/*

 * Copyright (c) 2005, 2006, 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.io.Reader;

import java.util.Map;

import java.util.Iterator;

/**

 * Provides a standard implementation for several of the variants of the <code>eval</code>

 * method.

 * <br><br>

 * <code><b>eval(Reader)</b></code><p><code><b>eval(String)</b></code><p>

 * <code><b>eval(String, Bindings)</b></code><p><code><b>eval(Reader, Bindings)</b></code>

 * <br><br> are implemented using the abstract methods

 * <br><br>

 * <code><b>eval(Reader,ScriptContext)</b></code> or

 * <code><b>eval(String, ScriptContext)</b></code>

 * <br><br>

 * with a <code>SimpleScriptContext</code>.

 * <br><br>

 * A <code>SimpleScriptContext</code> is used as the default <code>ScriptContext</code>

 * of the <code>AbstractScriptEngine</code>..

 *

 * @author Mike Grogan

 * @since 1.6

 */

public abstract class AbstractScriptEngine  implements ScriptEngine {

    /**

     * The default <code>ScriptContext</code> of this <code>AbstractScriptEngine</code>.

     */

    protected ScriptContext context;

    /**

     * Creates a new instance of AbstractScriptEngine using a <code>SimpleScriptContext</code>

     * as its default <code>ScriptContext</code>.

     */

    public AbstractScriptEngine() {

        context = new SimpleScriptContext();

    }

    /**

     * Creates a new instance using the specified <code>Bindings</code> as the

     * <code>ENGINE_SCOPE</code> <code>Bindings</code> in the protected <code>context</code> field.

     *

     * @param n The specified <code>Bindings</code>.

     * @throws NullPointerException if n is null.

     */

    public AbstractScriptEngine(Bindings n) {

        this();

        if (n == null) {

            throw new NullPointerException("n is null");

        }

        context.setBindings(n, ScriptContext.ENGINE_SCOPE);

    }

    /**

     * Sets the value of the protected <code>context</code> field to the specified

     * <code>ScriptContext</code>.

     *

     * @param ctxt The specified <code>ScriptContext</code>.

     * @throws NullPointerException if ctxt is null.

     */

    public void setContext(ScriptContext ctxt) {

        if (ctxt == null) {

            throw new NullPointerException("null context");

        }

        context = ctxt;

    }

    /**

     * Returns the value of the protected <code>context</code> field.

     *

     * @return The value of the protected <code>context</code> field.

     */

    public ScriptContext getContext() {

        return context;

    }

    /**

     * Returns the <code>Bindings</code> with the specified scope value in

     * the protected <code>context</code> field.

     *

     * @param scope The specified scope

     *

     * @return The corresponding <code>Bindings</code>.

     *

     * @throws IllegalArgumentException if the value of scope is

     * invalid for the type the protected <code>context</code> field.

     */

    public Bindings getBindings(int scope) {

        if (scope == ScriptContext.GLOBAL_SCOPE) {

            return context.getBindings(ScriptContext.GLOBAL_SCOPE);

        } else if (scope == ScriptContext.ENGINE_SCOPE) {

            return context.getBindings(ScriptContext.ENGINE_SCOPE);

        } else {

            throw new IllegalArgumentException("Invalid scope value.");

        }

    }

    /**

     * Sets the <code>Bindings</code> with the corresponding scope value in the

     * <code>context</code> field.

     *

     * @param bindings The specified <code>Bindings</code>.

     * @param scope The specified scope.

     *

     * @throws IllegalArgumentException if the value of scope is

     * invalid for the type the <code>context</code> field.

     * @throws NullPointerException if the bindings is null and the scope is

     * <code>ScriptContext.ENGINE_SCOPE</code>

     */

    public void setBindings(Bindings bindings, int scope) {

        if (scope == ScriptContext.GLOBAL_SCOPE) {

            context.setBindings(bindings, ScriptContext.GLOBAL_SCOPE);;

        } else if (scope == ScriptContext.ENGINE_SCOPE) {

            context.setBindings(bindings, ScriptContext.ENGINE_SCOPE);;

        } else {

            throw new IllegalArgumentException("Invalid scope value.");

        }

    }

    /**

     * Sets the specified value with the specified key in the <code>ENGINE_SCOPE</code>

     * <code>Bindings</code> of the protected <code>context</code> field.

     *

     * @param key The specified key.

     * @param value The specified value.

     *

     * @throws NullPointerException if key is null.

     * @throws IllegalArgumentException if key is empty.

     */

    public void put(String key, Object value) {

        Bindings nn = getBindings(ScriptContext.ENGINE_SCOPE);

        if (nn != null) {

            nn.put(key, value);

        }

    }

    /**

     * Gets the value for the specified key in the <code>ENGINE_SCOPE</code> of the

     * protected <code>context</code> field.

