Copyright (c) 2000, 2009 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2009 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.expressions;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.eclipse.core.expressions.IPropertyTester;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionDelta;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.IRegistryChangeEvent;
import org.eclipse.core.runtime.IRegistryChangeListener;
import org.eclipse.core.runtime.Platform;

public class TypeExtensionManager implements IRegistryChangeListener {

	private String fExtensionPoint;

	
Tells whether this class is in debug mode.
Since:
3.5/**
	 * Tells whether this class is in debug mode.
	 *
	 * @since 3.5
	 */
	private static boolean DEBUG= "true".equalsIgnoreCase(Platform.getDebugOption("org.eclipse.core.expressions/debug/TypeExtensionManager")); //$NON-NLS-1$//$NON-NLS-2$

	private static final String TYPE= "type"; //$NON-NLS-1$

	private static final IPropertyTester[] EMPTY_PROPERTY_TESTER_ARRAY= new IPropertyTester[0];

	private static final IPropertyTester NULL_PROPERTY_TESTER= new IPropertyTester() {
		@Override
		public boolean handles(String namespace, String property) {
			return false;
		}
		@Override
		public boolean isInstantiated() {
			return true;
		}
		@Override
		public boolean isDeclaringPluginActive() {
			return true;
		}
		@Override
		public IPropertyTester instantiate() throws CoreException {
			return this;
		}
		@Override
		public boolean test(Object receiver, String property, Object[] args, Object expectedValue) {
			return false;
		}
	};

	/*
	 * Map containing all already created type extension object.
	 */
	private Map<Class<?>, TypeExtension> fTypeExtensionMap;

	/*
	 * Table containing mapping of class name to configuration element
	 */
	private Map<String, List<IConfigurationElement>> fConfigurationElementMap;

	/*
	 * A cache to give fast access to the last 1000 method invocations.
	 */
	private PropertyCache fPropertyCache;


	public TypeExtensionManager(String extensionPoint) {
		Assert.isNotNull(extensionPoint);
		fExtensionPoint= extensionPoint;
		Platform.getExtensionRegistry().addRegistryChangeListener(this);
		initializeCaches();
	}

	public Property getProperty(Object receiver, String namespace, String method) throws CoreException  {
		return getProperty(receiver, namespace, method, false);
	}

	public synchronized Property getProperty(Object receiver, String namespace, String method, boolean forcePluginActivation) throws CoreException  {
		long start= 0;
		if (Expressions.TRACING)
			start= System.currentTimeMillis();

		// if we call a static method than the receiver is the class object
		Class<?> clazz= receiver instanceof Class ? (Class<?>)receiver : receiver.getClass();
		Property result= new Property(clazz, namespace, method);
		Property cached= fPropertyCache.get(result);
		if (cached != null) {
			if (cached.isValidCacheEntry(forcePluginActivation)) {
				if (Expressions.TRACING) {
					System.out.println("[Type Extension] - method " + //$NON-NLS-1$
						clazz.getName() + "#" + method + //$NON-NLS-1$
						" found in cache: " +  //$NON-NLS-1$
						(System.currentTimeMillis() - start) + " ms."); //$NON-NLS-1$
				}
				return cached;
			}
			// The type extender isn't loaded in the cached method but can be loaded
			// now. So remove method from cache and do the normal look up so that the
			// implementation class gets loaded.
			fPropertyCache.remove(cached);
		}
		TypeExtension extension= get(clazz);
		IPropertyTester extender= extension.findTypeExtender(this, namespace, method, receiver instanceof Class, forcePluginActivation);
		if (extender == TypeExtension.CONTINUE || extender == null) {
			Throwable t= null;
			if (DEBUG) {
				//XXX: more logging for https://bugs.eclipse.org/bugs/show_bug.cgi?id=239715 :
				t= new Throwable("forcePluginActivation: " + forcePluginActivation + ", receiver: " + receiver).fillInStackTrace(); //$NON-NLS-1$ //$NON-NLS-2$
			}

			throw new CoreException(new ExpressionStatus(
				ExpressionStatus.TYPE_EXTENDER_UNKOWN_METHOD,
				Messages.format(
					ExpressionMessages.TypeExtender_unknownMethod,
					new String[] {namespace + '.' + method, clazz.toString()}),
					t));
		}
		result.setPropertyTester(extender);
		fPropertyCache.put(result);
		if (Expressions.TRACING) {
			System.out.println("[Type Extension] - method " + //$NON-NLS-1$
				clazz.getName() + "#" + method + //$NON-NLS-1$
				" not found in cache: " +  //$NON-NLS-1$
				(System.currentTimeMillis() - start) + " ms."); //$NON-NLS-1$
		}
		return result;
	}

	/*
	 * This method doesn't need to be synchronized since it is called
	 * from withing the getProperty method which is synchronized
	 */
	/* package */ TypeExtension get(Class<?> clazz) {
		TypeExtension result= fTypeExtensionMap.get(clazz);
		if (result == null) {
			result= new TypeExtension(clazz);
			fTypeExtensionMap.put(clazz, result);
		}
		return result;
	}

	/*
	 * This method doesn't need to be synchronized since it is called
	 * from withing the getProperty method which is synchronized
	 */
	/* package */ IPropertyTester[] loadTesters(Class<?> type) {
		if (fConfigurationElementMap == null) {
			fConfigurationElementMap= new HashMap<>();
			IExtensionRegistry registry= Platform.getExtensionRegistry();
			IConfigurationElement[] ces= registry.getConfigurationElementsFor(
				ExpressionPlugin.getPluginId(),
				fExtensionPoint);
			for (IConfigurationElement config : ces) {
				String typeAttr= config.getAttribute(TYPE);
				List<IConfigurationElement> typeConfigs= fConfigurationElementMap.get(typeAttr);
				if (typeConfigs == null) {
					typeConfigs= new ArrayList<>();
					fConfigurationElementMap.put(typeAttr, typeConfigs);
				}
				typeConfigs.add(config);
			}
		}
		String typeName= type.getName();
		List<IConfigurationElement> typeConfigs= fConfigurationElementMap.get(typeName);
		if (typeConfigs == null)
			return EMPTY_PROPERTY_TESTER_ARRAY;
		else {
			IPropertyTester[] result= new IPropertyTester[typeConfigs.size()];
			for (int i= 0; i < result.length; i++) {
				IConfigurationElement config= typeConfigs.get(i);
				try {
					result[i]= new PropertyTesterDescriptor(config);
				} catch (CoreException e) {
					ExpressionPlugin.getDefault().getLog().log(e.getStatus());
					result[i]= NULL_PROPERTY_TESTER;
				}
			}
			fConfigurationElementMap.remove(typeName);
			return result;
		}
	}

	@Override
	public void registryChanged(IRegistryChangeEvent event) {
		IExtensionDelta[] deltas= event.getExtensionDeltas(ExpressionPlugin.getPluginId(), fExtensionPoint);
		if (deltas.length > 0) {
			initializeCaches();
		}
	}

	private synchronized void initializeCaches() {
		fTypeExtensionMap= new HashMap<>();
		fConfigurationElementMap= null;
		fPropertyCache= new PropertyCache(1000);
	}
}