# component/barsMultiSeries.js

    import * as d3 from "d3";
    import dataTransform from "../dataTransform.js";
    import componentBars from "./bars.js";

    /**
     * Reusable 3D Multi Series Bar Chart Component
     *
     * @module
     */
    export default function() {

    	/* Default Properties */
    	let dimensions = { x: 40, y: 40, z: 40 };
    	let colors = ["orange", "red", "yellow", "steelblue", "green"];
    	let classed = "d3X3dBarsMultiSeries";

    	/* Scales */
    	let xScale;
    	let yScale;
    	let zScale;
    	let colorScale;

    	/* Components */
    	const bars = componentBars();

    	/**
    	 * Initialise Data and Scales
    	 *
    	 * @private
    	 * @param {Array} data - Chart data.
    	 */
    	const init = function(data) {
    		const { rowKeys, columnKeys, valueMax } = dataTransform(data).summary();
    		const valueExtent = [0, valueMax];
    		const { x: dimensionX, y: dimensionY, z: dimensionZ } = dimensions;

    		if (typeof xScale === "undefined") {
    			xScale = d3.scaleBand()
    				.domain(columnKeys)
    				.range([0, dimensionX])
    				.padding(0.5);
    		}

    		if (typeof yScale === "undefined") {
    			yScale = d3.scaleLinear()
    				.domain(valueExtent)
    				.range([0, dimensionY])
    				.nice();
    		}

    		if (typeof zScale === "undefined") {
    			zScale = d3.scaleBand()
    				.domain(rowKeys)
    				.range([0, dimensionZ])
    				.padding(0.7);
    		}

    		if (typeof colorScale === "undefined") {
    			colorScale = d3.scaleOrdinal()
    				.domain(columnKeys)
    				.range(colors);
    		}
    	};

    	/**
    	 * Constructor
    	 *
    	 * @constructor
    	 * @alias barsMultiSeries
    	 * @param {d3.selection} selection - The chart holder D3 selection.
    	 */
    	const my = function(selection) {
    		selection.each(function(data) {
    			init(data);

    			const element = d3.select(this)
    				.classed(classed, true);

    			bars.xScale(xScale)
    				.yScale(yScale)
    				.dimensions({
    					x: dimensions.x,
    					y: dimensions.y,
    					z: zScale.bandwidth()
    				})
    				.colors(colors);

    			const addBars = function() {
    				d3.select(this).call(bars);
    			};

    			const barGroup = element.selectAll(".barGroup")
    				.data((d) => d, (d) => d.key);

    			barGroup.enter()
    				.append("Transform")
    				.classed("barGroup", true)
    				.merge(barGroup)
    				.transition()
    				.attr("translation", (d) => {
    					const x = 0;
    					const y = 0;
    					const z = zScale(d.key);
    					return x + " " + y + " " + z;
    				})
    				.each(addBars);

    			barGroup.exit()
    				.remove();
    		});
    	};

    	/**
    	 * Dimensions Getter / Setter
    	 *
    	 * @param {{x: number, y: number, z: number}} _v - 3D object dimensions.
    	 * @returns {*}
    	 */
    	my.dimensions = function(_v) {
    		if (!arguments.length) return dimensions;
    		dimensions = _v;
    		return this;
    	};

    	/**
    	 * X Scale Getter / Setter
    	 *
    	 * @param {d3.scale} _v - D3 scale.
    	 * @returns {*}
    	 */
    	my.xScale = function(_v) {
    		if (!arguments.length) return xScale;
    		xScale = _v;
    		return my;
    	};

    	/**
    	 * Y Scale Getter / Setter
    	 *
    	 * @param {d3.scale} _v - D3 scale.
    	 * @returns {*}
    	 */
    	my.yScale = function(_v) {
    		if (!arguments.length) return yScale;
    		yScale = _v;
    		return my;
    	};

    	/**
    	 * Z Scale Getter / Setter
    	 *
    	 * @param {d3.scale} _v - D3 scale.
    	 * @returns {*}
    	 */
    	my.zScale = function(_v) {
    		if (!arguments.length) return zScale;
    		zScale = _v;
    		return my;
    	};

    	/**
    	 * Color Scale Getter / Setter
    	 *
    	 * @param {d3.scale} _v - D3 color scale.
    	 * @returns {*}
    	 */
    	my.colorScale = function(_v) {
    		if (!arguments.length) return colorScale;
    		colorScale = _v;
    		return my;
    	};

    	/**
    	 * Colors Getter / Setter
    	 *
    	 * @param {Array} _v - Array of colours used by color scale.
    	 * @returns {*}
    	 */
    	my.colors = function(_v) {
    		if (!arguments.length) return colors;
    		colors = _v;
    		return my;
    	};

    	return my;
    }