/*
 * Copyright (c) 2001, 2021, 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
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package jdk.internal.reflect;

import jdk.internal.vm.annotation.Stable;

import java.lang.reflect.InvocationTargetException;
import java.util.Objects;

/** Delegates its invocation to another MethodAccessorImpl and can
    change its delegate at run time. */

class DelegatingMethodAccessorImpl extends MethodAccessorImpl {
    // initial non-null delegate
    private final MethodAccessorImpl initialDelegate;
    // alternative delegate: starts as null;
    // only single change from null -> non-null is guaranteed
    @Stable
    private MethodAccessorImpl altDelegate;

    DelegatingMethodAccessorImpl(MethodAccessorImpl delegate) {
        initialDelegate = Objects.requireNonNull(delegate);
    }

    @Override
    public Object invoke(Object obj, Object[] args)
        throws IllegalArgumentException, InvocationTargetException
    {
        return delegate().invoke(obj, args);
    }

    @Override
    public Object invoke(Object obj, Object[] args, Class<?> caller)
            throws IllegalArgumentException, InvocationTargetException
    {
        return delegate().invoke(obj, args, caller);
    }

    private MethodAccessorImpl delegate() {
        var d = altDelegate;
        return  d != null ? d : initialDelegate;
    }

    void setDelegate(MethodAccessorImpl delegate) {
        altDelegate = Objects.requireNonNull(delegate);
    }
}
