core.helpers.js

/* global window: false */
/* global document: false */
'use strict';

var color = require('chartjs-color');
var defaults = require('./core.defaults');
var helpers = require('../helpers/index');

module.exports = function() {

	// -- Basic js utility methods

	helpers.where = function(collection, filterCallback) {
		if (helpers.isArray(collection) && Array.prototype.filter) {
			return collection.filter(filterCallback);
		}
		var filtered = [];

		helpers.each(collection, function(item) {
			if (filterCallback(item)) {
				filtered.push(item);
			}
		});

		return filtered;
	};
	helpers.findIndex = Array.prototype.findIndex ?
		function(array, callback, scope) {
			return array.findIndex(callback, scope);
		} :
		function(array, callback, scope) {
			scope = scope === undefined ? array : scope;
			for (var i = 0, ilen = array.length; i < ilen; ++i) {
				if (callback.call(scope, array[i], i, array)) {
					return i;
				}
			}
			return -1;
		};
	helpers.findNextWhere = function(arrayToSearch, filterCallback, startIndex) {
		// Default to start of the array
		if (helpers.isNullOrUndef(startIndex)) {
			startIndex = -1;
		}
		for (var i = startIndex + 1; i < arrayToSearch.length; i++) {
			var currentItem = arrayToSearch[i];
			if (filterCallback(currentItem)) {
				return currentItem;
			}
		}
	};
	helpers.findPreviousWhere = function(arrayToSearch, filterCallback, startIndex) {
		// Default to end of the array
		if (helpers.isNullOrUndef(startIndex)) {
			startIndex = arrayToSearch.length;
		}
		for (var i = startIndex - 1; i >= 0; i--) {
			var currentItem = arrayToSearch[i];
			if (filterCallback(currentItem)) {
				return currentItem;
			}
		}
	};

	// -- Math methods
	helpers.isNumber = function(n) {
		return !isNaN(parseFloat(n)) && isFinite(n);
	};
	helpers.almostEquals = function(x, y, epsilon) {
		return Math.abs(x - y) < epsilon;
	};
	helpers.almostWhole = function(x, epsilon) {
		var rounded = Math.round(x);
		return (((rounded - epsilon) < x) && ((rounded + epsilon) > x));
	};
	helpers.max = function(array) {
		return array.reduce(function(max, value) {
			if (!isNaN(value)) {
				return Math.max(max, value);
			}
			return max;
		}, Number.NEGATIVE_INFINITY);
	};
	helpers.min = function(array) {
		return array.reduce(function(min, value) {
			if (!isNaN(value)) {
				return Math.min(min, value);
			}
			return min;
		}, Number.POSITIVE_INFINITY);
	};
	helpers.sign = Math.sign ?
		function(x) {
			return Math.sign(x);
		} :
		function(x) {
			x = +x; // convert to a number
			if (x === 0 || isNaN(x)) {
				return x;
			}
			return x > 0 ? 1 : -1;
		};
	helpers.log10 = Math.log10 ?
		function(x) {
			return Math.log10(x);
		} :
		function(x) {
			var exponent = Math.log(x) * Math.LOG10E; // Math.LOG10E = 1 / Math.LN10.
			// Check for whole powers of 10,
			// which due to floating point rounding error should be corrected.
			var powerOf10 = Math.round(exponent);
			var isPowerOf10 = x === Math.pow(10, powerOf10);

			return isPowerOf10 ? powerOf10 : exponent;
		};
	helpers.toRadians = function(degrees) {
		return degrees * (Math.PI / 180);
	};
	helpers.toDegrees = function(radians) {
		return radians * (180 / Math.PI);
	};

	/**
	 * Returns the number of decimal places
	 * i.e. the number of digits after the decimal point, of the value of this Number.
	 * @param {number} x - A number.
	 * @returns {number} The number of decimal places.
	 * @private
	 */
	helpers._decimalPlaces = function(x) {
		if (!helpers.isFinite(x)) {
			return;
		}
		var e = 1;
		var p = 0;
		while (Math.round(x * e) / e !== x) {
			e *= 10;
			p++;
		}
		return p;
	};

