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/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * Licensed 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 com.querydsl.jpa;

import com.mysema.commons.lang.CloseableIterator;
import com.mysema.commons.lang.IteratorAdapter;
import com.querydsl.core.types.FactoryExpression;
import jakarta.persistence.PersistenceException;
import jakarta.persistence.Query;
import java.io.Closeable;
import java.io.IOException;
import java.util.Iterator;
import java.util.stream.Stream;
import org.eclipse.persistence.config.HintValues;
import org.eclipse.persistence.config.QueryHints;
import org.eclipse.persistence.jpa.JpaQuery;
import org.eclipse.persistence.queries.Cursor;
import org.jetbrains.annotations.Nullable;

/**
 * {@code EclipseLinkHandler} is the {@link QueryHandler} implementation for EclipseLink
 *
 * @author tiwe
 */
class EclipseLinkHandler implements QueryHandler {

  @Override
  public void addEntity(Query query, String alias, Class type) {
    // do nothing
  }

  @Override
  public void addScalar(Query query, String alias, Class type) {
    // do nothing
  }

  @Override
  public boolean createNativeQueryTyped() {
    return true;
  }

  @SuppressWarnings("unchecked")
  @Override
  public  CloseableIterator iterate(Query query, FactoryExpression projection) {
    var canUseCursor = false;
    try {
      canUseCursor = query.unwrap(Query.class) instanceof JpaQuery;
    } catch (PersistenceException e) {
    } // can't unwrap, just ignore the exception

    Iterator iterator = null;
    Closeable closeable = null;
    if (canUseCursor) {
      query.setHint(QueryHints.CURSOR, HintValues.TRUE);
      final var cursor = (Cursor) query.getSingleResult();
      final var pageSize = cursor.getPageSize();
      closeable =
          new Closeable() {
            @Override
            public void close() throws IOException {
              cursor.close();
            }
          };
      iterator =
          new Iterator<>() {
            private int rowsSinceLastClear = 0;

            @Override
            public boolean hasNext() {
              return cursor.hasNext();
            }

            @Override
            public T next() {
              if (rowsSinceLastClear++ == pageSize) {
                rowsSinceLastClear = 0;
                cursor.clear();
              }
              return (T) cursor.next();
            }
          };
    } else {
      iterator = query.getResultList().iterator();
    }
    if (projection != null) {
      return new TransformingIterator<>(iterator, closeable, projection);
    } else {
      return new IteratorAdapter<>(iterator, closeable);
    }
  }

  @Override
  public  Stream stream(Query query, @Nullable FactoryExpression projection) {
    final var resultStream = query.getResultStream();
    if (projection != null) {
      return resultStream.map(
          element ->
              projection.newInstance(
                  (Object[]) (element.getClass().isArray() ? element : new Object[] {element})));
    }
    return resultStream;
  }

  @Override
  public boolean transform(Query query, FactoryExpression projection) {
    return false;
  }

  @Override
  public boolean wrapEntityProjections() {
    return false;
  }
}