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Library that provides facilities to allow project information to be manipulated in Java and .Net. Supports a range of data formats: Microsoft Project Exchange (MPX), Microsoft Project (MPP,MPT), Microsoft Project Data Interchange (MSPDI XML), Microsoft Project Database (MPD), Planner (XML), Primavera (PM XML, XER, and database), Asta Powerproject (PP, MDB), Asta Easyplan (PP), Phoenix Project Manager (PPX), FastTrack Schedule (FTS), and the Standard Data Exchange Format (SDEF).

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/*
 * file:       AbstractFieldContainer.java
 * author:     Jon Iles
 * copyright:  (c) Timephased Limited 2023
 * date:       2023-02-07
 */

/*
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * This library 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 Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */

package net.sf.mpxj;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;

import net.sf.mpxj.listener.FieldListener;

/**
 * Implementation of common functionality for the FieldContainer interface.
 *
 * @param  container type
 */
public abstract class AbstractFieldContainer extends ProjectEntity implements FieldContainer
{
   /**
    * Constructor.
    *
    * @param file Parent file
    */
   protected AbstractFieldContainer(ProjectFile file)
   {
      super(file);
   }

   /**
    * Invalidate the cache as a result of a field being updated.
    *
    * @param field updated field
    * @param oldValue old value of the updated field
    * @param newValue new value of the updated field
    */
   abstract void invalidateCache(FieldType field, Object oldValue, Object newValue);

   /**
    * Determine if the supplied field is always calculated.
    *
    * @param field field to check
    * @return true if this field is always calculated
    */
   abstract boolean getAlwaysCalculatedField(FieldType field);

   /**
    * Retrieve the method used to calculate the value of the supplied field.
    *
    * @param field target field
    * @return calculation function, or null if the field is not calculated
    */
   abstract Function getCalculationMethod(FieldType field);

   /**
    * Disable events firing when fields are updated.
    */
   public void disableEvents()
   {
      m_eventsEnabled = false;
   }

   /**
    * Enable events firing when fields are updated. This is the default state.
    */
   public void enableEvents()
   {
      m_eventsEnabled = true;
   }

   @Override public void set(FieldType field, Object value)
   {
      if (field != null)
      {
         Object oldValue = value == null ? m_fields.remove(field) : m_fields.put(field, value);
         if (m_eventsEnabled)
         {
            invalidateCache(field, oldValue, value);
            fireFieldChangeEvent(field, oldValue, value);
         }
      }
   }

   @SuppressWarnings("unchecked") @Override public Object get(FieldType field)
   {
      if (field == null)
      {
         return null;
      }

      boolean alwaysCalculatedField = getAlwaysCalculatedField(field);
      Object result = alwaysCalculatedField ? null : m_fields.get(field);
      if (result == null)
      {
         Function f = getCalculationMethod(field);
         if (f != null)
         {
            result = f.apply((T) this);
            if (result != null && !alwaysCalculatedField)
            {
               set(field, result);
            }
         }
      }

      return result;
   }

   @Override public Object getCachedValue(FieldType field)
   {
      return m_fields.get(field);
   }

   @Override public void addFieldListener(FieldListener listener)
   {
      if (m_listeners == null)
      {
         m_listeners = new ArrayList<>();
      }
      m_listeners.add(listener);
   }

   @Override public void removeFieldListener(FieldListener listener)
   {
      if (m_listeners != null)
      {
         m_listeners.remove(listener);
      }
   }

   /**
    * Send a change event to any external listeners.
    *
    * @param field field changed
    * @param oldValue old field value
    * @param newValue new field value
    */
   private void fireFieldChangeEvent(FieldType field, Object oldValue, Object newValue)
   {
      if (m_listeners != null)
      {
         m_listeners.forEach(l -> l.fieldChange(this, field, oldValue, newValue));
      }
   }

   private boolean m_eventsEnabled = true;
   private final Map m_fields = new HashMap<>();
   private List m_listeners;
}