/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.myfaces.orchestra.dynaForm.metadata.impl;
  
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeSet;
  
  import org.apache.myfaces.orchestra.dynaForm.metadata.MetaDataWritable;
  import org.apache.myfaces.orchestra.dynaForm.metadata.MetaField;
  
  /**
   * A convenience implementation of the MetaDataWritable interface.
   * <p>
   * An instance of this type can be created and then passed to a list of one or
   * more Extractor objects, together with a source object to be introspected.
   * The extractor instances deduce information about fields of the source
   * object and then add or update MetaField objects held by the MetaDataImpl.
   * <p>
   * The resulting populated object is then typically cast to the read-only
   * MetaData interface type and passed to objects that make use of the 
   * gathered metadata, such as dynaform "gui builders". 
   */
  public class MetaDataImpl implements MetaDataWritable
  {
      private final Set<String> requestedFields = new TreeSet<String>();
      private final Set<String> requestedFieldParents = new TreeSet<String>();
      
      // Here, a LinkedHashMap is used to ensure that fields can be iterated over
      // in the order in which they were added to the map.
      private final Map<String, MetaFieldImpl> fields = new LinkedHashMap<String, MetaFieldImpl>();
  
      private boolean lockFields = false;
  
      public MetaDataImpl()
      {
      }
  
      /**
       * Indicates whether metadata about this field is wanted.
       * <p>
       * If this object is not "locked", then this always returns true.
       * <p>
       * Even when locked, this returns true if:
       * <ul>
       * <li>The field is already added to this object, or
       * <li>The field has explicitly been "requested", or
       * <li>The name is of form "foo.bar", and "foo.bar.baz" has
       *  been added to the "requested" fields. 
       * </ul>
       *
       * @see #setLockFields(boolean)
       */
      public boolean isWantedField(String name)
      {
          return !lockFields 
              || isParentOfWantedField(name)
              || requestedFields.contains(name)
              || fields.containsKey(name);
      }
  
      /**
       * Is metadata about this field wanted because some child field of this
       * field has explicitly been marked as requested?
       *
       * @return true if the given name is the parent of one of the requestedFields
       * @see #processField(String)
       * @see #setLockFields(boolean)
       */
      public boolean isParentOfWantedField(String name)
      {
          return requestedFieldParents.contains(name);
      }
  
      /**
       * Allow a field to be added to this object even after this MetaData object is
       * "locked" for field addition.
       * <p>
       * This is used when traversing the object graph for linked entities.
       * <p>
      * When a name like "foo.bar.baz" is passed to this method, the requestedFieldsParent
      * list has "foo" and "foo.bar" added to it. 
      */
     public void requestField(String name)
     {
         int currIndex = name.indexOf('.');
         while (currIndex > -1)
         {
             String key = name.substring(0, currIndex);
             if (!requestedFieldParents.contains(key))
             {
                 requestedFieldParents.add(key);
             }
             currIndex = name.indexOf('.', currIndex + 1);
         }
 
         requestedFields.add(name);
     }
 
     public Set<String> getRequestedFields()
     {
         return Collections.unmodifiableSet(requestedFields);
     }
 
     /**
      * Add a new field to the metadata or return one if one already exists for
      * the given name
      */
     public MetaFieldImpl getOrCreateField(String name)
     {
         if (!isWantedField(name))
         {
             throw new SecurityException("Current state do not allow to add the field: " + name);
         }
 
         MetaFieldImpl field = fields.get(name);
         if (field == null)
         {
             field = new MetaFieldImpl(name);
             fields.put(name, field);
         }
         return field;
     }
 
     public int getFieldCount()
     {
         return fields.size();
     }
 
     public Iterator<String> iterFieldNames()
     {
         return fields.keySet().iterator();
     }
 
     public MetaField getField(String name)
     {
         return fields.get(name);
     }
 
     public String[] getFieldNames()
     {
         return fields.keySet().toArray(new String[fields.size()]);
     }
 
     /**
      * if set to true this avoids any field to be newly created, only already existent fields are to be processed
      */
     public boolean setLockFields(boolean lockFields)
     {
         boolean prev = this.lockFields;
         this.lockFields = lockFields;
         return prev;
     }
 }