/**
    * Copyright 2005-2014 The Kuali Foundation
    *
    * Licensed 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://www.opensource.org/licenses/ecl2.php
    *
   * 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.kuali.rice.krad.data.jpa.eclipselink;
  
  import org.apache.commons.lang.StringUtils;
  import org.eclipse.persistence.config.SessionCustomizer;
  import org.eclipse.persistence.descriptors.ClassDescriptor;
  import org.eclipse.persistence.exceptions.DescriptorException;
  import org.eclipse.persistence.internal.databaseaccess.Accessor;
  import org.eclipse.persistence.internal.descriptors.OptimisticLockingPolicy;
  import org.eclipse.persistence.internal.sessions.AbstractSession;
  import org.eclipse.persistence.mappings.DatabaseMapping;
  import org.eclipse.persistence.sequencing.Sequence;
  import org.eclipse.persistence.sessions.DatabaseLogin;
  import org.eclipse.persistence.sessions.JNDIConnector;
  import org.eclipse.persistence.sessions.Session;
  import org.kuali.rice.krad.data.jpa.DisableVersioning;
  import org.kuali.rice.krad.data.jpa.Filter;
  import org.kuali.rice.krad.data.jpa.FilterGenerator;
  import org.kuali.rice.krad.data.jpa.FilterGenerators;
  import org.kuali.rice.krad.data.jpa.PortableSequenceGenerator;
  import org.kuali.rice.krad.data.jpa.RemoveMapping;
  import org.kuali.rice.krad.data.jpa.RemoveMappings;
  import org.kuali.rice.krad.data.platform.MaxValueIncrementerFactory;
  import org.springframework.core.annotation.AnnotationUtils;
  import org.springframework.jdbc.support.incrementer.DataFieldMaxValueIncrementer;
  
  import javax.sql.DataSource;
  import java.lang.reflect.Field;
  import java.lang.reflect.Method;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.Map;
  import java.util.Vector;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  /**
   * EclipseLink Session Customizer which understands {@link org.kuali.rice.krad.data.jpa.PortableSequenceGenerator}
   * annotations and automatically registers custom EclipseLink Sequences.
   *
   * <p>
   * Since SessionCustomizers are stateless instances, and because concrete
   * {@link org.eclipse.persistence.sequencing.Sequence} objects must be registered individually with the EclipseLink
   * session, we lazy generate the Sequence objects using annotation inspection and then register them on each new
   * session using this customizer.
   * </p>
   *
   * @author Kuali Rice Team (rice.collab@kuali.org)
   */
  public class KradEclipseLinkCustomizer implements SessionCustomizer {
  
      private static ConcurrentMap<String, List<Sequence>> sequenceMap = new ConcurrentHashMap<String, List<Sequence>>(8,
              0.9f, 1);
  
      /* Keyed by the session name determines if the class descriptors have been modified for the current session. */
      private static ConcurrentMap<String, Boolean> modDescMap = new ConcurrentHashMap<String, Boolean>();
  
      private static ConcurrentMap<String, List<FilterGenerator>> queryCustomizerMap =
              new ConcurrentHashMap<String, List<FilterGenerator>>();
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void customize(Session session) throws Exception {
          String sessionName = session.getName();
  
          // double-checked locking on ConcurrentMap
          List<Sequence> sequences = sequenceMap.get(sessionName);
          if (sequences == null) {
              sequences = sequenceMap.putIfAbsent(sessionName, loadSequences(session));
              if (sequences == null) {
                  sequences = sequenceMap.get(sessionName);
              }
          }
  
          loadQueryCustomizers(session);
  
          DatabaseLogin login = session.getLogin();
          for (Sequence sequence : sequences) {
              login.addSequence(sequence);
          }
  
          handleDescriptorModifications(session);
 
     }
 
     /**
      * Load Query Customizer based on annotations on fields and call customizer to modify descriptor.
      *
      * @param session the EclipseLink session.
      */
     protected void loadQueryCustomizers(Session session) {
         Map<Class, ClassDescriptor> descriptors = session.getDescriptors();
         for (Class<?> entityClass : descriptors.keySet()) {
             for (Field field : entityClass.getDeclaredFields()) {
                 String queryCustEntry = entityClass.getName() + "_" + field.getName();
                 buildQueryCustomizers(entityClass,field,queryCustEntry);
 
                 List<FilterGenerator> queryCustomizers = queryCustomizerMap.get(queryCustEntry);
                 if (queryCustomizers != null && !queryCustomizers.isEmpty()) {
                     Filter.customizeField(queryCustomizers, descriptors.get(entityClass), field.getName());
                 }
             }
         }
 
