'use strict';

var defaults = require('./core.defaults');
var Element = require('./core.element');
var helpers = require('../helpers/index');

defaults._set('global', {
	tooltips: {
		enabled: true,
		custom: null,
		mode: 'nearest',
		position: 'average',
		intersect: true,
		backgroundColor: 'rgba(0,0,0,0.8)',
		titleFontStyle: 'bold',
		titleSpacing: 2,
		titleMarginBottom: 6,
		titleFontColor: '#fff',
		titleAlign: 'left',
		bodySpacing: 2,
		bodyFontColor: '#fff',
		bodyAlign: 'left',
		footerFontStyle: 'bold',
		footerSpacing: 2,
		footerMarginTop: 6,
		footerFontColor: '#fff',
		footerAlign: 'left',
		yPadding: 6,
		xPadding: 6,
		caretPadding: 2,
		caretSize: 5,
		cornerRadius: 6,
		multiKeyBackground: '#fff',
		displayColors: true,
		borderColor: 'rgba(0,0,0,0)',
		borderWidth: 0,
		callbacks: {
			// Args are: (tooltipItems, data)
			beforeTitle: helpers.noop,
			title: function(tooltipItems, data) {
				// Pick first xLabel for now
				var title = '';
				var labels = data.labels;
				var labelCount = labels ? labels.length : 0;

				if (tooltipItems.length > 0) {
					var item = tooltipItems[0];

					if (item.xLabel) {
						title = item.xLabel;
					} else if (labelCount > 0 && item.index < labelCount) {
						title = labels[item.index];
					}
				}

				return title;
			},
			afterTitle: helpers.noop,

			// Args are: (tooltipItems, data)
			beforeBody: helpers.noop,

			// Args are: (tooltipItem, data)
			beforeLabel: helpers.noop,
			label: function(tooltipItem, data) {
				var label = data.datasets[tooltipItem.datasetIndex].label || '';

				if (label) {
					label += ': ';
				}
				label += tooltipItem.yLabel;
				return label;
			},
			labelColor: function(tooltipItem, chart) {
				var meta = chart.getDatasetMeta(tooltipItem.datasetIndex);
				var activeElement = meta.data[tooltipItem.index];
				var view = activeElement._view;
				return {
					borderColor: view.borderColor,
					backgroundColor: view.backgroundColor
				};
			},
			labelTextColor: function() {
				return this._options.bodyFontColor;
			},
			afterLabel: helpers.noop,

			// Args are: (tooltipItems, data)
			afterBody: helpers.noop,

			// Args are: (tooltipItems, data)
			beforeFooter: helpers.noop,
			footer: helpers.noop,
			afterFooter: helpers.noop
		}
	}
});

module.exports = function(Chart) {

	/**
 	 * Helper method to merge the opacity into a color
 	 */
	function mergeOpacity(colorString, opacity) {
		var color = helpers.color(colorString);
		return color.alpha(opacity * color.alpha()).rgbaString();
	}

	// Helper to push or concat based on if the 2nd parameter is an array or not
	function pushOrConcat(base, toPush) {
		if (toPush) {
			if (helpers.isArray(toPush)) {
				// base = base.concat(toPush);
				Array.prototype.push.apply(base, toPush);
			} else {
				base.push(toPush);
			}
		}

		return base;
	}

	// Private helper to create a tooltip item model
	// @param element : the chart element (point, arc, bar) to create the tooltip item for
	// @return : new tooltip item
	function createTooltipItem(element) {
		var xScale = element._xScale;
		var yScale = element._yScale || element._scale; // handle radar || polarArea charts
		var index = element._index;
		var datasetIndex = element._datasetIndex;

		return {
			xLabel: xScale ? xScale.getLabelForIndex(index, datasetIndex) : '',
			yLabel: yScale ? yScale.getLabelForIndex(index, datasetIndex) : '',
			index: index,
			datasetIndex: datasetIndex,
			x: element._model.x,
			y: element._model.y
		};
	}

	/**
	 * Helper to get the reset model for the tooltip
	 * @param tooltipOpts {Object} the tooltip options
	 */
	function getBaseModel(tooltipOpts) {
		var globalDefaults = defaults.global;
		var valueOrDefault = helpers.valueOrDefault;

		return {
			// Positioning
			xPadding: tooltipOpts.xPadding,
			yPadding: tooltipOpts.yPadding,
			xAlign: tooltipOpts.xAlign,
			yAlign: tooltipOpts.yAlign,

