/*

 * Copyright (c) 2005, 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 javax.script;

import java.util.Map;

/**

 * Extended by classes that store results of compilations.  State

 * might be stored in the form of Java classes, Java class files or scripting

 * language opcodes.  The script may be executed repeatedly

 * without reparsing.

 * <br><br>

 * Each <code>CompiledScript</code> is associated with a <code>ScriptEngine</code> -- A call to an  <code>eval</code>

 * method of the <code>CompiledScript</code> causes the execution of the script by the

 * <code>ScriptEngine</code>.  Changes in the state of the <code>ScriptEngine</code> caused by execution

 *

 * @author Mike Grogan

 * @since 1.6

 */

public abstract class CompiledScript {

    /**

     * Executes the program stored in this <code>CompiledScript</code> object.

     *

     * @param context A <code>ScriptContext</code> that is used in the same way as

     * the <code>ScriptContext</code> passed to the <code>eval</code> methods of

     * <code>ScriptEngine</code>.

     *

     * @return The value returned by the script execution, if any.  Should return <code>null</code>

     * if no value is returned by the script execution.

     *

     * @throws ScriptException if an error occurs.

     * @throws NullPointerException if context is null.

     */

    public abstract Object eval(ScriptContext context) throws ScriptException;

    /**

     * Executes the program stored in the <code>CompiledScript</code> object using

     * the supplied <code>Bindings</code> of attributes as the <code>ENGINE_SCOPE</code> of the

     * associated <code>ScriptEngine</code> during script execution.  If bindings is null,

     * then the effect of calling this method is same as that of eval(getEngine().getContext()).

     * <p>.

     * The <code>GLOBAL_SCOPE</code> <code>Bindings</code>, <code>Reader</code> and <code>Writer</code>

     * associated with the default <code>ScriptContext</code> of the associated <code>ScriptEngine</code> are used.

     *

     * @param bindings The bindings of attributes used for the <code>ENGINE_SCOPE</code>.

     *

     * @return The return value from the script execution

     *

     * @throws ScriptException if an error occurs.

     */

    public Object eval(Bindings bindings) throws ScriptException {

        ScriptContext ctxt = getEngine().getContext();

        if (bindings != null) {

            SimpleScriptContext tempctxt = new SimpleScriptContext();

            tempctxt.setBindings(bindings, ScriptContext.ENGINE_SCOPE);

            tempctxt.setBindings(ctxt.getBindings(ScriptContext.GLOBAL_SCOPE),

                    ScriptContext.GLOBAL_SCOPE);

            tempctxt.setWriter(ctxt.getWriter());

            tempctxt.setReader(ctxt.getReader());

            tempctxt.setErrorWriter(ctxt.getErrorWriter());

            ctxt = tempctxt;

        }

        return eval(ctxt);

    }

    /**

     * Executes the program stored in the <code>CompiledScript</code> object.  The

     * default <code>ScriptContext</code> of the associated <code>ScriptEngine</code> is used.

     * The effect of calling this method is same as that of eval(getEngine().getContext()).

     *

     * @return The return value from the script execution

     *

     * @throws ScriptException if an error occurs.

     */

    public Object eval() throws ScriptException {

        return eval(getEngine().getContext());

    }

    /**

     * Returns the <code>ScriptEngine</code> whose <code>compile</code> method created this <code>CompiledScript</code>.

     * The <code>CompiledScript</code> will execute in this engine.

     *

     * @return The <code>ScriptEngine</code> that created this <code>CompiledScript</code>

     */

    public abstract ScriptEngine getEngine();

}