     }
 
     /**
      * Build and populate map of QueryCustomizer annotations.
      *
      * @param entityClass the type of the entity.
      * @param field the field to process.
      * @param key the id to store the customizer under.
      */
     protected void buildQueryCustomizers(Class<?> entityClass,Field field, String key){
         FilterGenerators customizers = field.getAnnotation(FilterGenerators.class);
         List<FilterGenerator> filterGenerators = new ArrayList<FilterGenerator>();
         if(customizers != null){
             filterGenerators.addAll(Arrays.asList(customizers.value()));
         } else {
             FilterGenerator customizer = field.getAnnotation(FilterGenerator.class);
             if(customizer != null){
                 filterGenerators.add(customizer);
             }
         }
         for(FilterGenerator customizer : filterGenerators){
             List<FilterGenerator> filterCustomizers = queryCustomizerMap.get(key);
             if (filterCustomizers == null) {
                 filterCustomizers =
                         new ArrayList<FilterGenerator>();
                 filterCustomizers.add(customizer);
                 queryCustomizerMap.putIfAbsent(key, filterCustomizers);
             } else {
                 filterCustomizers.add(customizer);
                 queryCustomizerMap.put(key,filterCustomizers);
             }
         }
     }
 
     /**
      * Determines if the class descriptors have been modified for the given session name.
      *
      * @param session the current session.
      */
     protected void handleDescriptorModifications(Session session) {
         String sessionName = session.getName();
 
         // double-checked locking on ConcurrentMap
         Boolean descModified = modDescMap.get(sessionName);
         if (descModified == null) {
             descModified = modDescMap.putIfAbsent(sessionName, Boolean.FALSE);
             if (descModified == null) {
                 descModified = modDescMap.get(sessionName);
             }
         }
 
         if (Boolean.FALSE.equals(descModified)) {
             modDescMap.put(sessionName, Boolean.TRUE);
             handleDisableVersioning(session);
             handleRemoveMapping(session);
         }
     }
 
     /**
      * Checks class descriptors for {@link @DisableVersioning} annotations at the class level and removes the version
      * database mapping for optimistic locking.
      *
      * @param session the current session.
      */
     protected void handleDisableVersioning(Session session) {
         Map<Class, ClassDescriptor> descriptors = session.getDescriptors();
 
         if (descriptors == null || descriptors.isEmpty()) {
             return;
         }
 
         for (ClassDescriptor classDescriptor : descriptors.values()) {
             if (classDescriptor != null && AnnotationUtils.findAnnotation(classDescriptor.getJavaClass(),
                     DisableVersioning.class) != null) {
                 OptimisticLockingPolicy olPolicy = classDescriptor.getOptimisticLockingPolicy();
                 if (olPolicy != null) {
                     classDescriptor.setOptimisticLockingPolicy(null);
                 }
             }
         }
     }
 
     /**
      * Checks class descriptors for {@link @RemoveMapping} and {@link RemoveMappings} annotations at the class level
      * and removes any specified mappings from the ClassDescriptor.
      *
      * @param session the current session.
      */
     protected void handleRemoveMapping(Session session) {
         Map<Class, ClassDescriptor> descriptors = session.getDescriptors();
 
         if (descriptors == null || descriptors.isEmpty()) {
             return;
         }
 
         for (ClassDescriptor classDescriptor : descriptors.values()) {
             List<RemoveMapping> removeMappings = scanForRemoveMappings(classDescriptor);
             if (!removeMappings.isEmpty()) {
                 List<DatabaseMapping> mappingsToRemove = new ArrayList<DatabaseMapping>();
                 for (RemoveMapping removeMapping : removeMappings) {
                     if (StringUtils.isBlank(removeMapping.name())) {
                         throw DescriptorException.attributeNameNotSpecified();
                     }
                     DatabaseMapping databaseMapping = classDescriptor.getMappingForAttributeName(removeMapping.name());
                     if (databaseMapping == null) {
                         throw DescriptorException.mappingForAttributeIsMissing(removeMapping.name(), classDescriptor);
                     }
                     mappingsToRemove.add(databaseMapping);
                 }
                 for (DatabaseMapping mappingToRemove : mappingsToRemove) {
                     classDescriptor.removeMappingForAttributeName(mappingToRemove.getAttributeName());
                 }
             }
         }
     }
 
     /**
      * Gets any {@link RemoveMapping}s out of the given {@link ClassDescriptor}.
      *
      * @param classDescriptor the {@link ClassDescriptor} to scan.
      * @return a list of {@link RemoveMapping}s from the given {@link ClassDescriptor}.
      */
     protected List<RemoveMapping> scanForRemoveMappings(ClassDescriptor classDescriptor) {
         List<RemoveMapping> removeMappings = new ArrayList<RemoveMapping>();
         RemoveMappings removeMappingsAnnotation = AnnotationUtils.findAnnotation(classDescriptor.getJavaClass(),
                 RemoveMappings.class);
         if (removeMappingsAnnotation == null) {
             RemoveMapping removeMappingAnnotation = AnnotationUtils.findAnnotation(classDescriptor.getJavaClass(),
                     RemoveMapping.class);
             if (removeMappingAnnotation != null) {
                 removeMappings.add(removeMappingAnnotation);
             }
         } else {
             for (RemoveMapping removeMapping : removeMappingsAnnotation.value()) {
                 removeMappings.add(removeMapping);
             }
         }
         return removeMappings;
     }
 