			// Body
			bodyFontColor: tooltipOpts.bodyFontColor,
			_bodyFontFamily: valueOrDefault(tooltipOpts.bodyFontFamily, globalDefaults.defaultFontFamily),
			_bodyFontStyle: valueOrDefault(tooltipOpts.bodyFontStyle, globalDefaults.defaultFontStyle),
			_bodyAlign: tooltipOpts.bodyAlign,
			bodyFontSize: valueOrDefault(tooltipOpts.bodyFontSize, globalDefaults.defaultFontSize),
			bodySpacing: tooltipOpts.bodySpacing,

			// Title
			titleFontColor: tooltipOpts.titleFontColor,
			_titleFontFamily: valueOrDefault(tooltipOpts.titleFontFamily, globalDefaults.defaultFontFamily),
			_titleFontStyle: valueOrDefault(tooltipOpts.titleFontStyle, globalDefaults.defaultFontStyle),
			titleFontSize: valueOrDefault(tooltipOpts.titleFontSize, globalDefaults.defaultFontSize),
			_titleAlign: tooltipOpts.titleAlign,
			titleSpacing: tooltipOpts.titleSpacing,
			titleMarginBottom: tooltipOpts.titleMarginBottom,

			// Footer
			footerFontColor: tooltipOpts.footerFontColor,
			_footerFontFamily: valueOrDefault(tooltipOpts.footerFontFamily, globalDefaults.defaultFontFamily),
			_footerFontStyle: valueOrDefault(tooltipOpts.footerFontStyle, globalDefaults.defaultFontStyle),
			footerFontSize: valueOrDefault(tooltipOpts.footerFontSize, globalDefaults.defaultFontSize),
			_footerAlign: tooltipOpts.footerAlign,
			footerSpacing: tooltipOpts.footerSpacing,
			footerMarginTop: tooltipOpts.footerMarginTop,

			// Appearance
			caretSize: tooltipOpts.caretSize,
			cornerRadius: tooltipOpts.cornerRadius,
			backgroundColor: tooltipOpts.backgroundColor,
			opacity: 0,
			legendColorBackground: tooltipOpts.multiKeyBackground,
			displayColors: tooltipOpts.displayColors,
			borderColor: tooltipOpts.borderColor,
			borderWidth: tooltipOpts.borderWidth
		};
	}

	/**
	 * Get the size of the tooltip
	 */
	function getTooltipSize(tooltip, model) {
		var ctx = tooltip._chart.ctx;

		var height = model.yPadding * 2; // Tooltip Padding
		var width = 0;

		// Count of all lines in the body
		var body = model.body;
		var combinedBodyLength = body.reduce(function(count, bodyItem) {
			return count + bodyItem.before.length + bodyItem.lines.length + bodyItem.after.length;
		}, 0);
		combinedBodyLength += model.beforeBody.length + model.afterBody.length;

		var titleLineCount = model.title.length;
		var footerLineCount = model.footer.length;
		var titleFontSize = model.titleFontSize;
		var bodyFontSize = model.bodyFontSize;
		var footerFontSize = model.footerFontSize;

		height += titleLineCount * titleFontSize; // Title Lines
		height += titleLineCount ? (titleLineCount - 1) * model.titleSpacing : 0; // Title Line Spacing
		height += titleLineCount ? model.titleMarginBottom : 0; // Title's bottom Margin
		height += combinedBodyLength * bodyFontSize; // Body Lines
		height += combinedBodyLength ? (combinedBodyLength - 1) * model.bodySpacing : 0; // Body Line Spacing
		height += footerLineCount ? model.footerMarginTop : 0; // Footer Margin
		height += footerLineCount * (footerFontSize); // Footer Lines
		height += footerLineCount ? (footerLineCount - 1) * model.footerSpacing : 0; // Footer Line Spacing

		// Title width
		var widthPadding = 0;
		var maxLineWidth = function(line) {
			width = Math.max(width, ctx.measureText(line).width + widthPadding);
		};

		ctx.font = helpers.fontString(titleFontSize, model._titleFontStyle, model._titleFontFamily);
		helpers.each(model.title, maxLineWidth);

		// Body width
		ctx.font = helpers.fontString(bodyFontSize, model._bodyFontStyle, model._bodyFontFamily);
		helpers.each(model.beforeBody.concat(model.afterBody), maxLineWidth);

