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221 lines
6.3 KiB
221 lines
6.3 KiB
/**
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* @constructor DataStep
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* The class DataStep is an iterator for data for the lineGraph. You provide a start data point and an
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* end data point. The class itself determines the best scale (step size) based on the
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* provided start Date, end Date, and minimumStep.
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*
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* If minimumStep is provided, the step size is chosen as close as possible
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* to the minimumStep but larger than minimumStep. If minimumStep is not
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* provided, the scale is set to 1 DAY.
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* The minimumStep should correspond with the onscreen size of about 6 characters
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*
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* Alternatively, you can set a scale by hand.
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* After creation, you can initialize the class by executing first(). Then you
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* can iterate from the start date to the end date via next(). You can check if
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* the end date is reached with the function hasNext(). After each step, you can
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* retrieve the current date via getCurrent().
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* The DataStep has scales ranging from milliseconds, seconds, minutes, hours,
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* days, to years.
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*
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* Version: 1.2
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*
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* @param {Date} [start] The start date, for example new Date(2010, 9, 21)
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* or new Date(2010, 9, 21, 23, 45, 00)
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* @param {Date} [end] The end date
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* @param {Number} [minimumStep] Optional. Minimum step size in milliseconds
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*/
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function DataStep(start, end, minimumStep, containerHeight, forcedStepSize) {
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// variables
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this.current = 0;
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this.autoScale = true;
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this.stepIndex = 0;
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this.step = 1;
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this.scale = 1;
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this.marginStart;
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this.marginEnd;
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this.majorSteps = [1, 2, 5, 10];
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this.minorSteps = [0.25, 0.5, 1, 2];
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this.setRange(start, end, minimumStep, containerHeight, forcedStepSize);
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}
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/**
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* Set a new range
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* If minimumStep is provided, the step size is chosen as close as possible
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* to the minimumStep but larger than minimumStep. If minimumStep is not
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* provided, the scale is set to 1 DAY.
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* The minimumStep should correspond with the onscreen size of about 6 characters
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* @param {Number} [start] The start date and time.
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* @param {Number} [end] The end date and time.
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* @param {Number} [minimumStep] Optional. Minimum step size in milliseconds
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*/
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DataStep.prototype.setRange = function(start, end, minimumStep, containerHeight, forcedStepSize) {
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this._start = start;
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this._end = end;
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if (start == end) {
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this._start = start - 0.75;
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this._end = end + 1;
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}
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if (this.autoScale) {
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this.setMinimumStep(minimumStep, containerHeight, forcedStepSize);
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}
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this.setFirst();
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};
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/**
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* Automatically determine the scale that bests fits the provided minimum step
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* @param {Number} [minimumStep] The minimum step size in milliseconds
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*/
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DataStep.prototype.setMinimumStep = function(minimumStep, containerHeight) {
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// round to floor
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var size = this._end - this._start;
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var safeSize = size * 1.1;
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var minimumStepValue = minimumStep * (safeSize / containerHeight);
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var orderOfMagnitude = Math.round(Math.log(safeSize)/Math.LN10);
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var minorStepIdx = -1;
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var magnitudefactor = Math.pow(10,orderOfMagnitude);
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var start = 0;
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if (orderOfMagnitude < 0) {
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start = orderOfMagnitude;
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}
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var solutionFound = false;
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for (var i = start; Math.abs(i) <= Math.abs(orderOfMagnitude); i++) {
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magnitudefactor = Math.pow(10,i);
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for (var j = 0; j < this.minorSteps.length; j++) {
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var stepSize = magnitudefactor * this.minorSteps[j];
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if (stepSize >= minimumStepValue) {
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solutionFound = true;
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minorStepIdx = j;
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break;
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}
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}
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if (solutionFound == true) {
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break;
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}
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}
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this.stepIndex = minorStepIdx;
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this.scale = magnitudefactor;
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this.step = magnitudefactor * this.minorSteps[minorStepIdx];
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};
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/**
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* Set the range iterator to the start date.
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*/
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DataStep.prototype.first = function() {
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this.setFirst();
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};
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/**
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* Round the current date to the first minor date value
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* This must be executed once when the current date is set to start Date
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*/
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DataStep.prototype.setFirst = function() {
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var niceStart = this._start - (this.scale * this.minorSteps[this.stepIndex]);
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var niceEnd = this._end + (this.scale * this.minorSteps[this.stepIndex]);
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this.marginEnd = this.roundToMinor(niceEnd);
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this.marginStart = this.roundToMinor(niceStart);
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this.marginRange = this.marginEnd - this.marginStart;
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this.current = this.marginEnd;
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};
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DataStep.prototype.roundToMinor = function(value) {
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var rounded = value - (value % (this.scale * this.minorSteps[this.stepIndex]));
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if (value % (this.scale * this.minorSteps[this.stepIndex]) > 0.5 * (this.scale * this.minorSteps[this.stepIndex])) {
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return rounded + (this.scale * this.minorSteps[this.stepIndex]);
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}
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else {
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return rounded;
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}
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}
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/**
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* Check if the there is a next step
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* @return {boolean} true if the current date has not passed the end date
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*/
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DataStep.prototype.hasNext = function () {
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return (this.current >= this.marginStart);
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};
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/**
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* Do the next step
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*/
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DataStep.prototype.next = function() {
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var prev = this.current;
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this.current -= this.step;
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// safety mechanism: if current time is still unchanged, move to the end
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if (this.current == prev) {
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this.current = this._end;
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}
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};
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/**
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* Do the next step
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*/
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DataStep.prototype.previous = function() {
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this.current += this.step;
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this.marginEnd += this.step;
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this.marginRange = this.marginEnd - this.marginStart;
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};
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/**
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* Get the current datetime
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* @return {String} current The current date
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*/
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DataStep.prototype.getCurrent = function() {
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var toPrecision = '' + Number(this.current).toPrecision(5);
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for (var i = toPrecision.length-1; i > 0; i--) {
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if (toPrecision[i] == "0") {
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toPrecision = toPrecision.slice(0,i);
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}
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else if (toPrecision[i] == "." || toPrecision[i] == ",") {
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toPrecision = toPrecision.slice(0,i);
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break;
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}
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else{
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break;
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}
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}
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return toPrecision;
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};
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/**
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* Snap a date to a rounded value.
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* The snap intervals are dependent on the current scale and step.
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* @param {Date} date the date to be snapped.
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* @return {Date} snappedDate
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*/
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DataStep.prototype.snap = function(date) {
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};
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/**
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* Check if the current value is a major value (for example when the step
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* is DAY, a major value is each first day of the MONTH)
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* @return {boolean} true if current date is major, else false.
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*/
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DataStep.prototype.isMajor = function() {
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return (this.current % (this.scale * this.majorSteps[this.stepIndex]) == 0);
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};
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module.exports = DataStep;
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