/*

 * 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.runtime.ECMAErrors.typeError;

import static jdk.nashorn.internal.runtime.ScriptRuntime.UNDEFINED;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodType;

import java.lang.reflect.Method;

import java.lang.reflect.Modifier;

import java.util.Map;

import jdk.internal.dynalink.CallSiteDescriptor;

import jdk.internal.dynalink.beans.BeansLinker;

import jdk.internal.dynalink.linker.GuardedInvocation;

import jdk.internal.dynalink.linker.GuardingDynamicLinker;

import jdk.internal.dynalink.linker.GuardingTypeConverterFactory;

import jdk.internal.dynalink.linker.LinkRequest;

import jdk.internal.dynalink.linker.LinkerServices;

import jdk.internal.dynalink.support.Guards;

import jdk.nashorn.internal.runtime.Context;

import jdk.nashorn.internal.runtime.JSType;

import jdk.nashorn.internal.runtime.ScriptRuntime;

/**

 * Nashorn bottom linker; used as a last-resort catch-all linker for all linking requests that fall through all other

 * linkers (see how {@link Bootstrap} class configures the dynamic linker in its static initializer). It will throw

 * appropriate ECMAScript errors for attempts to invoke operations on {@code null}, link no-op property getters and

 * setters for Java objects that couldn't be linked by any other linker, and throw appropriate ECMAScript errors for

 * attempts to invoke arbitrary Java objects as functions or constructors.

 */

final class NashornBottomLinker implements GuardingDynamicLinker, GuardingTypeConverterFactory {

    @Override

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

            throws Exception {

        final Object self = linkRequest.getReceiver();

        if (self == null) {

            return linkNull(linkRequest);

        }

        // None of the objects that can be linked by NashornLinker should ever reach here. Basically, anything below

        // this point is a generic Java bean. Therefore, reaching here with a ScriptObject is a Nashorn bug.

        assert isExpectedObject(self) : "Couldn't link " + linkRequest.getCallSiteDescriptor() + " for " + self.getClass().getName();

        return linkBean(linkRequest, linkerServices);

    }

    private static final MethodHandle EMPTY_PROP_GETTER =

            MH.dropArguments(MH.constant(Object.class, UNDEFINED), 0, Object.class);

    private static final MethodHandle EMPTY_ELEM_GETTER =

            MH.dropArguments(EMPTY_PROP_GETTER, 0, Object.class);

    private static final MethodHandle EMPTY_PROP_SETTER =

            MH.asType(EMPTY_ELEM_GETTER, EMPTY_ELEM_GETTER.type().changeReturnType(void.class));

    private static final MethodHandle EMPTY_ELEM_SETTER =

            MH.dropArguments(EMPTY_PROP_SETTER, 0, Object.class);

    private static GuardedInvocation linkBean(final LinkRequest linkRequest, final LinkerServices linkerServices) throws Exception {

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

        final Object self = linkRequest.getReceiver();

        final String operator = desc.getFirstOperator();

        switch (operator) {

        case "new":

            if(BeansLinker.isDynamicMethod(self)) {

                throw typeError("method.not.constructor", ScriptRuntime.safeToString(self));

            }

            throw typeError("not.a.function", ScriptRuntime.safeToString(self));

        case "call":

            // Support dyn:call on any object that supports some @FunctionalInterface

            // annotated interface. This way Java method, constructor references or

            // implementations of java.util.function.* interfaces can be called as though

            // those are script functions.

            final Method m = getFunctionalInterfaceMethod(self.getClass());

            if (m != null) {

                final MethodType callType = desc.getMethodType();

                // 'callee' and 'thiz' passed from script + actual arguments

                if (callType.parameterCount() != m.getParameterCount() + 2) {

                    throw typeError("no.method.matches.args", ScriptRuntime.safeToString(self));

                }

                return new GuardedInvocation(

                        // drop 'thiz' passed from the script.

                        MH.dropArguments(desc.getLookup().unreflect(m), 1, callType.parameterType(1)),

                        Guards.getInstanceOfGuard(m.getDeclaringClass())).asType(callType);

            }

            if(BeansLinker.isDynamicMethod(self)) {

                throw typeError("no.method.matches.args", ScriptRuntime.safeToString(self));

            }

            throw typeError("not.a.function", ScriptRuntime.safeToString(self));

        case "callMethod":

        case "getMethod":

            throw typeError("no.such.function", getArgument(linkRequest), ScriptRuntime.safeToString(self));

        case "getProp":

        case "getElem":

            if (desc.getOperand() != null) {

                return getInvocation(EMPTY_PROP_GETTER, self, linkerServices, desc);