		// Body lines may include some extra width due to the color box
		widthPadding = model.displayColors ? (bodyFontSize + 2) : 0;
		helpers.each(body, function(bodyItem) {
			helpers.each(bodyItem.before, maxLineWidth);
			helpers.each(bodyItem.lines, maxLineWidth);
			helpers.each(bodyItem.after, maxLineWidth);
		});

		// Reset back to 0
		widthPadding = 0;

		// Footer width
		ctx.font = helpers.fontString(footerFontSize, model._footerFontStyle, model._footerFontFamily);
		helpers.each(model.footer, maxLineWidth);

		// Add padding
		width += 2 * model.xPadding;

		return {
			width: width,
			height: height
		};
	}

	/**
	 * Helper to get the alignment of a tooltip given the size
	 */
	function determineAlignment(tooltip, size) {
		var model = tooltip._model;
		var chart = tooltip._chart;
		var chartArea = tooltip._chart.chartArea;
		var xAlign = 'center';
		var yAlign = 'center';

		if (model.y < size.height) {
			yAlign = 'top';
		} else if (model.y > (chart.height - size.height)) {
			yAlign = 'bottom';
		}

		var lf, rf; // functions to determine left, right alignment
		var olf, orf; // functions to determine if left/right alignment causes tooltip to go outside chart
		var yf; // function to get the y alignment if the tooltip goes outside of the left or right edges
		var midX = (chartArea.left + chartArea.right) / 2;
		var midY = (chartArea.top + chartArea.bottom) / 2;

		if (yAlign === 'center') {
			lf = function(x) {
				return x <= midX;
			};
			rf = function(x) {
				return x > midX;
			};
		} else {
			lf = function(x) {
				return x <= (size.width / 2);
			};
			rf = function(x) {
				return x >= (chart.width - (size.width / 2));
			};
		}

		olf = function(x) {
			return x + size.width > chart.width;
		};
		orf = function(x) {
			return x - size.width < 0;
		};
		yf = function(y) {
			return y <= midY ? 'top' : 'bottom';
		};

		if (lf(model.x)) {
			xAlign = 'left';

			// Is tooltip too wide and goes over the right side of the chart.?
			if (olf(model.x)) {
				xAlign = 'center';
				yAlign = yf(model.y);
			}
		} else if (rf(model.x)) {
			xAlign = 'right';

			// Is tooltip too wide and goes outside left edge of canvas?
			if (orf(model.x)) {
				xAlign = 'center';
				yAlign = yf(model.y);
			}
		}

		var opts = tooltip._options;
		return {
			xAlign: opts.xAlign ? opts.xAlign : xAlign,
			yAlign: opts.yAlign ? opts.yAlign : yAlign
		};
	}

	/**
	 * @Helper to get the location a tooltip needs to be placed at given the initial position (via the vm) and the size and alignment
	 */
	function getBackgroundPoint(vm, size, alignment) {
		// Background Position
		var x = vm.x;
		var y = vm.y;

		var caretSize = vm.caretSize;
		var caretPadding = vm.caretPadding;
		var cornerRadius = vm.cornerRadius;
		var xAlign = alignment.xAlign;
		var yAlign = alignment.yAlign;
		var paddingAndSize = caretSize + caretPadding;
		var radiusAndPadding = cornerRadius + caretPadding;

		if (xAlign === 'right') {
			x -= size.width;
		} else if (xAlign === 'center') {
			x -= (size.width / 2);
		}

		if (yAlign === 'top') {
			y += paddingAndSize;
		} else if (yAlign === 'bottom') {
			y -= size.height + paddingAndSize;
		} else {
			y -= (size.height / 2);
		}

		if (yAlign === 'center') {
			if (xAlign === 'left') {
				x += paddingAndSize;
			} else if (xAlign === 'right') {
				x -= paddingAndSize;
			}
		} else if (xAlign === 'left') {
			x -= radiusAndPadding;
		} else if (xAlign === 'right') {
			x += radiusAndPadding;
		}

		return {
			x: x,
			y: y
		};
	}

	Chart.Tooltip = Element.extend({
		initialize: function() {
			this._model = getBaseModel(this._options);
		},

