# component/axis.js

    import * as d3 from "d3";
    import { colorParse } from "../colorHelper";

    /**
     * Reusable 3D Axis Component
     *
     * @module
     */
    export default function() {

    	/* Default Properties */
    	let dimensions = { x: 40, y: 40, z: 40 };
    	let color = "black";
    	let classed = "d3X3dAxis";
    	let labelPosition = "proximal";
    	let labelInset = labelPosition === "distal" ? 1 : -1;

    	/* Scale and Axis Options */
    	let scale;
    	let direction;
    	let tickDirection;
    	let tickArguments = [];
    	let tickValues = null;
    	let tickFormat = null;
    	let tickSize = 1.5;
    	let tickPadding = 2.0;

    	const axisDirectionVectors = {
    		x: [1, 0, 0],
    		y: [0, 1, 0],
    		z: [0, 0, 1]
    	};

    	const axisRotationVectors = {
    		x: [1, 1, 0, Math.PI],
    		y: [0, 0, 0, 0],
    		z: [0, 1, 1, Math.PI]
    	};

    	/**
    	 * Get Axis Direction Vector
    	 *
    	 * @private
    	 * @param {string} axisDir
    	 * @returns {number[]}
    	 */
    	const getAxisDirectionVector = function(axisDir) {
    		return axisDirectionVectors[axisDir];
    	};

    	/**
    	 * Get Axis Rotation Vector
    	 *
    	 * @private
    	 * @param {string} axisDir
    	 * @returns {number[]}
    	 */
    	const getAxisRotationVector = function(axisDir) {
    		return axisRotationVectors[axisDir];
    	};

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

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

    			const range = scale.range();
    			const range0 = range[0];
    			const range1 = range[range.length - 1];

    			const axisDirectionVector = getAxisDirectionVector(direction);
    			const tickDirectionVector = getAxisDirectionVector(tickDirection);
    			const axisRotationVector = getAxisRotationVector(direction);
    			const tickRotationVector = getAxisRotationVector(tickDirection);

    			/*
    			// FIXME: Currently the tickArguments option does not work.
    			const tickValuesDefault = scale.ticks ? scale.ticks.apply(scale, tickArguments) : scale.domain();
    			tickValues = tickValues === null ? tickValuesDefault : tickValues;
    			*/
    			tickValues = scale.ticks ? scale.ticks.apply(scale, tickArguments) : scale.domain();

    			const tickFormatDefault = scale.tickFormat ? scale.tickFormat.apply(scale, tickArguments) : (d) => d;
    			tickFormat = tickFormat === null ? tickFormatDefault : tickFormat;

    			const shape = (el, radius, height, color) => {
    				const shape = el.append("Shape");

    				shape.append("Cylinder")
    					.attr("radius", radius)
    					.attr("height", height);

    				shape.append("Appearance")
    					.append("Material")
    					.attr("diffuseColor", colorParse(color));
    			};

    			const makeSolid = (el, color) => {
    				el.append("Appearance")
    					.append("Material")
    					.attr("diffuseColor", colorParse(color) || "0 0 0");
    			};

    			// Main Lines
    			const domain = element.selectAll(".domain")
    				.data([null]);

    			domain.enter()
    				.append("Transform")
    				.attr("class", "domain")
    				.attr("rotation", axisRotationVector.join(" "))
    				.attr("translation", axisDirectionVector.map((d) => (d * (range0 + range1) / 2)).join(" "))
    				.call(shape, 0.1, range1 - range0, color)
    				.merge(domain);

    			domain.exit()
    				.remove();

    			// Tick Lines
    			const ticks = element.selectAll(".tick")
    				.data(tickValues, (d) => d);

    			ticks.enter()
    				.append("Transform")
    				.attr("class", "tick")
    				.attr("translation", (t) => (axisDirectionVector.map((a) => (scale(t) * a)).join(" ")))
    				.append("Transform")
    				.attr("translation", tickDirectionVector.map((d) => (d * tickSize / 2)).join(" "))
    				.attr("rotation", tickRotationVector.join(" "))
    				.call(shape, 0.05, tickSize, "#e3e3e3")
    				.merge(ticks);

    			ticks.transition()
    				.attr("translation", (t) => (axisDirectionVector.map((a) => (scale(t) * a)).join(" ")));

    			ticks.exit()
    				.remove();

