/*

 *  Copyright (c) 2020, 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 java.lang.invoke;

import jdk.internal.vm.annotation.ForceInline;

import jdk.internal.vm.annotation.Stable;

import java.util.List;

import java.util.function.BiFunction;

/**

 * An indirect var handle can be thought of as an aggregate of the method handles implementing its supported access modes.

 * Its varform contains no method name table (given that some of the method handles composing a bound var handle might

 * not be direct). The set of method handles constituting an indirect var handle are retrieved lazily, to minimize

 * code spinning (since not all the access modes will be used anyway).

 * Indirect var handles are useful when constructing var handle adapters - that is, an adapter var handle

 * can be constructed by extracting the method handles constituting the target var handle, adapting them

 * (using the method handle combinator API) and then repackaging the adapted method handles into a new, indirect

 * var handle.

 */

/* package */ class IndirectVarHandle extends VarHandle {

    @Stable

    private final MethodHandle[] handleMap = new MethodHandle[AccessMode.COUNT];

    private final VarHandle directTarget; // cache, for performance reasons

    private final VarHandle target;

    private final BiFunction<AccessMode, MethodHandle, MethodHandle> handleFactory;

    private final Class<?> value;

    private final Class<?>[] coordinates;

    IndirectVarHandle(VarHandle target, Class<?> value, Class<?>[] coordinates, BiFunction<AccessMode, MethodHandle, MethodHandle> handleFactory) {

        this(target, value, coordinates, handleFactory, new VarForm(value, coordinates), false);

    }

    private IndirectVarHandle(VarHandle target, Class<?> value, Class<?>[] coordinates,

                      BiFunction<AccessMode, MethodHandle, MethodHandle> handleFactory, VarForm form, boolean exact) {

        super(form, exact);

        this.handleFactory = handleFactory;

        this.target = target;

        this.directTarget = target.asDirect();

        this.value = value;

        this.coordinates = coordinates;

    }

    @Override

    public Class<?> varType() {

        return value;

    }

    @Override

    public List<Class<?>> coordinateTypes() {

        return List.of(coordinates);

    }

    @Override

    MethodType accessModeTypeUncached(AccessType at) {

        return at.accessModeType(null, value, coordinates);

    }

    @Override

    boolean isDirect() {

        return false;

    }

    @Override

    VarHandle asDirect() {

        return directTarget;

    }

    VarHandle target() {

        return target;

    }

    @Override

    public VarHandle withInvokeExactBehavior() {

        return hasInvokeExactBehavior()

            ? this

            : new IndirectVarHandle(target, value, coordinates, handleFactory, vform, true);

    }

    @Override

    public VarHandle withInvokeBehavior() {

        return !hasInvokeExactBehavior()

            ? this

            : new IndirectVarHandle(target, value, coordinates, handleFactory, vform, false);

    }

    @Override

    @ForceInline

    MethodHandle getMethodHandle(int mode) {

        MethodHandle handle = handleMap[mode];

        if (handle == null) {

            MethodHandle targetHandle = target.getMethodHandle(mode); // might throw UOE of access mode is not supported, which is ok

            handle = handleMap[mode] = handleFactory.apply(AccessMode.values()[mode], targetHandle);

        }

        return handle;

    }

    @Override

    public MethodHandle toMethodHandle(AccessMode accessMode) {

        return getMethodHandle(accessMode.ordinal()).bindTo(directTarget);

    }

}