/*

  * Copyright 2007-2009 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.kew.useroptions;

 import java.lang.ref.SoftReference;

 import java.util.Collection;

 import java.util.List;

 import java.util.Map;

 import org.kuali.rice.ksb.api.KsbApiServiceLocator;

 /**

  * This class decorates a UserOptionsService and provides distributed caching for findByOptionId calls, and 

  * intelligently clears cache entries on update/delete type calls.

  * 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  *

  */

 public class UserOptionsServiceCache implements UserOptionsService {

         private UserOptionsService inner;

         private final ClusterSafeMethodCache cache = new ClusterSafeMethodCache(UserOptionsService.class.getSimpleName()); 

         /**

          * clears any entry in the cache for this option id

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#deleteUserOptions(org.kuali.rice.kew.useroptions.UserOptions)

          */

         public void deleteUserOptions(UserOptions userOptions) {

                 if (userOptions != null && userOptions.getWorkflowId() != null) {

                         cache.clearCacheEntry(userOptions.getWorkflowId(), "findByOptionId", userOptions.getOptionId(), userOptions.getWorkflowId());

                 }

                 inner.deleteUserOptions(userOptions);

         }

         /**

          * Checks the cache for results.  On cache miss, delegates the call and caches the result before returning.

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#findByOptionId(java.lang.String, java.lang.String)

          */

         public UserOptions findByOptionId(String optionId, String principalId) {

                 Object result = null;

                 if (optionId != null && principalId != null) {

                         String methodName = "findByOptionId";

                         Object [] arguments = {optionId, principalId};

                         result = cache.getFromCache(principalId, methodName, arguments);

                         if (result == null) {

                                 result = inner.findByOptionId(optionId, principalId);

                                 cache.putInCache(principalId, methodName, (result != null) ? result : cache.NULL_OBJECT, arguments);

                         }

                 } else {

                         // just delegate on bad inputs:

                         result = inner.findByOptionId(optionId, principalId);

                 }

             return (result == cache.NULL_OBJECT) ? null : (UserOptions) result;                

         }

         /**

          * This overridden method delegates the call.

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#findByOptionValue(java.lang.String, java.lang.String)

          */

         public Collection<UserOptions> findByOptionValue(String optionId,

                         String optionValue) {

                 // no caching for this method since it doesn't discriminate by user

                 return inner.findByOptionValue(optionId, optionValue);

         }

         /**

          * This overridden method delegates the call.

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#findByUserQualified(java.lang.String, java.lang.String)

          */

         public List<UserOptions> findByUserQualified(String principalId,

                         String likeString) {

                 // no caching for this method since it could be pulling in saveRefreshUserOption generated UserOptions

                 return inner.findByUserQualified(principalId, likeString);

         }

         /**

          * This overridden method delegates the call.

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#findByWorkflowUser(java.lang.String)

          */

         public Collection<UserOptions> findByWorkflowUser(String principalId) {

                 // no caching for this method since it could be pulling in saveRefreshUserOption generated UserOptions

                 return inner.findByWorkflowUser(principalId);

         }

         /**

          * This overridden method ...

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#refreshActionList(java.lang.String)

          */

         public boolean refreshActionList(String principalId) {

         // ignore the cache for this user option, as these are generated with unique numbers and shouldn't be

             // retrieved more then once, as they are deleted once retrieved

                 return inner.refreshActionList(principalId);

         }

         /**

          * This overridden method ...

          * 

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#save(java.lang.String, java.util.Map)

          */

         public void save(String principalId, Map<String, String> optionsMap) {

                 inner.save(principalId, optionsMap);

                 cache.clearCacheGroup(principalId);

         }

         /**

          * This overridden method ...

          * 

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#save(java.lang.String, java.lang.String, java.lang.String)

          */

         public void save(String principalId, String optionId, String optionValue) {

                 inner.save(principalId, optionId, optionValue);

                 cache.clearCacheGroup(principalId);

         }

         /**

          * This overridden method ...

          * 

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#save(org.kuali.rice.kew.useroptions.UserOptions)

          */

         public void save(UserOptions userOptions) {

                 inner.save(userOptions);

                 cache.clearCacheGroup(userOptions.getWorkflowId());

         }

         /**

          * This overridden method ...

