controller.bar.js

'use strict';

var DatasetController = require('../core/core.datasetController');
var defaults = require('../core/core.defaults');
var elements = require('../elements/index');
var helpers = require('../helpers/index');

defaults._set('bar', {
	hover: {
		mode: 'label'
	},

	scales: {
		xAxes: [{
			type: 'category',
			categoryPercentage: 0.8,
			barPercentage: 0.9,
			offset: true,
			gridLines: {
				offsetGridLines: true
			}
		}],

		yAxes: [{
			type: 'linear'
		}]
	}
});

/**
 * Computes the "optimal" sample size to maintain bars equally sized while preventing overlap.
 * @private
 */
function computeMinSampleSize(scale, pixels) {
	var min = scale.isHorizontal() ? scale.width : scale.height;
	var ticks = scale.getTicks();
	var prev, curr, i, ilen;

	for (i = 1, ilen = pixels.length; i < ilen; ++i) {
		min = Math.min(min, Math.abs(pixels[i] - pixels[i - 1]));
	}

	for (i = 0, ilen = ticks.length; i < ilen; ++i) {
		curr = scale.getPixelForTick(i);
		min = i > 0 ? Math.min(min, curr - prev) : min;
		prev = curr;
	}

	return min;
}

/**
 * Computes an "ideal" category based on the absolute bar thickness or, if undefined or null,
 * uses the smallest interval (see computeMinSampleSize) that prevents bar overlapping. This
 * mode currently always generates bars equally sized (until we introduce scriptable options?).
 * @private
 */
function computeFitCategoryTraits(index, ruler, options) {
	var thickness = options.barThickness;
	var count = ruler.stackCount;
	var curr = ruler.pixels[index];
	var size, ratio;

	if (helpers.isNullOrUndef(thickness)) {
		size = ruler.min * options.categoryPercentage;
		ratio = options.barPercentage;
	} else {
		// When bar thickness is enforced, category and bar percentages are ignored.
		// Note(SB): we could add support for relative bar thickness (e.g. barThickness: '50%')
		// and deprecate barPercentage since this value is ignored when thickness is absolute.
		size = thickness * count;
		ratio = 1;
	}

	return {
		chunk: size / count,
		ratio: ratio,
		start: curr - (size / 2)
	};
}

/**
 * Computes an "optimal" category that globally arranges bars side by side (no gap when
 * percentage options are 1), based on the previous and following categories. This mode
 * generates bars with different widths when data are not evenly spaced.
 * @private
 */
function computeFlexCategoryTraits(index, ruler, options) {
	var pixels = ruler.pixels;
	var curr = pixels[index];
	var prev = index > 0 ? pixels[index - 1] : null;
	var next = index < pixels.length - 1 ? pixels[index + 1] : null;
	var percent = options.categoryPercentage;
	var start, size;

	if (prev === null) {
		// first data: its size is double based on the next point or,
		// if it's also the last data, we use the scale size.
		prev = curr - (next === null ? ruler.end - ruler.start : next - curr);
	}

	if (next === null) {
		// last data: its size is also double based on the previous point.
		next = curr + curr - prev;
	}

	start = curr - (curr - Math.min(prev, next)) / 2 * percent;
	size = Math.abs(next - prev) / 2 * percent;

	return {
		chunk: size / ruler.stackCount,
		ratio: options.barPercentage,
		start: start
	};
}

module.exports = DatasetController.extend({

	dataElementType: elements.Rectangle,

	/**
	 * @private
	 */
	_dataElementOptions: [
		'backgroundColor',
		'borderColor',
		'borderSkipped',
		'borderWidth'
	],

	initialize: function() {
		var me = this;
		var meta;

		DatasetController.prototype.initialize.apply(me, arguments);

		meta = me.getMeta();
		meta.stack = me.getDataset().stack;
		meta.bar = true;
	},

	update: function(reset) {
		var me = this;
		var rects = me.getMeta().data;
		var i, ilen;

		me._ruler = me.getRuler();

		for (i = 0, ilen = rects.length; i < ilen; ++i) {
			me.updateElement(rects[i], i, reset);
		}
	},

	updateElement: function(rectangle, index, reset) {
		var me = this;
		var meta = me.getMeta();
		var dataset = me.getDataset();
		var options = me._resolveDataElementOptions(rectangle, index);

		rectangle._xScale = me.getScaleForId(meta.xAxisID);
		rectangle._yScale = me.getScaleForId(meta.yAxisID);
		rectangle._datasetIndex = me.index;
		rectangle._index = index;
		rectangle._model = {
			backgroundColor: options.backgroundColor,
			borderColor: options.borderColor,
			borderSkipped: options.borderSkipped,
			borderWidth: options.borderWidth,
			datasetLabel: dataset.label,
			label: me.chart.data.labels[index]
		};

		me._updateElementGeometry(rectangle, index, reset);

		rectangle.pivot();
	},

	/**
	 * @private
	 */
	_updateElementGeometry: function(rectangle, index, reset) {
		var me = this;
		var model = rectangle._model;
		var vscale = me._getValueScale();
		var base = vscale.getBasePixel();
		var horizontal = vscale.isHorizontal();
		var ruler = me._ruler || me.getRuler();
		var vpixels = me.calculateBarValuePixels(me.index, index);
		var ipixels = me.calculateBarIndexPixels(me.index, index, ruler);

		model.horizontal = horizontal;
		model.base = reset ? base : vpixels.base;
		model.x = horizontal ? reset ? base : vpixels.head : ipixels.center;
		model.y = horizontal ? ipixels.center : reset ? base : vpixels.head;
		model.height = horizontal ? ipixels.size : undefined;
		model.width = horizontal ? undefined : ipixels.size;
	},

