/*
 * Copyright (c) 2018, 2018, 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
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 */
package com.oracle.svm.reflect.helpers;

//Checkstyle: allow reflection

import java.lang.reflect.Field;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

import com.oracle.svm.core.util.VMError;
import com.oracle.svm.util.ReflectionUtil;

public class ReflectionProxyHelper {
    private static final Field hField = ReflectionUtil.lookupField(Proxy.class, "h");

    private static Object toStringInvocationHandler(Object proxy, Method method, @SuppressWarnings("unused") Object[] args) {
        if (method.getName().equals("toString")) {
            return proxy.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(proxy));
        }

        if (method.getName().equals("hashCode") || method.getName().equals("equals") || method.getName().equals("invoke")) {
            throw VMError.shouldNotReachHere("You should not call " + method + " on an instance of " + proxy.getClass() + " during image building.");
        }

        throw VMError.shouldNotReachHere("Unknown method " + method + " called on an instance of " + proxy.getClass() + ".");
    }

    
Set a default invocation handler for a ReflectionProxy proxy instance. At runtime the "h"
field is not used as the methods (invoke, toString, hashCode, equals) that would use the
handler are substituted (see ReflectionSubstitutionType). However the handler is needed when
the proxy instance is used during image building, e.g., toString() is called on it for error
reporting (see NativeImageHeap.addObjectToBootImageHeap()).
/**
     * Set a default invocation handler for a ReflectionProxy proxy instance. At runtime the "h"
     * field is not used as the methods (invoke, toString, hashCode, equals) that would use the
     * handler are substituted (see ReflectionSubstitutionType). However the handler is needed when
     * the proxy instance is used during image building, e.g., toString() is called on it for error
     * reporting (see NativeImageHeap.addObjectToBootImageHeap()).
     */
    public static void setDefaultInvocationHandler(Proxy proxyInstance) {
        VMError.guarantee(ReflectionProxy.class.isAssignableFrom(proxyInstance.getClass()));
        try {
            hField.set(proxyInstance, (InvocationHandler) ReflectionProxyHelper::toStringInvocationHandler);
        } catch (IllegalAccessException e) {
            throw VMError.shouldNotReachHere(e);
        }
    }
}