/*

 * Copyright (c) 2014, 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.linker;

import static jdk.nashorn.internal.runtime.linker.BrowserJSObjectLinker.JSObjectHandles.JSOBJECT_GETMEMBER;

import static jdk.nashorn.internal.runtime.linker.BrowserJSObjectLinker.JSObjectHandles.JSOBJECT_GETSLOT;

import static jdk.nashorn.internal.runtime.linker.BrowserJSObjectLinker.JSObjectHandles.JSOBJECT_SETMEMBER;

import static jdk.nashorn.internal.runtime.linker.BrowserJSObjectLinker.JSObjectHandles.JSOBJECT_SETSLOT;

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.linker.LinkRequest;

import jdk.internal.dynalink.linker.LinkerServices;

import jdk.internal.dynalink.linker.TypeBasedGuardingDynamicLinker;

import jdk.internal.dynalink.support.CallSiteDescriptorFactory;

import jdk.nashorn.internal.lookup.MethodHandleFactory;

import jdk.nashorn.internal.lookup.MethodHandleFunctionality;

import jdk.nashorn.internal.runtime.JSType;

/**

 * A Dynalink linker to handle web browser built-in JS (DOM etc.) objects.

 */

final class BrowserJSObjectLinker implements TypeBasedGuardingDynamicLinker {

    private static ClassLoader extLoader;

    static {

        extLoader = BrowserJSObjectLinker.class.getClassLoader();

        // in case nashorn is loaded as bootstrap!

        if (extLoader == null) {

            extLoader = ClassLoader.getSystemClassLoader().getParent();

        }

    }

    private static final String JSOBJECT_CLASS = "netscape.javascript.JSObject";

    // not final because this is lazily initialized

    // when we hit a subclass for the first time.

    private static volatile Class<?> jsObjectClass;

    private final NashornBeansLinker nashornBeansLinker;

    BrowserJSObjectLinker(final NashornBeansLinker nashornBeansLinker) {

        this.nashornBeansLinker = nashornBeansLinker;

    }

    @Override

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

        return canLinkTypeStatic(type);

    }

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

        if (jsObjectClass != null && jsObjectClass.isAssignableFrom(type)) {

            return true;

        }

        // check if this class is a subclass of JSObject

        Class<?> clazz = type;

        while (clazz != null) {

            if (clazz.getClassLoader() == extLoader &&

                clazz.getName().equals(JSOBJECT_CLASS)) {

                jsObjectClass = clazz;

                return true;

            }

            clazz = clazz.getSuperclass();

        }

        return false;

    }

    private static void checkJSObjectClass() {

        assert jsObjectClass != null : JSOBJECT_CLASS + " not found!";

    }

    @Override

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

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

        final Object self = requestWithoutContext.getReceiver();

        final CallSiteDescriptor desc = requestWithoutContext.getCallSiteDescriptor();

        checkJSObjectClass();

        if (desc.getNameTokenCount() < 2 || !"dyn".equals(desc.getNameToken(CallSiteDescriptor.SCHEME))) {

            // We only support standard "dyn:*[:*]" operations

            return null;

        }

        final GuardedInvocation inv;

        if (jsObjectClass.isInstance(self)) {

            inv = lookup(desc, request, linkerServices);

        } else {

            throw new AssertionError(); // Should never reach here.

        }

        return Bootstrap.asTypeSafeReturn(inv, linkerServices, desc);

    }

    private GuardedInvocation lookup(final CallSiteDescriptor desc, final LinkRequest request, final LinkerServices linkerServices) throws Exception {

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

        final int c = desc.getNameTokenCount();

        switch (operator) {

            case "getProp":

            case "getElem":

            case "getMethod":

                if (c > 2) {

                    return findGetMethod(desc);

                }

            // For indexed get, we want GuardedInvocation from beans linker and pass it.