		// Get the title
		// Args are: (tooltipItem, data)
		getTitle: function() {
			var me = this;
			var opts = me._options;
			var callbacks = opts.callbacks;

			var beforeTitle = callbacks.beforeTitle.apply(me, arguments);
			var title = callbacks.title.apply(me, arguments);
			var afterTitle = callbacks.afterTitle.apply(me, arguments);

			var lines = [];
			lines = pushOrConcat(lines, beforeTitle);
			lines = pushOrConcat(lines, title);
			lines = pushOrConcat(lines, afterTitle);

			return lines;
		},

		// Args are: (tooltipItem, data)
		getBeforeBody: function() {
			var lines = this._options.callbacks.beforeBody.apply(this, arguments);
			return helpers.isArray(lines) ? lines : lines !== undefined ? [lines] : [];
		},

		// Args are: (tooltipItem, data)
		getBody: function(tooltipItems, data) {
			var me = this;
			var callbacks = me._options.callbacks;
			var bodyItems = [];

			helpers.each(tooltipItems, function(tooltipItem) {
				var bodyItem = {
					before: [],
					lines: [],
					after: []
				};
				pushOrConcat(bodyItem.before, callbacks.beforeLabel.call(me, tooltipItem, data));
				pushOrConcat(bodyItem.lines, callbacks.label.call(me, tooltipItem, data));
				pushOrConcat(bodyItem.after, callbacks.afterLabel.call(me, tooltipItem, data));

				bodyItems.push(bodyItem);
			});

			return bodyItems;
		},

		// Args are: (tooltipItem, data)
		getAfterBody: function() {
			var lines = this._options.callbacks.afterBody.apply(this, arguments);
			return helpers.isArray(lines) ? lines : lines !== undefined ? [lines] : [];
		},

		// Get the footer and beforeFooter and afterFooter lines
		// Args are: (tooltipItem, data)
		getFooter: function() {
			var me = this;
			var callbacks = me._options.callbacks;

			var beforeFooter = callbacks.beforeFooter.apply(me, arguments);
			var footer = callbacks.footer.apply(me, arguments);
			var afterFooter = callbacks.afterFooter.apply(me, arguments);

			var lines = [];
			lines = pushOrConcat(lines, beforeFooter);
			lines = pushOrConcat(lines, footer);
			lines = pushOrConcat(lines, afterFooter);

			return lines;
		},

		update: function(changed) {
			var me = this;
			var opts = me._options;

			// Need to regenerate the model because its faster than using extend and it is necessary due to the optimization in Chart.Element.transition
			// that does _view = _model if ease === 1. This causes the 2nd tooltip update to set properties in both the view and model at the same time
			// which breaks any animations.
			var existingModel = me._model;
			var model = me._model = getBaseModel(opts);
			var active = me._active;

			var data = me._data;

			// In the case where active.length === 0 we need to keep these at existing values for good animations
			var alignment = {
				xAlign: existingModel.xAlign,
				yAlign: existingModel.yAlign
			};
			var backgroundPoint = {
				x: existingModel.x,
				y: existingModel.y
			};
			var tooltipSize = {
				width: existingModel.width,
				height: existingModel.height
			};
			var tooltipPosition = {
				x: existingModel.caretX,
				y: existingModel.caretY
			};

			var i, len;

			if (active.length) {
				model.opacity = 1;

				var labelColors = [];
				var labelTextColors = [];
				tooltipPosition = Chart.Tooltip.positioners[opts.position](active, me._eventPosition);

				var tooltipItems = [];
				for (i = 0, len = active.length; i < len; ++i) {
					tooltipItems.push(createTooltipItem(active[i]));
				}

				// If the user provided a filter function, use it to modify the tooltip items
				if (opts.filter) {
					tooltipItems = tooltipItems.filter(function(a) {
						return opts.filter(a, data);
					});
				}

				// If the user provided a sorting function, use it to modify the tooltip items
				if (opts.itemSort) {
					tooltipItems = tooltipItems.sort(function(a, b) {
						return opts.itemSort(a, b, data);
					});
				}

				// Determine colors for boxes
				helpers.each(tooltipItems, function(tooltipItem) {
					labelColors.push(opts.callbacks.labelColor.call(me, tooltipItem, me._chart));
					labelTextColors.push(opts.callbacks.labelTextColor.call(me, tooltipItem, me._chart));
				});


				// Build the Text Lines
				model.title = me.getTitle(tooltipItems, data);
				model.beforeBody = me.getBeforeBody(tooltipItems, data);
				model.body = me.getBody(tooltipItems, data);
				model.afterBody = me.getAfterBody(tooltipItems, data);
				model.footer = me.getFooter(tooltipItems, data);

