/*
    * 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.oaipmh.persistence.impl;
  
  import org.opencastproject.db.DBSession;
  import org.opencastproject.mediapackage.MediaPackage;
  import org.opencastproject.mediapackage.MediaPackageElement;
  import org.opencastproject.mediapackage.MediaPackageParser;
  import org.opencastproject.oaipmh.persistence.OaiPmhDatabase;
  import org.opencastproject.oaipmh.persistence.OaiPmhDatabaseException;
  import org.opencastproject.oaipmh.persistence.OaiPmhElementEntity;
  import org.opencastproject.oaipmh.persistence.OaiPmhEntity;
  import org.opencastproject.oaipmh.persistence.OaiPmhSetDefinition;
  import org.opencastproject.oaipmh.persistence.OaiPmhSetDefinitionFilter;
  import org.opencastproject.oaipmh.persistence.Query;
  import org.opencastproject.oaipmh.persistence.SearchResult;
  import org.opencastproject.oaipmh.persistence.SearchResultElementItem;
  import org.opencastproject.oaipmh.persistence.SearchResultItem;
  import org.opencastproject.security.api.SecurityService;
  import org.opencastproject.util.MimeTypes;
  import org.opencastproject.util.NotFoundException;
  import org.opencastproject.util.XmlUtil;
  import org.opencastproject.workspace.api.Workspace;
  
  import org.apache.commons.io.IOUtils;
  import org.apache.commons.lang3.StringUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.InputStream;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Date;
  import java.util.List;
  import java.util.concurrent.locks.ReadWriteLock;
  import java.util.concurrent.locks.ReentrantReadWriteLock;
  import java.util.regex.Pattern;
  
  import javax.persistence.EntityManager;
  import javax.persistence.NoResultException;
  import javax.persistence.TypedQuery;
  import javax.persistence.criteria.CriteriaBuilder;
  import javax.persistence.criteria.CriteriaQuery;
  import javax.persistence.criteria.Predicate;
  import javax.persistence.criteria.Root;
  
  public abstract class AbstractOaiPmhDatabase implements OaiPmhDatabase {
    /** Logging utilities */
    private static final Logger logger = LoggerFactory.getLogger(AbstractOaiPmhDatabase.class);
  
    private ReadWriteLock dbAccessLock = new ReentrantReadWriteLock();
  
    public abstract DBSession getDBSession();
  
    public abstract SecurityService getSecurityService();
  
    public abstract Workspace getWorkspace();
  
    @Override
    public void store(MediaPackage mediaPackage, String repository) throws OaiPmhDatabaseException {
      try {
        dbAccessLock.writeLock().lock();
        storeInternal(mediaPackage, repository);
      } finally {
        dbAccessLock.writeLock().unlock();
      }
    }
  
    private void storeInternal(MediaPackage mediaPackage, String repository) throws OaiPmhDatabaseException {
      try {
        getDBSession().execTx(em -> {
          OaiPmhEntity entity = getOaiPmhEntity(mediaPackage.getIdentifier().toString(), repository, em);
          if (entity == null) {
            // no entry found, create new entity
            entity = new OaiPmhEntity();
            updateEntity(entity, mediaPackage, repository);
            em.persist(entity);
          } else {
            // entry found, update existing
            updateEntity(entity, mediaPackage, repository);
            em.merge(entity);
         }
       });
     } catch (Exception e) {
       logger.error("Could not store mediapackage '{}' to OAI-PMH repository '{}'", mediaPackage.getIdentifier(),
             repository, e);
       throw new OaiPmhDatabaseException(e);
     }
   }
 
   public void updateEntity(OaiPmhEntity entity, MediaPackage mediaPackage, String repository) {
     entity.setOrganization(getSecurityService().getOrganization().getId());
     entity.setDeleted(false);
     entity.setRepositoryId(repository);
 
     entity.setMediaPackageId(mediaPackage.getIdentifier().toString());
     entity.setMediaPackageXML(MediaPackageParser.getAsXml(mediaPackage));
     entity.setSeries(mediaPackage.getSeries());
     entity.removeAllMediaPackageElements();
 
 
     for (MediaPackageElement mpe : mediaPackage.getElements()) {
       if (mpe.getFlavor() == null) {
         logger.debug("A flavor must be set on media package elements for publishing");
         continue;
       }
 
       if (mpe.getElementType() != MediaPackageElement.Type.Catalog
               && mpe.getElementType() != MediaPackageElement.Type.Attachment) {
         logger.debug("Only catalog and attachment types are currently supported");
         continue;
       }
 
