/**
    * This file Copyright (c) 2015 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.config.registry;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * A builder that allows to construct a {@link info.magnolia.config.registry.DefinitionProvider}s progressively,
   * without nesting try/catch blocks.
   *
   * @see #newBuilder()
   *
   * @param <T> the type the built provider will provide
   */
  public class DefinitionProviderBuilder<T> {
      public static <T> DefinitionProviderBuilder<T> newBuilder() {
          return new DefinitionProviderBuilder<>();
      }
  
      private static final List<String> NO_ERRORS = Collections.emptyList();
      private DefinitionMetadataBuilder metadata;
      private DefinitionRawView rawView;
      private T definition;
      private List<String> errorMessages = null;
  
      private DefinitionProviderBuilder() {
      }
  
      public DefinitionProviderBuilder<T> metadata(DefinitionMetadataBuilder metadata) {
          this.metadata = metadata;
          return this;
      }
  
      public DefinitionProviderBuilder<T> rawView(DefinitionRawView rawView) {
          this.rawView = rawView;
          return this;
      }
  
      public DefinitionProviderBuilder<T> definition(T definition) {
          this.definition = definition;
          return this;
      }
  
      public DefinitionProviderBuilder<T> addErrorMessage(String errorMessage) {
          // Let's be lazy here ...
          if (this.errorMessages == null) {
              this.errorMessages = new ArrayList<>();
          }
          this.errorMessages.add(errorMessage);
          return this;
      }
  
      public DefinitionProvider<T> build() {
          return new DefinitionProviderImpl<>(
                  this.metadata.build(),
                  this.rawView,
                  this.definition,
                  this.errorMessages != null ? this.errorMessages : NO_ERRORS
          );
      }
  
      /**
       * Implementation of DefinitionProviderBuilder.
       */
      static class DefinitionProviderImpl<T> implements DefinitionProvider<T> {
          private final DefinitionMetadata metadata;
         private final DefinitionRawView rawView;
         private final T definition;
         private final List<String> errorMessages;
         private final boolean valid;
 
         protected DefinitionProviderImpl(DefinitionMetadata metadata, DefinitionRawView rawView, T definition, List<String> errorMessages) {
             this.metadata = metadata;
             this.rawView = rawView;
             this.definition = definition;
             this.errorMessages = errorMessages;
 
             this.valid = (metadata != null && rawView != null && definition != null && errorMessages.isEmpty());
         }
 
         @Override
         public DefinitionMetadata getMetadata() {
             return metadata;
         }
 
         @Override
         public DefinitionRawView getRaw() {
             return rawView;
         }
 
         @Override
         public T get() {
             if (!isValid()) {
                 throw new Registry.InvalidDefinitionException(metadata.getReferenceId());
             }
             return definition;
         }
 
         @Override
         public boolean isValid() {
             return valid;
         }
 
         @Override
         public List<String> getErrorMessages() {
             return errorMessages;
         }
 
     }
 }