TimeInterval.js

define([
        './Check',
        './defaultValue',
        './defined',
        './defineProperties',
        './freezeObject',
        './JulianDate'
    ], function(
        Check,
        defaultValue,
        defined,
        defineProperties,
        freezeObject,
        JulianDate) {
    'use strict';

    /**
     * An interval defined by a start and a stop time; optionally including those times as part of the interval.
     * Arbitrary data can optionally be associated with each instance for used with {@link TimeIntervalCollection}.
     *
     * @alias TimeInterval
     * @constructor
     *
     * @param {Object} [options] Object with the following properties:
     * @param {JulianDate} [options.start=new JulianDate()] The start time of the interval.
     * @param {JulianDate} [options.stop=new JulianDate()] The stop time of the interval.
     * @param {Boolean} [options.isStartIncluded=true] <code>true</code> if <code>options.start</code> is included in the interval, <code>false</code> otherwise.
     * @param {Boolean} [options.isStopIncluded=true] <code>true</code> if <code>options.stop</code> is included in the interval, <code>false</code> otherwise.
     * @param {Object} [options.data] Arbitrary data associated with this interval.
     *
     * @example
     * // Create an instance that spans August 1st, 1980 and is associated
     * // with a Cartesian position.
     * var timeInterval = new Cesium.TimeInterval({
     *     start : Cesium.JulianDate.fromIso8601('1980-08-01T00:00:00Z'),
     *     stop : Cesium.JulianDate.fromIso8601('1980-08-02T00:00:00Z'),
     *     isStartIncluded : true,
     *     isStopIncluded : false,
     *     data : Cesium.Cartesian3.fromDegrees(39.921037, -75.170082)
     * });
     *
     * @example
     * // Create two instances from ISO 8601 intervals with associated numeric data
     * // then compute their intersection, summing the data they contain.
     * var left = Cesium.TimeInterval.fromIso8601({
     *     iso8601 : '2000/2010',
     *     data : 2
     * });
     *
     * var right = Cesium.TimeInterval.fromIso8601({
     *     iso8601 : '1995/2005',
     *     data : 3
     * });
     *
     * //The result of the below intersection will be an interval equivalent to
     * //var intersection = Cesium.TimeInterval.fromIso8601({
     * //  iso8601 : '2000/2005',
     * //  data : 5
     * //});
     * var intersection = new Cesium.TimeInterval();
     * Cesium.TimeInterval.intersect(left, right, intersection, function(leftData, rightData) {
     *     return leftData + rightData;
     * });
     *
     * @example
     * // Check if an interval contains a specific time.
     * var dateToCheck = Cesium.JulianDate.fromIso8601('1982-09-08T11:30:00Z');
     * var containsDate = Cesium.TimeInterval.contains(timeInterval, dateToCheck);
     */
    function TimeInterval(options) {
        options = defaultValue(options, defaultValue.EMPTY_OBJECT);
        /**
         * Gets or sets the start time of this interval.
         * @type {JulianDate}
         */
        this.start = defined(options.start) ? JulianDate.clone(options.start) : new JulianDate();

        /**
         * Gets or sets the stop time of this interval.
         * @type {JulianDate}
         */
        this.stop = defined(options.stop) ? JulianDate.clone(options.stop) : new JulianDate();

        /**
         * Gets or sets the data associated with this interval.
         * @type {Object}
         */
        this.data = options.data;

        /**
         * Gets or sets whether or not the start time is included in this interval.
         * @type {Boolean}
         * @default true
         */
        this.isStartIncluded = defaultValue(options.isStartIncluded, true);

        /**
         * Gets or sets whether or not the stop time is included in this interval.
         * @type {Boolean}
         * @default true
         */
        this.isStopIncluded = defaultValue(options.isStopIncluded, true);
    }

    defineProperties(TimeInterval.prototype, {
        /**
         * Gets whether or not this interval is empty.
         * @memberof TimeInterval.prototype
         * @type {Boolean}
         * @readonly
         */
        isEmpty : {
            get : function() {
                var stopComparedToStart = JulianDate.compare(this.stop, this.start);
                return stopComparedToStart < 0 || (stopComparedToStart === 0 && (!this.isStartIncluded || !this.isStopIncluded));
            }
        }
    });

    var scratchInterval = {
        start : undefined,
        stop : undefined,
        isStartIncluded : undefined,
        isStopIncluded : undefined,
        data : undefined
    };

