package com.atlassian.user.impl.cache;
   
   import com.atlassian.cache.Cache;
   import com.atlassian.cache.CacheFactory;
   import com.atlassian.user.Entity;
   import com.atlassian.user.EntityException;
   import com.atlassian.user.User;
   import com.atlassian.user.UserManager;
   import com.atlassian.user.impl.DefaultUser;
  import com.atlassian.user.repository.RepositoryIdentifier;
  import com.atlassian.user.search.page.Pager;
  import com.atlassian.user.security.password.Credential;
  import org.apache.log4j.Logger;
  
  public class CachingUserManager implements UserManager
  {
      private static final Logger log = (Logger) Logger.getLogger(CachingUserManager.class);
  
      private final UserManager underlyingUserManager;
      private final CacheFactory cacheFactory;
  
      private String userCacheName = null;
      private String userROCacheName = null;
      private String repositoryCacheName = null;
  
      private static final String CACHE_SUFFIX_USERS = "users";
      private static final String CACHE_SUFFIX_USERS_RO = "users_ro";
      private static final String CACHE_SUFFIX_REPOSITORIES = "repository";
  
      protected static User NULL_USER = new DefaultUser()
      {
          public String toString()
          {
              return "NULL USER";
          }
      };
  
      public CachingUserManager(UserManager underlyingUserManager, CacheFactory cacheFactory)
      {
          this.underlyingUserManager = underlyingUserManager;
          this.cacheFactory = cacheFactory;
      }
  
      public Pager<User> getUsers() throws EntityException
      {
          return underlyingUserManager.getUsers();
      }
  
      public Pager<String> getUserNames() throws EntityException
      {
          return underlyingUserManager.getUserNames();
      }
  
      /**
       * Caches users retrieved.<br>
       * Will also cache the fact that a user could not be found (so that we don't incur the expense of another search when have previously determined that a user doesn't exist)
       * Hence this method will also cache null results.
       *
       * @return - an {@link com.atlassian.user.User} if one could be found, otherwise null.
       * @throws com.atlassian.user.EntityException
       *          - representing the exception which prohibited looking for or
       *          retrieving the user.
       */
      public User getUser(String username) throws EntityException
      {
          User cachedUser = (User) getUserCache().get(username);
          if (cachedUser != null)
          {
              return NULL_USER.equals(cachedUser) ? null : cachedUser;
          }
          else
          {
              User user = underlyingUserManager.getUser(username);
              cacheUser(username, user);
              return user;
          }
      }
  
      private void cacheUser(String username, User user)
      {
          getUserCache().put(username, user == null ? NULL_USER : user);
      }
  
      private void cacheRepository(String username, RepositoryIdentifier repository)
      {
          getRepositoryCache().put(username, repository);
      }
  
      private void cacheUserROFlag(User user, boolean ro)
      {
          getUserROFlagCache().put(user.getName(), ro);
      }
  
      private Cache getUserCache()
      {
          synchronized(this)
          {
              if (userCacheName == null)
                  userCacheName = getCacheKey(CACHE_SUFFIX_USERS);
         }
         return cacheFactory.getCache(userCacheName);
     }
 
     private Cache getUserROFlagCache()
     {
         synchronized(this)
         {
             if (userROCacheName == null)
                 userROCacheName = getCacheKey(CACHE_SUFFIX_USERS_RO);
         }
         return cacheFactory.getCache(userROCacheName);
     }
 
     private Cache getRepositoryCache()
     {
         synchronized(this)
         {
             if (repositoryCacheName == null)
                 repositoryCacheName = getCacheKey(CACHE_SUFFIX_REPOSITORIES);
         }
         return cacheFactory.getCache(repositoryCacheName);
     }
 
     public User createUser(String username) throws EntityException
     {
         User user = underlyingUserManager.createUser(username);
 
         if (user != null)
             cacheUser(user.getName(), user);
 
         return user;
     }
 
     public User createUser(User userTemplate, Credential credential) throws EntityException
     {
         User user = underlyingUserManager.createUser(userTemplate, credential);
 