          * 

          * @see org.kuali.rice.kew.useroptions.UserOptionsService#saveRefreshUserOption(java.lang.String)

          */

         public void saveRefreshUserOption(String principalId) {

                 // this shouldn't impact our simple cache since we're only caching single options queries, and this will 

                 // generate a key that hasn't been used previously

                 inner.saveRefreshUserOption(principalId);

         }

         /**

          * @param inner the decorated service

          */

         public void setInnerService(UserOptionsService inner) {

                 this.inner = inner;

         }

         /**

          * a helper class to encapsulate cluster safe cache functionality 

          * 

          * @author Kuali Rice Team (rice.collab@kuali.org)

          *

          */

     private static class ClusterSafeMethodCache {

             public static final Object NULL_OBJECT = new Object(); 

             public final String cachedServiceName;

             /**

                  * This constructs a ClusterSaveMethodCache

                  * 

                  * @param cachedServiceName a name for the service being cached

                  */

                 public ClusterSafeMethodCache(String cachedServiceName) {

                         this.cachedServiceName = cachedServiceName;

                 }

             /**

              * build a cache key based on the user, method name and the parameters

              * 

              * @param methodName

              * @param args

              * @return

              */

             private String getCacheKey(String principalId, String methodName, Object ... args) {

                     StringBuilder sb = new StringBuilder(principalId);

                     sb.append("/");

                     sb.append(cachedServiceName);

                     sb.append(".");

                     sb.append(methodName);

                     sb.append(":");

                     boolean first = true;

                     for (Object arg : args) {

                             if (first) {

                                     first = false;

                             } else {

                                     sb.append(",");

                             }

                             sb.append((arg == null) ? "null" : arg.toString());

                     }

                     return sb.toString();

             }

             /**

              * caches a method result

              * 

              * @param principalId the principal for whom the call is being cached

              * @param methodName the name of the method whose result is being cached

              * @param value 

              * @param keySource the parameters to the method call that is being cached.  These are used to build the cache key, so order is important. 

              */

             @SuppressWarnings("unchecked")

             public void putInCache(String principalId, String methodName, Object value, Object ... keySource) {

                     if (value != null) {

                             KsbApiServiceLocator.getCacheAdministrator().putInCache(getCacheKey(principalId, methodName, keySource), new SoftReference(value), getCacheGroup(principalId));

                     } else {

                             KsbApiServiceLocator.getCacheAdministrator().putInCache(getCacheKey(principalId, methodName, keySource), NULL_OBJECT, getCacheGroup(principalId));

                     }

             }

             /**

              * retrieves a method result from the cache.  If the static final NULL_OBJECT is returned then the cached result

              * was null.

              * 

              * @param principalId the principal for whom the call is being cached

              * @param methodName the name of the method whose result is being cached

              * @param keySource the parameters to the method call that is being cached.  These are used to build the cache key, so order is important. 

              * @return

              */

             @SuppressWarnings("unchecked")

             public Object getFromCache(String principalId, String methodName, Object ... keySource) {

                     Object result = null;

                     Object cacheReturned = KsbApiServiceLocator.getCacheAdministrator().getFromCache(getCacheKey(principalId, methodName, keySource));

                     if (cacheReturned == NULL_OBJECT) {

                             result = cacheReturned;

                     } else {

                             SoftReference reference = (SoftReference)cacheReturned;

                             if (reference != null) {

                                     result = reference.get();

                             }

                     }

                     return result;

             }

             /**

              * This method clears all cached calls for the given principal

              * 

              * @param principalId the principal for whom the cache is being cleared

              */

             public void clearCacheGroup(String principalId) {

                     if (principalId != null) {

                             KsbApiServiceLocator.getCacheAdministrator().flushGroup(getCacheGroup(principalId));

                     }

             }

             /**

              * This method clears a cache entry for a given method call / arguments combination

              * 

              * @param principalId the principal for whom the cache entry is being cleared

              * @param methodName the name of the method whose result is being cached

              * @param keySource the parameters to the method call that is being cached.  These are used to build the cache key, so order is important.

              */

             public void clearCacheEntry(String principalId, String methodName, Object ... keySource) {

                     KsbApiServiceLocator.getCacheAdministrator().flushEntry(getCacheKey(principalId, methodName, keySource));

             }

             /**

              * This method gets the cache group name (an entire cache group can be cleared at once)

              * 

              * @param principalId the principal whose cache group name is being generated

              * @return the cache group name

              */

             private String getCacheGroup(String principalId) {

                     return principalId + "/" + cachedServiceName;

             }

     }

 }