    /**
     * Creates a new instance from an {@link http://en.wikipedia.org/wiki/ISO_8601|ISO 8601} interval.
     *
     * @param {Object} options Object with the following properties:
     * @param {String} options.iso8601 An ISO 8601 interval.
     * @param {Boolean} [options.isStartIncluded=true] <code>true</code> if <code>options.start</code> is included in the interval, <code>false</code> otherwise.
     * @param {Boolean} [options.isStopIncluded=true] <code>true</code> if <code>options.stop</code> is included in the interval, <code>false</code> otherwise.
     * @param {Object} [options.data] Arbitrary data associated with this interval.
     * @param {TimeInterval} [result] An existing instance to use for the result.
     * @returns {TimeInterval} The modified result parameter or a new instance if none was provided.
     */
    TimeInterval.fromIso8601 = function(options, result) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.object('options', options);
        Check.typeOf.string('options.iso8601', options.iso8601);
        //>>includeEnd('debug');

        var dates = options.iso8601.split('/');
        var start = JulianDate.fromIso8601(dates[0]);
        var stop = JulianDate.fromIso8601(dates[1]);
        var isStartIncluded = defaultValue(options.isStartIncluded, true);
        var isStopIncluded = defaultValue(options.isStopIncluded, true);
        var data = options.data;

        if (!defined(result)) {
            scratchInterval.start = start;
            scratchInterval.stop = stop;
            scratchInterval.isStartIncluded = isStartIncluded;
            scratchInterval.isStopIncluded = isStopIncluded;
            scratchInterval.data = data;
            return new TimeInterval(scratchInterval);
        }

        result.start = start;
        result.stop = stop;
        result.isStartIncluded = isStartIncluded;
        result.isStopIncluded = isStopIncluded;
        result.data = data;
        return result;
    };

    /**
     * Creates an ISO8601 representation of the provided interval.
     *
     * @param {TimeInterval} timeInterval The interval to be converted.
     * @param {Number} [precision] The number of fractional digits used to represent the seconds component.  By default, the most precise representation is used.
     * @returns {String} The ISO8601 representation of the provided interval.
     */
    TimeInterval.toIso8601 = function(timeInterval, precision) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.object('timeInterval', timeInterval);
        //>>includeEnd('debug');

        return JulianDate.toIso8601(timeInterval.start, precision) + '/' + JulianDate.toIso8601(timeInterval.stop, precision);
    };

    /**
     * Duplicates the provided instance.
     *
     * @param {TimeInterval} [timeInterval] The instance to clone.
     * @param {TimeInterval} [result] An existing instance to use for the result.
     * @returns {TimeInterval} The modified result parameter or a new instance if none was provided.
     */
    TimeInterval.clone = function(timeInterval, result) {
        if (!defined(timeInterval)) {
            return undefined;
        }
        if (!defined(result)) {
            return new TimeInterval(timeInterval);
        }
        result.start = timeInterval.start;
        result.stop = timeInterval.stop;
        result.isStartIncluded = timeInterval.isStartIncluded;
        result.isStopIncluded = timeInterval.isStopIncluded;
        result.data = timeInterval.data;
        return result;
    };

    /**
     * Compares two instances and returns <code>true</code> if they are equal, <code>false</code> otherwise.
     *
     * @param {TimeInterval} [left] The first instance.
     * @param {TimeInterval} [right] The second instance.
     * @param {TimeInterval~DataComparer} [dataComparer] A function which compares the data of the two intervals.  If omitted, reference equality is used.
     * @returns {Boolean} <code>true</code> if the dates are equal; otherwise, <code>false</code>.
     */
    TimeInterval.equals = function(left, right, dataComparer) {
        return left === right ||
               defined(left) && defined(right) &&
               (left.isEmpty && right.isEmpty ||
                left.isStartIncluded === right.isStartIncluded &&
                left.isStopIncluded === right.isStopIncluded &&
                JulianDate.equals(left.start, right.start) &&
                JulianDate.equals(left.stop, right.stop) &&
                (left.data === right.data || (defined(dataComparer) && dataComparer(left.data, right.data))));
    };