				// Initial positioning and colors
				model.x = Math.round(tooltipPosition.x);
				model.y = Math.round(tooltipPosition.y);
				model.caretPadding = opts.caretPadding;
				model.labelColors = labelColors;
				model.labelTextColors = labelTextColors;

				// data points
				model.dataPoints = tooltipItems;

				// We need to determine alignment of the tooltip
				tooltipSize = getTooltipSize(this, model);
				alignment = determineAlignment(this, tooltipSize);
				// Final Size and Position
				backgroundPoint = getBackgroundPoint(model, tooltipSize, alignment);
			} else {
				model.opacity = 0;
			}

			model.xAlign = alignment.xAlign;
			model.yAlign = alignment.yAlign;
			model.x = backgroundPoint.x;
			model.y = backgroundPoint.y;
			model.width = tooltipSize.width;
			model.height = tooltipSize.height;

			// Point where the caret on the tooltip points to
			model.caretX = tooltipPosition.x;
			model.caretY = tooltipPosition.y;

			me._model = model;

			if (changed && opts.custom) {
				opts.custom.call(me, model);
			}

			return me;
		},
		drawCaret: function(tooltipPoint, size) {
			var ctx = this._chart.ctx;
			var vm = this._view;
			var caretPosition = this.getCaretPosition(tooltipPoint, size, vm);

			ctx.lineTo(caretPosition.x1, caretPosition.y1);
			ctx.lineTo(caretPosition.x2, caretPosition.y2);
			ctx.lineTo(caretPosition.x3, caretPosition.y3);
		},
		getCaretPosition: function(tooltipPoint, size, vm) {
			var x1, x2, x3, y1, y2, y3;
			var caretSize = vm.caretSize;
			var cornerRadius = vm.cornerRadius;
			var xAlign = vm.xAlign;
			var yAlign = vm.yAlign;
			var ptX = tooltipPoint.x;
			var ptY = tooltipPoint.y;
			var width = size.width;
			var height = size.height;

			if (yAlign === 'center') {
				y2 = ptY + (height / 2);

				if (xAlign === 'left') {
					x1 = ptX;
					x2 = x1 - caretSize;
					x3 = x1;

					y1 = y2 + caretSize;
					y3 = y2 - caretSize;
				} else {
					x1 = ptX + width;
					x2 = x1 + caretSize;
					x3 = x1;

					y1 = y2 - caretSize;
					y3 = y2 + caretSize;
				}
			} else {
				if (xAlign === 'left') {
					x2 = ptX + cornerRadius + (caretSize);
					x1 = x2 - caretSize;
					x3 = x2 + caretSize;
				} else if (xAlign === 'right') {
					x2 = ptX + width - cornerRadius - caretSize;
					x1 = x2 - caretSize;
					x3 = x2 + caretSize;
				} else {
					x2 = ptX + (width / 2);
					x1 = x2 - caretSize;
					x3 = x2 + caretSize;
				}
				if (yAlign === 'top') {
					y1 = ptY;
					y2 = y1 - caretSize;
					y3 = y1;
				} else {
					y1 = ptY + height;
					y2 = y1 + caretSize;
					y3 = y1;
					// invert drawing order
					var tmp = x3;
					x3 = x1;
					x1 = tmp;
				}
			}
			return {x1: x1, x2: x2, x3: x3, y1: y1, y2: y2, y3: y3};
		},
		drawTitle: function(pt, vm, ctx, opacity) {
			var title = vm.title;

			if (title.length) {
				ctx.textAlign = vm._titleAlign;
				ctx.textBaseline = 'top';

				var titleFontSize = vm.titleFontSize;
				var titleSpacing = vm.titleSpacing;

				ctx.fillStyle = mergeOpacity(vm.titleFontColor, opacity);
				ctx.font = helpers.fontString(titleFontSize, vm._titleFontStyle, vm._titleFontFamily);

				var i, len;
				for (i = 0, len = title.length; i < len; ++i) {
					ctx.fillText(title[i], pt.x, pt.y);
					pt.y += titleFontSize + titleSpacing; // Line Height and spacing

					if (i + 1 === title.length) {
						pt.y += vm.titleMarginBottom - titleSpacing; // If Last, add margin, remove spacing
					}
				}
			}
		},
		drawBody: function(pt, vm, ctx, opacity) {
			var bodyFontSize = vm.bodyFontSize;
			var bodySpacing = vm.bodySpacing;
			var body = vm.body;

			ctx.textAlign = vm._bodyAlign;
			ctx.textBaseline = 'top';
			ctx.font = helpers.fontString(bodyFontSize, vm._bodyFontStyle, vm._bodyFontFamily);

