/*

 * Copyright (c) 2009, 2011, 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 java.lang.invoke;

import sun.invoke.util.*;

import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;

/**

 * Adapters which manage inexact MethodHandle.invoke calls.

 * The JVM calls one of these when the exact type match fails.

 * @author jrose

 */

class InvokeGeneric {

    // erased type for the call, which originates from an inexact invoke site

    private final MethodType erasedCallerType;

    // an invoker of type (MT, MH; A...) -> R

    private final MethodHandle initialInvoker;

    /** Compute and cache information for this adapter, so that it can

     *  call out to targets of the erasure-family of the given erased type.

     */

    /*non-public*/ InvokeGeneric(MethodType erasedCallerType) throws ReflectiveOperationException {

        assert(erasedCallerType.equals(erasedCallerType.erase()));

        this.erasedCallerType = erasedCallerType;

        this.initialInvoker = makeInitialInvoker();

        assert initialInvoker.type().equals(erasedCallerType

                                            .insertParameterTypes(0, MethodType.class, MethodHandle.class))

            : initialInvoker.type();

    }

    private static MethodHandles.Lookup lookup() {

        return IMPL_LOOKUP;

    }

    /** Return the adapter information for this type's erasure. */

    /*non-public*/ static MethodHandle generalInvokerOf(MethodType erasedCallerType) throws ReflectiveOperationException {

        InvokeGeneric gen = new InvokeGeneric(erasedCallerType);

        return gen.initialInvoker;

    }

    private MethodHandle makeInitialInvoker() throws ReflectiveOperationException {

        // postDispatch = #(MH'; MT, MH; A...){MH'(MT, MH; A)}

        MethodHandle postDispatch = makePostDispatchInvoker();

        MethodHandle invoker;

        if (returnConversionPossible()) {

            invoker = MethodHandles.foldArguments(postDispatch,

                                                  dispatcher("dispatchWithConversion"));

        } else {

            invoker = MethodHandles.foldArguments(postDispatch, dispatcher("dispatch"));

        }

        return invoker;

    }

    private static final Class<?>[] EXTRA_ARGS = { MethodType.class, MethodHandle.class };

    private MethodHandle makePostDispatchInvoker() {

        // Take (MH'; MT, MH; A...) and run MH'(MT, MH; A...).

        MethodType invokerType = erasedCallerType.insertParameterTypes(0, EXTRA_ARGS);

        return invokerType.invokers().exactInvoker();

    }

    private MethodHandle dropDispatchArguments(MethodHandle targetInvoker) {

        assert(targetInvoker.type().parameterType(0) == MethodHandle.class);

        return MethodHandles.dropArguments(targetInvoker, 1, EXTRA_ARGS);

    }

    private MethodHandle dispatcher(String dispatchName) throws ReflectiveOperationException {

        return lookup().bind(this, dispatchName,

                             MethodType.methodType(MethodHandle.class,

                                                   MethodType.class, MethodHandle.class));

    }

    static final boolean USE_AS_TYPE_PATH = true;

    /** Return a method handle to invoke on the callerType, target, and remaining arguments.

     *  The method handle must finish the call.

     *  This is the first look at the caller type and target.

     */

    private MethodHandle dispatch(MethodType callerType, MethodHandle target) {

        MethodType targetType = target.type();

        if (USE_AS_TYPE_PATH || target.isVarargsCollector()) {

            MethodHandle newTarget = target.asType(callerType);

            targetType = callerType;

            Invokers invokers = targetType.invokers();

            MethodHandle invoker = invokers.erasedInvokerWithDrops;

            if (invoker == null) {

                invokers.erasedInvokerWithDrops = invoker =

                    dropDispatchArguments(invokers.erasedInvoker());

            }

            return invoker.bindTo(newTarget);

        }

        throw new RuntimeException("NYI");

    }

    private MethodHandle dispatchWithConversion(MethodType callerType, MethodHandle target) {

        MethodHandle finisher = dispatch(callerType, target);

        if (returnConversionNeeded(callerType, target))

            finisher = addReturnConversion(finisher, callerType.returnType());  //FIXME: slow

        return finisher;

    }

    private boolean returnConversionPossible() {

        Class<?> needType = erasedCallerType.returnType();

        return !needType.isPrimitive();

    }

    private boolean returnConversionNeeded(MethodType callerType, MethodHandle target) {

        Class<?> needType = callerType.returnType();

        if (needType == erasedCallerType.returnType())

            return false;  // no conversions possible, since must be primitive or Object

        Class<?> haveType = target.type().returnType();

        if (VerifyType.isNullConversion(haveType, needType) && !needType.isInterface())

            return false;

        return true;

    }

    private MethodHandle addReturnConversion(MethodHandle finisher, Class<?> type) {

        // FIXME: This is slow because it creates a closure node on every call that requires a return cast.

        MethodType finisherType = finisher.type();

        MethodHandle caster = ValueConversions.identity(type);

        caster = caster.asType(caster.type().changeParameterType(0, finisherType.returnType()));

        finisher = MethodHandles.filterReturnValue(finisher, caster);

        return finisher.asType(finisherType);

    }

    public String toString() {

        return "InvokeGeneric"+erasedCallerType;

    }

}