dateStr, format);
                    dateStr = d.getDate() +'/'+ (d.getMonth()+1) +'/'+
                        d.getFullYear();
                    format = 'DMY';
                }
            }
            if((format.indexOf('M') === -1) || (format.indexOf('D') === -1) ||
                (format.indexOf('Y') === -1)){
                format = 'DMY';
            }
            var reg1, reg2;
            // If the year is first
            if(format.substring(0, 1) == 'Y') {
                  reg1 = /^\d{2}(\-|\/|\.)\d{1,2}\1\d{1,2}$/;
                  reg2 = /^\d{4}(\-|\/|\.)\d{1,2}\1\d{1,2}$/;
            } else if(format.substring(1, 2) == 'Y') { // If the year is second
                  reg1 = /^\d{1,2}(\-|\/|\.)\d{2}\1\d{1,2}$/;
                  reg2 = /^\d{1,2}(\-|\/|\.)\d{4}\1\d{1,2}$/;
            } else { // The year must be third
                  reg1 = /^\d{1,2}(\-|\/|\.)\d{1,2}\1\d{2}$/;
                  reg2 = /^\d{1,2}(\-|\/|\.)\d{1,2}\1\d{4}$/;
            }
            // If it doesn't conform to the right format (with either a 2 digit year or
            // 4 digit year), fail
            if(reg1.test(dateStr) === false && reg2.test(dateStr) === false) {
                return false;
            }
            // Split into 3 parts based on what the divider was
            var parts = dateStr.split(RegExp.$1);
            var mm, dd, yy;
            // Check to see if the 3 parts end up making a valid date
            if(format.substring(0, 1) === 'M'){
                mm = parts[0];
            } else if(format.substring(1, 2) === 'M'){
                mm = parts[1];
            } else {
                mm = parts[2];
            }
            if(format.substring(0, 1) === 'D'){
                dd = parts[0];
            } else if(format.substring(1, 2) === 'D'){
                dd = parts[1];
            } else {
                dd = parts[2];
            }
            if(format.substring(0, 1) === 'Y'){
                yy = parts[0];
            } else if(format.substring(1, 2) === 'Y'){
                yy = parts[1];
            } else {
                yy = parts[2];
            }
            if(parseInt(yy, 10) <= 50){
                yy = (parseInt(yy, 10) + 2000).toString();
            }
            if(parseInt(yy, 10) <= 99){
                yy = (parseInt(yy, 10) + 1900).toString();
            }
            var dt = new Date(
                parseInt(yy, 10), parseInt(mm, 10)-1, parseInt(dd, 10),
                0, 0, 0, 0);
            if(parseInt(dd, 10) != dt.getDate()){
                return false;
            }
            if(parseInt(mm, 10)-1 != dt.getMonth()){
                return false;
            }
            return true;
        },
        format: function(dateStr, format){
            if(!format){
                format = 'DMY';
            }
            if(!dateStr || dateStr === ''){
                return new Date(1001, 0, 1);
            }
            var oDate, parts;

            function y2kDate(yr){
                if(yr === undefined){
                    return 0;
                }
                if(yr.length>2){
                    return yr;
                }
                var y;
                //>50 belong to 1900
                if(yr <= 99 && yr>50){
                    y = '19' + yr;
                }
                //<50 belong to 2000
                if(yr<50 || yr === '00'){
                    y = '20' + yr;
                }
                return y;
            }

            function mmm2mm(mmm){
                if(mmm === undefined){
                    return 0;
                }
                var mondigit;
                var MONTH_NAMES = [
                    'january','february','march','april','may','june','july',
                    'august','september','october','november','december',
                    'jan','feb','mar','apr','may','jun','jul','aug','sep','oct',
                    'nov','dec'
                ];
                for(var m_i=0; m_i < MONTH_NAMES.length; m_i++){
                        var month_name = MONTH_NAMES[m_i];
                        if (mmm.toLowerCase() === month_name){
                            mondigit = m_i+1;
                            break;
                        }
                }
                if(mondigit > 11 || mondigit < 23){
                    mondigit = mondigit - 12;
                }
                if(mondigit < 1 || mondigit > 12){
                    return 0;
                }
                return mondigit;
            }

            switch(format.toUpperCase()){
                case 'DDMMMYYYY':
                    parts = dateStr.replace(/[- \/.]/g,' ').split(' ');
                    oDate = new Date(y2kDate(parts[2]),mmm2mm(parts[1])-1,parts[0]);
                break;
                case 'DMY':
                    parts = dateStr.replace(
                        /^(0?[1-9]|[12][0-9]|3[01])([- \/.])(0?[1-9]|1[012])([- \/.])((\d\d)?\d\d)$/,'$1 $3 $5').split(' ');
                    oDate = new Date(y2kDate(parts[2]),parts[1]-1,parts[0]);
                break;
                case 'MDY':
                    parts = dateStr.replace(
                        /^(0?[1-9]|1[012])([- \/.])(0?[1-9]|[12][0-9]|3[01])([- \/.])((\d\d)?\d\d)$/,'$1 $3 $5').split(' ');
                    oDate = new Date(y2kDate(parts[2]),parts[0]-1,parts[1]);
                break;
                case 'YMD':
                    parts = dateStr.replace(/^((\d\d)?\d\d)([- \/.])(0?[1-9]|1[012])([- \/.])(0?[1-9]|[12][0-9]|3[01])$/,'$1 $4 $6').split(' ');
                    oDate = new Date(y2kDate(parts[0]),parts[1]-1,parts[2]);
                break;
                default: //in case format is not correct
                    parts = dateStr.replace(/^(0?[1-9]|[12][0-9]|3[01])([- \/.])(0?[1-9]|1[012])([- \/.])((\d\d)?\d\d)$/,'$1 $3 $5').split(' ');
                    oDate = new Date(y2kDate(parts[2]),parts[1]-1,parts[0]);
                break;
            }
            return oDate;
        }
    };

    return DateHelper;
});