     *

     * @return The value for the specified key.

     *

     * @throws NullPointerException if key is null.

     * @throws IllegalArgumentException if key is empty.

     */

    public Object get(String key) {

        Bindings nn = getBindings(ScriptContext.ENGINE_SCOPE);

        if (nn != null) {

            return nn.get(key);

        }

        return null;

    }

    /**

     * <code>eval(Reader, Bindings)</code> calls the abstract

     * <code>eval(Reader, ScriptContext)</code> method, passing it a <code>ScriptContext</code>

     * whose Reader, Writers and Bindings for scopes other that <code>ENGINE_SCOPE</code>

     * are identical to those members of the protected <code>context</code> field.  The specified

     * <code>Bindings</code> is used instead of the <code>ENGINE_SCOPE</code>

     *

     * <code>Bindings</code> of the <code>context</code> field.

     *

     * @param reader A <code>Reader</code> containing the source of the script.

     * @param bindings A <code>Bindings</code> to use for the <code>ENGINE_SCOPE</code>

     * while the script executes.

     *

     * @return The return value from <code>eval(Reader, ScriptContext)</code>

     * @throws ScriptException if an error occurs in script.

     * @throws NullPointerException if any of the parameters is null.

     */

    public Object eval(Reader reader, Bindings bindings ) throws ScriptException {

        ScriptContext ctxt = getScriptContext(bindings);

        return eval(reader, ctxt);

    }

    /**

     * Same as <code>eval(Reader, Bindings)</code> except that the abstract

     * <code>eval(String, ScriptContext)</code> is used.

     *

     * @param script A <code>String</code> containing the source of the script.

     *

     * @param bindings A <code>Bindings</code> to use as the <code>ENGINE_SCOPE</code>

     * while the script executes.

     *

     * @return The return value from <code>eval(String, ScriptContext)</code>

     * @throws ScriptException if an error occurs in script.

     * @throws NullPointerException if any of the parameters is null.

     */

    public Object eval(String script, Bindings bindings) throws ScriptException {

        ScriptContext ctxt = getScriptContext(bindings);

        return eval(script , ctxt);

    }

    /**

     * <code>eval(Reader)</code> calls the abstract

     * <code>eval(Reader, ScriptContext)</code> passing the value of the <code>context</code>

     * field.

     *

     * @param reader A <code>Reader</code> containing the source of the script.

     * @return The return value from <code>eval(Reader, ScriptContext)</code>

     * @throws ScriptException if an error occurs in script.

     * @throws NullPointerException if any of the parameters is null.

     */

    public Object eval(Reader reader) throws ScriptException {

        return eval(reader, context);

    }

    /**

     * Same as <code>eval(Reader)</code> except that the abstract

     * <code>eval(String, ScriptContext)</code> is used.

     *

     * @param script A <code>String</code> containing the source of the script.

     * @return The return value from <code>eval(String, ScriptContext)</code>

     * @throws ScriptException if an error occurrs in script.

     * @throws NullPointerException if any of the parameters is null.

     */

    public Object eval(String script) throws ScriptException {

        return eval(script, context);

    }

    /**

     * Returns a <code>SimpleScriptContext</code>.  The <code>SimpleScriptContext</code>:

     *<br><br>

     * <ul>

     * <li>Uses the specified <code>Bindings</code> for its <code>ENGINE_SCOPE</code>

     * </li>

     * <li>Uses the <code>Bindings</code> returned by the abstract <code>getGlobalScope</code>

     * method as its <code>GLOBAL_SCOPE</code>

     * </li>

     * <li>Uses the Reader and Writer in the default <code>ScriptContext</code> of this

     * <code>ScriptEngine</code>

     * </li>

     * </ul>

     * <br><br>

     * A <code>SimpleScriptContext</code> returned by this method is used to implement eval methods

     * using the abstract <code>eval(Reader,Bindings)</code> and <code>eval(String,Bindings)</code>

     * versions.

     *

     * @param nn Bindings to use for the <code>ENGINE_SCOPE</code>

     * @return The <code>SimpleScriptContext</code>

     */

    protected ScriptContext getScriptContext(Bindings nn) {

        SimpleScriptContext ctxt = new SimpleScriptContext();

        Bindings gs = getBindings(ScriptContext.GLOBAL_SCOPE);

        if (gs != null) {

            ctxt.setBindings(gs, ScriptContext.GLOBAL_SCOPE);

        }

        if (nn != null) {

            ctxt.setBindings(nn,

                    ScriptContext.ENGINE_SCOPE);

        } else {

            throw new NullPointerException("Engine scope Bindings may not be null.");

        }

        ctxt.setReader(context.getReader());

        ctxt.setWriter(context.getWriter());

        ctxt.setErrorWriter(context.getErrorWriter());

        return ctxt;

    }

}