/* DebuggerFactory.java

	Purpose:
		
	Description:
		
	History:
		2013/1/7 Created by Dennis Chen

Copyright (C) 2013 Potix Corporation. All Rights Reserved.
*/
package org.zkoss.bind.sys.debugger;

import org.zkoss.bind.sys.debugger.impl.DefaultDebuggerFactory;
import org.zkoss.lang.Classes;
import org.zkoss.lang.Library;
import org.zkoss.lang.Strings;
import org.zkoss.zk.ui.UiException;

/**
 * The factory to provide {@link DebuggerFactory} instance.
 * It is also possible to provide null instance depends on the configuration(a production env should always provide nothing) 
 * @author dennis
 * @since 6.5.2
 */
public abstract class DebuggerFactory {

	private static DebuggerFactory _factory;
	private static boolean _instanceSet;

	public static final String ENABLE_PROP = "org.zkoss.bind.DebuggerFactory.enable";
	public static final String FACTORY_CLASS_PROP = "org.zkoss.bind.DebuggerFactory.class";

	/**
	 * Get the collector, the sub-class have to consider the thread-safe issue when implementing.
	 * @return the BindingExecutionInfoCollector or null if isn't existed
	 */
	public abstract BindingExecutionInfoCollector getExecutionInfoCollector();

	/**
	 * Get the checker, the sub-class have to consider the thread-safe issue when implementing.
	 * @return the BindingAnnotationInfoChecker or null if isn't existed
	 */
	public abstract BindingAnnotationInfoChecker getAnnotationInfoChecker();

	/**  
	 * Thread safe method to get the factory instance
	 * @return default factory, null if there is no factory existed
	 */
	public static DebuggerFactory getInstance() {
		if (_instanceSet) {
			return _factory;
		}
		synchronized (DebuggerFactory.class) {
			if (_instanceSet) { //check again
				return _factory;
			}
			_instanceSet = true;

			if ("true".equalsIgnoreCase(Library.getProperty(ENABLE_PROP))) {
				String clz = Library.getProperty(FACTORY_CLASS_PROP);
				if (!Strings.isEmpty(clz)) {
					try {
						_factory = (DebuggerFactory) Classes.forNameByThread(clz).newInstance();
					} catch (Exception e) {
						throw UiException.Aide.wrap(e, e.getMessage());
					}
				} else {
					_factory = new DefaultDebuggerFactory();
				}
			}
			return _factory;
		}
	}
}