/**
    * Copyright 2005-2011 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.kim.service.impl;
  
  import org.apache.commons.lang.StringUtils;
  import org.apache.log4j.Level;
  import org.apache.log4j.Logger;
  import org.kuali.rice.core.api.config.property.ConfigurationService;
  import org.kuali.rice.kim.api.KimConstants;
  import org.kuali.rice.kim.impl.identity.IdentityArchiveService;
  import org.kuali.rice.kim.api.identity.entity.EntityDefault;
  import org.kuali.rice.kim.api.identity.principal.Principal;
  import org.kuali.rice.kim.impl.identity.EntityDefaultInfoCacheBo;
  import org.kuali.rice.krad.service.BusinessObjectService;
  import org.kuali.rice.krad.service.KRADServiceLocatorInternal;
  import org.kuali.rice.ksb.service.KSBServiceLocator;
  import org.springframework.beans.factory.DisposableBean;
  import org.springframework.beans.factory.InitializingBean;
  import org.springframework.transaction.PlatformTransactionManager;
  import org.springframework.transaction.TransactionStatus;
  import org.springframework.transaction.support.TransactionCallback;
  import org.springframework.transaction.support.TransactionTemplate;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ConcurrentLinkedQueue;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * This is the default implementation for the IdentityArchiveService.
   * @see IdentityArchiveService
   * @author Kuali Rice Team (rice.collab@kuali.org)
   *
   */
  public class IdentityArchiveServiceImpl implements IdentityArchiveService, InitializingBean, DisposableBean {
  	private static final Logger LOG = Logger.getLogger( IdentityArchiveServiceImpl.class );
  
  	private BusinessObjectService businessObjectService;
  	private ConfigurationService kualiConfigurationService;
  
  	private static final String EXEC_INTERVAL_SECS = "kim.identityArchiveServiceImpl.executionIntervalSeconds";
  	private static final String MAX_WRITE_QUEUE_SIZE = "kim.identityArchiveServiceImpl.maxWriteQueueSize";
  	private static final int EXECUTION_INTERVAL_SECONDS_DEFAULT = 600; // by default, flush the write queue this often
  	private static final int MAX_WRITE_QUEUE_SIZE_DEFAULT = 300; // cache this many KEDI's before forcing write
  
  	private final WriteQueue writeQueue = new WriteQueue();
  	private final EntityArchiveWriter writer = new EntityArchiveWriter();
  
  	// all this ceremony just decorates the writer so it logs a message first, and converts the Callable to Runnable
  	private final Runnable maxQueueSizeExceededWriter =
  		new CallableAdapter(new PreLogCallableWrapper<Boolean>(writer, Level.DEBUG, "max size exceeded, flushing write queue"));
  
  	// ditto
  	private final Runnable scheduledWriter =
  		new CallableAdapter(new PreLogCallableWrapper<Boolean>(writer, Level.DEBUG, "scheduled write out, flushing write queue"));
  
  	// ditto
  	private final Runnable shutdownWriter =
  		new CallableAdapter(new PreLogCallableWrapper<Boolean>(writer, Level.DEBUG, "rice is shutting down, flushing write queue"));
  	
  	private int getExecutionIntervalSeconds() {
  		final String prop = kualiConfigurationService.getPropertyValueAsString(EXEC_INTERVAL_SECS);
  		try {
  			return Integer.valueOf(prop).intValue();
  		} catch (NumberFormatException e) {
  			return EXECUTION_INTERVAL_SECONDS_DEFAULT;
  		}
  	}
  	
  	private int getMaxWriteQueueSize() {
  		final String prop = kualiConfigurationService.getPropertyValueAsString(MAX_WRITE_QUEUE_SIZE);
  		try {
  			return Integer.valueOf(prop).intValue();
  		} catch (NumberFormatException e) {
  			return MAX_WRITE_QUEUE_SIZE_DEFAULT;
 		}
 	}
 
 	@Override
 	public EntityDefault getEntityDefaultFromArchive( String entityId ) {
     	if (StringUtils.isBlank(entityId)) {
             throw new IllegalArgumentException("entityId is blank");
         }
 
         Map<String,String> criteria = new HashMap<String, String>(1);
     	criteria.put(KimConstants.PrimaryKeyConstants.SUB_ENTITY_ID, entityId);
     	EntityDefaultInfoCacheBo cachedValue = businessObjectService.findByPrimaryKey(EntityDefaultInfoCacheBo.class, criteria);
     	return (cachedValue == null) ? null : cachedValue.convertCacheToEntityDefaultInfo();
     }
 
     @Override
 	public EntityDefault getEntityDefaultFromArchiveByPrincipalId(String principalId) {
     	if (StringUtils.isBlank(principalId)) {
             throw new IllegalArgumentException("principalId is blank");
         }
 
