/*
 * Copyright 2014
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); 
 * you may not use this file except in compliance with the License. 
 * You may obtain a copy of the License at:
 * 
 * http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, 
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 
 * implied. See the License for the specific language governing 
 * permissions and limitations under the License.
 */
package org.openntf.domino.impl;

import java.util.HashSet;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.openntf.domino.utils.Factory;

/**
 * A common Base class for those org.openntf.domino objects, which shouldn't be shared across threads.
 * 
 * @param <T>
 *            the generic type
 * @param <D>
 *            the delegate type
 * @param <P>
 *            the parent type
 * 
 */
public abstract class BaseNonThreadSafe<T extends org.openntf.domino.Base<D>, D extends lotus.domino.Base, P extends org.openntf.domino.Base<?>>
		extends Base<T, D, P> {

	/** The Constant log_. */
	private static final Logger log_ = Logger.getLogger(BaseNonThreadSafe.class.getName());

	/** The delegate_. */
	protected transient D delegate_;

	/** The Thread, in which wrapper was generated */
	private transient Thread _myThread = Thread.currentThread();

	static {
		Factory.addTerminateHook(new Runnable() {
			@Override
			public void run() {
				setAllowAccessAcrossThreads(false);
			}
		}, true);
	}

	/**
	 * Instantiates a new base.
	 * 
	 * @param delegate
	 *            the delegate
	 * @param parent
	 *            the parent (may be null)
	 * @param classId
	 *            the class id
	 */
	protected BaseNonThreadSafe(final D delegate, final P parent, final int classId) {
		super(delegate, parent, classId);
	}

	/**
	 * Constructor for deserialization
	 * 
	 * @param classId
	 */
	protected BaseNonThreadSafe(final int classId) {
		super(classId);
	}

	/**
	 * Sets the delegate on init or if resurrect occurred
	 * 
	 * @param delegate
	 *            the delegate
	 * @param cppId
	 *            the cpp-id
	 */
	@Override
	protected final void setDelegate(final D delegate, final boolean fromResurrect) {
		delegate_ = delegate;

		if (fromResurrect) {
			// an other object is set now, so we must recache that object
			getFactory().recacheLotusObject(delegate, this, parent);
			if (log_.isLoggable(Level.FINEST)) {
				log_.log(Level.FINE, "Object of class " + this.getClass().getName() + " was recached. Changes may be lost", new Throwable());
			}
		}
	}

	private static Set<Thread> _allowDirtyAccess4ThreadList = null;

	/**
	 * Enables Thread support (sharing Notes-objects across threads). But you _SHOULD_ really avoid this! <br/>
	 * <br/>
	 * 
	 * <b>NOTE:</b> Sharing Notes-objects across threads is supported for objects of class {@link BaseThreadSafe}, and there are no problems
	 * to be expected. <br/>
	 * <br/>
	 * 
	 * To share objects not extending BaseThreadSafe, you have to explicitly allow it by calling setAllowAccessAcrossThreads(true), which
	 * allows objects wrapped in the current thread being accessed in other threads. But it not recommended to do so. Or rather it is
	 * strongly recommended NOT to do so. Neither the ODA is tested, nor IBM recommend this. You should also read the paragraph <a
	 * href="http://www-01.ibm.com/support/knowledgecenter/SSVRGU_8.5.3/com.ibm.designer.domino.main.doc/H_NOTESTHREAD_CLASS_JAVA.html"
	 * >Multithreading issues</a> before using it.
	 * 
	 * @param allow
	 *            enables thread support (and thread problems)
	 */
	protected static void setAllowAccessAcrossThreads(final boolean allow) {
		if (!allow && _allowDirtyAccess4ThreadList == null)
			return;
		Thread curr = Thread.currentThread();
		synchronized (BaseNonThreadSafe.class) {
			if (allow) {
				if (_allowDirtyAccess4ThreadList == null)
					_allowDirtyAccess4ThreadList = new HashSet<Thread>();
				_allowDirtyAccess4ThreadList.add(curr);
			} else {
				_allowDirtyAccess4ThreadList.remove(curr);
				if (_allowDirtyAccess4ThreadList.isEmpty())
					_allowDirtyAccess4ThreadList = null;
			}
		}
	}

	/**
	 * @param t
	 *            the Thread in which the Notes object was wrapped
	 * @return true if it is allowed
	 */
	protected static boolean isAllowAccessAcrossThreads(final Thread t) {
		return _allowDirtyAccess4ThreadList != null && _allowDirtyAccess4ThreadList.contains(t);
	}

	/**
	 * Gets the delegate without Resurrect
	 * 
	 * @return the delegate
	 */
	@Override
	protected D getDelegate_unchecked() {
		if (_myThread != Thread.currentThread() && !isAllowAccessAcrossThreads(_myThread))
			throw new IllegalStateException("Notes-Object of type " + this.getClass().getName() + " is used across threads! This Thread: "
					+ Thread.currentThread() + " correct Thread: " + _myThread);
		return delegate_;
	}

}