/*

 * Copyright (c) 2006, 2016, 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 netscape.javascript;

import jdk.internal.netscape.javascript.spi.JSObjectProvider;

import java.applet.Applet;

import java.security.AccessController;

import java.security.PrivilegedAction;

import java.util.Iterator;

import java.util.ServiceLoader;

/**

 * <p>

 * Allows Java code to manipulate JavaScript objects.

 * </p>

 *

 * <p>

 * When a JavaScript object is passed or returned to Java code, it

 * is wrapped in an instance of {@code JSObject}. When a

 * {@code JSObject} instance is passed to the JavaScript engine,

 * it is unwrapped back to its original JavaScript object. The

 * {@code JSObject} class provides a way to invoke JavaScript

 * methods and examine JavaScript properties.

 * </p>

 *

 * <p> Any data returned from the JavaScript engine to Java is

 * converted to Java data types. Certain data passed to the JavaScript

 * engine is converted to JavaScript data types.

 * </p>

 *

 */

public abstract class JSObject {

    /**

     * Constructs a new JSObject. Users should neither call this method nor

     * subclass JSObject.

     */

    protected JSObject()  {

    }

    /**

     * Calls a JavaScript method. Equivalent to

     * "this.methodName(args[0], args[1], ...)" in JavaScript.

     *

     * @param methodName The name of the JavaScript method to be invoked.

     * @param args the Java objects passed as arguments to the method.

     * @return Result of the method.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract Object call(String methodName, Object... args) throws JSException;

    /**

     * Evaluates a JavaScript expression. The expression is a string of

     * JavaScript source code which will be evaluated in the context given by

     * "this".

     *

     * @param s The JavaScript expression.

     * @return Result of the JavaScript evaluation.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract Object eval(String s) throws JSException;

    /**

     * Retrieves a named member of a JavaScript object. Equivalent to

     * "this.name" in JavaScript.

     *

     * @param name The name of the JavaScript property to be accessed.

     * @return The value of the propery.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract Object getMember(String name) throws JSException;

    /**

     * Sets a named member of a JavaScript object. Equivalent to

     * "this.name = value" in JavaScript.

     *

     * @param name The name of the JavaScript property to be accessed.

     * @param value The value of the propery.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract void setMember(String name, Object value) throws JSException;

    /**

     * Removes a named member of a JavaScript object. Equivalent

     * to "delete this.name" in JavaScript.

     *

     * @param name The name of the JavaScript property to be removed.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract void removeMember(String name) throws JSException;

    /**

     * Retrieves an indexed member of a JavaScript object. Equivalent to

     * "this[index]" in JavaScript.

     *

     * @param index The index of the array to be accessed.

     * @return The value of the indexed member.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract Object getSlot(int index) throws JSException;

    /**

     * Sets an indexed member of a JavaScript object. Equivalent to

     * "this[index] = value" in JavaScript.

     *

     * @param index The index of the array to be accessed.

     * @param value The value to set

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine.

     */

    public abstract void setSlot(int index, Object value) throws JSException;

    /**

     * Returns a JSObject for the window containing the given applet. This

     * method only works when the Java code is running in a browser as an

     * applet. The object returned may be used to access the HTML DOM directly.

     *

     * @param applet The applet.

     * @return JSObject representing the window containing the given applet or

     * {@code null} if we are not connected to a browser.

     * @throws JSException when an error is reported from the browser or

     * JavaScript engine or if applet is {@code null}

     */

    public static JSObject getWindow(Applet applet) throws JSException {

        return ProviderLoader.callGetWindow(applet);

    }

    private static class ProviderLoader {

        private static final JSObjectProvider provider;

        static {

            provider = AccessController.doPrivileged(

                new PrivilegedAction<>() {

                    @Override

                    public JSObjectProvider run() {

                        Iterator<JSObjectProvider> providers =

                            ServiceLoader.loadInstalled(JSObjectProvider.class).iterator();

                        if (providers.hasNext()) {

                            return providers.next();

                        }

                        return null;

                    }

                }

            );

        }

        private static JSObject callGetWindow(Applet applet) {

            if (provider != null) {

                return provider.getWindow(applet);

            }

            return null;

        }

    }

}