/*

 * Copyright 2008-2009 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.dyn;

import java.dyn.JavaMethodHandle;

import java.dyn.MethodHandle;

import java.dyn.MethodHandles;

import java.dyn.MethodType;

/**

 * Unary function composition, useful for many small plumbing jobs.

 * The invoke method takes a single reference argument, and returns a reference

 * Internally, it first calls the {@code filter} method on the argument,

 * Making up the difference between the raw method type and the

 * final method type is the responsibility of a JVM-level adapter.

 * @author jrose

 */

public class FilterOneArgument extends JavaMethodHandle {

    protected final MethodHandle filter;  // Object -> Object

    protected final MethodHandle target;  // Object -> Object

    protected Object entryPoint(Object argument) {

        Object filteredArgument = filter.<Object>invoke(argument);

        return target.<Object>invoke(filteredArgument);

    }

    private static final MethodHandle entryPoint =

        MethodHandleImpl.IMPL_LOOKUP.findVirtual(FilterOneArgument.class, "entryPoint", MethodType.makeGeneric(1));

    protected FilterOneArgument(MethodHandle filter, MethodHandle target) {

        super(entryPoint);

        this.filter = filter;

        this.target = target;

    }

    public static MethodHandle make(MethodHandle filter, MethodHandle target) {

        if (filter == null)  return target;

        if (target == null)  return filter;

        return new FilterOneArgument(filter, target);

    }

    public String toString() {

        return filter + "|>" + target;

    }

//    MethodHandle make(MethodHandle filter1, MethodHandle filter2, MethodHandle target) {

//        MethodHandle filter = make(filter1, filter2);

//        return make(filter, target);

//    }

}