(function(root, factory) {
	if (typeof module === 'object' && module.exports) {
		var d3 = require('d3');
		module.exports = factory(d3);
	} else if(typeof define === 'function' && define.amd) {
		try {
			var d3 = require('d3');
		} catch (e) {
			d3 = root.d3;
		}

		d3.contextMenu = factory(d3);
		define([], function() {
			return d3.contextMenu;
		});
	} else if(root.d3) {
		root.d3.contextMenu = factory(root.d3);
	}
}(this,
	function (d3) {
		var utils = {
			noop: function () {},
			
			/**
			 * @param {*} value
			 * @returns {Boolean}
			 */
			isFn: function (value) {
				return typeof value === 'function';
			},

			/**
			 * @param {*} value
			 * @returns {Function}
			 */
			const: function (value) {
				return function () { return value; };
			},

			/**
			 * @param {Function|*} value
			 * @param {*} [fallback]
			 * @returns {Function}
			 */
			toFactory: function (value, fallback) {
				value = (value === undefined) ? fallback : value;
				return utils.isFn(value) ? value : utils.const(value);
			}
		};

		// global state for d3-context-menu
		var d3ContextMenu = null;

		var closeMenu = function () {
			// global state is populated if a menu is currently opened
			if (d3ContextMenu) {
				d3.select('.d3-context-menu').remove();
				d3.select('body').on('mousedown.d3-context-menu', null);
				d3ContextMenu.boundCloseCallback();
				d3ContextMenu = null;
			}
		};

		/**
		 * Calls API method (e.g. `close`) or
		 * returns handler function for the `contextmenu` event
		 * @param {Function|Array|String} menuItems
		 * @param {Function|Object} config
		 * @returns {?Function}
		 */
		return function (menuItems, config) {
			// allow for `d3.contextMenu('close');` calls
			// to programatically close the menu
			if (menuItems === 'close') {
				return closeMenu();
			}

			// for convenience, make `menuItems` a factory
			// and `config` an object
			menuItems = utils.toFactory(menuItems);

			if (utils.isFn(config)) {
				config = { onOpen: config };
			}
			else {
				config = config || {};
			}

			// resolve config
			var openCallback = config.onOpen || utils.noop;
			var closeCallback = config.onClose || utils.noop;
			var positionFactory = utils.toFactory(config.position);
			var themeFactory = utils.toFactory(config.theme, 'd3-context-menu-theme');

			/**
			 * Context menu event handler
			 * @param {*} data
			 * @param {Number} index
			 */
			return function (data, index) {
				var element = this;

				// close any menu that's already opened
				closeMenu();

				// store close callback already bound to the correct args and scope
				d3ContextMenu = {
					boundCloseCallback: closeCallback.bind(element, data, index)
				};

				// create the div element that will hold the context menu
				d3.selectAll('.d3-context-menu').data([1])
					.enter()
					.append('div')
					.attr('class', 'd3-context-menu ' + themeFactory.bind(element)(data, index));

				// close menu on mousedown outside
				d3.select('body').on('mousedown.d3-context-menu', closeMenu);

				var list = d3.selectAll('.d3-context-menu')
					.on('contextmenu', function() {
						closeMenu();
						d3.event.preventDefault();
						d3.event.stopPropagation();
					})
					.append('ul');
				
				list.selectAll('li').data(menuItems.bind(element)(data, index)).enter()
					.append('li')
					.attr('class', function(d) {
						var ret = '';
						if (utils.toFactory(d.divider).bind(element)(data, index)) {
							ret += ' is-divider';
						}
						if (utils.toFactory(d.disabled).bind(element)(data, index)) {
							ret += ' is-disabled';
						}
						if (!d.action) {
							ret += ' is-header';
						}
						return ret;
					})
					.html(function(d) {
						if (utils.toFactory(d.divider).bind(element)(data, index)) {
							return '<hr>';
						}
						if (!d.title) {
							console.error('No title attribute set. Check the spelling of your options.');
						}
						return utils.toFactory(d.title).bind(element)(data, index);
					})
					.on('click', function(d, i) {
						if (utils.toFactory(d.disabled).bind(element)(data, index)) return; // do nothing if disabled
						if (!d.action) return; // headers have no "action"
						d.action.bind(element)(data, index);
						closeMenu();
					});

				// the openCallback allows an action to fire before the menu is displayed
				// an example usage would be closing a tooltip
				if (openCallback.bind(element)(data, index) === false) {
					return;
				}

				// get position
				var position = positionFactory.bind(element)(data, index);

				// display context menu
				d3.select('.d3-context-menu')
					.style('left', (position ? position.left : d3.event.pageX - 2) + 'px')
					.style('top', (position ? position.top : d3.event.pageY - 2) + 'px')
					.style('display', 'block');

				d3.event.preventDefault();
				d3.event.stopPropagation();
			};
		};
	}
));