    /**
     * Compares two instances and returns <code>true</code> if they are within <code>epsilon</code> seconds of
     * each other.  That is, in order for the dates to be considered equal (and for
     * this function to return <code>true</code>), the absolute value of the difference between them, in
     * seconds, must be less than <code>epsilon</code>.
     *
     * @param {TimeInterval} [left] The first instance.
     * @param {TimeInterval} [right] The second instance.
     * @param {Number} epsilon The maximum number of seconds that should separate the two instances.
     * @param {TimeInterval~DataComparer} [dataComparer] A function which compares the data of the two intervals.  If omitted, reference equality is used.
     * @returns {Boolean} <code>true</code> if the two dates are within <code>epsilon</code> seconds of each other; otherwise <code>false</code>.
     */
    TimeInterval.equalsEpsilon = function(left, right, epsilon, dataComparer) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.number('epsilon', epsilon);
        //>>includeEnd('debug');

        return left === right ||
               defined(left) && defined(right) &&
               (left.isEmpty && right.isEmpty ||
                left.isStartIncluded === right.isStartIncluded &&
                left.isStopIncluded === right.isStopIncluded &&
                JulianDate.equalsEpsilon(left.start, right.start, epsilon) &&
                JulianDate.equalsEpsilon(left.stop, right.stop, epsilon) &&
                (left.data === right.data || (defined(dataComparer) && dataComparer(left.data, right.data))));
    };

    /**
     * Computes the intersection of two intervals, optionally merging their data.
     *
     * @param {TimeInterval} left The first interval.
     * @param {TimeInterval} [right] The second interval.
     * @param {TimeInterval} result An existing instance to use for the result.
     * @param {TimeInterval~MergeCallback} [mergeCallback] A function which merges the data of the two intervals. If omitted, the data from the left interval will be used.
     * @returns {TimeInterval} The modified result parameter.
     */
    TimeInterval.intersect = function(left, right, result, mergeCallback) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.object('left', left);
        Check.typeOf.object('result', result);
        //>>includeEnd('debug');

        if (!defined(right)) {
            return TimeInterval.clone(TimeInterval.EMPTY, result);
        }

        var leftStart = left.start;
        var leftStop = left.stop;

        var rightStart = right.start;
        var rightStop = right.stop;

        var intersectsStartRight = JulianDate.greaterThanOrEquals(rightStart, leftStart) && JulianDate.greaterThanOrEquals(leftStop, rightStart);
        var intersectsStartLeft = !intersectsStartRight && JulianDate.lessThanOrEquals(rightStart, leftStart) && JulianDate.lessThanOrEquals(leftStart, rightStop);

        if (!intersectsStartRight && !intersectsStartLeft) {
            return TimeInterval.clone(TimeInterval.EMPTY, result);
        }

        var leftIsStartIncluded = left.isStartIncluded;
        var leftIsStopIncluded = left.isStopIncluded;
        var rightIsStartIncluded = right.isStartIncluded;
        var rightIsStopIncluded = right.isStopIncluded;
        var leftLessThanRight = JulianDate.lessThan(leftStop, rightStop);

        result.start = intersectsStartRight ? rightStart : leftStart;
        result.isStartIncluded = (leftIsStartIncluded && rightIsStartIncluded) || (!JulianDate.equals(rightStart, leftStart) && ((intersectsStartRight && rightIsStartIncluded) || (intersectsStartLeft && leftIsStartIncluded)));
        result.stop = leftLessThanRight ? leftStop : rightStop;
        result.isStopIncluded = leftLessThanRight ? leftIsStopIncluded : (leftIsStopIncluded && rightIsStopIncluded) || (!JulianDate.equals(rightStop, leftStop) && rightIsStopIncluded);
        result.data = defined(mergeCallback) ? mergeCallback(left.data, right.data) : left.data;
        return result;
    };