            // BrowserJSObjectLinker.get uses this fallback getter for explicit signature method access.

            return findGetIndexMethod(nashornBeansLinker.getGuardedInvocation(request, linkerServices));

            case "setProp":

            case "setElem":

                return c > 2 ? findSetMethod(desc) : findSetIndexMethod();

            default:

                return null;

        }

    }

    private static GuardedInvocation findGetMethod(final CallSiteDescriptor desc) {

        final String name = desc.getNameToken(CallSiteDescriptor.NAME_OPERAND);

        final MethodHandle getter = MH.insertArguments(JSOBJECT_GETMEMBER, 1, name);

        return new GuardedInvocation(getter, IS_JSOBJECT_GUARD);

    }

    private static GuardedInvocation findGetIndexMethod(final GuardedInvocation inv) {

        final MethodHandle getter = MH.insertArguments(JSOBJECTLINKER_GET, 0, inv.getInvocation());

        return inv.replaceMethods(getter, inv.getGuard());

    }

    private static GuardedInvocation findSetMethod(final CallSiteDescriptor desc) {

        final MethodHandle getter = MH.insertArguments(JSOBJECT_SETMEMBER, 1, desc.getNameToken(2));

        return new GuardedInvocation(getter, IS_JSOBJECT_GUARD);

    }

    private static GuardedInvocation findSetIndexMethod() {

        return new GuardedInvocation(JSOBJECTLINKER_PUT, IS_JSOBJECT_GUARD);

    }

    @SuppressWarnings("unused")

    private static boolean isJSObject(final Object self) {

        return jsObjectClass.isInstance(self);

    }

    @SuppressWarnings("unused")

    private static Object get(final MethodHandle fallback, final Object jsobj, final Object key) throws Throwable {

        if (key instanceof Integer) {

            return JSOBJECT_GETSLOT.invokeExact(jsobj, (int)key);

        } else if (key instanceof Number) {

            final int index = getIndex((Number)key);

            if (index > -1) {

                return JSOBJECT_GETSLOT.invokeExact(jsobj, index);

            }

        } else if (key instanceof String) {

            final String name = (String)key;

            if (name.indexOf('(') != -1) {

                return fallback.invokeExact(jsobj, key);

            }

            return JSOBJECT_GETMEMBER.invokeExact(jsobj, (String)key);

        }

        return null;

    }

    @SuppressWarnings("unused")

    private static void put(final Object jsobj, final Object key, final Object value) throws Throwable {

        if (key instanceof Integer) {

            JSOBJECT_SETSLOT.invokeExact(jsobj, (int)key, value);

        } else if (key instanceof Number) {

            JSOBJECT_SETSLOT.invokeExact(jsobj, getIndex((Number)key), value);

        } else if (key instanceof String) {

            JSOBJECT_SETMEMBER.invokeExact(jsobj, (String)key, value);

        }

    }

    private static int getIndex(final Number n) {

        final double value = n.doubleValue();

        return JSType.isRepresentableAsInt(value) ? (int)value : -1;

    }

    private static final MethodHandleFunctionality MH = MethodHandleFactory.getFunctionality();

    // method handles of the current class

    private static final MethodHandle IS_JSOBJECT_GUARD  = findOwnMH_S("isJSObject", boolean.class, Object.class);

    private static final MethodHandle JSOBJECTLINKER_GET = findOwnMH_S("get", Object.class, MethodHandle.class, Object.class, Object.class);

    private static final MethodHandle JSOBJECTLINKER_PUT = findOwnMH_S("put", Void.TYPE, Object.class, Object.class, Object.class);

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

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

    }

    // method handles of netscape.javascript.JSObject class

    // These are in separate class as we lazily initialize these

    // method handles when we hit a subclass of JSObject first time.

    static class JSObjectHandles {

        // method handles of JSObject class

        static final MethodHandle JSOBJECT_GETMEMBER     = findJSObjectMH_V("getMember", Object.class, String.class).asType(MH.type(Object.class, Object.class, String.class));

        static final MethodHandle JSOBJECT_GETSLOT       = findJSObjectMH_V("getSlot", Object.class, int.class).asType(MH.type(Object.class, Object.class, int.class));

        static final MethodHandle JSOBJECT_SETMEMBER     = findJSObjectMH_V("setMember", Void.TYPE, String.class, Object.class).asType(MH.type(Void.TYPE, Object.class, String.class, Object.class));

        static final MethodHandle JSOBJECT_SETSLOT       = findJSObjectMH_V("setSlot", Void.TYPE, int.class, Object.class).asType(MH.type(Void.TYPE, Object.class, int.class, Object.class));

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

            checkJSObjectClass();

            return MH.findVirtual(MethodHandles.publicLookup(), jsObjectClass, name, MH.type(rtype, types));

        }

    }

}