/*

 * 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 com.sun.script.util;

import javax.script.*;

import java.lang.reflect.*;

import java.security.*;

/*

 * java.lang.reflect.Proxy based interface implementor. This is meant

 * to be used to implement Invocable.getInterface.

 *

 * @author Mike Grogan

 * @since 1.6

 */

public class InterfaceImplementor {

    private Invocable engine;

    /** Creates a new instance of Invocable */

    public InterfaceImplementor(Invocable engine) {

        this.engine = engine;

    }

    private final class InterfaceImplementorInvocationHandler

                        implements InvocationHandler {

        private Object thiz;

        private AccessControlContext accCtxt;

        public InterfaceImplementorInvocationHandler(Object thiz,

            AccessControlContext accCtxt) {

            this.thiz = thiz;

            this.accCtxt = accCtxt;

        }

        public Object invoke(Object proxy , Method method, Object[] args)

        throws java.lang.Throwable {

            // give chance to convert input args

            args = convertArguments(method, args);

            Object result;

            final Method m = method;

            final Object[] a = args;

            result = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {

                public Object run() throws Exception {

                    if (thiz == null) {

                        return engine.invokeFunction(m.getName(), a);

                    } else {

                        return engine.invokeMethod(thiz, m.getName(), a);

                    }

                }

            }, accCtxt);

            // give chance to convert the method result

            return convertResult(method, result);

        }

    }

    public <T> T getInterface(Object thiz, Class<T> iface)

    throws ScriptException {

        if (iface == null || !iface.isInterface()) {

            throw new IllegalArgumentException("interface Class expected");

        }

        if (! isImplemented(thiz, iface)) {

            return null;

        }

        AccessControlContext accCtxt = AccessController.getContext();

        return iface.cast(Proxy.newProxyInstance(iface.getClassLoader(),

            new Class[]{iface},

            new InterfaceImplementorInvocationHandler(thiz, accCtxt)));

    }

    protected boolean isImplemented(Object thiz, Class<?> iface) {

        return true;

    }

    // called to convert method result after invoke

    protected Object convertResult(Method method, Object res)

                                   throws ScriptException {

        // default is identity conversion

        return res;

    }

    // called to convert method arguments before invoke

    protected Object[] convertArguments(Method method, Object[] args)

                                      throws ScriptException {

        // default is identity conversion

        return args;

    }

}