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   *   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
   *
   *    https://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.cayenne.util;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  import org.apache.cayenne.CayenneRuntimeException;
  import org.apache.cayenne.QueryResult;
  import org.apache.cayenne.QueryResultItem;
  
  /**
   * @since 4.0
   */
  public class QueryResultBuilder {
  
      protected List<QueryResultItem> queryResult;
  
      public static QueryResultBuilder builder() {
          return new QueryResultBuilder(3);
      }
  
      public static QueryResultBuilder builder(int expectedSize) {
          return new QueryResultBuilder(expectedSize);
      }
  
      public static QueryResult empty() {
          return new GenericQueryResult(Collections.<QueryResultItem>emptyList());
      }
  
      public static QueryResult singleSelect(List<?> selectResult) {
          return new GenericQueryResult(Collections.<QueryResultItem>singletonList(new SelectResult<>(selectResult)));
      }
  
      public static QueryResult singleObjectSelect(Object selectObject) {
          List<Object> result = Collections.singletonList(selectObject);
          return new GenericQueryResult(Collections.<QueryResultItem>singletonList(new SelectResult<>(result)));
      }
  
      QueryResultBuilder(int expectedSize) {
          this.queryResult = new ArrayList<>(expectedSize);
      }
  
      public QueryResultBuilder addSelectResult(List<?> result) {
          queryResult.add(new SelectResult<>(result));
          return this;
      }
  
      public QueryResultBuilder addBatchUpdateResult(int[] result) {
          queryResult.add(new BatchUpdateResult(result));
          return this;
      }
  
      public QueryResult build() {
          return new GenericQueryResult(queryResult);
      }
  
      private static class SelectResult<T> implements QueryResultItem<T> {
  
          private List<T> result;
  
          SelectResult(List<T> result) {
              this.result = result;
          }
  
          @Override
          public boolean isSelectResult() {
              return true;
          }
  
          @Override
          public boolean isBatchUpdate() {
              return false;
          }
  
          @Override
          public List<T> getSelectResult() {
              return result;
          }
  
          @Override
          public int getUpdateCount() {
              throw new CayenneRuntimeException("Can't access update result. This result is a select");
          }
  
          @Override
          public int[] getBatchUpdateCounts() {
              throw new CayenneRuntimeException("Can't access update result. This result is a select");
          }
      }
  
      private static class BatchUpdateResult implements QueryResultItem {
  
          private int[] result;
  
          BatchUpdateResult(int[] result) {
              this.result = result;
          }
  
          @Override
          public boolean isSelectResult() {
              return false;
          }
  
          @Override
          public boolean isBatchUpdate() {
              return result.length > 1;
          }
  
          @Override
          public List<?> getSelectResult() {
              throw new CayenneRuntimeException("Can't access select result. This result is an update");
          }
  
          @Override
          public int getUpdateCount() {
              if (result.length == 0) {
                  throw new CayenneRuntimeException("No update results");
              }
  
              if (result.length == 1) {
                  return result[0];
              }
  
              throw new CayenneRuntimeException("This result is a batch update");
          }
  
          @Override
          public int[] getBatchUpdateCounts() {
              return result;
          }
      }
  }
  