/*
 * @(#)SimpleScriptContext.java	1.6 06/06/19 20:55:48
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTAIL. Use is subject to license terms.
 */

package javax.script;

import java.util.*;
import java.io.*;

/**
 * Simple implementation of ScriptContext.
 *
 * @author Mike Grogan
 * @version 1.0
 * @since 1.6
 */
public class SimpleScriptContext  implements ScriptContext {
    
    /**
     * This is the writer to be used to output from scripts.
     * By default, a <code>PrintWriter</code> based on <code>System.out</code>
     * is used. Accessor methods getWriter, setWriter are used to manage
     * this field.
     * @see java.lang.System#out
     * @see java.io.PrintWriter
     */
    protected Writer writer;
    
    /**
     * This is the writer to be used to output errors from scripts.
     * By default, a <code>PrintWriter</code> based on <code>System.err</code> is
     * used. Accessor methods getErrorWriter, setErrorWriter are used to manage
     * this field.
     * @see java.lang.System#err
     * @see java.io.PrintWriter
     */
    protected Writer errorWriter;
    
    /**
     * This is the reader to be used for input from scripts.
     * By default, a <code>InputStreamReader</code> based on <code>System.in</code>
     * is used and default charset is used by this reader. Accessor methods 
     * getReader, setReader are used to manage this field.
     * @see java.lang.System#in
     * @see java.io.InputStreamReader
     */
    protected Reader reader;
    
    
    /**
     * This is the engine scope bindings.
     * By default, a <code>SimpleBindings</code> is used. Accessor
     * methods setBindings, getBindings are used to manage this field.
     * @see SimpleBindings
     */
    protected Bindings engineScope;
    
    /**
     * This is the global scope bindings.
     * By default, a null value (which means no global scope) is used. Accessor
     * methods setBindings, getBindings are used to manage this field.
     */
    protected Bindings globalScope;
    
    
    public SimpleScriptContext() {       
        engineScope = new SimpleBindings();
        globalScope = null;
        reader = new InputStreamReader(System.in);
        writer = new PrintWriter(System.out , true);
        errorWriter = new PrintWriter(System.err, true);        
    }
    
    /**
     * Sets a <code>Bindings</code> of attributes for the given scope.  If the value
     * of scope is <code>ENGINE_SCOPE</code> the given <code>Bindings</code> replaces the
     * <code>engineScope</code> field.  If the value
     * of scope is <code>GLOBAL_SCOPE</code> the given <code>Bindings</code> replaces the
     * <code>globalScope</code> field.
     *
     * @param bindings The <code>Bindings</code> of attributes to set.
     * @param scope The value of the scope in which the attributes are set.
     *
     * @throws IllegalArgumentException if scope is invalid.
     * @throws NullPointerException if the value of scope is <code>ENGINE_SCOPE</code> and
     * the specified <code>Bindings</code> is null.
     */
    public void setBindings(Bindings bindings, int scope) {
        
        switch (scope) {
            
            case ENGINE_SCOPE:
                if (bindings == null) {
                    throw new NullPointerException("Engine scope cannot be null.");
                }
                engineScope = bindings;
                break;