            }

            return getInvocation(EMPTY_ELEM_GETTER, self, linkerServices, desc);

        case "setProp":

        case "setElem":

            if (desc.getOperand() != null) {

                return getInvocation(EMPTY_PROP_SETTER, self, linkerServices, desc);

            }

            return getInvocation(EMPTY_ELEM_SETTER, self, linkerServices, desc);

        default:

            break;

        }

        throw new AssertionError("unknown call type " + desc);

    }

    @Override

        final GuardedInvocation gi = convertToTypeNoCast(sourceType, targetType);

    }

    /**

     * Main part of the implementation of {@link GuardingTypeConverterFactory#convertToType(Class, Class)} that doesn't

     * care about adapting the method signature; that's done by the invoking method. Returns conversion from Object to String/number/boolean (JS primitive types).

     * @param sourceType the source type

     * @param targetType the target type

     * @return a guarded invocation that converts from the source type to the target type.

     * @throws Exception if something goes wrong

     */

    private static GuardedInvocation convertToTypeNoCast(final Class<?> sourceType, final Class<?> targetType) throws Exception {

        final MethodHandle mh = CONVERTERS.get(targetType);

        if (mh != null) {

            return new GuardedInvocation(mh, null);

        }

        return null;

    }

    private static GuardedInvocation getInvocation(final MethodHandle handle, final Object self, final LinkerServices linkerServices, final CallSiteDescriptor desc) {

        return Bootstrap.asType(new GuardedInvocation(handle, Guards.getClassGuard(self.getClass())), linkerServices, desc);

    }

    // Used solely in an assertion to figure out if the object we get here is something we in fact expect. Objects

    // linked by NashornLinker should never reach here.

    private static boolean isExpectedObject(final Object obj) {

        return !(NashornLinker.canLinkTypeStatic(obj.getClass()));

    }

    private static GuardedInvocation linkNull(final LinkRequest linkRequest) {

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

        final String operator = desc.getFirstOperator();

        switch (operator) {

        case "new":

        case "call":

            throw typeError("not.a.function", "null");

        case "callMethod":

        case "getMethod":

            throw typeError("no.such.function", getArgument(linkRequest), "null");

        case "getProp":

        case "getElem":

            throw typeError("cant.get.property", getArgument(linkRequest), "null");

        case "setProp":

        case "setElem":

            throw typeError("cant.set.property", getArgument(linkRequest), "null");

        default:

            break;

        }

        throw new AssertionError("unknown call type " + desc);

    }

    private static final Map<Class<?>, MethodHandle> CONVERTERS = new HashMap<>();

    static {

        CONVERTERS.put(boolean.class, JSType.TO_BOOLEAN.methodHandle());

        CONVERTERS.put(double.class, JSType.TO_NUMBER.methodHandle());

        CONVERTERS.put(int.class, JSType.TO_INTEGER.methodHandle());

        CONVERTERS.put(long.class, JSType.TO_LONG.methodHandle());

        CONVERTERS.put(String.class, JSType.TO_STRING.methodHandle());

    }

    private static String getArgument(final LinkRequest linkRequest) {

        final CallSiteDescriptor desc = linkRequest.getCallSiteDescriptor();

        if (desc.getNameTokenCount() > 2) {

            return desc.getNameToken(2);

        }

        return ScriptRuntime.safeToString(linkRequest.getArguments()[1]);

    }

    // cache of @FunctionalInterface method of implementor classes

    private static final ClassValue<Method> FUNCTIONAL_IFACE_METHOD = new ClassValue<Method>() {

        @Override

        protected Method computeValue(final Class<?> type) {

            return findFunctionalInterfaceMethod(type);

        }

        private Method findFunctionalInterfaceMethod(final Class<?> clazz) {

            if (clazz == null) {

                return null;

            }

            for (Class<?> iface : clazz.getInterfaces()) {

                // check accessiblity up-front

                if (! Context.isAccessibleClass(iface)) {

                    continue;

                }

                // check for @FunctionalInterface

                if (iface.isAnnotationPresent(FunctionalInterface.class)) {

                    // return the first abstract method

                    for (final Method m : iface.getMethods()) {

                        if (Modifier.isAbstract(m.getModifiers())) {

                            return m;

                        }

                    }

                }

            }

            // did not find here, try super class

            return findFunctionalInterfaceMethod(clazz.getSuperclass());

        }

    };

    // Returns @FunctionalInterface annotated interface's single abstract

    // method. If not found, returns null.

    static Method getFunctionalInterfaceMethod(final Class<?> clazz) {

        return FUNCTIONAL_IFACE_METHOD.get(clazz);

    }

}