/*

 * 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

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

 * questions.

 */

package jdk.nashorn.internal.runtime;

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

import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;

import java.lang.invoke.MethodHandle;

import java.lang.invoke.MethodHandles;

import jdk.internal.dynalink.CallSiteDescriptor;

import jdk.internal.dynalink.linker.GuardedInvocation;

import jdk.internal.dynalink.support.CallSiteDescriptorFactory;

import jdk.internal.dynalink.support.Guards;

import jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor;

/**

 * Unique instance of this class is used to represent JavaScript undefined.

 */

public final class Undefined extends DefaultPropertyAccess {

    private Undefined() {

    }

    private static final Undefined UNDEFINED = new Undefined();

    private static final Undefined EMPTY     = new Undefined();

    // Guard used for indexed property access/set on the Undefined instance

    private static final MethodHandle UNDEFINED_GUARD = Guards.getIdentityGuard(UNDEFINED);

    /**

     * Get the value of {@code undefined}, this is represented as a global singleton

     * instance of this class. It can always be reference compared

     *

     * @return the undefined object

     */

    public static Undefined getUndefined() {

        return UNDEFINED;

    }

    /**

     * Get the value of {@code empty}. This is represented as a global singleton

     * instanceof this class. It can always be reference compared.

     * <p>

     * We need empty to differentiate behavior in things like array iterators

     * <p>

     * @return the empty object

     */

    public static Undefined getEmpty() {

        return EMPTY;

    }

    /**

     * Get the class name of Undefined

     * @return "Undefined"

     */

    @SuppressWarnings("static-method")

    public String getClassName() {

        return "Undefined";

    }

    @Override

    public String toString() {

        return "undefined";

    }

    /**

     * Lookup the appropriate method for an invoke dynamic call.

     * @param desc The invoke dynamic callsite descriptor.

     * @return GuardedInvocation to be invoked at call site.

     */

    public static GuardedInvocation lookup(final CallSiteDescriptor desc) {

        final String operator = CallSiteDescriptorFactory.tokenizeOperators(desc).get(0);

        switch (operator) {

        case "new":

        case "callMethod":

            throw lookupTypeError("cant.read.property.of.undefined", desc);

        // NOTE: we support getElem and setItem as JavaScript doesn't distinguish items from properties. Nashorn itself

        // emits "dyn:getProp:identifier" for "<expr>.<identifier>" and "dyn:getElem" for "<expr>[<expr>]", but we are

        // more flexible here and dispatch not on operation name (getProp vs. getElem), but rather on whether the

        // operation has an associated name or not.

        case "getProp":

        case "getElem":

        case "getMethod":

            if (desc.getNameTokenCount() < 3) {

                return findGetIndexMethod(desc);

            }

            return findGetMethod(desc);

        case "setProp":

        case "setElem":

            if (desc.getNameTokenCount() < 3) {

                return findSetIndexMethod(desc);

            }

            return findSetMethod(desc);

        default:

            break;

        }

        return null;

    }

    private static ECMAException lookupTypeError(final String msg, final CallSiteDescriptor desc) {

    }

    private static final MethodHandle GET_METHOD = findOwnMH("get", Object.class, Object.class);

    private static final MethodHandle SET_METHOD = MH.insertArguments(findOwnMH("set", void.class, Object.class, Object.class, int.class), 3, NashornCallSiteDescriptor.CALLSITE_STRICT);

    private static GuardedInvocation findGetMethod(final CallSiteDescriptor desc) {

        return new GuardedInvocation(MH.insertArguments(GET_METHOD, 1, desc.getNameToken(2)), UNDEFINED_GUARD).asType(desc);

    }

    private static GuardedInvocation findGetIndexMethod(final CallSiteDescriptor desc) {

        return new GuardedInvocation(GET_METHOD, UNDEFINED_GUARD).asType(desc);

    }

    private static GuardedInvocation findSetMethod(final CallSiteDescriptor desc) {

        return new GuardedInvocation(MH.insertArguments(SET_METHOD, 1, desc.getNameToken(2)), UNDEFINED_GUARD).asType(desc);

    }

    private static GuardedInvocation findSetIndexMethod(final CallSiteDescriptor desc) {

        return new GuardedInvocation(SET_METHOD, UNDEFINED_GUARD).asType(desc);

    }

    @Override

    public Object get(final Object key) {

        throw typeError("cant.read.property.of.undefined", ScriptRuntime.safeToString(key));

    }

    @Override

    public void set(final Object key, final Object value, final int flags) {

        throw typeError("cant.set.property.of.undefined", ScriptRuntime.safeToString(key));

    }

    @Override

    public boolean delete(final Object key, final boolean strict) {

        throw typeError("cant.delete.property.of.undefined", ScriptRuntime.safeToString(key));

    }

    @Override

    public boolean has(final Object key) {

        return false;

    }

    @Override

    public boolean hasOwnProperty(final Object key) {

        return false;

    }

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

        return MH.findVirtual(MethodHandles.lookup(), Undefined.class, name, MH.type(rtype, types));

    }

}