tutorial / directive

"use strict";

module.exports = function(Chart) {

	var helpers = Chart.helpers;

	var defaultConfig = {
		position: "left",

		// label settings
		ticks: {
			callback: function(value, index, arr) {
				var remain = value / (Math.pow(10, Math.floor(helpers.log10(value))));

				if (remain === 1 || remain === 2 || remain === 5 || index === 0 || index === arr.length - 1) {
					return value.toExponential();
				} else {
					return '';
				}
			}
		}
	};

	var LogarithmicScale = Chart.Scale.extend({
		determineDataLimits: function() {
			var me = this;
			var opts = me.options;
			var tickOpts = opts.ticks;
			var chart = me.chart;
			var data = chart.data;
			var datasets = data.datasets;
			var getValueOrDefault = helpers.getValueOrDefault;
			var isHorizontal = me.isHorizontal();
			function IDMatches(meta) {
				return isHorizontal ? meta.xAxisID === me.id : meta.yAxisID === me.id;
			}

			// Calculate Range
			me.min = null;
			me.max = null;

			if (opts.stacked) {
				var valuesPerType = {};

				helpers.each(datasets, function(dataset, datasetIndex) {
					var meta = chart.getDatasetMeta(datasetIndex);
					if (chart.isDatasetVisible(datasetIndex) && IDMatches(meta)) {
						if (valuesPerType[meta.type] === undefined) {
							valuesPerType[meta.type] = [];
						}

						helpers.each(dataset.data, function(rawValue, index) {
							var values = valuesPerType[meta.type];
							var value = +me.getRightValue(rawValue);
							if (isNaN(value) || meta.data[index].hidden) {
								return;
							}

							values[index] = values[index] || 0;

							if (opts.relativePoints) {
								values[index] = 100;
							} else {
								// Don't need to split positive and negative since the log scale can't handle a 0 crossing
								values[index] += value;
							}
						});
					}
				});

				helpers.each(valuesPerType, function(valuesForType) {
					var minVal = helpers.min(valuesForType);
					var maxVal = helpers.max(valuesForType);
					me.min = me.min === null ? minVal : Math.min(me.min, minVal);
					me.max = me.max === null ? maxVal : Math.max(me.max, maxVal);
				});

			} else {
				helpers.each(datasets, function(dataset, datasetIndex) {
					var meta = chart.getDatasetMeta(datasetIndex);
					if (chart.isDatasetVisible(datasetIndex) && IDMatches(meta)) {
						helpers.each(dataset.data, function(rawValue, index) {
							var value = +me.getRightValue(rawValue);
							if (isNaN(value) || meta.data[index].hidden) {
								return;
							}

							if (me.min === null) {
								me.min = value;
							} else if (value < me.min) {
								me.min = value;
							}

							if (me.max === null) {
								me.max = value;
							} else if (value > me.max) {
								me.max = value;
							}
						});
					}
				});
			}

			me.min = getValueOrDefault(tickOpts.min, me.min);
			me.max = getValueOrDefault(tickOpts.max, me.max);

			if (me.min === me.max) {
				if (me.min !== 0 && me.min !== null) {
					me.min = Math.pow(10, Math.floor(helpers.log10(me.min)) - 1);
					me.max = Math.pow(10, Math.floor(helpers.log10(me.max)) + 1);
				} else {
					me.min = 1;
					me.max = 10;
				}
			}
		},
		buildTicks: function() {
			var me = this;
			var opts = me.options;
			var tickOpts = opts.ticks;
			var getValueOrDefault = helpers.getValueOrDefault;

			// Reset the ticks array. Later on, we will draw a grid line at these positions
			// The array simply contains the numerical value of the spots where ticks will be
			var ticks = me.ticks = [];

			// Figure out what the max number of ticks we can support it is based on the size of
			// the axis area. For now, we say that the minimum tick spacing in pixels must be 50
			// We also limit the maximum number of ticks to 11 which gives a nice 10 squares on
			// the graph

			var tickVal = getValueOrDefault(tickOpts.min, Math.pow(10, Math.floor(helpers.log10(me.min))));

			while (tickVal < me.max) {
				ticks.push(tickVal);

				var exp = Math.floor(helpers.log10(tickVal));
				var significand = Math.floor(tickVal / Math.pow(10, exp)) + 1;

				if (significand === 10) {
					significand = 1;
					++exp;
				}

				tickVal = significand * Math.pow(10, exp);
			}

			var lastTick = getValueOrDefault(tickOpts.max, tickVal);
			ticks.push(lastTick);

			if (!me.isHorizontal()) {
				// We are in a vertical orientation. The top value is the highest. So reverse the array
				ticks.reverse();
			}

			// At this point, we need to update our max and min given the tick values since we have expanded the
			// range of the scale
			me.max = helpers.max(ticks);
			me.min = helpers.min(ticks);

			if (tickOpts.reverse) {
				ticks.reverse();

				me.start = me.max;
				me.end = me.min;
			} else {
				me.start = me.min;
				me.end = me.max;
			}
		},
		convertTicksToLabels: function() {
			this.tickValues = this.ticks.slice();

			Chart.Scale.prototype.convertTicksToLabels.call(this);
		},
		// Get the correct tooltip label
		getLabelForIndex: function(index, datasetIndex) {
			return +this.getRightValue(this.chart.data.datasets[datasetIndex].data[index]);
		},
		getPixelForTick: function(index, includeOffset) {
			return this.getPixelForValue(this.tickValues[index], null, null, includeOffset);
		},
		getPixelForValue: function(value, index, datasetIndex, includeOffset) {
			var me = this;
			var innerDimension;
			var pixel;

			var start = me.start;
			var newVal = +me.getRightValue(value);
			var range = helpers.log10(me.end) - helpers.log10(start);
			var paddingTop = me.paddingTop;
			var paddingBottom = me.paddingBottom;
			var paddingLeft = me.paddingLeft;

			if (me.isHorizontal()) {

				if (newVal === 0) {
					pixel = me.left + paddingLeft;
				} else {
					innerDimension = me.width - (paddingLeft + me.paddingRight);
					pixel = me.left + (innerDimension / range * (helpers.log10(newVal) - helpers.log10(start)));
					pixel += paddingLeft;
				}
			} else {
				// Bottom - top since pixels increase downard on a screen
				if (newVal === 0) {
					pixel = me.top + paddingTop;
				} else {
					innerDimension = me.height - (paddingTop + paddingBottom);
					pixel = (me.bottom - paddingBottom) - (innerDimension / range * (helpers.log10(newVal) - helpers.log10(start)));
				}
			}

			return pixel;
		},
		getValueForPixel: function(pixel) {
			var me = this;
			var offset;
			var range = helpers.log10(me.end) - helpers.log10(me.start);
			var value;
			var innerDimension;

			if (me.isHorizontal()) {
				innerDimension = me.width - (me.paddingLeft + me.paddingRight);
				value = me.start * Math.pow(10, (pixel - me.left - me.paddingLeft) * range / innerDimension);
			} else {
				innerDimension = me.height - (me.paddingTop + me.paddingBottom);
				value = Math.pow(10, (me.bottom - me.paddingBottom - pixel) * range / innerDimension) / me.start;
			}

			return value;
		}
	});
	Chart.scaleService.registerScaleType("logarithmic", LogarithmicScale, defaultConfig);

};