     /**
      * Gets any {@link Sequence} from the session.
      *
      * @param session the current session.
      * @return a list of {@link Sequence}s.
      */
     protected List<Sequence> loadSequences(Session session) {
         Map<Class, ClassDescriptor> descriptors = session.getDescriptors();
         List<PortableSequenceGenerator> sequenceGenerators = new ArrayList<PortableSequenceGenerator>();
         for (Class<?> entityClass : descriptors.keySet()) {
             PortableSequenceGenerator sequenceGenerator = AnnotationUtils.findAnnotation(entityClass,
                     PortableSequenceGenerator.class);
             if (sequenceGenerator != null) {
                 sequenceGenerators.add(sequenceGenerator);
             }
             loadFieldSequences(entityClass, sequenceGenerators);
             for (Method method : entityClass.getMethods()) {
                 PortableSequenceGenerator methodSequenceGenerator = method.getAnnotation(
                         PortableSequenceGenerator.class);
                 if (methodSequenceGenerator != null) {
                     sequenceGenerators.add(methodSequenceGenerator);
                 }
             }
         }
         List<Sequence> sequences = new ArrayList<Sequence>();
         for (PortableSequenceGenerator sequenceGenerator : sequenceGenerators) {
             Sequence sequence = new MaxValueIncrementerSequenceWrapper(sequenceGenerator);
             sequences.add(sequence);
         }
         return sequences;
     }
 
     /**
      * Loads any field-based sequences from the given type.
      *
      * @param entityClass the type of the entity.
      * @param sequenceGenerators the current list of sequence generators.
      */
     protected void loadFieldSequences(Class<?> entityClass, List<PortableSequenceGenerator> sequenceGenerators) {
         for (Field field : entityClass.getDeclaredFields()) {
             PortableSequenceGenerator fieldSequenceGenerator = field.getAnnotation(PortableSequenceGenerator.class);
             if (fieldSequenceGenerator != null) {
                 sequenceGenerators.add(fieldSequenceGenerator);
             }
         }
         // next, walk up and check the super class...
         if (entityClass.getSuperclass() != null) {
             loadFieldSequences(entityClass.getSuperclass(), sequenceGenerators);
         }
     }
 
     /**
      * Translates our {@link PortableSequenceGenerator} into an EclipseLink {@link Sequence}.
      */
     private static final class MaxValueIncrementerSequenceWrapper extends Sequence {
 
         private static final long serialVersionUID = 2375805962996574386L;
 
         private final String sequenceName;
 
         /**
          * Creates a sequence wrapper for our {@link PortableSequenceGenerator}.
          *
          * @param sequenceGenerator the {@link PortableSequenceGenerator} to process.
          */
         MaxValueIncrementerSequenceWrapper(PortableSequenceGenerator sequenceGenerator) {
             super(sequenceGenerator.name(), 0);
             // default sequenceName to the name of the sequence generator if the sequence name was not provided
             if (StringUtils.isBlank(sequenceGenerator.sequenceName())) {
                 sequenceName = sequenceGenerator.name();
             } else {
                 sequenceName = sequenceGenerator.sequenceName();
             }
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean shouldAcquireValueAfterInsert() {
             return false;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean shouldUseTransaction() {
             return true;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public boolean shouldUsePreallocation() {
             return false;
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public Object getGeneratedValue(Accessor accessor, AbstractSession writeSession, String seqName) {
             DataSource dataSource = ((JNDIConnector) writeSession.getLogin().getConnector()).getDataSource();
             DataFieldMaxValueIncrementer incrementer = MaxValueIncrementerFactory.getIncrementer(dataSource,
                     sequenceName);
             return Long.valueOf(incrementer.nextLongValue());
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public Vector<?> getGeneratedVector(Accessor accessor, AbstractSession writeSession, String seqName, int size) {
             // we're not in the business of pre-fetching/allocating ids
             throw new UnsupportedOperationException(getClass().getName() + " does pre-generate sequence ids");
         }
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void onConnect() {}
 
         /**
          * {@inheritDoc}
          */
         @Override
         public void onDisconnect() {}
 
         /**
          * {@inheritDoc}
          */
         @Override
         public MaxValueIncrementerSequenceWrapper clone() {
             return (MaxValueIncrementerSequenceWrapper) super.clone();
         }
 
     }
 
 }