class Scene {
	constructor(id) {
		this.id = id;

		this.viewControllers = [ ];

		this.modalContainer = document.createElement("DIV");
		this.modalContainer.className = "modal-container";
		document.body.appendChild(this.modalContainer);

		//Create the vertical centerer helper line.
		var verticalCenterer = document.createElement("DIV");
		verticalCenterer.className = "vertical-centerer";
		this.modalContainer.appendChild(verticalCenterer);

		this.popoverContainer = document.createElement("DIV");
		this.popoverContainer.className = "popover-container";
		document.body.appendChild(this.popoverContainer);
	}

	addViewController(viewController) {
		if (viewController.scene) {
			viewController.scene.removeViewController(viewController);
		}
		viewController.scene = this;

		this.viewControllers.push(viewController);
	}

	removeViewController(viewController) {
		var index = this.viewControllers.indexOf(viewController);
		if (index != -1) {
			this.viewControllers.splice(index, 1);
		}
	}

	/**
	 * Shows the active view controller of this scene.
	 * If no view controller is active, the default view controller is shown.
	 * If a view controller is passes as a parameter, it is used as the view controller to show the scene with.
	 */
	show(viewControllerToShow = null) {
		this.hide();

		var newLastViewController = this.activeViewController;
		if (viewControllerToShow) {
			this.activeViewController = viewControllerToShow;
		}
		this.lastViewController = newLastViewController;

		viewControllerToShow = this.activeViewController;

		if (!viewControllerToShow) {
			viewControllerToShow = this.initialViewController;
		}

		if (!viewControllerToShow) {
			console.error("Attempted to show a scene that has no initial view controller whatsoever.");
			return;
		}

		UIKit.activeScene = this;

		this.showViewControllerInternal(viewControllerToShow);
	}

	/**
	 * Shows this scene and the given view controller.
	 */
	showWithViewController(viewController) {
		this.show(viewController);
	}

	/**
	 * Hides the active view controller of this scene.
	 */
	hide() {
		if (this.activeViewController) {
			this.hideViewControllerInternal(this.activeViewController);
		}

		if (UIKit.activeScene == this) {
			UIKit.activeScene = null;
		}
	}

	/**
	 * Activates and shows the given view controller inside the scene, given the fact that it is actually a view controller of this scene.
	 */
	showViewController(viewController) {
		var controllerIndex = this.viewControllers.indexOf(viewController);
		if (controllerIndex == -1) {
			return;
		}

		for (var i = 0; i < this.viewControllers.length; i++) {
			var thisViewController = this.viewControllers[i];
			if (i == controllerIndex) {
				this.showViewControllerInternal(thisViewController);
			}
			else {
				this.hideViewControllerInternal(thisViewController);
			}
		}

		var newLastViewController = this.activeViewController;
		this.activeViewController = viewController;
		this.lastViewController = newLastViewController;
	}

	showViewControllerModally(viewController) {
		var controllerIndex = this.viewControllers.indexOf(viewController);
		if (controllerIndex == -1) {
			return;
		}

		if (this.modalViewController) {
			this.dismissModalViewController();
		}
		this.modalViewController = viewController;

		this.showViewControllerInternal(viewController);

		this.previousParent = viewController.element.parentNode;
		this.modalContainer.appendChild(viewController.element);
		this.modalContainer.className = "modal-container visible";
	}

	dismissModalViewController() {
		if (this.modalViewController) {
			if (this.previousParent) {
				this.previousParent.appendChild(this.modalViewController.element);
			}

			//Clear the hash if is the modal view controller's hash.
			if ("#" + this.modalViewController.hash == window.location.hash) {
				window.location.hash = "";
			}

			//HINT: Moved inside the if (was two lines below before) because of an error when trying to dismiss a modal view controller without it being presented.
			this.hideViewControllerInternal(this.modalViewController);
		}

		this.modalViewController = null;
		this.modalContainer.className = "modal-container";
	}

	/**
	 * Shows the given popover in this scene's popover layer.
	 */
	showPopover(popover) {
		if (!this.activePopoverData) {
			this.activePopoverData = { };
		}

		//Check if this popover is already visible (not being dismissed).
		if ((popover.id in this.activePopoverData) && (!this.dismissingPopovers || this.dismissingPopovers.indexOf(popover) == -1)) {
			//Call the disappearing and appearing functions in order.
			//The popover might want to prepare itself for being re-shown.
			popover.viewWillDisappear();
			popover.viewDidDisappear();
			popover.viewWillAppear();
			popover.viewDidAppear();

			//Do nothing more because the popover will stay visible.
			return;
		}

		//Stop dismissing if this popover is already being dismissed.
		var dismissingIndex = (this.dismissingPopovers ? this.dismissingPopovers.indexOf(popover) : -1);
		if (dismissingIndex != -1) {
			if (popover.id in this.activePopoverData) {
				clearTimeout(this.activePopoverData[popover.id].dismissPopoverTimeout);
			}

