controller.bar.js

'use strict';

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',

			// Specific to Bar Controller
			categoryPercentage: 0.8,
			barPercentage: 0.9,

			// offset settings
			offset: true,

			// grid line settings
			gridLines: {
				offsetGridLines: true
			}
		}],

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

defaults._set('horizontalBar', {
	hover: {
		mode: 'index',
		axis: 'y'
	},

	scales: {
		xAxes: [{
			type: 'linear',
			position: 'bottom'
		}],

		yAxes: [{
			position: 'left',
			type: 'category',

			// Specific to Horizontal Bar Controller
			categoryPercentage: 0.8,
			barPercentage: 0.9,

			// offset settings
			offset: true,

			// grid line settings
			gridLines: {
				offsetGridLines: true
			}
		}]
	},

	elements: {
		rectangle: {
			borderSkipped: 'left'
		}
	},

	tooltips: {
		callbacks: {
			title: function(item, data) {
				// Pick first xLabel for now
				var title = '';

				if (item.length > 0) {
					if (item[0].yLabel) {
						title = item[0].yLabel;
					} else if (data.labels.length > 0 && item[0].index < data.labels.length) {
						title = data.labels[item[0].index];
					}
				}

				return title;
			},

			label: function(item, data) {
				var datasetLabel = data.datasets[item.datasetIndex].label || '';
				return datasetLabel + ': ' + item.xLabel;
			}
		},
		mode: 'index',
		axis: 'y'
	}
});

/**
 * 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, 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 end extremity.
		prev = curr - (next === null ? ruler.end - curr : next - curr);
	}

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

	start = curr - ((curr - prev) / 2) * percent;
	size = ((next - prev) / 2) * percent;

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

module.exports = function(Chart) {

	Chart.controllers.bar = Chart.DatasetController.extend({

		dataElementType: elements.Rectangle,

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

			Chart.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._resolveElementOptions(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;
		},

		/**
		 * @private
		 */
		getValueScaleId: function() {
			return this.getMeta().yAxisID;
		},

		/**
		 * @private
		 */
		getIndexScaleId: function() {
			return this.getMeta().xAxisID;
		},

		/**
		 * @private
		 */
		getValueScale: function() {
			return this.getScaleForId(this.getValueScaleId());
		},

		/**
		 * @private
		 */
		getIndexScale: function() {
			return this.getScaleForId(this.getIndexScaleId());
		},

		/**
		 * Returns the stacks based on groups and bar visibility.
		 * @param {Number} [last] - The dataset index
		 * @returns {Array} The stack list
		 * @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) / 2;

			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);
		},

		/**
		 * @private
		 */
		_resolveElementOptions: function(rectangle, index) {
			var me = this;
			var chart = me.chart;
			var datasets = chart.data.datasets;
			var dataset = datasets[me.index];
			var custom = rectangle.custom || {};
			var options = chart.options.elements.rectangle;
			var resolve = helpers.options.resolve;
			var values = {};
			var i, ilen, key;

			// Scriptable options
			var context = {
				chart: chart,
				dataIndex: index,
				dataset: dataset,
				datasetIndex: me.index
			};

			var keys = [
				'backgroundColor',
				'borderColor',
				'borderSkipped',
				'borderWidth'
			];

			for (i = 0, ilen = keys.length; i < ilen; ++i) {
				key = keys[i];
				values[key] = resolve([
					custom[key],
					dataset[key],
					options[key]
				], context, index);
			}

			return values;
		}
	});

	Chart.controllers.horizontalBar = Chart.controllers.bar.extend({
		/**
		 * @private
		 */
		getValueScaleId: function() {
			return this.getMeta().xAxisID;
		},

		/**
		 * @private
		 */
		getIndexScaleId: function() {
			return this.getMeta().yAxisID;
		}
	});
};