/*******************************************************************************
 * Copyright (c) 2008-2011 Chair for Applied Software Engineering,
 * Technische Universitaet Muenchen.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 ******************************************************************************/
package org.eclipse.emf.emfstore.server.core;

import java.util.HashMap;

import org.eclipse.emf.emfstore.server.accesscontrol.AuthorizationControl;
import org.eclipse.emf.emfstore.server.exceptions.FatalEmfStoreException;
import org.eclipse.emf.emfstore.server.exceptions.InvalidInputException;
import org.eclipse.emf.emfstore.server.model.ServerSpace;

/**
 * Super class of all EmfstoreInterfaces. Emfstore interfaces performs sanity checks, runs accesscontrol and then
 * delegates the method call to the relating subinterface which actually implements the functionality. Using
 * {@link InternalCommand} it is possible to access the interface without accesscontrol.
 * 
 * @see AbstractSubEmfstoreInterface
 * @see org.eclipse.emf.emfstore.server.EmfStoreInterface
 * @author wesendon
 */
public abstract class AbstractEmfstoreInterface {

	private AuthorizationControl authorizationControl;
	private HashMap<Class<? extends AbstractSubEmfstoreInterface>, AbstractSubEmfstoreInterface> subInterfaces;
	private boolean accessControlDisabled;
	private final ServerSpace serverSpace;

	/**
	 * Default constructor.
	 * 
	 * @param serverSpace the serverspace
	 * @param authorizationControl accesscontrol
	 * @throws FatalEmfStoreException if initialization fails
	 */
	public AbstractEmfstoreInterface(ServerSpace serverSpace, AuthorizationControl authorizationControl)
		throws FatalEmfStoreException {
		this.serverSpace = serverSpace;
		if (serverSpace == null || authorizationControl == null) {
			throw new FatalEmfStoreException();
		}
		this.authorizationControl = authorizationControl;
		accessControlDisabled = false;
		subInterfaces = new HashMap<Class<? extends AbstractSubEmfstoreInterface>, AbstractSubEmfstoreInterface>();
		initSubInterfaces();
		for (AbstractSubEmfstoreInterface subInterface : subInterfaces.values()) {
			subInterface.initSubInterface();
		}
	}

	/**
	 * Implement this method in order to add subinterfaces. Therefor use the
	 * {@link #addSubInterface(AbstractSubEmfstoreInterface)} method.
	 * 
	 * @throws FatalEmfStoreException in case of failure
	 */
	protected abstract void initSubInterfaces() throws FatalEmfStoreException;

	/**
	 * Adds a subinterface to the parent interface. If the subinterface exists already, the present instance is
	 * overwritten by the new one.
	 * 
	 * @param subInterface the subinterface
	 */
	protected void addSubInterface(AbstractSubEmfstoreInterface subInterface) {
		if (subInterface != null) {
			getSubInterfaces().put(subInterface.getClass(), subInterface);
		}
	}

	/**
	 * Returns list of subinterfaces.
	 * 
	 * @return list of subinterfaces
	 */
	protected HashMap<Class<? extends AbstractSubEmfstoreInterface>, AbstractSubEmfstoreInterface> getSubInterfaces() {
		return subInterfaces;
	}

	/**
	 * Returns the requested subinterface if available.
	 * 
	 * @param <T> subinterface type
	 * @param clazz subinterface class type
	 * @return subinterface
	 */
	@SuppressWarnings("unchecked")
	protected <T> T getSubInterface(Class<T> clazz) {
		return (T) subInterfaces.get(clazz);
	}

	/**
	 * Returns the serverspace. Please always use a monitor ({@link #getMonitor()}) when operating on the serverspace.
	 * 
	 * @return serverspace
	 */
	protected ServerSpace getServerSpace() {
		return serverSpace;
	}

	/**
	 * Return a monitor object which should be used when operating on the serverspace.
	 * 
	 * @return monitor object
	 */
	protected Object getMonitor() {
		return MonitorProvider.getInstance().getMonitor();
	}

	/**
	 * Returns the authorizationControl.
	 * 
	 * @return authorizationControl
	 */
	protected AuthorizationControl getAuthorizationControl() {
		return authorizationControl;
	}

	/**
	 * Applies a sanity check {@link #sanityCheckObject(Object)} to all given objects. Elements will be checked in the
	 * same order as the input. This allows you to check attributes as well. E.g.: <code>sanityCheckObjects(element,
	 * element.getAttribute())</code>. Due to the order, it is important to enter the element BEFORE the attribute,
	 * otherwise a NPE would occur, if the element would be null.
	 * 
	 * @param objects objects to check
	 * @throws InvalidInputException is thrown if the check fails
	 */
	protected void sanityCheckObjects(Object... objects) throws InvalidInputException {
		for (Object object : objects) {
			sanityCheckObject(object);
		}
	}

	/**
	 * Checks whether a given object is null. Further sanity checks could be added. <strong>Note:</strong> Maybe we
	 * should use specialized sanity checks for EObjects or other types.
	 * 
	 * @param object object to check
	 * @throws InvalidInputException is thrown if the check fails
	 */
	private void sanityCheckObject(Object object) throws InvalidInputException {
		if (object == null) {
			throw new InvalidInputException();
		}
	}

	/**
	 * Runs an internal command, in order to avoid accesscontrol.
	 * 
	 * @param command internal command
	 */
	public synchronized void runCommand(InternalCommand<? extends AbstractEmfstoreInterface> command) {
		accessControlDisabled = true;
		command.setInterface(this);
		command.doExecute();
		accessControlDisabled = false;
	}
}