         if (user != null)
             cacheUser(user.getName(), user);
 
         return user;
     }
 
     /**
      * Encrypts the plain password, sets it on the user, and saves the user.
      */
     public void alterPassword(User user, String plainTextPass) throws EntityException
     {
         underlyingUserManager.alterPassword(user, plainTextPass);
         if (user != null)
             cacheUser(user.getName(), underlyingUserManager.getUser(user.getName()));
     }
 
     public void saveUser(User user) throws EntityException
     {
         underlyingUserManager.saveUser(user);
 
         if (user != null)
             cacheUser(user.getName(), user);
     }
 
     /**
      * Removes the specified group, if it is present.
      */
     public void removeUser(User user) throws EntityException
     {
         if (log.isDebugEnabled())
             log.debug("removing user: " + user.getName());
         underlyingUserManager.removeUser(user);
         if (log.isDebugEnabled())
             log.debug("user " + user.getName() + " removed from underlying user manager " + underlyingUserManager.getIdentifier().getName());
 
         try
         {
             if (log.isDebugEnabled())
                 log.debug("removing user from cache: " + user.getName());
             removeUserFromCache(user);
             if (log.isDebugEnabled())
             {
                 log.debug("removed user from cache: " + user.getName());
                 // Lets be paranoid
                 // TODO delete it
                 if (getUserCache().get(user.getName()) != null)
                 {
                     log.error("WTF???");    
                 }
             }
         }
         catch (Exception e)
         {
             throw new EntityException("User removed in underlying repository but could not remove from cache");
         }
     }
 
     private void removeUserFromCache(User user)
     {
         if (user != null)
             getUserCache().remove(user.getName());
     }
 
     /**
      * @return true indicates that information on the user object cannot be altered in the storage system
      *         (see {@link com.atlassian.user.repository.RepositoryIdentifier}),
      *         false indicates that the storage system will save changes or that this {@link com.atlassian.user.UserManager} does not
      *         know about the {@link com.atlassian.user.User}.
      *
      */
     public boolean isReadOnly(User user) throws EntityException
     {
         Boolean cachedROFlag = (Boolean) getUserROFlagCache().get(user.getName());
 
         if (cachedROFlag == null)
         {
             boolean ro = underlyingUserManager.isReadOnly(user);
             cacheUserROFlag(user, ro);
             return ro;
         }
         else
         {
             return cachedROFlag;
         }
     }
 
     public RepositoryIdentifier getIdentifier()
     {
         return underlyingUserManager.getIdentifier();
     }
 
     /**
      * @return the {@link com.atlassian.user.repository.RepositoryIdentifier} in which the entity is stored, otherwise null.
      */
     public RepositoryIdentifier getRepository(Entity entity) throws EntityException
     {
         RepositoryIdentifier cachedRepository = (RepositoryIdentifier) getRepositoryCache().get(entity.getName());
         if (cachedRepository != null)
             return cachedRepository;
 
         RepositoryIdentifier repository = underlyingUserManager.getRepository(entity);
         cacheRepository(entity.getName(), repository);
         return repository;
     }
 
     /**
      * Used to detemine whether an entity can be created (eg, can call {@link com.atlassian.user.UserManager#createUser(String)} or
      * {@link com.atlassian.user.GroupManager#createGroup(String)}
      *
      * @return true to indicate that {@link com.atlassian.user.Entity} objects can be created by this manager, or false to indicate
      *         not.
      */
     public boolean isCreative()
     {
         return underlyingUserManager.isCreative();
     }
 
     /**
      * Generates a unique cache key. This cache key should not be shared by other instances of CachingUserManager that delegate to different underlying user managers.
      * @return cache key
      */
     private String getCacheKey(String cacheName)
     {
         String className = underlyingUserManager.getClass().getName();
         String repositoryKey = underlyingUserManager.getIdentifier().getKey(); // use the repository key to compose the cache key, so we can have a cache per (repository + userManager) combination.
         return className + "." + repositoryKey + "." + cacheName;
     }
 
 }