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	/*
	* Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package sun.tracing;

	import java.lang.reflect.InvocationHandler;
	import java.lang.reflect.Method;
	import java.lang.reflect.Proxy;
	import java.lang.reflect.InvocationTargetException;
	import java.lang.reflect.AnnotatedElement;
	import java.lang.annotation.Annotation;
	import java.util.HashMap;
	import java.security.AccessController;
	import java.security.PrivilegedAction;

	import com.sun.tracing.Provider;
	import com.sun.tracing.Probe;
	import com.sun.tracing.ProviderName;

	/**
	* Provides a common code for implementation of {@code Provider} classes.
	*
	* Each tracing subsystem needs to provide three classes, a factory
	* (derived from {@code ProviderFactory}, a provider (a subclass of
	* {@code Provider}, and a probe type (subclass of {@code ProbeSkeleton}).
	*
	* The factory object takes a user-defined interface and provides an
	* implementation of it whose method calls will trigger probes in the
	* tracing framework.
	*
	* The framework's provider class, and its instances, are not seen by the
	* user at all -- they usually sit in the background and receive and dispatch
	* the calls to the user's provider interface. The {@code ProviderSkeleton}
	* class provides almost all of the implementation needed by a framework
	* provider. Framework providers must only provide a constructor and
	* disposal method, and implement the {@code createProbe} method to create
	* an appropriate {@code ProbeSkeleton} subclass.
	*
	* The framework's probe class provides the implementation of the two
	* probe methods, {@code isEnabled()} and {@code uncheckedTrigger()}. Both are
	* framework-dependent implementations.
	*
	* @since 1.7
	*/

	public abstract class ProviderSkeleton implements InvocationHandler, Provider {

	protected boolean active; // set to false after dispose() is called
	protected Class<? extends Provider> providerType; // user's interface
	protected HashMap<Method, ProbeSkeleton> probes; // methods to probes


	/**
	* Creates a framework-specific probe subtype.
	*
	* This method is implemented by the framework's provider and returns
	* framework-specific probes for a method.
	*
	* @param method A method in the user's interface
	* @return a subclass of ProbeSkeleton for the particular framework.
	*/
	protected abstract ProbeSkeleton createProbe(Method method);

	/**
	* Initializes the provider.
	*
	* @param type the user's interface
	*/
	protected ProviderSkeleton(Class<? extends Provider> type) {
	this.active = false; // in case of some error during initialization
	this.providerType = type;
	this.probes = new HashMap<Method,ProbeSkeleton>();
	}

	/**
	* Post-constructor initialization routine.
	*
	* Subclass instances must be initialized before they can create probes.
	* It is up to the factory implementations to call this after construction.
	*/
	public void init() {
	Method[] methods = AccessController.doPrivileged(new PrivilegedAction<Method[]>() {
	public Method[] run() {
	return providerType.getDeclaredMethods();
	}
	});

	for (Method m : methods) {
	if ( m.getReturnType() != Void.TYPE ) {
	throw new IllegalArgumentException(
	"Return value of method is not void");
	} else {
	probes.put(m, createProbe(m));
	}
	}
	this.active = true;
	}

	/**
	* Magic routine which creates an implementation of the user's interface.
	*
	* This method creates the instance of the user's interface which is
	* passed back to the user. Every call upon that interface will be
	* redirected to the {@code invoke()} method of this class (until
	* overridden by the VM).
	*
	* @return an implementation of the user's interface
	*/
	@SuppressWarnings("unchecked")
	public <T extends Provider> T newProxyInstance() {
	final InvocationHandler ih = this;
	return AccessController.doPrivileged(new PrivilegedAction<T>() {
	public T run() {
	return (T)Proxy.newProxyInstance(providerType.getClassLoader(),
	new Class<?>[] { providerType }, ih);
	}});
	}

	/**
	* Triggers a framework probe when a user interface method is called.
	*
	* This method dispatches a user interface method call to the appropriate
	* probe associated with this framework.
	*
	* If the invoked method is not a user-defined member of the interface,
	* then it is a member of {@code Provider} or {@code Object} and we
	* invoke the method directly.
	*
	* @param proxy the instance whose method was invoked
	* @param method the method that was called
	* @param args the arguments passed in the call.
	* @return always null, if the method is a user-defined probe
	*/
	public Object invoke(Object proxy, Method method, Object[] args) {
	Class declaringClass = method.getDeclaringClass();
	// not a provider subtype's own method
	if (declaringClass != providerType) {
	try {
	// delegate only to methods declared by
	// com.sun.tracing.Provider or java.lang.Object
	if (declaringClass == Provider.class \|\|
	declaringClass == Object.class) {
	return method.invoke(this, args);
	} else {
	// assert false : "this should never happen"
	// reaching here would indicate a breach
	// in security in the higher layers
	throw new SecurityException();
	}
	} catch (IllegalAccessException e) {
	assert false;
	} catch (InvocationTargetException e) {
	assert false;
	}
	} else {
	triggerProbe(method, args);
	}
	return null;
	}

	/**
	* Direct accessor for {@code Probe} objects.
	*
	* @param m the method corresponding to a probe
	* @return the method associated probe object, or null
	*/
	public Probe getProbe(Method m) {
	return active ? probes.get(m) : null;
	}

	/**
	* Default provider disposal method.
	*
	* This is overridden in subclasses as needed.
	*/
	public void dispose() {
	active = false;
	probes.clear();
	}

	/**
	* Gets the user-specified provider name for the user's interface.
	*
	* If the user's interface has a {@ProviderName} annotation, that value
	* is used. Otherwise we use the simple name of the user interface's class.
	* @return the provider name
	*/
	protected String getProviderName() {
	return getAnnotationString(
	providerType, ProviderName.class, providerType.getSimpleName());
	}

	/**
	* Utility method for getting a string value from an annotation.
	*
	* Used for getting a string value from an annotation with a 'value' method.
	*
	* @param element the element that was annotated, either a class or method
	* @param annotation the class of the annotation we're interested in
	* @param defaultValue the value to return if the annotation doesn't
	* exist, doesn't have a "value", or the value is empty.
	*/
	protected static String getAnnotationString(
	AnnotatedElement element, Class<? extends Annotation> annotation,
	String defaultValue) {
	String ret = (String)getAnnotationValue(
	element, annotation, "value", defaultValue);
	return ret.isEmpty() ? defaultValue : ret;
	}

	/**
	* Utility method for calling an arbitrary method in an annotation.
	*
	* @param element the element that was annotated, either a class or method
	* @param annotation the class of the annotation we're interested in
	* @param methodName the name of the method in the annotation we wish
	* to call.
	* @param defaultValue the value to return if the annotation doesn't
	* exist, or we couldn't invoke the method for some reason.
	* @return the result of calling the annotation method, or the default.
	*/
	protected static Object getAnnotationValue(
	AnnotatedElement element, Class<? extends Annotation> annotation,
	String methodName, Object defaultValue) {
	Object ret = defaultValue;
	try {
	Method m = annotation.getMethod(methodName);
	Annotation a = element.getAnnotation(annotation);
	ret = m.invoke(a);
	} catch (NoSuchMethodException e) {
	assert false;
	} catch (IllegalAccessException e) {
	assert false;
	} catch (InvocationTargetException e) {
	assert false;
	} catch (NullPointerException e) {
	assert false;
	}
	return ret;
	}

	protected void triggerProbe(Method method, Object[] args) {
	if (active) {
	ProbeSkeleton p = probes.get(method);
	if (p != null) {
	// Skips argument check -- already done by javac
	p.uncheckedTrigger(args);
	}
	}
	}
	}

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