	// Gets the angle from vertical upright to the point about a centre.
	helpers.getAngleFromPoint = function(centrePoint, anglePoint) {
		var distanceFromXCenter = anglePoint.x - centrePoint.x;
		var distanceFromYCenter = anglePoint.y - centrePoint.y;
		var radialDistanceFromCenter = Math.sqrt(distanceFromXCenter * distanceFromXCenter + distanceFromYCenter * distanceFromYCenter);

		var angle = Math.atan2(distanceFromYCenter, distanceFromXCenter);

		if (angle < (-0.5 * Math.PI)) {
			angle += 2.0 * Math.PI; // make sure the returned angle is in the range of (-PI/2, 3PI/2]
		}

		return {
			angle: angle,
			distance: radialDistanceFromCenter
		};
	};
	helpers.distanceBetweenPoints = function(pt1, pt2) {
		return Math.sqrt(Math.pow(pt2.x - pt1.x, 2) + Math.pow(pt2.y - pt1.y, 2));
	};

	/**
	 * Provided for backward compatibility, not available anymore
	 * @function Chart.helpers.aliasPixel
	 * @deprecated since version 2.8.0
	 * @todo remove at version 3
	 */
	helpers.aliasPixel = function(pixelWidth) {
		return (pixelWidth % 2 === 0) ? 0 : 0.5;
	};

	/**
	 * Returns the aligned pixel value to avoid anti-aliasing blur
	 * @param {Chart} chart - The chart instance.
	 * @param {number} pixel - A pixel value.
	 * @param {number} width - The width of the element.
	 * @returns {number} The aligned pixel value.
	 * @private
	 */
	helpers._alignPixel = function(chart, pixel, width) {
		var devicePixelRatio = chart.currentDevicePixelRatio;
		var halfWidth = width / 2;
		return Math.round((pixel - halfWidth) * devicePixelRatio) / devicePixelRatio + halfWidth;
	};

	helpers.splineCurve = function(firstPoint, middlePoint, afterPoint, t) {
		// Props to Rob Spencer at scaled innovation for his post on splining between points
		// http://scaledinnovation.com/analytics/splines/aboutSplines.html

		// This function must also respect "skipped" points

		var previous = firstPoint.skip ? middlePoint : firstPoint;
		var current = middlePoint;
		var next = afterPoint.skip ? middlePoint : afterPoint;

		var d01 = Math.sqrt(Math.pow(current.x - previous.x, 2) + Math.pow(current.y - previous.y, 2));
		var d12 = Math.sqrt(Math.pow(next.x - current.x, 2) + Math.pow(next.y - current.y, 2));

		var s01 = d01 / (d01 + d12);
		var s12 = d12 / (d01 + d12);

		// If all points are the same, s01 & s02 will be inf
		s01 = isNaN(s01) ? 0 : s01;
		s12 = isNaN(s12) ? 0 : s12;

		var fa = t * s01; // scaling factor for triangle Ta
		var fb = t * s12;

		return {
			previous: {
				x: current.x - fa * (next.x - previous.x),
				y: current.y - fa * (next.y - previous.y)
			},
			next: {
				x: current.x + fb * (next.x - previous.x),
				y: current.y + fb * (next.y - previous.y)
			}
		};
	};
	helpers.EPSILON = Number.EPSILON || 1e-14;
	helpers.splineCurveMonotone = function(points) {
		// This function calculates Bézier control points in a similar way than |splineCurve|,
		// but preserves monotonicity of the provided data and ensures no local extremums are added
		// between the dataset discrete points due to the interpolation.
		// See : https://en.wikipedia.org/wiki/Monotone_cubic_interpolation

		var pointsWithTangents = (points || []).map(function(point) {
			return {
				model: point._model,
				deltaK: 0,
				mK: 0
			};
		});

		// Calculate slopes (deltaK) and initialize tangents (mK)
		var pointsLen = pointsWithTangents.length;
		var i, pointBefore, pointCurrent, pointAfter;
		for (i = 0; i < pointsLen; ++i) {
			pointCurrent = pointsWithTangents[i];
			if (pointCurrent.model.skip) {
				continue;
			}

			pointBefore = i > 0 ? pointsWithTangents[i - 1] : null;
			pointAfter = i < pointsLen - 1 ? pointsWithTangents[i + 1] : null;
			if (pointAfter && !pointAfter.model.skip) {
				var slopeDeltaX = (pointAfter.model.x - pointCurrent.model.x);

				// In the case of two points that appear at the same x pixel, slopeDeltaX is 0
				pointCurrent.deltaK = slopeDeltaX !== 0 ? (pointAfter.model.y - pointCurrent.model.y) / slopeDeltaX : 0;
			}

			if (!pointBefore || pointBefore.model.skip) {
				pointCurrent.mK = pointCurrent.deltaK;
			} else if (!pointAfter || pointAfter.model.skip) {
				pointCurrent.mK = pointBefore.deltaK;
			} else if (this.sign(pointBefore.deltaK) !== this.sign(pointCurrent.deltaK)) {
				pointCurrent.mK = 0;
			} else {
				pointCurrent.mK = (pointBefore.deltaK + pointCurrent.deltaK) / 2;
			}
		}