         Map<String,String> criteria = new HashMap<String, String>(1);
     	criteria.put("principalId", principalId);
     	EntityDefaultInfoCacheBo cachedValue = businessObjectService.findByPrimaryKey(EntityDefaultInfoCacheBo.class, criteria);
     	return (cachedValue == null) ? null : cachedValue.convertCacheToEntityDefaultInfo();
     }
 
     @Override
 	public EntityDefault getEntityDefaultFromArchiveByPrincipalName(String principalName) {
     	if (StringUtils.isBlank(principalName)) {
             throw new IllegalArgumentException("principalName is blank");
         }
 
         Map<String,String> criteria = new HashMap<String, String>(1);
     	criteria.put("principalName", principalName);
     	Collection<EntityDefaultInfoCacheBo> entities = businessObjectService.findMatching(EntityDefaultInfoCacheBo.class, criteria);
     	return (entities == null || entities.isEmpty()) ? null : entities.iterator().next().convertCacheToEntityDefaultInfo();
     }
 
     @Override
 	public void saveEntityDefaultToArchive(EntityDefault entity) {
     	if (entity == null) {
             throw new IllegalArgumentException("entity is blank");
         }
 
     	// if the max size has been reached, schedule now
     	if (getMaxWriteQueueSize() <= writeQueue.offerAndGetSize(entity) /* <- this enqueues the KEDI */ &&
     			writer.requestSubmit()) {
     		KSBServiceLocator.getThreadPool().execute(maxQueueSizeExceededWriter);
     	}
     }
 
 	public void setBusinessObjectService(BusinessObjectService businessObjectService) {
 		this.businessObjectService = businessObjectService;
 	}
 
 	public void setKualiConfigurationService(
 			ConfigurationService kualiConfigurationService) {
 		this.kualiConfigurationService = kualiConfigurationService;
 	}
     
     /** schedule the writer on the KSB scheduled pool. */
 	@Override
 	public void afterPropertiesSet() throws Exception {
 		LOG.info("scheduling writer...");
 		KSBServiceLocator.getScheduledPool().scheduleAtFixedRate(scheduledWriter,
 				getExecutionIntervalSeconds(), getExecutionIntervalSeconds(), TimeUnit.SECONDS);
 	}
 
 	/** flush the write queue immediately. */
 	@Override
 	public void destroy() throws Exception {
 		KSBServiceLocator.getThreadPool().execute(shutdownWriter);
 	}
 
 	/**
 	 * store the person to the database, but do this an alternate thread to
 	 * prevent transaction issues since this service is non-transactional
 	 *
 	 * @author Kuali Rice Team (rice.collab@kuali.org)
 	 *
 	 */
 	private class EntityArchiveWriter implements Callable {
 
 		// flag used to prevent multiple processes from being submitted at once
 		AtomicBoolean currentlySubmitted = new AtomicBoolean(false);
 
 		private final Comparator<Comparable> nullSafeComparator = new Comparator<Comparable>() {
 			@Override
 			public int compare(Comparable i1, Comparable i2) {
 				if (i1 != null && i2 != null) {
 					return i1.compareTo(i2);
 				} else if (i1 == null) {
 					if (i2 == null) {
 						return 0;
 					} else {
 						return -1;
 					}
 				} else { // if (entityId2 == null) {
 					return 1;
 				}
 			};
 		};
 
 		/**
 		 * Comparator that attempts to impose a total ordering on EntityDefault instances
 		 */
 		private final Comparator<EntityDefault> kediComparator = new Comparator<EntityDefault>() {
 			/**
 			 * compares by entityId value
 			 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
 			 */
 			@Override
 			public int compare(EntityDefault o1, EntityDefault o2) {
 				String entityId1 = (o1 == null) ? null : o1.getEntityId();
 				String entityId2 = (o2 == null) ? null : o2.getEntityId();
 
 				int result = nullSafeComparator.compare(entityId1, entityId2);
 
 				if (result == 0) {
 					result = getPrincipalIdsString(o1).compareTo(getPrincipalIdsString(o2));
 				}
 
 				return result;
 			}
 
 			/**
 			 * This method builds a newline delimited String containing the identity's principal IDs in sorted order
 			 *
 			 * @param entity
 			 * @return
 			 */
 			private String getPrincipalIdsString(EntityDefault entity) {
 				String result = "";
 				if (entity != null) {
 					List<Principal> principals = entity.getPrincipals();
 					if (principals != null) {
 						if (principals.size() == 1) { // one
 							result = principals.get(0).getPrincipalId();
 						} else { // multiple
 							String [] ids = new String [principals.size()];
 							int insertIndex = 0;
 							for (Principal principal : principals) {
 								ids[insertIndex++] = principal.getPrincipalId();
 							}
 							Arrays.sort(ids);
 							result = StringUtils.join(ids, "\n");
 						}
 					}
 				}
 				return result;
 			}
 		};
 
 		public boolean requestSubmit() {
 			return currentlySubmitted.compareAndSet(false, true);
 		}
 