       if (mpe.getMimeType() == null || !mpe.getMimeType().eq(MimeTypes.XML)) {
         logger.debug("Only media package elements with mime type XML are supported");
         continue;
       }
       String catalogXml = null;
       try (InputStream in = getWorkspace().read(mpe.getURI())) {
         catalogXml = IOUtils.toString(in, "UTF-8");
       } catch (Throwable e) {
         logger.warn("Unable to load catalog {} from media package {}",
                 mpe.getIdentifier(), mediaPackage.getIdentifier().toString(), e);
         continue;
       }
       if (catalogXml == null || StringUtils.isBlank(catalogXml) || !XmlUtil.parseNs(catalogXml).isRight()) {
         logger.warn("The catalog {} from media package {} isn't a well formatted XML document",
                 mpe.getIdentifier(), mediaPackage.getIdentifier().toString());
         continue;
       }
 
       entity.addMediaPackageElement(new OaiPmhElementEntity(
               mpe.getElementType().name(), mpe.getFlavor().toString(), catalogXml));
     }
   }
 
   @Override
   public void delete(String mediaPackageId, String repository) throws OaiPmhDatabaseException, NotFoundException {
     try {
       dbAccessLock.writeLock().lock();
       deleteInternal(mediaPackageId, repository);
     } finally {
       dbAccessLock.writeLock().unlock();
     }
   }
 
   private void deleteInternal(String mediaPackageId, String repository) throws OaiPmhDatabaseException, NotFoundException {
     try {
       getDBSession().execTxChecked(em -> {
         OaiPmhEntity oaiPmhEntity = getOaiPmhEntity(mediaPackageId, repository, em);
         if (oaiPmhEntity == null)
           throw new NotFoundException("No media package with id " + mediaPackageId + " exists");
 
         oaiPmhEntity.setDeleted(true);
         em.merge(oaiPmhEntity);
       });
     } catch (NotFoundException e) {
       throw e;
     } catch (Exception e) {
       logger.error("Could not delete mediapackage '{}' from OAI-PMH repository '{}'", mediaPackageId, repository, e);
       throw new OaiPmhDatabaseException(e);
     }
   }
 
   @Override
   public SearchResult search(Query query) {
     try {
       final int chunkSize = query.getLimit().getOrElse(-1);
       dbAccessLock.readLock().lock();
       return searchInternal(query, chunkSize);
     } finally {
       dbAccessLock.readLock().unlock();
     }
   }
 
   private SearchResult searchInternal(Query query, int chunkSize) {
     final String requestSetSpec = query.getSetSpec().getOrElseNull();
     Date lastDate = new Date();
     long resultSize;
     long resultOffset;
     long resultLimit;
     SearchResult result = getDBSession().exec(em -> {
       CriteriaBuilder cb = em.getCriteriaBuilder();
       CriteriaQuery<OaiPmhEntity> q = cb.createQuery(OaiPmhEntity.class);
       Root<OaiPmhEntity> c = q.from(OaiPmhEntity.class);
       q.select(c);
 
       // create predicates joined in an "and" expression
       final List<Predicate> predicates = new ArrayList<>();
       predicates.add(cb.equal(c.get("organization"), getSecurityService().getOrganization().getId()));
 
       for (String p : query.getMediaPackageId())
         predicates.add(cb.equal(c.get("mediaPackageId"), p));
       for (String p : query.getRepositoryId())
         predicates.add(cb.equal(c.get("repositoryId"), p));
       for (String p : query.getSeriesId())
         predicates.add(cb.equal(c.get("series"), p));
       for (Boolean p : query.isDeleted())
         predicates.add(cb.equal(c.get("deleted"), p));
       if (query.isSubsequentRequest()) {
         for (Date p : query.getModifiedAfter())
           predicates.add(cb.greaterThan(c.get("modificationDate").as(Date.class), p));
       } else {
         for (Date p : query.getModifiedAfter())
           predicates.add(cb.greaterThanOrEqualTo(c.get("modificationDate").as(Date.class), p));
       }
       for (Date p : query.getModifiedBefore())
         predicates.add(cb.lessThanOrEqualTo(c.get("modificationDate").as(Date.class), p));
 
       q.where(cb.and(predicates.toArray(new Predicate[0])));
       q.orderBy(cb.asc(c.get("modificationDate")));
 
       TypedQuery<OaiPmhEntity> typedQuery = em.createQuery(q);
       if (chunkSize > 0) {
         typedQuery.setMaxResults(chunkSize);
       }
       for (int startPosition : query.getOffset()) {
         logger.warn("I'm pretty sure things break if this is used");
         typedQuery.setFirstResult(startPosition);
       }
 
       return createSearchResult(typedQuery);
     });
 
     if (requestSetSpec == null) {
       return new SearchResultImpl(result.getOffset(), result.getLimit(), result.getItems());
     }
 
