/*global window: false */
"use strict";

var moment = require('moment');
moment = typeof(moment) === 'function' ? moment : window.moment;

module.exports = function(Chart) {

	var helpers = Chart.helpers;

	if (!moment) {
		console.warn('Chart.js - Moment.js could not be found! You must include it before Chart.js to use the time scale. Download at http://momentjs.com/');
		return;
	}

	var time = {
		units: [{
			name: 'millisecond',
			steps: [1, 2, 5, 10, 20, 50, 100, 250, 500]
		}, {
			name: 'second',
			steps: [1, 2, 5, 10, 30]
		}, {
			name: 'minute',
			steps: [1, 2, 5, 10, 30]
		}, {
			name: 'hour',
			steps: [1, 2, 3, 6, 12]
		}, {
			name: 'day',
			steps: [1, 2, 5]
		}, {
			name: 'week',
			maxStep: 4
		}, {
			name: 'month',
			maxStep: 3
		}, {
			name: 'quarter',
			maxStep: 4
		}, {
			name: 'year',
			maxStep: false
		}]
	};

	var defaultConfig = {
		position: "bottom",

		time: {
			format: false, // false == date objects or use pattern string from http://momentjs.com/docs/#/parsing/string-format/
			unit: false, // false == automatic or override with week, month, year, etc.
			round: false, // none, or override with week, month, year, etc.
			displayFormat: false, // DEPRECATED

			// defaults to unit's corresponding unitFormat below or override using pattern string from http://momentjs.com/docs/#/displaying/format/
			displayFormats: {
				'millisecond': 'h:mm:ss.SSS a', // 11:20:01.123 AM,
				'second': 'h:mm:ss a', // 11:20:01 AM
				'minute': 'h:mm:ss a', // 11:20:01 AM
				'hour': 'MMM D, hA', // Sept 4, 5PM
				'day': 'll', // Sep 4 2015
				'week': 'll', // Week 46, or maybe "[W]WW - YYYY" ?
				'month': 'MMM YYYY', // Sept 2015
				'quarter': '[Q]Q - YYYY', // Q3
				'year': 'YYYY' // 2015
			}
		},
		ticks: {
			autoSkip: false,
		}
	};

	var TimeScale = Chart.Scale.extend({
		getLabelMoment: function(datasetIndex, index) {
			return this.labelMoments[datasetIndex][index];
		},
		determineDataLimits: function() {
			this.labelMoments = [];

			// Only parse these once. If the dataset does not have data as x,y pairs, we will use
			// these
			var scaleLabelMoments = [];
			if (this.chart.data.labels && this.chart.data.labels.length > 0) {
				helpers.each(this.chart.data.labels, function(label, index) {
					var labelMoment = this.parseTime(label);
					if (this.options.time.round) {
						labelMoment.startOf(this.options.time.round);
					}
					scaleLabelMoments.push(labelMoment);
				}, this);

				this.firstTick = moment.min.call(this, scaleLabelMoments);
				this.lastTick = moment.max.call(this, scaleLabelMoments);
			} else {
				this.firstTick = null;
				this.lastTick = null;
			}

			helpers.each(this.chart.data.datasets, function(dataset, datasetIndex) {
				var momentsForDataset = [];

				if (typeof dataset.data[0] === 'object') {
					helpers.each(dataset.data, function(value, index) {
						var labelMoment = this.parseTime(this.getRightValue(value));
						if (this.options.time.round) {
							labelMoment.startOf(this.options.time.round);
						}
						momentsForDataset.push(labelMoment);

						// May have gone outside the scale ranges, make sure we keep the first and last ticks updated
						this.firstTick = this.firstTick !== null ? moment.min(this.firstTick, labelMoment) : labelMoment;
						this.lastTick = this.lastTick !== null ? moment.max(this.lastTick, labelMoment) : labelMoment;
					}, this);
				} else {
					// We have no labels. Use the ones from the scale
					momentsForDataset = scaleLabelMoments;
				}

				this.labelMoments.push(momentsForDataset);
			}, this);

			// Set these after we've done all the data
			if (this.options.time.min) {
				this.firstTick = this.parseTime(this.options.time.min);
			}

			if (this.options.time.max) {
				this.lastTick = this.parseTime(this.options.time.max);
			}

			// We will modify these, so clone for later
			this.firstTick = (this.firstTick || moment()).clone();
			this.lastTick = (this.lastTick || moment()).clone();
		},
		buildTicks: function(index) {

			this.ticks = [];
			this.unitScale = 1; // How much we scale the unit by, ie 2 means 2x unit per step

			// Set unit override if applicable
			if (this.options.time.unit) {
				this.tickUnit = this.options.time.unit || 'day';
				this.displayFormat = this.options.time.displayFormats[this.tickUnit];
				this.tickRange = Math.ceil(this.lastTick.diff(this.firstTick, this.tickUnit, true));
			} else {
				// Determine the smallest needed unit of the time
				var innerWidth = this.isHorizontal() ? this.width - (this.paddingLeft + this.paddingRight) : this.height - (this.paddingTop + this.paddingBottom);
				var labelCapacity = innerWidth / (this.options.ticks.fontSize + 10);
				var buffer = this.options.time.round ? 0 : 1;

				// Start as small as possible
				this.tickUnit = 'millisecond';
				this.tickRange = Math.ceil(this.lastTick.diff(this.firstTick, this.tickUnit, true) + buffer);
				this.displayFormat = this.options.time.displayFormats[this.tickUnit];

				var unitDefinitionIndex = 0;
				var unitDefinition = time.units[unitDefinitionIndex];