 		/**
 		 * Call that tries to flush the write queue.
 		 * @see Callable#call()
 		 */
 		@Override
 		public Object call() {
 			try {
 				// the strategy is to grab chunks of entities, dedupe & sort them, and insert them in a big
 				// batch to reduce transaction overhead.  Sorting is done so insertion order is guaranteed, which
 				// prevents deadlocks between concurrent writers to the database.
 				PlatformTransactionManager transactionManager = KRADServiceLocatorInternal.getTransactionManager();
 				TransactionTemplate template = new TransactionTemplate(transactionManager);
 				template.execute(new TransactionCallback() {
 					@Override
 					public Object doInTransaction(TransactionStatus status) {
 						EntityDefault entity = null;
 						ArrayList<EntityDefault> entitiesToInsert = new ArrayList<EntityDefault>(getMaxWriteQueueSize());
 						Set<String> deduper = new HashSet<String>(getMaxWriteQueueSize());
 
 						// order is important in this conditional so that elements aren't dequeued and then ignored
 						while (entitiesToInsert.size() < getMaxWriteQueueSize() && null != (entity = writeQueue.poll())) {
 							if (deduper.add(entity.getEntityId())) {
 								entitiesToInsert.add(entity);
 							}
 						}
 
 						Collections.sort(entitiesToInsert, kediComparator);
                         List<EntityDefaultInfoCacheBo> entityCache = new ArrayList<EntityDefaultInfoCacheBo>(entitiesToInsert.size());
                         for (EntityDefault entityToInsert : entitiesToInsert) {
                             entityCache.add(new EntityDefaultInfoCacheBo( entityToInsert ));
                         }
                         businessObjectService.save(entityCache);
 						//for (EntityDefault entityToInsert : entitiesToInsert) {
 						//	businessObjectService.save( new EntityDefaultInfoCacheBo( entityToInsert ) );
 						//}
 						return null;
 					}
 				});
 			} finally { // make sure our running flag is unset, otherwise we'll never run again
 				currentlySubmitted.compareAndSet(true, false);
 			}
 
 			return Boolean.TRUE;
 		}
 	}
 
 	/**
 	 * A class encapsulating a {@link ConcurrentLinkedQueue} and an {@link AtomicInteger} to
 	 * provide fast offer(enqueue)/poll(dequeue) and size checking.  Size may be approximate due to concurrent
 	 * activity, but for our purposes that is fine.
 	 *
 	 * @author Kuali Rice Team (rice.collab@kuali.org)
 	 *
 	 */
 	private static class WriteQueue {
 		AtomicInteger writeQueueSize = new AtomicInteger(0);
 		ConcurrentLinkedQueue<EntityDefault> queue = new ConcurrentLinkedQueue<EntityDefault>();
 
 		public int offerAndGetSize(EntityDefault entity) {
 			queue.add(entity);
 			return writeQueueSize.incrementAndGet();
 		}
 
 		private EntityDefault poll() {
 			EntityDefault result = queue.poll();
 			if (result != null) { writeQueueSize.decrementAndGet(); }
 			return result;
 		}
 	}
 
 	/**
 	 * decorator for a callable to log a message before it is executed
 	 *
 	 * @author Kuali Rice Team (rice.collab@kuali.org)
 	 *
 	 */
 	private static class PreLogCallableWrapper<A> implements Callable<A> {
 		
 		private final Callable inner;
 		private final Level level;
 		private final String message;
 
 		public PreLogCallableWrapper(Callable inner, Level level, String message) {
 			this.inner = inner;
 			this.level = level;
 			this.message = message;
 		}
 
 		/**
 		 * logs the message then calls the inner Callable
 		 * 
 		 * @see java.util.concurrent.Callable#call()
 		 */
 		@Override
 		@SuppressWarnings("unchecked")
 		public A call() throws Exception {
 			LOG.log(level, message);
 			return (A)inner.call();
 		}
 	}
 
 	/**
 	 * Adapts a Callable to be Runnable
 	 *
 	 * @author Kuali Rice Team (rice.collab@kuali.org)
 	 *
 	 */
 	private static class CallableAdapter implements Runnable {
 
 		private final Callable callable;
 
 		public CallableAdapter(Callable callable) {
 			this.callable = callable;
 		}
 
 		@Override
 		public void run() {
 			try {
 				callable.call();
 			} catch (Exception e) {
 				throw new RuntimeException(e);
 			}
 		}
 	}
 }