api/fluro.date.js



import _ from 'lodash';
import moment from 'moment-timezone';
import FluroUtils from './fluro.utils';

///////////////////////////////////////////////////////////////////////////////


/**
 * @classdesc A static service that provides useful functions for working with dates and timestamps.
 * @class
 * @hideconstructor
 */

const FluroDate = {
    defaultTimezone:Intl.DateTimeFormat().resolvedOptions().timeZone,
}

///////////////////////////////////////////////////////////////////////////////

/**
 * A function that will return a date in context of a specified timezone
 * If no timezone is specified then the default timezone of the current clock will be used.
 * This will return dates that are incorrect on purpose. So that it can appear to the user as if they were in another timezone.
 * As Javascript dates are always in the context of the timezone they are being viewed in, this function will give you a date that is technically
 * not the Universal point in time of the date, but rather a time that reads in your timezone as if you were in the specified timezone.
 * @alias FluroDate.localDate
 * @param  {Date} date      Either a javascript date object, or a string timestamp representing a javascript date object        
 * @param  {String} specifiedTimezone The timezone to retrieve the date in eg. Australia/Melbourne   
 * @return {Date}                   A javascript date object transformed to match the specified timezone
 */
FluroDate.localDate = function(d, specifiedTimezone) {
    
    // console.log('LOCAL DATE', d, specifiedTimezone);
    //Date
    var date;// = new Date(d);

    if(!d) {
        date = new Date();
    } else {
        date = new Date(d);
    }

    ///////////////////////////////////////////

    var timezoneOffset;
    var browserOffset = date.getTimezoneOffset();

    ///////////////////////////////////////////

    if(!specifiedTimezone) {
        specifiedTimezone = FluroDate.defaultTimezone;
    }

    if(specifiedTimezone) {
        timezoneOffset = moment.tz(date, specifiedTimezone).utcOffset();
        browserOffset = moment(date).utcOffset();

        var difference = (timezoneOffset - browserOffset);
        var offsetDifference = difference * 60 * 1000;
        var prevDate = new Date(date);
        date.setTime(date.getTime() + offsetDifference);
    }

    return date;
}

///////////////////////////////////////////////////////////////////////////////

// https://momentjs.com/docs/#/displaying/format/
FluroDate.formatDate = function(dateString, format, timezone) {    
    var date = FluroDate.localDate(dateString, timezone);

    return moment(date).format(format);
}

FluroDate.dateFromID = function(id, format, timezone) {
    id = FluroUtils.getStringID(id);
    var date = new Date(parseInt(id.substring(0, 8), 16) * 1000);

    return FluroDate.formatDate(date, format, timezone);
}

///////////////////////////////////////

/**
 * A helper function that can display a human-readable date for an event
 * taking into consideration the context of the current time, the event's start and end time.
 * This is often used as a string filter
 * and what is relevant
 * @alias FluroDate.readableEventDate
 * @param  {Object} event An object that has both a startDate and endDate property, Usually an event object from the Fluro API
 * @param  {String} style Whether to return a 'short', 'medium' or 'long' date
 * @return {String}       The human readable date for the event
 * @example
 * //Returns 5:30pm 1 May
 * FluroDate.readableEventDate({"startDate": "2019-05-01T07:30:00.000Z", "endDate":"2019-05-01T07:30:00.000Z"})

 * //Returns 5:30pm - 7:30pm 1 May
 * FluroDate.readableEventDate({"startDate": "2019-05-01T07:30:00.000Z", "endDate":"2019-05-01T09:30:00.000Z"})


 * //Returns 1 - 5 May 2015
 * FluroDate.readableEventDate({"startDate": "2015-05-01T07:30:00.000Z", "endDate":"2015-05-05T09:30:00.000Z"})

 * //1 May - 21 Jun 2019
 * FluroDate.readableEventDate({"startDate": "2019-05-01T07:30:00.000Z", "endDate":"2019-06-21T09:30:00.000Z"})

 */
FluroDate.readableEventDate = function(event, style) {

    ////////////////////////////////////////

    var startDate;
    var endDate;

    ////////////////////////////////////////

    if (!event) return;

    ////////////////////////////////////////

    if (event.startDate) {
        startDate = FluroDate.localDate(event.startDate, event.timezone);
    } else {
        return;
    }

    if (!event.endDate) {
        endDate = FluroDate.localDate(event.endDate, event.timezone);
    } else {
        endDate = startDate;
    }


    ///////////////////////////////////////////////

    startDate = moment(startDate);
    endDate = moment(endDate);

    ///////////////////////////////////////////////

    var noEndDate = startDate.format('h:mma D MMM YYYY') == endDate.format('h:mma D MMM YYYY');
    var sameYear = (startDate.format('YYYY') == endDate.format('YYYY'));
    var sameMonth = (startDate.format('MMM YYYY') == endDate.format('MMM YYYY'));
    var sameDay = (startDate.format('D MMM YYYY') == endDate.format('D MMM YYYY'));

    switch (style) {
        case 'short':
            // console.log('SHORT', startDate, endDate);
            if (noEndDate) {
                return startDate.format('D MMM')
            }

            if (sameDay) {
                //8am - 9am Thursday 21 May 2016
                return startDate.format('D MMM')
            }

            if (sameMonth) {
                //20 - 21 May 2016
                return startDate.format('D') + '-' + endDate.format('D MMM')
            }

            if (sameYear) {
                //20 Aug - 21 Sep 2016
                return startDate.format('D') + '-' + endDate.format('D MMM')
            }

            //20 Aug 2015 - 21 Sep 2016
            return startDate.format('D MMM Y') + ' - ' + endDate.format('D MMM Y')

            break;
        default:
            if (noEndDate) {
                return startDate.format('h:mma dddd D MMM Y')
            }

            if (sameDay) {
                //8am - 9am Thursday 21 May 2016
                return startDate.format('h:mma') + ' - ' + endDate.format('h:mma dddd D MMM Y')
            }

            if (sameMonth) {
                //20 - 21 May 2016
                return startDate.format('D') + '-' + endDate.format('D MMM Y')
            }

            if (sameYear) {
                //20 Aug - 21 Sep 2016
                return startDate.format('D MMM') + ' - ' + endDate.format('D MMM Y')
            }

            //20 Aug 2015 - 21 Sep 2016
            return startDate.format('D MMM Y') + ' - ' + endDate.format('D MMM Y')

            break;
    }

}

///////////////////////////////////////////////////////////////////////////////

export default FluroDate;