/* A rectangular panel that is absolutely positioned over other content
------------------------------------------------------------------------------------------------------------------------
Options:
	- className (string)
	- content (HTML string or jQuery element set)
	- parentEl
	- top
	- left
	- right (the x coord of where the right edge should be. not a "CSS" right)
	- autoHide (boolean)
	- show (callback)
	- hide (callback)
*/

function Popover(options) {
	this.options = options || {};
}


Popover.prototype = {

	isHidden: true,
	options: null,
	el: null, // the container element for the popover. generated by this object
	documentMousedownProxy: null, // document mousedown handler bound to `this`
	margin: 10, // the space required between the popover and the edges of the scroll container


	// Shows the popover on the specified position. Renders it if not already
	show: function() {
		if (this.isHidden) {
			if (!this.el) {
				this.render();
			}
			this.el.show();
			this.position();
			this.isHidden = false;
			this.trigger('show');
		}
	},


	// Hides the popover, through CSS, but does not remove it from the DOM
	hide: function() {
		if (!this.isHidden) {
			this.el.hide();
			this.isHidden = true;
			this.trigger('hide');
		}
	},


	// Creates `this.el` and renders content inside of it
	render: function() {
		var _this = this;
		var options = this.options;

		this.el = $('<div class="fc-popover"/>')
			.addClass(options.className || '')
			.css({
				// position initially to the top left to avoid creating scrollbars
				top: 0,
				left: 0
			})
			.append(options.content)
			.appendTo(options.parentEl);

		// when a click happens on anything inside with a 'fc-close' className, hide the popover
		this.el.on('click', '.fc-close', function() {
			_this.hide();
		});

		if (options.autoHide) {
			$(document).on('mousedown', this.documentMousedownProxy = $.proxy(this, 'documentMousedown'));
		}
	},


	// Triggered when the user clicks *anywhere* in the document, for the autoHide feature
	documentMousedown: function(ev) {
		// only hide the popover if the click happened outside the popover
		if (this.el && !$(ev.target).closest(this.el).length) {
			this.hide();
		}
	},


	// Hides and unregisters any handlers
	destroy: function() {
		this.hide();

		if (this.el) {
			this.el.remove();
			this.el = null;
		}

		$(document).off('mousedown', this.documentMousedownProxy);
	},


	// Positions the popover optimally, using the top/left/right options
	position: function() {
		var options = this.options;
		var origin = this.el.offsetParent().offset();
		var width = this.el.outerWidth();
		var height = this.el.outerHeight();
		var windowEl = $(window);
		var viewportEl = getScrollParent(this.el);
		var viewportTop;
		var viewportLeft;
		var viewportOffset;
		var top; // the "position" (not "offset") values for the popover
		var left; //

		// compute top and left
		top = options.top || 0;
		if (options.left !== undefined) {
			left = options.left;
		}
		else if (options.right !== undefined) {
			left = options.right - width; // derive the left value from the right value
		}
		else {
			left = 0;
		}

		if (viewportEl.is(window) || viewportEl.is(document)) { // normalize getScrollParent's result
			viewportEl = windowEl;
			viewportTop = 0; // the window is always at the top left
			viewportLeft = 0; // (and .offset() won't work if called here)
		}
		else {
			viewportOffset = viewportEl.offset();
			viewportTop = viewportOffset.top;
			viewportLeft = viewportOffset.left;
		}

		// if the window is scrolled, it causes the visible area to be further down
		viewportTop += windowEl.scrollTop();
		viewportLeft += windowEl.scrollLeft();

		// constrain to the view port. if constrained by two edges, give precedence to top/left
		if (options.viewportConstrain !== false) {
			top = Math.min(top, viewportTop + viewportEl.outerHeight() - height - this.margin);
			top = Math.max(top, viewportTop + this.margin);
			left = Math.min(left, viewportLeft + viewportEl.outerWidth() - width - this.margin);
			left = Math.max(left, viewportLeft + this.margin);
		}

		this.el.css({
			top: top - origin.top,
			left: left - origin.left
		});
	},


	// Triggers a callback. Calls a function in the option hash of the same name.
	// Arguments beyond the first `name` are forwarded on.
	// TODO: better code reuse for this. Repeat code
	trigger: function(name) {
		if (this.options[name]) {
			this.options[name].apply(this, Array.prototype.slice.call(arguments, 1));
		}
	}

};