				// While we aren't ideal and we don't have units left
				while (unitDefinitionIndex < time.units.length) {
					// Can we scale this unit. If `false` we can scale infinitely
					this.unitScale = 1;

					if (helpers.isArray(unitDefinition.steps) && Math.ceil(this.tickRange / labelCapacity) < helpers.max(unitDefinition.steps)) {
						// Use one of the prefedined steps
						for (var idx = 0; idx < unitDefinition.steps.length; ++idx) {
							if (unitDefinition.steps[idx] > Math.ceil(this.tickRange / labelCapacity)) {
								this.unitScale = unitDefinition.steps[idx];
								break;
							}
						}

						break;
					} else if ((unitDefinition.maxStep === false) || (Math.ceil(this.tickRange / labelCapacity) < unitDefinition.maxStep)) {
						// We have a max step. Scale this unit
						this.unitScale = Math.ceil(this.tickRange / labelCapacity);
						break;
					} else {
						// Move to the next unit up
						++unitDefinitionIndex;
						unitDefinition = time.units[unitDefinitionIndex];

						this.tickUnit = unitDefinition.name;
						this.tickRange = Math.ceil(this.lastTick.diff(this.firstTick, this.tickUnit) + buffer);
						this.displayFormat = this.options.time.displayFormats[unitDefinition.name];
					}
				}
			}

			var roundedStart;

			// Only round the first tick if we have no hard minimum
			if (!this.options.time.min) {
				this.firstTick.startOf(this.tickUnit);
				roundedStart = this.firstTick;
			} else {
				roundedStart = this.firstTick.clone().startOf(this.tickUnit);
			}

			// Only round the last tick if we have no hard maximum
			if (!this.options.time.max) {
				this.lastTick.endOf(this.tickUnit);
			}

			this.smallestLabelSeparation = this.width;

			helpers.each(this.chart.data.datasets, function(dataset, datasetIndex) {
				for (var i = 1; i < this.labelMoments[datasetIndex].length; i++) {
					this.smallestLabelSeparation = Math.min(this.smallestLabelSeparation, this.labelMoments[datasetIndex][i].diff(this.labelMoments[datasetIndex][i - 1], this.tickUnit, true));
				}
			}, this);

			// Tick displayFormat override
			if (this.options.time.displayFormat) {
				this.displayFormat = this.options.time.displayFormat;
			}

			// first tick. will have been rounded correctly if options.time.min is not specified
			this.ticks.push(this.firstTick.clone());

			// For every unit in between the first and last moment, create a moment and add it to the ticks tick
			for (var i = 1; i < this.tickRange; ++i) {
				var newTick = roundedStart.clone().add(i, this.tickUnit);

				// Are we greater than the max time
				if (this.options.time.max && newTick.diff(this.lastTick, this.tickUnit, true) >= 0) {
					break;
				}

				if (i % this.unitScale === 0) {
					this.ticks.push(newTick);
				}
			}

			// Always show the right tick
			if (this.options.time.max) {
				this.ticks.push(this.lastTick.clone());
			} else if (this.ticks[this.ticks.length - 1].diff(this.lastTick, this.tickUnit, true) !== 0) {
				this.tickRange = Math.ceil(this.tickRange / this.unitScale) * this.unitScale;
				this.ticks.push(this.firstTick.clone().add(this.tickRange, this.tickUnit));
				this.lastTick = this.ticks[this.ticks.length - 1].clone();
			}
		},
		// Get tooltip label
		getLabelForIndex: function(index, datasetIndex) {
			var label = this.chart.data.labels && index < this.chart.data.labels.length ? this.chart.data.labels[index] : '';

			if (typeof this.chart.data.datasets[datasetIndex].data[0] === 'object') {
				label = this.getRightValue(this.chart.data.datasets[datasetIndex].data[index]);
			}

			// Format nicely
			if (this.options.time.tooltipFormat) {
				label = this.parseTime(label).format(this.options.time.tooltipFormat);
			}

			return label;
		},
		convertTicksToLabels: function() {
			this.ticks = this.ticks.map(function(tick, index, ticks) {
				var formattedTick = tick.format(this.displayFormat);

				if (this.options.ticks.userCallback) {
					return this.options.ticks.userCallback(formattedTick, index, ticks);
				} else {
					return formattedTick;
				}
			}, this);
		},
		getPixelForValue: function(value, index, datasetIndex, includeOffset) {
			var labelMoment = this.getLabelMoment(datasetIndex, index);
			var offset = labelMoment.diff(this.firstTick, this.tickUnit, true);

			var decimal = offset / this.tickRange;

			if (this.isHorizontal()) {
				var innerWidth = this.width - (this.paddingLeft + this.paddingRight);
				var valueWidth = innerWidth / Math.max(this.ticks.length - 1, 1);
				var valueOffset = (innerWidth * decimal) + this.paddingLeft;

				return this.left + Math.round(valueOffset);
			} else {
				var innerHeight = this.height - (this.paddingTop + this.paddingBottom);
				var valueHeight = innerHeight / Math.max(this.ticks.length - 1, 1);
				var heightOffset = (innerHeight * decimal) + this.paddingTop;

				return this.top + Math.round(heightOffset);
			}
		},
		parseTime: function(label) {
			// Date objects
			if (typeof label.getMonth === 'function' || typeof label === 'number') {
				return moment(label);
			}
			// Moment support
			if (label.isValid && label.isValid()) {
				return label;
			}
			// Custom parsing (return an instance of moment)
			if (typeof this.options.time.format !== 'string' && this.options.time.format.call) {
				return this.options.time.format(label);
			}
			// Moment format parsing
			return moment(label, this.options.time.format);
		}
	});
	Chart.scaleService.registerScaleType("time", TimeScale, defaultConfig);

};