		// Adjust tangents to ensure monotonic properties
		var alphaK, betaK, tauK, squaredMagnitude;
		for (i = 0; i < pointsLen - 1; ++i) {
			pointCurrent = pointsWithTangents[i];
			pointAfter = pointsWithTangents[i + 1];
			if (pointCurrent.model.skip || pointAfter.model.skip) {
				continue;
			}

			if (helpers.almostEquals(pointCurrent.deltaK, 0, this.EPSILON)) {
				pointCurrent.mK = pointAfter.mK = 0;
				continue;
			}

			alphaK = pointCurrent.mK / pointCurrent.deltaK;
			betaK = pointAfter.mK / pointCurrent.deltaK;
			squaredMagnitude = Math.pow(alphaK, 2) + Math.pow(betaK, 2);
			if (squaredMagnitude <= 9) {
				continue;
			}

			tauK = 3 / Math.sqrt(squaredMagnitude);
			pointCurrent.mK = alphaK * tauK * pointCurrent.deltaK;
			pointAfter.mK = betaK * tauK * pointCurrent.deltaK;
		}

		// Compute control points
		var deltaX;
		for (i = 0; i < pointsLen; ++i) {
			pointCurrent = pointsWithTangents[i];
			if (pointCurrent.model.skip) {
				continue;
			}

			pointBefore = i > 0 ? pointsWithTangents[i - 1] : null;
			pointAfter = i < pointsLen - 1 ? pointsWithTangents[i + 1] : null;
			if (pointBefore && !pointBefore.model.skip) {
				deltaX = (pointCurrent.model.x - pointBefore.model.x) / 3;
				pointCurrent.model.controlPointPreviousX = pointCurrent.model.x - deltaX;
				pointCurrent.model.controlPointPreviousY = pointCurrent.model.y - deltaX * pointCurrent.mK;
			}
			if (pointAfter && !pointAfter.model.skip) {
				deltaX = (pointAfter.model.x - pointCurrent.model.x) / 3;
				pointCurrent.model.controlPointNextX = pointCurrent.model.x + deltaX;
				pointCurrent.model.controlPointNextY = pointCurrent.model.y + deltaX * pointCurrent.mK;
			}
		}
	};
	helpers.nextItem = function(collection, index, loop) {
		if (loop) {
			return index >= collection.length - 1 ? collection[0] : collection[index + 1];
		}
		return index >= collection.length - 1 ? collection[collection.length - 1] : collection[index + 1];
	};
	helpers.previousItem = function(collection, index, loop) {
		if (loop) {
			return index <= 0 ? collection[collection.length - 1] : collection[index - 1];
		}
		return index <= 0 ? collection[0] : collection[index - 1];
	};
	// Implementation of the nice number algorithm used in determining where axis labels will go
	helpers.niceNum = function(range, round) {
		var exponent = Math.floor(helpers.log10(range));
		var fraction = range / Math.pow(10, exponent);
		var niceFraction;

		if (round) {
			if (fraction < 1.5) {
				niceFraction = 1;
			} else if (fraction < 3) {
				niceFraction = 2;
			} else if (fraction < 7) {
				niceFraction = 5;
			} else {
				niceFraction = 10;
			}
		} else if (fraction <= 1.0) {
			niceFraction = 1;
		} else if (fraction <= 2) {
			niceFraction = 2;
		} else if (fraction <= 5) {
			niceFraction = 5;
		} else {
			niceFraction = 10;
		}

		return niceFraction * Math.pow(10, exponent);
	};
	// Request animation polyfill - https://www.paulirish.com/2011/requestanimationframe-for-smart-animating/
	helpers.requestAnimFrame = (function() {
		if (typeof window === 'undefined') {
			return function(callback) {
				callback();
			};
		}
		return window.requestAnimationFrame ||
			window.webkitRequestAnimationFrame ||
			window.mozRequestAnimationFrame ||
			window.oRequestAnimationFrame ||
			window.msRequestAnimationFrame ||
			function(callback) {
				return window.setTimeout(callback, 1000 / 60);
			};
	}());
	// -- DOM methods
	helpers.getRelativePosition = function(evt, chart) {
		var mouseX, mouseY;
		var e = evt.originalEvent || evt;
		var canvas = evt.target || evt.srcElement;
		var boundingRect = canvas.getBoundingClientRect();

		var touches = e.touches;
		if (touches && touches.length > 0) {
			mouseX = touches[0].clientX;
			mouseY = touches[0].clientY;

