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Nuts'n'Bolts Utilities
There is a newer version: 6.2.0
/*
 * Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 David Berkman
 *
 * This file is part of the SmallMind Code Project.
 *
 * The SmallMind Code Project is free software, you can redistribute
 * it and/or modify it under either, at your discretion...
 *
 * 1) The terms of GNU Affero General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 *
 * ...or...
 *
 * 2) The terms of the Apache License, Version 2.0.
 *
 * The SmallMind Code Project 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 or Apache License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * and the Apache License along with the SmallMind Code Project. If not, see
 *  or .
 *
 * Additional permission under the GNU Affero GPL version 3 section 7
 * ------------------------------------------------------------------
 * If you modify this Program, or any covered work, by linking or
 * combining it with other code, such other code is not for that reason
 * alone subject to any of the requirements of the GNU Affero GPL
 * version 3.
 */
package org.smallmind.nutsnbolts.reflection;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import org.smallmind.nutsnbolts.lang.TypeMismatchException;

public interface Overlay> {

  default void overliad () {

  }

  default O overlay (O[] overlays) {

    return overlay(overlays, null);
  }

  default O overlay (O[] overlays, Field[] exclusions) {

    if ((overlays != null) && (overlays.length > 0)) {
      for (O overlay : overlays) {
        overlay(overlay, exclusions);
      }
    }

    return (O)this;
  }

  default O overlay (O overlay) {

    return overlay(overlay, null);
  }

  default O overlay (O overlay, Field[] exclusions) {

    if (overlay != null) {
      if (!overlay.getClass().isAssignableFrom(this.getClass())) {
        throw new TypeMismatchException("Overlays must be assignable from type(%s)", this.getClass());
      } else {

        boolean excluded;

        for (FieldAccessor fieldAccessor : FieldUtility.getFieldAccessors(this.getClass())) {

          excluded = false;

          if ((exclusions != null) && (exclusions.length > 0)) {
            for (Field exclusion : exclusions) {
              if (!exclusion.getDeclaringClass().isAssignableFrom(this.getClass())) {
                throw new TypeMismatchException("The type(%s) does not contain the excluded field(%s)", this.getClass().getName(), exclusion.getName());
              } else if (exclusion.equals(fieldAccessor.getField())) {
                excluded = true;
                break;
              }
            }
          }

          if (!excluded) {

            Object value;

            try {
              if ((value = fieldAccessor.get(overlay)) != null) {
                if (Overlay.class.isAssignableFrom(fieldAccessor.getType())) {

                  Overlay original;

                  if ((original = (Overlay)fieldAccessor.get(this)) != null) {
                    fieldAccessor.set(this, fieldAccessor.getType().cast(original.overlay((Overlay)value)));
                  } else {
                    fieldAccessor.set(this, value);
                  }
                } else {
                  fieldAccessor.set(this, value);
                }
              }
            } catch (IllegalAccessException | InvocationTargetException exception) {
              throw new OverlayException(exception);
            }
          }
        }
      }
    }

    this.overliad();

    return (O)this;
  }
}