/*

 * Copyright (c) 2010, 2012, 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

 * or visit www.oracle.com if you need additional information or have any

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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 static jdk.nashorn.internal.runtime.linker.Lookup.MH;

import java.lang.invoke.MethodHandle;

import jdk.nashorn.internal.runtime.Context;

import jdk.nashorn.internal.runtime.ScriptObject;

import jdk.nashorn.internal.runtime.ScriptRuntime;

import org.dynalang.dynalink.CallSiteDescriptor;

import org.dynalang.dynalink.linker.GuardedInvocation;

import org.dynalang.dynalink.linker.GuardingDynamicLinker;

import org.dynalang.dynalink.linker.LinkRequest;

import org.dynalang.dynalink.linker.LinkerServices;

import org.dynalang.dynalink.support.Guards;

/**

 * 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.

 */

class NashornBottomLinker implements GuardingDynamicLinker {

    @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) {

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

        final Object self = linkRequest.getReceiver();

        final String operator = desc.getFirstOperator();

        switch (operator) {

        case "new":

            if(isJavaDynamicMethod(self)) {

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

            } else {

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

            }

            break;

        case "call":

            if(isJavaDynamicMethod(self)) {

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

            } else {

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

            }

            break;

        case "callMethod":

        case "getMethod":

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

            break;

        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);

    }

    /**

     * Returns true if the object is a Dynalink dynamic method. Unfortunately, the dynamic method classes are package

     * private in Dynalink, so this is the closest we can get to determining it.

     * @param obj the object we want to test for being a dynamic method

     * @return true if it is a dynamic method, false otherwise.

     */

    private static boolean isJavaDynamicMethod(Object obj) {

        return obj.getClass().getName().endsWith("DynamicMethod");

    }

    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 ScriptObject global = Context.getGlobal();

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

        final String operator = desc.getFirstOperator();

        switch (operator) {

        case "new":

        case "call":

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

            break;

        case "callMethod":

        case "getMethod":

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

            break;

        case "getProp":

        case "getElem":

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

            break;

        case "setProp":

        case "setElem":

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

            break;

        default:

            break;

        }

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

    }

    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]);

    }

}