/*
 * Copyright (c) 2005, 2013, 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.*;
import java.io.*;

/**
 * Simple implementation of ScriptContext.
 *
 * @author Mike Grogan
 * @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;

 /**
 * Create a {@code SimpleScriptContext}.
 */
 public SimpleScriptContext() {
 this(new InputStreamReader(System.in),
 new PrintWriter(System.out , true),
 new PrintWriter(System.err, true));
 engineScope = new SimpleBindings();
 globalScope = null;
 }

 /**
 * Package-private constructor to avoid needless creation of reader and writers.
 * It is the caller's responsability to initialize the engine scope.
 *
 * @param reader the reader
 * @param writer the writer
 * @param errorWriter the error writer
 */
 SimpleScriptContext(Reader reader, Writer writer, Writer errorWriter) {
 this.reader = reader;
 this.writer = writer;
 this.errorWriter = errorWriter;
 }

 /**
 * 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;
 case GLOBAL_SCOPE:
 globalScope = bindings;
 break;
 default:
 throw new IllegalArgumentException("Invalid scope value.");
 }
 }


 /**
 * Retrieves the value of the attribute with the given name in
 * the scope occurring earliest in the search order. The order
 * is determined by the numeric value of the scope parameter (lowest
 * scope values first.)
 *
 * @param name The name of the attribute to retrieve.
 * @return The value of the attribute in the lowest scope for
 * which an attribute with the given name is defined. Returns
 * null if no attribute with the name exists in any scope.
 * @throws NullPointerException if the name is null.
 * @throws IllegalArgumentException if the name is empty.
 */
 public Object getAttribute(String name) {
 checkName(name);
 if (engineScope.containsKey(name)) {
 return getAttribute(name, ENGINE_SCOPE);
 } else if (globalScope != null && globalScope.containsKey(name)) {
 return getAttribute(name, GLOBAL_SCOPE);
 }

 return null;
 }

 /**
 * Gets the value of an attribute in a given scope.
 *
 * @param name The name of the attribute to retrieve.
 * @param scope The scope in which to retrieve the attribute.
 * @return The value of the attribute. Returns <code>null</code> is the name
 * does not exist in the given scope.
 *
 * @throws IllegalArgumentException
 * if the name is empty or if the value of scope is invalid.
 * @throws NullPointerException if the name is null.
 */
 public Object getAttribute(String name, int scope) {
 checkName(name);
 switch (scope) {

 case ENGINE_SCOPE:
 return engineScope.get(name);

 case GLOBAL_SCOPE:
 if (globalScope != null) {
 return globalScope.get(name);
 }
 return null;

 default:
 throw new IllegalArgumentException("Illegal scope value.");
 }
 }

 /**
 * Remove an attribute in a given scope.
 *
 * @param name The name of the attribute to remove
 * @param scope The scope in which to remove the attribute
 *
 * @return The removed value.
 * @throws IllegalArgumentException
 * if the name is empty or if the scope is invalid.
 * @throws NullPointerException if the name is null.
 */
 public Object removeAttribute(String name, int scope) {
 checkName(name);
 switch (scope) {

 case ENGINE_SCOPE:
 if (getBindings(ENGINE_SCOPE) != null) {
 return getBindings(ENGINE_SCOPE).remove(name);
 }
 return null;

 case GLOBAL_SCOPE:
 if (getBindings(GLOBAL_SCOPE) != null) {
 return getBindings(GLOBAL_SCOPE).remove(name);
 }
 return null;

 default:
 throw new IllegalArgumentException("Illegal scope value.");
 }
 }

 /**
 * Sets the value of an attribute in a given scope. If the scope is <code>GLOBAL_SCOPE</code>
 * and no Bindings is set for <code>GLOBAL_SCOPE</code>, then setAttribute call is a no-op.
 *
 * @param name The name of the attribute to set
 * @param value The value of the attribute
 * @param scope The scope in which to set the attribute
 *
 * @throws IllegalArgumentException
 * if the name is empty or if the scope is invalid.
 * @throws NullPointerException if the name is null.
 */
 public void setAttribute(String name, Object value, int scope) {
 checkName(name);
 switch (scope) {

 case ENGINE_SCOPE:
 engineScope.put(name, value);
 return;

 case GLOBAL_SCOPE:
 if (globalScope != null) {
 globalScope.put(name, value);
 }
 return;

 default:
 throw new IllegalArgumentException("Illegal scope value.");
 }
 }

 /** {@inheritDoc} */
 public Writer getWriter() {
 return writer;
 }

 /** {@inheritDoc} */
 public Reader getReader() {
 return reader;
 }

 /** {@inheritDoc} */
 public void setReader(Reader reader) {
 this.reader = reader;
 }

 /** {@inheritDoc} */
 public void setWriter(Writer writer) {
 this.writer = writer;
 }

 /** {@inheritDoc} */
 public Writer getErrorWriter() {
 return errorWriter;
 }

 /** {@inheritDoc} */
 public void setErrorWriter(Writer writer) {
 this.errorWriter = writer;
 }

 /**
 * Get the lowest scope in which an attribute is defined.
 * @param name Name of the attribute
 * .
 * @return The lowest scope. Returns -1 if no attribute with the given
 * name is defined in any scope.
 * @throws NullPointerException if name is null.
 * @throws IllegalArgumentException if name is empty.
 */
 public int getAttributesScope(String name) {
 checkName(name);
 if (engineScope.containsKey(name)) {
 return ENGINE_SCOPE;
 } else if (globalScope != null && globalScope.containsKey(name)) {
 return GLOBAL_SCOPE;
 } else {
 return -1;
 }
 }

 /**
 * Returns the value of the <code>engineScope</code> field if specified scope is
 * <code>ENGINE_SCOPE</code>. Returns the value of the <code>globalScope</code> field if the specified scope is
 * <code>GLOBAL_SCOPE</code>.
 *
 * @param scope The specified scope
 * @return The value of either the <code>engineScope</code> or <code>globalScope</code> field.
 * @throws IllegalArgumentException if the value of scope is invalid.
 */
 public Bindings getBindings(int scope) {
 if (scope == ENGINE_SCOPE) {
 return engineScope;
 } else if (scope == GLOBAL_SCOPE) {
 return globalScope;
 } else {
 throw new IllegalArgumentException("Illegal scope value.");
 }
 }

 /** {@inheritDoc} */
 public List<Integer> getScopes() {
 return scopes;
 }

 private void checkName(String name) {
 Objects.requireNonNull(name);
 if (name.isEmpty()) {
 throw new IllegalArgumentException("name cannot be empty");
 }
 }

 private static List<Integer> scopes;
 static {
 scopes = new ArrayList<Integer>(2);
 scopes.add(ENGINE_SCOPE);
 scopes.add(GLOBAL_SCOPE);
 scopes = Collections.unmodifiableList(scopes);
 }
}