			//Move the dismissing popover all the way to the first position in the array and then call the finishing function.
			this.dismissingPopovers.splice(dismissingIndex, 1);
			this.finishDismissingPopover(popover);
		}

		//Add an object to the active popover data object. This is the indicator that the popover with the key index is active.
		this.activePopoverData[popover.id] = { disableBackground: popover.disableBackground };

		popover.viewWillAppear();
		this.popoverContainer.appendChild(popover.element);
		this.popoverContainer.className = "popover-container visible" + (this.anyPopoverDisablesBackground() ? "" : " click-through");
		popover.viewDidAppear();
	}

	/**
	 * Hides the specified popover, if it is visible.
	 */
	dismissPopover(popover, animated = true) {
		if (!this.activePopoverData || !(popover.id in this.activePopoverData)) {
			return;
		}

		if (!this.dismissingPopovers) {
			this.dismissingPopovers = [ ];
		}

		//Do not do anything if the popover is already being dismissed.
		if (this.dismissingPopovers.indexOf(popover) != -1) {
			return;
		}

		//Tell the popover to prepare for disappearing.
		popover.viewWillDisappear();

		popover.visible = false;

		//Start the fade animation.
		popover.element.classList.add("dismissing");

		//Make the popover container click-through while dismissing.
		//Only do this if no other non-click-through popover is currently visible.
		if (!this.anyPopoverDisablesBackground(popover.id)) {
			this.popoverContainer.className = "popover-container visible click-through";
		}

		//Add the popover to the end of the list of dismissing popovers if the process is animated.
		if (animated) {
			this.dismissingPopovers.push(popover);
		}

		//Set the timeout for definitely hiding the element.
		if (animated) {
			this.activePopoverData[popover.id].dismissPopoverTimeout = setTimeout(this.finishDismissingPopover.bind(this), 410);
		}
		else {
			this.finishDismissingPopover(popover);
		}
	}

	/**
	 * Returns true if any visible popover requires the background to be disabled, false otherwise.
	 */
	anyPopoverDisablesBackground(exceptionId = null) {
		if (!this.activePopoverData) {
			return false;
		}

		for (var id in this.activePopoverData) {
			if (id != exceptionId && this.activePopoverData[id].disableBackground) {
				return true;
			}
		}

		return false;
	}

	finishDismissingPopover(dismissingPopover = null) {
		if (!dismissingPopover) {
			//Fetch the popover to dismiss from the queue if it is not provided directly.
			dismissingPopover = this.dismissingPopovers[0];
			this.dismissingPopovers.splice(0, 1);
		}

		if (!dismissingPopover || dismissingPopover.element.parentNode != this.popoverContainer) {
			return;
		}

		this.popoverContainer.removeChild(dismissingPopover.element);
		dismissingPopover.element.className = "";
		dismissingPopover.viewDidDisappear();
		delete this.activePopoverData[dismissingPopover.id];

		//If in the meantime no other popover was shown, hide the popover container.
		if (Object.keys(this.activePopoverData).length == 0) {
			this.popoverContainer.className = "popover-container";
		}
	}

	showViewControllerInternal(viewController) {
		if (!viewController.visible) {
			viewController.element.style.visibility = "hidden";
			if (viewController.element.className.indexOf("visible") == -1) {
				viewController.element.classList.add("visible");
			}
			viewController.viewWillAppear();
			viewController.subviewsWillAppear();
			document.body.appendChild(viewController.element);
			viewController.element.style.visibility = "";
			viewController.visible = true;
			viewController.viewDidAppear();
			viewController.subviewsDidAppear();
		}
	}

	hideViewControllerInternal(viewController) {
		if (viewController.visible) {
			viewController.viewWillDisappear();
			viewController.subviewsWillDisappear();
			viewController.element.classList.remove("visible");
			viewController.visible = false;
			document.body.removeChild(viewController.element);
			viewController.viewDidDisappear();
			viewController.subviewsDidDisappear();
		}
	}

	showLastViewController() {
		if (this.lastViewController) {
			this.showViewController(this.lastViewController);
		}
	}

	/**
	 * Returns true if this scene contains the given view controller, false otherwise.
	 */
	containsViewController(viewController) {
		for (var i = 0; i < this.viewControllers.length; i++) {
			if (this.viewControllers[i] == viewController) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Looks for any view controller inside this scene that has the given hash and returns it.
	 */
	getViewControllerWithHash(hash) {
		for (var i = 0; i < this.viewControllers.length; i++) {
			if (this.viewControllers[i].hash == hash) {
				return this.viewControllers[i];
			}
		}

		return null;
	}

	/**
	 * Looks for any view controller inside this scene that has the given request path and returns it.
	 */
	getViewControllerWithRequestPath(requestPath) {
		for (var i = 0; i < this.viewControllers.length; i++) {
			if (this.viewControllers[i].requestPath == requestPath) {
				return this.viewControllers[i];
			}
		}

		return null;
	}
}