/*

  * Copyright 2002-2009 the original author or authors.

  *

  * Licensed under the Apache License, Version 2.0 (the "License");

  * you may not use this file except in compliance with the License.

  * You may obtain a copy of the License at

  *

  *      http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  */

 package net.sf.json.util;

 import net.sf.json.JSONArray;

 import net.sf.json.JSONException;

 import net.sf.json.JSONObject;

 /**

  * Base class for cycle detection in a hierarchy.<br>

  * The JSON spec forbides cycles in a hierarchy and most parsers will raise and

  * error when a cycle is detected. This class defines a contract for handling

  * those cycles and two base implementations:

  * <ul>

  * <li>STRICT - will throw a JSONException if a cycle is found.</li>

  * <li>LENIENT - will return an empty array or null object if a cycle is found.</li>

  * </ul>

  *

  * @author Andres Almiray <aalmiray@users.sourceforge.net>

  */

 public abstract class CycleDetectionStrategy {

    public static final JSONArray IGNORE_PROPERTY_ARR = new JSONArray();

    public static final JSONObject IGNORE_PROPERTY_OBJ = new JSONObject();

    /** Returns empty array and null object */

    public static final CycleDetectionStrategy LENIENT = new LenientCycleDetectionStrategy();

    /**

     * Returns a special object (IGNORE_PROPERTY_OBJ) that indicates the entire

     * property should be ignored

     */

    public static final CycleDetectionStrategy NOPROP = new LenientNoRefCycleDetectionStrategy();

    /** Throws a JSONException */

    public static final CycleDetectionStrategy STRICT = new StrictCycleDetectionStrategy();

    /**

     * Handle a repeated reference<br>

     * Must return a valid JSONArray or null.

     *

     * @param reference the repeated reference.

     */

    public abstract JSONArray handleRepeatedReferenceAsArray( Object reference );

    /**

     * Handle a repeated reference<br>

     * Must return a valid JSONObject or null.

     *

     * @param reference the repeated reference.

     */

    public abstract JSONObject handleRepeatedReferenceAsObject( Object reference );

    private static final class LenientCycleDetectionStrategy extends CycleDetectionStrategy {

       public JSONArray handleRepeatedReferenceAsArray( Object reference ) {

          return new JSONArray();

       }

       public JSONObject handleRepeatedReferenceAsObject( Object reference ) {

          return new JSONObject( true );

       }

    }

    /**

     * A cycle detection strategy that prevents any mention of the possible

     * conflict from appearing.

     *

     * @author small

     */

    private static final class LenientNoRefCycleDetectionStrategy extends CycleDetectionStrategy {

       public JSONArray handleRepeatedReferenceAsArray( Object reference ) {

          return IGNORE_PROPERTY_ARR;

       }

       public JSONObject handleRepeatedReferenceAsObject( Object reference ) {

          return IGNORE_PROPERTY_OBJ;

       }

    }

    private static final class StrictCycleDetectionStrategy extends CycleDetectionStrategy {

       public JSONArray handleRepeatedReferenceAsArray( Object reference ) {

          throw new JSONException( "There is a cycle in the hierarchy!" );

       }

       public JSONObject handleRepeatedReferenceAsObject( Object reference ) {

          throw new JSONException( "There is a cycle in the hierarchy!" );

       }

    }

 }