/*

 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.

 * Copyright (c) 2019, Red Hat, Inc.

 *

 * 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 jdk.jfr.internal;

import java.util.StringJoiner;

import jdk.internal.org.objectweb.asm.ClassWriter;

import jdk.internal.org.objectweb.asm.MethodVisitor;

import jdk.internal.org.objectweb.asm.Opcodes;

import jdk.internal.org.objectweb.asm.Type;

import jdk.internal.org.objectweb.asm.commons.Method;

import jdk.jfr.Event;

import jdk.jfr.EventType;

import jdk.jfr.internal.handlers.EventHandler;

/*

 * Generates an EventHandler subclass dynamically, named EventHandlerProxy.

 * EventHandlerProxy is located in a publicly accessible package (jdk.jfr)

 * and is used as a superclass for classes generated by EventHandlerCreator.

 * The rationale behind this scheme is to block access to jdk.jfr.internal

 * package and sub-packages when there is a SecurityManager installed, while

 * allowing application-defined event classes to invoke the required internal

 * APIs.

 */

final class EventHandlerProxyCreator {

    private static final int CLASS_VERSION = 52;

    private final static Type TYPE_EVENT_TYPE = Type.getType(EventType.class);

    private final static Type TYPE_EVENT_CONTROL = Type.getType(EventControl.class);

    private final static String DESCRIPTOR_EVENT_HANDLER = "(" + Type.BOOLEAN_TYPE.getDescriptor() + TYPE_EVENT_TYPE.getDescriptor() + TYPE_EVENT_CONTROL.getDescriptor() + ")V";

    private final static Method METHOD_EVENT_HANDLER_CONSTRUCTOR = new Method("<init>", DESCRIPTOR_EVENT_HANDLER);

    private final static String DESCRIPTOR_TIME_STAMP = "()" + Type.LONG_TYPE.getDescriptor();

    private final static Method METHOD_TIME_STAMP = new Method("timestamp", DESCRIPTOR_TIME_STAMP);

    private final static String DESCRIPTOR_DURATION = "(" + Type.LONG_TYPE.getDescriptor() + ")" + Type.LONG_TYPE.getDescriptor();

    private final static Method METHOD_DURATION = new Method("duration", DESCRIPTOR_DURATION);

    private final static ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);

    private final static String className = "jdk.jfr.proxy.internal.EventHandlerProxy";

    private final static String internalClassName = ASMToolkit.getInternalName(className);

    // Create the Proxy class instance after all the previous static fields were initialized (textual order)

    static final Class<? extends EventHandler> proxyClass = EventHandlerProxyCreator.makeEventHandlerProxyClass();

    static void ensureInitialized() {

        // trigger clinit which will setup the EventHandlerProxy class.

    }

    public static Class<? extends EventHandler> makeEventHandlerProxyClass() {

        buildClassInfo();

        buildConstructor();

        buildTimestampMethod();

        buildDurationMethod();

        byte[] bytes = classWriter.toByteArray();

        ASMToolkit.logASM(className, bytes);

        return SecuritySupport.defineClass(className, bytes, Event.class.getClassLoader()).asSubclass(EventHandler.class);

    }

    private static void buildConstructor() {

        MethodVisitor mv = classWriter.visitMethod(0x0, METHOD_EVENT_HANDLER_CONSTRUCTOR.getName(), makeConstructorDescriptor(), null, null);

        mv.visitVarInsn(Opcodes.ALOAD, 0); // this

        mv.visitVarInsn(Opcodes.ILOAD, 1); // registered

        mv.visitVarInsn(Opcodes.ALOAD, 2); // event type

        mv.visitVarInsn(Opcodes.ALOAD, 3); // event control

        mv.visitMethodInsn(Opcodes.INVOKESPECIAL, Type.getInternalName(EventHandler.class), METHOD_EVENT_HANDLER_CONSTRUCTOR.getName(), METHOD_EVENT_HANDLER_CONSTRUCTOR.getDescriptor(), false);

        mv.visitInsn(Opcodes.RETURN);

        mv.visitMaxs(0, 0);

        mv.visitEnd();

    }

    private static void buildClassInfo() {

        String internalSuperName = ASMToolkit.getInternalName(EventHandler.class.getName());

        classWriter.visit(CLASS_VERSION, Opcodes.ACC_PUBLIC + Opcodes.ACC_ABSTRACT + Opcodes.ACC_SUPER, internalClassName, null, internalSuperName, null);

    }

    private static void buildTimestampMethod() {

        MethodVisitor mv = classWriter.visitMethod(Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, METHOD_TIME_STAMP.getName(), METHOD_TIME_STAMP.getDescriptor(), null, null);

        mv.visitCode();

        mv.visitMethodInsn(Opcodes.INVOKESTATIC, Type.getInternalName(EventHandler.class), METHOD_TIME_STAMP.getName(), METHOD_TIME_STAMP.getDescriptor(), false);

        mv.visitInsn(Opcodes.LRETURN);

        mv.visitMaxs(0, 0);

        mv.visitEnd();

    }

    private static void buildDurationMethod() {

        MethodVisitor mv = classWriter.visitMethod(Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, METHOD_DURATION.getName(), METHOD_DURATION.getDescriptor(), null, null);

        mv.visitCode();

        mv.visitVarInsn(Opcodes.LLOAD, 0);

        mv.visitMethodInsn(Opcodes.INVOKESTATIC, Type.getInternalName(EventHandler.class), METHOD_DURATION.getName(), METHOD_DURATION.getDescriptor(), false);

        mv.visitInsn(Opcodes.LRETURN);

        mv.visitMaxs(0, 0);

        mv.visitEnd();

    }

    private static String makeConstructorDescriptor() {

        StringJoiner constructordescriptor = new StringJoiner("", "(", ")V");

        constructordescriptor.add(Type.BOOLEAN_TYPE.getDescriptor());

        constructordescriptor.add(Type.getType(EventType.class).getDescriptor());

        constructordescriptor.add(Type.getType(EventControl.class).getDescriptor());

        return constructordescriptor.toString();

    }

}