		} else {
			mouseX = e.clientX;
			mouseY = e.clientY;
		}

		// Scale mouse coordinates into canvas coordinates
		// by following the pattern laid out by 'jerryj' in the comments of
		// https://www.html5canvastutorials.com/advanced/html5-canvas-mouse-coordinates/
		var paddingLeft = parseFloat(helpers.getStyle(canvas, 'padding-left'));
		var paddingTop = parseFloat(helpers.getStyle(canvas, 'padding-top'));
		var paddingRight = parseFloat(helpers.getStyle(canvas, 'padding-right'));
		var paddingBottom = parseFloat(helpers.getStyle(canvas, 'padding-bottom'));
		var width = boundingRect.right - boundingRect.left - paddingLeft - paddingRight;
		var height = boundingRect.bottom - boundingRect.top - paddingTop - paddingBottom;

		// We divide by the current device pixel ratio, because the canvas is scaled up by that amount in each direction. However
		// the backend model is in unscaled coordinates. Since we are going to deal with our model coordinates, we go back here
		mouseX = Math.round((mouseX - boundingRect.left - paddingLeft) / (width) * canvas.width / chart.currentDevicePixelRatio);
		mouseY = Math.round((mouseY - boundingRect.top - paddingTop) / (height) * canvas.height / chart.currentDevicePixelRatio);

		return {
			x: mouseX,
			y: mouseY
		};

	};

	// Private helper function to convert max-width/max-height values that may be percentages into a number
	function parseMaxStyle(styleValue, node, parentProperty) {
		var valueInPixels;
		if (typeof styleValue === 'string') {
			valueInPixels = parseInt(styleValue, 10);

			if (styleValue.indexOf('%') !== -1) {
				// percentage * size in dimension
				valueInPixels = valueInPixels / 100 * node.parentNode[parentProperty];
			}
		} else {
			valueInPixels = styleValue;
		}

		return valueInPixels;
	}

	/**
	 * Returns if the given value contains an effective constraint.
	 * @private
	 */
	function isConstrainedValue(value) {
		return value !== undefined && value !== null && value !== 'none';
	}

	/**
	 * Returns the max width or height of the given DOM node in a cross-browser compatible fashion
	 * @param {HTMLElement} domNode - the node to check the constraint on
	 * @param {string} maxStyle - the style that defines the maximum for the direction we are using ('max-width' / 'max-height')
	 * @param {string} percentageProperty - property of parent to use when calculating width as a percentage
	 * @see {@link https://www.nathanaeljones.com/blog/2013/reading-max-width-cross-browser}
	 */
	function getConstraintDimension(domNode, maxStyle, percentageProperty) {
		var view = document.defaultView;
		var parentNode = helpers._getParentNode(domNode);
		var constrainedNode = view.getComputedStyle(domNode)[maxStyle];
		var constrainedContainer = view.getComputedStyle(parentNode)[maxStyle];
		var hasCNode = isConstrainedValue(constrainedNode);
		var hasCContainer = isConstrainedValue(constrainedContainer);
		var infinity = Number.POSITIVE_INFINITY;

		if (hasCNode || hasCContainer) {
			return Math.min(
				hasCNode ? parseMaxStyle(constrainedNode, domNode, percentageProperty) : infinity,
				hasCContainer ? parseMaxStyle(constrainedContainer, parentNode, percentageProperty) : infinity);
		}

		return 'none';
	}
	// returns Number or undefined if no constraint
	helpers.getConstraintWidth = function(domNode) {
		return getConstraintDimension(domNode, 'max-width', 'clientWidth');
	};
	// returns Number or undefined if no constraint
	helpers.getConstraintHeight = function(domNode) {
		return getConstraintDimension(domNode, 'max-height', 'clientHeight');
	};
	/**
	 * @private
 	 */
	helpers._calculatePadding = function(container, padding, parentDimension) {
		padding = helpers.getStyle(container, padding);

		return padding.indexOf('%') > -1 ? parentDimension * parseInt(padding, 10) / 100 : parseInt(padding, 10);
	};
	/**
	 * @private
	 */
	helpers._getParentNode = function(domNode) {
		var parent = domNode.parentNode;
		if (parent && parent.toString() === '[object ShadowRoot]') {
			parent = parent.host;
		}
		return parent;
	};
	helpers.getMaximumWidth = function(domNode) {
		var container = helpers._getParentNode(domNode);
		if (!container) {
			return domNode.clientWidth;
		}

		var clientWidth = container.clientWidth;
		var paddingLeft = helpers._calculatePadding(container, 'padding-left', clientWidth);
		var paddingRight = helpers._calculatePadding(container, 'padding-right', clientWidth);

