class Navigation {
	static initialize() {
		Navigation.allSubviews = [ ];

		Navigation.element = document.body.querySelector("tab-bar");

		//Process the tab bar like a view controller.
		UIKit.processViewControllerElement(Navigation.element, Navigation);

		Navigation.barItems = document.body.querySelectorAll("tab-bar bar-button-item:not(.user-menu-button)");

		for (var i = 0; i < Navigation.barItems.length; i++) {
			Navigation.barItems[i].addEventListener("click", Navigation.onBarItemSelected);
		}

		//Bind user listener, which will then bind a role listener.
		TimeCards.dataManager.addDataListener("user", {
			is_session_user: true
		}, Navigation.onSessionUserUpdate);
	}

	/**
	 * Hides all elements from the navigation that should not be visible on the login screen.
	 */
	static displayForLogin() {
		Navigation.element.classList.add("login-view");
	}

	/**
	 * Shows all elements again that were not visible on the login screen.
	 */
	static endDisplayForLogin() {
		Navigation.element.classList.remove("login-view");
	}

	/**
	 * Called whenever the session user changes.
	 * Will make sure we have a data listener on the user's role.
	 * @param {number} userId 
	 * @param {object} user 
	 */
	static onSessionUserUpdate(userId, user) {
		//Remove existing role listener.
		TimeCards.dataManager.removeDataListener("user_role", Navigation.onRoleUpdate);

		//Add new role listener.
		TimeCards.dataManager.addDataListener("user_role", {
			role_id: user.id_role
		}, Navigation.onRoleUpdate);
	}

	/**
	 * Called whenever the session user's role changes.
	 * @param {number} roleId 
	 * @param {object} role 
	 */
	static onRoleUpdate(roleId, role) {
		Navigation.onHashChanged();
	}

	static onHashChanged(event) {
		const hash = window.location.hash;

		let foundItem = false;
		for (let i = 0; i < Navigation.barItems.length; i++) {
			const item = Navigation.barItems[i];

			if (item.getAttribute("target") == hash && Navigation.hasPermissionForItem(item)) {
				if (item.className.indexOf("active") == -1) {
					item.classList.add("active");
				}
				foundItem = true;
			}
			else {
				item.classList.remove("active");
			}
		}

		//If no item was found (either invalid hash or missing permission), select first available item.
		//NOTE: This also overrides UIKit's initial view controller behavior.
		if (!foundItem) {
			for (let i = 0; i < Navigation.barItems.length; i++) {
				const item = Navigation.barItems[i];

				//Do not select if no permission.
				if (!Navigation.hasPermissionForItem(item)) {
					continue;
				}

				//Do not select if no target attribute.
				if (!item.hasAttribute("target")) {
					continue;
				}

				const redirectHash = item.getAttribute("target");

				//Do not select if we are already trying to select this one.
				if (redirectHash == hash) {
					continue;
				}

				//Do not select if no hash target.
				if (!redirectHash.startsWith("#")) {
					continue;
				}

				//Redirect to this item's target.
				window.location.hash = redirectHash;
				break;
			}
		}
	}

	static hasPermissionForItem(item) {
		for (const className of item.classList) {
			if (!className.startsWith("require_")) {
				continue;
			}

			if ((className.startsWith("require_w__") && !Authentication.isResourceAvailable(className.replace("require_w__", ""), "w")) || (className.startsWith("require__") && !Authentication.isResourceAvailable(className.replace("require__", ""), "r"))) {
				return false;
			}
		}

		return true;
	}

	static onBarItemSelected(event) {
		var target = event.currentTarget.getAttribute("target");

		if (!target) {
			return;
		}

		if (target.startsWith("#")) {
			window.location.hash = target;
			return;
		}
	}

	static onUserIconClicked(event) {
		var userMenu = UIKit.getPopoverById("user-menu");

		//Inform the context menu about the summoning view controller and view.
		userMenu.setViewController(Navigation);
		//userMenu.setView(Navigation);

		userMenu.showForElement(event.currentTarget, "right");

		event.stopPropagation();
	}

	static onLogOutMenuItemPressed(event) {
		Authentication.logOut();
	}
}

window.addEventListener("hashchange", Navigation.onHashChanged);