     // If we are here, setSpec request is ongoing
     final List<SearchResultItem> filteredItems = new ArrayList<>();
     for (SearchResultItem item : result.getItems()) {
       for (OaiPmhSetDefinition setDef : query.getSetDefinitions()) {
         if (matchSetDef(setDef, item.getElements())) {
           item.addSetSpec(setDef.getSetSpec());
         }
       }
       if (item.getSetSpecs().contains(requestSetSpec)) {
         filteredItems.add(item);
       } else {
         // If the setSpec does not match, we should mark this item as deleted for this specific setSpec
         filteredItems.add(new SearchResultItemImpl(item.getId(), item.getMediaPackageXml(), item.getOrganization(),
             item.getRepository(), item.getModificationDate(), true, item.getMediaPackage(),
             item.getElements(), Arrays.asList(requestSetSpec)));
       }
 
     }
     return new SearchResultImpl(result.getOffset(), result.getLimit(), filteredItems);
   }
 
   /**
    * Returns true if all set definition filters matches.
    *
    * @param setDef set definition to test
    * @param elements media package elements to test
    * @return returns true if all set definition filters matches, otherwise false
    */
   protected boolean matchSetDef(OaiPmhSetDefinition setDef, List<SearchResultElementItem> elements) {
     // all filters should match
     for (OaiPmhSetDefinitionFilter filter : setDef.getFilters()) {
       if (!matchSetDefFilter(filter, elements)) {
         return false;
       }
     }
     return true;
   }
 
   /**
    * Returns true if any filter criterion matches
    *
    * @param filter filter to test
    * @param elements media package elements to test filter criteria on
    * @return true if any filter criteria matches, otherwise false
    */
   private boolean matchSetDefFilter(OaiPmhSetDefinitionFilter filter, List<SearchResultElementItem> elements) {
     // At least one filter criterion should match
     for (String criterion : filter.getCriteria().keySet()) {
       if (StringUtils.equals(OaiPmhSetDefinitionFilter.CRITERION_CONTAINS, criterion)) {
         for (SearchResultElementItem element : elements) {
           if (!StringUtils.equals(filter.getFlavor(), element.getFlavor())) {
             continue;
           }
           for (String criterionValue : filter.getCriteria().get(criterion)) {
             if (StringUtils.contains(element.getXml(), criterionValue)) {
               return true;
             }
           }
         }
       } else if (StringUtils.equals(OaiPmhSetDefinitionFilter.CRITERION_CONTAINSNOT, criterion)) {
         for (SearchResultElementItem element : elements) {
           if (!StringUtils.equals(filter.getFlavor(), element.getFlavor())) {
             continue;
           }
           for (String criterionValue : filter.getCriteria().get(criterion)) {
             if (!StringUtils.contains(element.getXml(), criterionValue)) {
               return true;
             }
           }
         }
       } else if (StringUtils.equals(OaiPmhSetDefinitionFilter.CRITERION_MATCH, criterion)) {
         for (String criterionValue : filter.getCriteria().get(criterion)) {
           Pattern matchPattern = null; // wait with initialization until we found an element to test
           for (SearchResultElementItem element : elements) {
             if (!StringUtils.equals(filter.getFlavor(), element.getFlavor())) {
               continue;
             }
             // initialize regex pattern once and only if we need it (for performance reasons)
             if (matchPattern == null) {
               matchPattern = Pattern.compile(criterionValue);
             }
             if (matchPattern.matcher(element.getXml()).find()) {
               return true;
             }
           }
         }
       } else {
         logger.warn("Unknown OAI-PMH set filter criterion '{}'. Ignore it.", criterion);
       }
     }
     return false;
   }
 
   /**
    * Gets a OAI-PMH entity by it's id, using the current organizational context.
    *
    * @param id
    *          the media package identifier
    * @param repository
    *          the OAI-PMH repository
    * @param em
    *          an open entity manager
    * @return the OAI-PMH entity, or null if not found
    */
   private OaiPmhEntity getOaiPmhEntity(String id, String repository, EntityManager em) {
     final String orgId = getSecurityService().getOrganization().getId();
     javax.persistence.Query q = em.createNamedQuery("OaiPmh.findById").setParameter("mediaPackageId", id)
             .setParameter("repository", repository).setParameter("organization", orgId);
     try {
       return (OaiPmhEntity) q.getSingleResult();
     } catch (NoResultException e) {
       return null;
     }
   }
 
   /**
    * Creates a search result from a given JPA query
    *
    * @param query
    *          the query
    * @return The search result.
    */
   private SearchResult createSearchResult(TypedQuery<OaiPmhEntity> query) {
     // Create and configure the query result
     final long offset = query.getFirstResult();
     final long limit = query.getMaxResults() != Integer.MAX_VALUE ? query.getMaxResults() : 0;
     final List<SearchResultItem> items = new ArrayList<>();
     for (OaiPmhEntity oaipmhEntity : query.getResultList()) {
       try {
         items.add(new SearchResultItemImpl(oaipmhEntity));
       } catch (Exception ex) {
         logger.warn("Unable to parse an OAI-PMH database entry", ex);
       }
     }
     return new SearchResultImpl(offset, limit, items);
   }
 }