/*

 * Copyright (c) 2010, 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

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package jdk.nashorn.internal.runtime.linker;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.MethodType;

import jdk.internal.dynalink.beans.BeansLinker;

import jdk.internal.dynalink.linker.ConversionComparator.Comparison;

import jdk.internal.dynalink.linker.GuardedInvocation;

import jdk.internal.dynalink.linker.GuardingDynamicLinker;

import jdk.internal.dynalink.linker.LinkRequest;

import jdk.internal.dynalink.linker.LinkerServices;

import jdk.internal.dynalink.support.Lookup;

import jdk.nashorn.internal.runtime.ConsString;

/**

 * This linker delegates to a {@code BeansLinker} but passes it a special linker services object that has a modified

 * {@code asType} method that will ensure that we never pass internal engine objects that should not be externally

 * observable (currently only ConsString) to Java APIs, but rather that we flatten it into a String. We can't just add

 * this functionality as custom converters via {@code GuaardingTypeConverterFactory}, since they are not consulted when

 * the target method handle parameter signature is {@code Object}.

 */

public class NashornBeansLinker implements GuardingDynamicLinker {

    private static final MethodHandle EXPORT_ARGUMENT = new Lookup(MethodHandles.lookup()).findOwnStatic("exportArgument", Object.class, Object.class);

    private final BeansLinker beansLinker = new BeansLinker();

    @Override

    public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {

        return getGuardedInvocation(beansLinker, linkRequest, linkerServices);

    }

    /**

     * Delegates to the specified linker but injects its linker services wrapper so that it will apply all special

     * conversions that this class does.

     * @param delegateLinker the linker to which the actual work is delegated to.

     * @param linkRequest the delegated link request

     * @param linkerServices the original link services that will be augmented with special conversions

     * @return the guarded invocation from the delegate, possibly augmented with special conversions

     * @throws Exception if the delegate throws an exception

     */

    public static GuardedInvocation getGuardedInvocation(final GuardingDynamicLinker delegateLinker, final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {

        return delegateLinker.getGuardedInvocation(linkRequest, new NashornBeansLinkerServices(linkerServices));

    }

    static Object exportArgument(final Object arg) {

        return arg instanceof ConsString ? arg.toString() : arg;

    }

    private static class NashornBeansLinkerServices implements LinkerServices {

        private final LinkerServices linkerServices;

        NashornBeansLinkerServices(final LinkerServices linkerServices) {

            this.linkerServices = linkerServices;

        }

        @Override

        public MethodHandle asType(final MethodHandle handle, final MethodType fromType) {

            final MethodHandle typed = linkerServices.asType(handle, fromType);

            final MethodType handleType = handle.type();

            final int paramCount = handleType.parameterCount();

            assert fromType.parameterCount() == handleType.parameterCount();

            MethodHandle[] filters = null;

            for(int i = 0; i < paramCount; ++i) {

                if(shouldConvert(handleType.parameterType(i), fromType.parameterType(i))) {

                    if(filters == null) {

                        filters = new MethodHandle[paramCount];

                    }

                    filters[i] = EXPORT_ARGUMENT;

                }

            }

            return filters != null ? MethodHandles.filterArguments(typed, 0, filters) : typed;

        }

        @Override

        public MethodHandle asTypeLosslessReturn(final MethodHandle handle, final MethodType fromType) {

            return Implementation.asTypeLosslessReturn(this, handle, fromType);

        }

        private static boolean shouldConvert(final Class<?> handleType, final Class<?> fromType) {

            return handleType == Object.class && fromType == Object.class;

        }

        @Override

        public MethodHandle getTypeConverter(final Class<?> sourceType, final Class<?> targetType) {

            return linkerServices.getTypeConverter(sourceType, targetType);

        }

        @Override

        public boolean canConvert(final Class<?> from, final Class<?> to) {

            return linkerServices.canConvert(from, to);

        }

        @Override

        public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest) throws Exception {

            return linkerServices.getGuardedInvocation(linkRequest);

        }

        @Override

        public Comparison compareConversion(final Class<?> sourceType, final Class<?> targetType1, final Class<?> targetType2) {

            return linkerServices.compareConversion(sourceType, targetType1, targetType2);

        }

    }

}