			// Before Body
			var xLinePadding = 0;
			var fillLineOfText = function(line) {
				ctx.fillText(line, pt.x + xLinePadding, pt.y);
				pt.y += bodyFontSize + bodySpacing;
			};

			// Before body lines
			helpers.each(vm.beforeBody, fillLineOfText);

			var drawColorBoxes = vm.displayColors;
			xLinePadding = drawColorBoxes ? (bodyFontSize + 2) : 0;

			// Draw body lines now
			helpers.each(body, function(bodyItem, i) {
				helpers.each(bodyItem.before, fillLineOfText);

				helpers.each(bodyItem.lines, function(line) {
					// Draw Legend-like boxes if needed
					if (drawColorBoxes) {
						// Fill a white rect so that colours merge nicely if the opacity is < 1
						ctx.fillStyle = mergeOpacity(vm.legendColorBackground, opacity);
						ctx.fillRect(pt.x, pt.y, bodyFontSize, bodyFontSize);

						// Border
						ctx.lineWidth = 1;
						ctx.strokeStyle = mergeOpacity(vm.labelColors[i].borderColor, opacity);
						ctx.strokeRect(pt.x, pt.y, bodyFontSize, bodyFontSize);

						// Inner square
						ctx.fillStyle = mergeOpacity(vm.labelColors[i].backgroundColor, opacity);
						ctx.fillRect(pt.x + 1, pt.y + 1, bodyFontSize - 2, bodyFontSize - 2);
						var textColor = mergeOpacity(vm.labelTextColors[i], opacity);
						ctx.fillStyle = textColor;
					}

					fillLineOfText(line);
				});

				helpers.each(bodyItem.after, fillLineOfText);
			});

			// Reset back to 0 for after body
			xLinePadding = 0;

			// After body lines
			helpers.each(vm.afterBody, fillLineOfText);
			pt.y -= bodySpacing; // Remove last body spacing
		},
		drawFooter: function(pt, vm, ctx, opacity) {
			var footer = vm.footer;

			if (footer.length) {
				pt.y += vm.footerMarginTop;

				ctx.textAlign = vm._footerAlign;
				ctx.textBaseline = 'top';

				ctx.fillStyle = mergeOpacity(vm.footerFontColor, opacity);
				ctx.font = helpers.fontString(vm.footerFontSize, vm._footerFontStyle, vm._footerFontFamily);

				helpers.each(footer, function(line) {
					ctx.fillText(line, pt.x, pt.y);
					pt.y += vm.footerFontSize + vm.footerSpacing;
				});
			}
		},
		drawBackground: function(pt, vm, ctx, tooltipSize, opacity) {
			ctx.fillStyle = mergeOpacity(vm.backgroundColor, opacity);
			ctx.strokeStyle = mergeOpacity(vm.borderColor, opacity);
			ctx.lineWidth = vm.borderWidth;
			var xAlign = vm.xAlign;
			var yAlign = vm.yAlign;
			var x = pt.x;
			var y = pt.y;
			var width = tooltipSize.width;
			var height = tooltipSize.height;
			var radius = vm.cornerRadius;

			ctx.beginPath();
			ctx.moveTo(x + radius, y);
			if (yAlign === 'top') {
				this.drawCaret(pt, tooltipSize);
			}
			ctx.lineTo(x + width - radius, y);
			ctx.quadraticCurveTo(x + width, y, x + width, y + radius);
			if (yAlign === 'center' && xAlign === 'right') {
				this.drawCaret(pt, tooltipSize);
			}
			ctx.lineTo(x + width, y + height - radius);
			ctx.quadraticCurveTo(x + width, y + height, x + width - radius, y + height);
			if (yAlign === 'bottom') {
				this.drawCaret(pt, tooltipSize);
			}
			ctx.lineTo(x + radius, y + height);
			ctx.quadraticCurveTo(x, y + height, x, y + height - radius);
			if (yAlign === 'center' && xAlign === 'left') {
				this.drawCaret(pt, tooltipSize);
			}
			ctx.lineTo(x, y + radius);
			ctx.quadraticCurveTo(x, y, x + radius, y);
			ctx.closePath();

			ctx.fill();

			if (vm.borderWidth > 0) {
				ctx.stroke();
			}
		},
		draw: function() {
			var ctx = this._chart.ctx;
			var vm = this._view;

			if (vm.opacity === 0) {
				return;
			}

			var tooltipSize = {
				width: vm.width,
				height: vm.height
			};
			var pt = {
				x: vm.x,
				y: vm.y
			};