    			// Labels
    			if (tickFormat !== "") {
    				const labels = element.selectAll(".label")
    					.data(tickValues, (d) => d);

    				labels.enter()
    					.append("Transform")
    					.attr("class", "label")
    					.attr("translation", (t) => (axisDirectionVector.map((a) => (scale(t) * a)).join(" ")))
    					.append("Transform")
    					.attr("translation", tickDirectionVector.map((d, i) => (labelInset * d * tickPadding) + (((labelInset + 1) / 2) * tickSize * tickDirectionVector[i])))
    					.append("Billboard")
    					.attr("axisOfRotation", "0 0 0")
    					.append("Shape")
    					.call(makeSolid, "black")
    					.append("Text")
    					.attr("string", (d) => `"${tickFormat(d)}"`)
    					.append("FontStyle")
    					.attr("size", 1.3)
    					.attr("family", "\"SANS\"")
    					.attr("style", "BOLD")
    					.attr("justify", "\"MIDDLE\" \"MIDDLE\"")
    					.merge(labels);

    				labels.transition()
    					.attr("translation", (t) => (axisDirectionVector.map((a) => (scale(t) * a)).join(" ")))
    					.select("Transform")
    					.attr("translation", tickDirectionVector.map((d, i) => (labelInset * d * tickPadding) + (((labelInset + 1) / 2) * tickSize * tickDirectionVector[i])))
    					.on("start", function() {
    						d3.select(this)
    							.select("Billboard")
    							.select("Shape")
    							.select("Text")
    							.attr("string", (d) => `"${tickFormat(d)}"`);
    					});

    				labels.exit()
    					.remove();
    			} else {
    				element.selectAll(".label")
    					.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 my;
    	};

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

    	/**
    	 * Direction Getter / Setter
    	 *
    	 * @param {string} _v - Direction of Axis (e.g. "x", "y", "z").
    	 * @returns {*}
    	 */
    	my.direction = function(_v) {
    		if (!arguments.length) return direction;
    		direction = _v;
    		return my;
    	};

    	/**
    	 * Tick Direction Getter / Setter
    	 *
    	 * @param {string} _v - Direction of Ticks (e.g. "x", "y", "z").
    	 * @returns {*}
    	 */
    	my.tickDirection = function(_v) {
    		if (!arguments.length) return tickDirection;
    		tickDirection = _v;
    		return my;
    	};

    	/**
    	 * Tick Arguments Getter / Setter
    	 *
    	 * @param {Array} _v - Tick arguments.
    	 * @returns {Array<*>}
    	 */
    	my.tickArguments = function(_v) {
    		if (!arguments.length) return tickArguments;
    		tickArguments = _v;
    		return my;
    	};

    	/**
    	 * Tick Values Getter / Setter
    	 *
    	 * @param {Array} _v - Tick values.
    	 * @returns {*}
    	 */
    	my.tickValues = function(_v) {
    		if (!arguments.length) return tickValues;
    		tickValues = _v;
    		return my;
    	};

    	/**
    	 * Tick Format Getter / Setter
    	 *
    	 * @param {string} _v - Tick format.
    	 * @returns {*}
    	 */
    	my.tickFormat = function(_v) {
    		if (!arguments.length) return tickFormat;
    		tickFormat = _v;
    		return my;
    	};

    	/**
    	 * Tick Size Getter / Setter
    	 *
    	 * @param {number} _v - Tick length.
    	 * @returns {*}
    	 */
    	my.tickSize = function(_v) {
    		if (!arguments.length) return tickSize;
    		tickSize = _v;
    		return my;
    	};

    	/**
    	 * Tick Padding Getter / Setter
    	 *
    	 * @param {number} _v - Tick padding size.
    	 * @returns {*}
    	 */
    	my.tickPadding = function(_v) {
    		if (!arguments.length) return tickPadding;
    		tickPadding = _v;
    		return my;
    	};

    	/**
    	 * Color Getter / Setter
    	 *
    	 * @param {string} _v - Color (e.g. "red" or "#ff0000").
    	 * @returns {*}
    	 */
    	my.color = function(_v) {
    		if (!arguments.length) return color;
    		color = _v;
    		return my;
    	};

    	/**
    	 * Label Position Getter / Setter
    	 *
    	 * @param {string} _v - Position ("proximal" or "distal")
    	 * @returns {*}
    	 */
    	my.labelPosition = function(_v) {
    		if (!arguments.length) return labelPosition;
    		labelPosition = _v;
    		labelInset = labelPosition === "distal" ? 1 : -1;
    		return my;
    	};

    	return my;
    }