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 * 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 static jdk.nashorn.internal.lookup.Lookup.MH;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import jdk.internal.dynalink.linker.ConversionComparator;

import jdk.internal.dynalink.linker.GuardedInvocation;

import jdk.internal.dynalink.linker.GuardedTypeConversion;

import jdk.internal.dynalink.linker.GuardingTypeConverterFactory;

import jdk.internal.dynalink.linker.LinkRequest;

import jdk.internal.dynalink.linker.LinkerServices;

import jdk.internal.dynalink.linker.TypeBasedGuardingDynamicLinker;

import jdk.internal.dynalink.support.TypeUtilities;

import jdk.nashorn.internal.objects.Global;

import jdk.nashorn.internal.runtime.ConsString;

import jdk.nashorn.internal.runtime.ScriptRuntime;

/**

 * Internal linker for String, Boolean, and Number objects, only ever used by Nashorn engine and not exposed to other

 * engines. It is used for treatment of strings, boolean, and numbers as JavaScript primitives. Also provides ECMAScript

 * primitive type conversions for these types when linking to Java methods.

 */

final class NashornPrimitiveLinker implements TypeBasedGuardingDynamicLinker, GuardingTypeConverterFactory, ConversionComparator {

    private static final GuardedTypeConversion VOID_TO_OBJECT = new GuardedTypeConversion(

            new GuardedInvocation(MethodHandles.constant(Object.class, ScriptRuntime.UNDEFINED)), true);

    @Override

    public boolean canLinkType(final Class<?> type) {

        return canLinkTypeStatic(type);

    }

    private static boolean canLinkTypeStatic(final Class<?> type) {

        return type == String.class || type == Boolean.class || type == ConsString.class || Number.class.isAssignableFrom(type);

    }

    @Override

    public GuardedInvocation getGuardedInvocation(final LinkRequest origRequest, final LinkerServices linkerServices)

            throws Exception {

        final LinkRequest request = origRequest.withoutRuntimeContext(); // Nashorn has no runtime context

        final Object self = request.getReceiver();

        final NashornCallSiteDescriptor desc = (NashornCallSiteDescriptor) request.getCallSiteDescriptor();

        return Bootstrap.asTypeSafeReturn(Global.primitiveLookup(request, self), linkerServices, desc);

    }

    /**

     * This implementation of type converter factory will pretty much allow implicit conversions of anything to anything

     * else that's allowed among JavaScript primitive types (string to number, boolean to string, etc.)

     * @param sourceType the type to convert from

     * @param targetType the type to convert to

     * @return a conditional converter from source to target type

     */

    @Override

    public GuardedTypeConversion convertToType(final Class<?> sourceType, final Class<?> targetType) {

        final MethodHandle mh = JavaArgumentConverters.getConverter(targetType);

        if (mh == null) {

            if(targetType == Object.class && sourceType == void.class) {

                return VOID_TO_OBJECT;

            }

            return null;

        }

        return new GuardedTypeConversion(new GuardedInvocation(mh, canLinkTypeStatic(sourceType) ? null : GUARD_PRIMITIVE).asType(mh.type().changeParameterType(0, sourceType)), true);

    }

    /**

     * Implements the somewhat involved prioritization of JavaScript primitive types conversions. Instead of explaining

     * it here in prose, just follow the source code comments.

     * @param sourceType the source type to convert from

     * @param targetType1 one candidate target type

     * @param targetType2 another candidate target type

     * @return one of {@link jdk.internal.dynalink.linker.ConversionComparator.Comparison} values signifying which

     * target type should be favored for conversion.

     */

    @Override

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

        final Class<?> wrapper1 = getWrapperTypeOrSelf(targetType1);

        if (sourceType == wrapper1) {

            // Source type exactly matches target 1

            return Comparison.TYPE_1_BETTER;

        }

        final Class<?> wrapper2 = getWrapperTypeOrSelf(targetType2);

        if (sourceType == wrapper2) {

            // Source type exactly matches target 2

            return Comparison.TYPE_2_BETTER;

        }

        if (Number.class.isAssignableFrom(sourceType)) {

            // If exactly one of the targets is a number, pick it.

            if (Number.class.isAssignableFrom(wrapper1)) {

                if (!Number.class.isAssignableFrom(wrapper2)) {

                    return Comparison.TYPE_1_BETTER;

                }

            } else if (Number.class.isAssignableFrom(wrapper2)) {

                return Comparison.TYPE_2_BETTER;

            }

            // If exactly one of the targets is a character, pick it. Numbers can be reasonably converted to chars using

            // the UTF-16 values.

            if (Character.class == wrapper1) {

                return Comparison.TYPE_1_BETTER;

            } else if (Character.class == wrapper2) {

                return Comparison.TYPE_2_BETTER;

            }

            // For all other cases, we fall through to the next if statement - not that we repeat the condition in it

            // too so if we entered this branch, we'll enter the below if statement too.

        }

        if (sourceType == String.class || sourceType == Boolean.class || Number.class.isAssignableFrom(sourceType)) {

            // Treat wrappers as primitives.

            final Class<?> primitiveType1 = getPrimitiveTypeOrSelf(targetType1);

            final Class<?> primitiveType2 = getPrimitiveTypeOrSelf(targetType2);

            // Basically, choose the widest possible primitive type. (First "if" returning TYPE_2_BETTER is correct;

            // when faced with a choice between double and int, choose double).

            if (TypeUtilities.isMethodInvocationConvertible(primitiveType1, primitiveType2)) {

                return Comparison.TYPE_2_BETTER;

            } else if (TypeUtilities.isMethodInvocationConvertible(primitiveType2, primitiveType1)) {

                return Comparison.TYPE_1_BETTER;

            }

            // Ok, at this point we're out of possible number conversions, so try strings. A String can represent any

            // value without loss, so if one of the potential targets is string, go for it.

            if (targetType1 == String.class) {

                return Comparison.TYPE_1_BETTER;

            }

            if (targetType2 == String.class) {

                return Comparison.TYPE_2_BETTER;

            }

        }

        return Comparison.INDETERMINATE;

    }

    private static Class<?> getPrimitiveTypeOrSelf(final Class<?> type) {

        final Class<?> primitive = TypeUtilities.getPrimitiveType(type);

        return primitive == null ? type : primitive;

    }

    private static Class<?> getWrapperTypeOrSelf(final Class<?> type) {

        final Class<?> wrapper = TypeUtilities.getWrapperType(type);

        return wrapper == null ? type : wrapper;

    }

    @SuppressWarnings("unused")

    private static boolean isJavaScriptPrimitive(final Object o) {

    }

    private static final MethodHandle GUARD_PRIMITIVE = findOwnMH("isJavaScriptPrimitive", boolean.class, Object.class);

    private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {

        return MH.findStatic(MethodHandles.lookup(), NashornPrimitiveLinker.class, name, MH.type(rtype, types));

    }

}