			// IE11/Edge does not like very small opacities, so snap to 0
			var opacity = Math.abs(vm.opacity < 1e-3) ? 0 : vm.opacity;

			// Truthy/falsey value for empty tooltip
			var hasTooltipContent = vm.title.length || vm.beforeBody.length || vm.body.length || vm.afterBody.length || vm.footer.length;

			if (this._options.enabled && hasTooltipContent) {
				// Draw Background
				this.drawBackground(pt, vm, ctx, tooltipSize, opacity);

				// Draw Title, Body, and Footer
				pt.x += vm.xPadding;
				pt.y += vm.yPadding;

				// Titles
				this.drawTitle(pt, vm, ctx, opacity);

				// Body
				this.drawBody(pt, vm, ctx, opacity);

				// Footer
				this.drawFooter(pt, vm, ctx, opacity);
			}
		},

		/**
		 * Handle an event
		 * @private
		 * @param {IEvent} event - The event to handle
		 * @returns {Boolean} true if the tooltip changed
		 */
		handleEvent: function(e) {
			var me = this;
			var options = me._options;
			var changed = false;

			me._lastActive = me._lastActive || [];

			// Find Active Elements for tooltips
			if (e.type === 'mouseout') {
				me._active = [];
			} else {
				me._active = me._chart.getElementsAtEventForMode(e, options.mode, options);
			}

			// Remember Last Actives
			changed = !helpers.arrayEquals(me._active, me._lastActive);

			// If tooltip didn't change, do not handle the target event
			if (!changed) {
				return false;
			}

			me._lastActive = me._active;

			if (options.enabled || options.custom) {
				me._eventPosition = {
					x: e.x,
					y: e.y
				};

				var model = me._model;
				me.update(true);
				me.pivot();

				// See if our tooltip position changed
				changed |= (model.x !== me._model.x) || (model.y !== me._model.y);
			}

			return changed;
		}
	});

	/**
	 * @namespace Chart.Tooltip.positioners
	 */
	Chart.Tooltip.positioners = {
		/**
		 * Average mode places the tooltip at the average position of the elements shown
		 * @function Chart.Tooltip.positioners.average
		 * @param elements {ChartElement[]} the elements being displayed in the tooltip
		 * @returns {Point} tooltip position
		 */
		average: function(elements) {
			if (!elements.length) {
				return false;
			}

			var i, len;
			var x = 0;
			var y = 0;
			var count = 0;

			for (i = 0, len = elements.length; i < len; ++i) {
				var el = elements[i];
				if (el && el.hasValue()) {
					var pos = el.tooltipPosition();
					x += pos.x;
					y += pos.y;
					++count;
				}
			}

			return {
				x: Math.round(x / count),
				y: Math.round(y / count)
			};
		},

		/**
		 * Gets the tooltip position nearest of the item nearest to the event position
		 * @function Chart.Tooltip.positioners.nearest
		 * @param elements {Chart.Element[]} the tooltip elements
		 * @param eventPosition {Point} the position of the event in canvas coordinates
		 * @returns {Point} the tooltip position
		 */
		nearest: function(elements, eventPosition) {
			var x = eventPosition.x;
			var y = eventPosition.y;
			var minDistance = Number.POSITIVE_INFINITY;
			var i, len, nearestElement;

			for (i = 0, len = elements.length; i < len; ++i) {
				var el = elements[i];
				if (el && el.hasValue()) {
					var center = el.getCenterPoint();
					var d = helpers.distanceBetweenPoints(eventPosition, center);

					if (d < minDistance) {
						minDistance = d;
						nearestElement = el;
					}
				}
			}

			if (nearestElement) {
				var tp = nearestElement.tooltipPosition();
				x = tp.x;
				y = tp.y;
			}

			return {
				x: x,
				y: y
			};
		}
	};
};
