/*

 * 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);

    }

}