	/**
	 * Returns the stacks based on groups and bar visibility.
	 * @param {number} [last] - The dataset index
	 * @returns {string[]} The list of stack IDs
	 * @private
	 */
	_getStacks: function(last) {
		var me = this;
		var chart = me.chart;
		var scale = me._getIndexScale();
		var stacked = scale.options.stacked;
		var ilen = last === undefined ? chart.data.datasets.length : last + 1;
		var stacks = [];
		var i, meta;

		for (i = 0; i < ilen; ++i) {
			meta = chart.getDatasetMeta(i);
			if (meta.bar && chart.isDatasetVisible(i) &&
				(stacked === false ||
				(stacked === true && stacks.indexOf(meta.stack) === -1) ||
				(stacked === undefined && (meta.stack === undefined || stacks.indexOf(meta.stack) === -1)))) {
				stacks.push(meta.stack);
			}
		}

		return stacks;
	},

	/**
	 * Returns the effective number of stacks based on groups and bar visibility.
	 * @private
	 */
	getStackCount: function() {
		return this._getStacks().length;
	},

	/**
	 * Returns the stack index for the given dataset based on groups and bar visibility.
	 * @param {number} [datasetIndex] - The dataset index
	 * @param {string} [name] - The stack name to find
	 * @returns {number} The stack index
	 * @private
	 */
	getStackIndex: function(datasetIndex, name) {
		var stacks = this._getStacks(datasetIndex);
		var index = (name !== undefined)
			? stacks.indexOf(name)
			: -1; // indexOf returns -1 if element is not present

		return (index === -1)
			? stacks.length - 1
			: index;
	},

	/**
	 * @private
	 */
	getRuler: function() {
		var me = this;
		var scale = me._getIndexScale();
		var stackCount = me.getStackCount();
		var datasetIndex = me.index;
		var isHorizontal = scale.isHorizontal();
		var start = isHorizontal ? scale.left : scale.top;
		var end = start + (isHorizontal ? scale.width : scale.height);
		var pixels = [];
		var i, ilen, min;

		for (i = 0, ilen = me.getMeta().data.length; i < ilen; ++i) {
			pixels.push(scale.getPixelForValue(null, i, datasetIndex));
		}

		min = helpers.isNullOrUndef(scale.options.barThickness)
			? computeMinSampleSize(scale, pixels)
			: -1;

		return {
			min: min,
			pixels: pixels,
			start: start,
			end: end,
			stackCount: stackCount,
			scale: scale
		};
	},

	/**
	 * Note: pixel values are not clamped to the scale area.
	 * @private
	 */
	calculateBarValuePixels: function(datasetIndex, index) {
		var me = this;
		var chart = me.chart;
		var meta = me.getMeta();
		var scale = me._getValueScale();
		var isHorizontal = scale.isHorizontal();
		var datasets = chart.data.datasets;
		var value = +scale.getRightValue(datasets[datasetIndex].data[index]);
		var minBarLength = scale.options.minBarLength;
		var stacked = scale.options.stacked;
		var stack = meta.stack;
		var start = 0;
		var i, imeta, ivalue, base, head, size;

		if (stacked || (stacked === undefined && stack !== undefined)) {
			for (i = 0; i < datasetIndex; ++i) {
				imeta = chart.getDatasetMeta(i);

				if (imeta.bar &&
					imeta.stack === stack &&
					imeta.controller._getValueScaleId() === scale.id &&
					chart.isDatasetVisible(i)) {

					ivalue = +scale.getRightValue(datasets[i].data[index]);
					if ((value < 0 && ivalue < 0) || (value >= 0 && ivalue > 0)) {
						start += ivalue;
					}
				}
			}
		}

		base = scale.getPixelForValue(start);
		head = scale.getPixelForValue(start + value);
		size = head - base;

		if (minBarLength !== undefined && Math.abs(size) < minBarLength) {
			size = minBarLength;
			if (value >= 0 && !isHorizontal || value < 0 && isHorizontal) {
				head = base - minBarLength;
			} else {
				head = base + minBarLength;
			}
		}

		return {
			size: size,
			base: base,
			head: head,
			center: head + size / 2
		};
	},

	/**
	 * @private
	 */
	calculateBarIndexPixels: function(datasetIndex, index, ruler) {
		var me = this;
		var options = ruler.scale.options;
		var range = options.barThickness === 'flex'
			? computeFlexCategoryTraits(index, ruler, options)
			: computeFitCategoryTraits(index, ruler, options);

		var stackIndex = me.getStackIndex(datasetIndex, me.getMeta().stack);
		var center = range.start + (range.chunk * stackIndex) + (range.chunk / 2);
		var size = Math.min(
			helpers.valueOrDefault(options.maxBarThickness, Infinity),
			range.chunk * range.ratio);

		return {
			base: center - size / 2,
			head: center + size / 2,
			center: center,
			size: size
		};
	},

	draw: function() {
		var me = this;
		var chart = me.chart;
		var scale = me._getValueScale();
		var rects = me.getMeta().data;
		var dataset = me.getDataset();
		var ilen = rects.length;
		var i = 0;

		helpers.canvas.clipArea(chart.ctx, chart.chartArea);

		for (; i < ilen; ++i) {
			if (!isNaN(scale.getRightValue(dataset.data[i]))) {
				rects[i].draw();
			}
		}

		helpers.canvas.unclipArea(chart.ctx);
	}
});