/*
    * Licensed to The Apereo Foundation under one or more contributor license
    * agreements. See the NOTICE file distributed with this work for additional
    * information regarding copyright ownership.
    *
    *
    * The Apereo Foundation licenses this file to you under the Educational
    * Community 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://opensource.org/licenses/ecl2.txt
   *
   * 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.opencastproject.assetmanager.impl.query;
  
  import org.opencastproject.assetmanager.api.Version;
  import org.opencastproject.assetmanager.api.query.Predicate;
  import org.opencastproject.assetmanager.api.query.VersionField;
  import org.opencastproject.assetmanager.impl.RuntimeTypes;
  import org.opencastproject.assetmanager.impl.persistence.QSnapshotDto;
  
  import com.mysema.query.jpa.JPASubQuery;
  
  public class VersionFieldImpl extends AbstractSnapshotField<Version, Long> implements VersionField {
    private static final QSnapshotDto Q_SNAPSHOT_ALIAS = new QSnapshotDto("s");
  
    public VersionFieldImpl() {
      super(Q_SNAPSHOT.version);
    }
  
    @Override protected Long extract(Version version) {
      return RuntimeTypes.convert(version).value();
    }
  
    @Override public Predicate isLatest() {
      return mkFirstLatestPredicate(true);
    }
  
    @Override public Predicate isFirst() {
      return mkFirstLatestPredicate(false);
    }
  
    /**
     * @param isLatest
     *         true - latest version; false - first version
     */
    private Predicate mkFirstLatestPredicate(boolean isLatest) {
      return mkPredicate(Q_SNAPSHOT.version.eq(
              new JPASubQuery().from(Q_SNAPSHOT_ALIAS)
                      .where(Q_SNAPSHOT_ALIAS.mediaPackageId.eq(Q_SNAPSHOT.mediaPackageId))
                      .unique(isLatest ? Q_SNAPSHOT_ALIAS.version.max() : Q_SNAPSHOT_ALIAS.version.min())));
    }
  }