    /**
     * Checks if the specified date is inside the provided interval.
     *
     * @param {TimeInterval} timeInterval The interval.
     * @param {JulianDate} julianDate The date to check.
     * @returns {Boolean} <code>true</code> if the interval contains the specified date, <code>false</code> otherwise.
     */
    TimeInterval.contains = function(timeInterval, julianDate) {
        //>>includeStart('debug', pragmas.debug);
        Check.typeOf.object('timeInterval', timeInterval);
        Check.typeOf.object('julianDate', julianDate);
        //>>includeEnd('debug');

        if (timeInterval.isEmpty) {
            return false;
        }

        var startComparedToDate = JulianDate.compare(timeInterval.start, julianDate);
        if (startComparedToDate === 0) {
            return timeInterval.isStartIncluded;
        }

        var dateComparedToStop = JulianDate.compare(julianDate, timeInterval.stop);
        if (dateComparedToStop === 0) {
            return timeInterval.isStopIncluded;
        }

        return startComparedToDate < 0 && dateComparedToStop < 0;
    };

    /**
     * Duplicates this instance.
     *
     * @param {TimeInterval} [result] An existing instance to use for the result.
     * @returns {TimeInterval} The modified result parameter or a new instance if none was provided.
     */
    TimeInterval.prototype.clone = function(result) {
        return TimeInterval.clone(this, result);
    };

    /**
     * Compares this instance against the provided instance componentwise and returns
     * <code>true</code> if they are equal, <code>false</code> otherwise.
     *
     * @param {TimeInterval} [right] The right hand side interval.
     * @param {TimeInterval~DataComparer} [dataComparer] A function which compares the data of the two intervals.  If omitted, reference equality is used.
     * @returns {Boolean} <code>true</code> if they are equal, <code>false</code> otherwise.
     */
    TimeInterval.prototype.equals = function(right, dataComparer) {
        return TimeInterval.equals(this, right, dataComparer);
    };

    /**
     * Compares this instance against the provided instance componentwise and returns
     * <code>true</code> if they are within the provided epsilon,
     * <code>false</code> otherwise.
     *
     * @param {TimeInterval} [right] The right hand side interval.
     * @param {Number} epsilon The epsilon to use for equality testing.
     * @param {TimeInterval~DataComparer} [dataComparer] A function which compares the data of the two intervals.  If omitted, reference equality is used.
     * @returns {Boolean} <code>true</code> if they are within the provided epsilon, <code>false</code> otherwise.
     */
    TimeInterval.prototype.equalsEpsilon = function(right, epsilon, dataComparer) {
        return TimeInterval.equalsEpsilon(this, right, epsilon, dataComparer);
    };

    /**
     * Creates a string representing this TimeInterval in ISO8601 format.
     *
     * @returns {String} A string representing this TimeInterval in ISO8601 format.
     */
    TimeInterval.prototype.toString = function() {
        return TimeInterval.toIso8601(this);
    };

    /**
     * An immutable empty interval.
     *
     * @type {TimeInterval}
     * @constant
     */
    TimeInterval.EMPTY = freezeObject(new TimeInterval({
        start : new JulianDate(),
        stop : new JulianDate(),
        isStartIncluded : false,
        isStopIncluded : false
    }));

    /**
     * Function interface for merging interval data.
     * @callback TimeInterval~MergeCallback
     *
     * @param {Object} leftData The first data instance.
     * @param {Object} rightData The second data instance.
     * @returns {Object} The result of merging the two data instances.
     */

    /**
     * Function interface for comparing interval data.
     * @callback TimeInterval~DataComparer
     * @param {Object} leftData The first data instance.
     * @param {Object} rightData The second data instance.
     * @returns {Boolean} <code>true</code> if the provided instances are equal, <code>false</code> otherwise.
     */

    return TimeInterval;
});