		var w = clientWidth - paddingLeft - paddingRight;
		var cw = helpers.getConstraintWidth(domNode);
		return isNaN(cw) ? w : Math.min(w, cw);
	};
	helpers.getMaximumHeight = function(domNode) {
		var container = helpers._getParentNode(domNode);
		if (!container) {
			return domNode.clientHeight;
		}

		var clientHeight = container.clientHeight;
		var paddingTop = helpers._calculatePadding(container, 'padding-top', clientHeight);
		var paddingBottom = helpers._calculatePadding(container, 'padding-bottom', clientHeight);

		var h = clientHeight - paddingTop - paddingBottom;
		var ch = helpers.getConstraintHeight(domNode);
		return isNaN(ch) ? h : Math.min(h, ch);
	};
	helpers.getStyle = function(el, property) {
		return el.currentStyle ?
			el.currentStyle[property] :
			document.defaultView.getComputedStyle(el, null).getPropertyValue(property);
	};
	helpers.retinaScale = function(chart, forceRatio) {
		var pixelRatio = chart.currentDevicePixelRatio = forceRatio || (typeof window !== 'undefined' && window.devicePixelRatio) || 1;
		if (pixelRatio === 1) {
			return;
		}

		var canvas = chart.canvas;
		var height = chart.height;
		var width = chart.width;

		canvas.height = height * pixelRatio;
		canvas.width = width * pixelRatio;
		chart.ctx.scale(pixelRatio, pixelRatio);

		// If no style has been set on the canvas, the render size is used as display size,
		// making the chart visually bigger, so let's enforce it to the "correct" values.
		// See https://github.com/chartjs/Chart.js/issues/3575
		if (!canvas.style.height && !canvas.style.width) {
			canvas.style.height = height + 'px';
			canvas.style.width = width + 'px';
		}
	};
	// -- Canvas methods
	helpers.fontString = function(pixelSize, fontStyle, fontFamily) {
		return fontStyle + ' ' + pixelSize + 'px ' + fontFamily;
	};
	helpers.longestText = function(ctx, font, arrayOfThings, cache) {
		cache = cache || {};
		var data = cache.data = cache.data || {};
		var gc = cache.garbageCollect = cache.garbageCollect || [];

		if (cache.font !== font) {
			data = cache.data = {};
			gc = cache.garbageCollect = [];
			cache.font = font;
		}

		ctx.font = font;
		var longest = 0;
		helpers.each(arrayOfThings, function(thing) {
			// Undefined strings and arrays should not be measured
			if (thing !== undefined && thing !== null && helpers.isArray(thing) !== true) {
				longest = helpers.measureText(ctx, data, gc, longest, thing);
			} else if (helpers.isArray(thing)) {
				// if it is an array lets measure each element
				// to do maybe simplify this function a bit so we can do this more recursively?
				helpers.each(thing, function(nestedThing) {
					// Undefined strings and arrays should not be measured
					if (nestedThing !== undefined && nestedThing !== null && !helpers.isArray(nestedThing)) {
						longest = helpers.measureText(ctx, data, gc, longest, nestedThing);
					}
				});
			}
		});

		var gcLen = gc.length / 2;
		if (gcLen > arrayOfThings.length) {
			for (var i = 0; i < gcLen; i++) {
				delete data[gc[i]];
			}
			gc.splice(0, gcLen);
		}
		return longest;
	};
	helpers.measureText = function(ctx, data, gc, longest, string) {
		var textWidth = data[string];
		if (!textWidth) {
			textWidth = data[string] = ctx.measureText(string).width;
			gc.push(string);
		}
		if (textWidth > longest) {
			longest = textWidth;
		}
		return longest;
	};
	helpers.numberOfLabelLines = function(arrayOfThings) {
		var numberOfLines = 1;
		helpers.each(arrayOfThings, function(thing) {
			if (helpers.isArray(thing)) {
				if (thing.length > numberOfLines) {
					numberOfLines = thing.length;
				}
			}
		});
		return numberOfLines;
	};

	helpers.color = !color ?
		function(value) {
			console.error('Color.js not found!');
			return value;
		} :
		function(value) {
			/* global CanvasGradient */
			if (value instanceof CanvasGradient) {
				value = defaults.global.defaultColor;
			}

			return color(value);
		};

	helpers.getHoverColor = function(colorValue) {
		/* global CanvasPattern */
		return (colorValue instanceof CanvasPattern || colorValue instanceof CanvasGradient) ?
			colorValue :
			helpers.color(colorValue).saturate(0.5).darken(0.1).rgbString();
	};
};