package com.atlassian.user.impl.delegation;
   
   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.DuplicateEntityException;
   import com.atlassian.user.impl.delegation.repository.DelegatingRepository;
   import com.atlassian.user.repository.RepositoryIdentifier;
  import com.atlassian.user.search.page.Pager;
  import com.atlassian.user.search.page.PagerFactory;
  import com.atlassian.user.util.Assert;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  
  /*
   * User manager with a list of other user managers to delegate to.
   * The user managers are tried in the iteration order of the list.
   */
  public class DelegatingUserManager implements UserManager
  {
      private final List<UserManager> userManagers;
  
      public DelegatingUserManager(List<UserManager> userManagers)
      {
          this.userManagers = userManagers;
      }
  
      public Pager<User> getUsers() throws EntityException
      {
          ArrayList<Pager<User>> pagers = new ArrayList<Pager<User>>();
  
          for (UserManager userManager : userManagers)
          {
              pagers.add(userManager.getUsers());
          }
  
          return PagerFactory.getPager(pagers);
      }
  
      public Pager<String> getUserNames() throws EntityException
      {
          ArrayList<Pager<String>> pagers = new ArrayList<Pager<String>>();
  
          for (UserManager userManager : userManagers)
          {
              pagers.add(userManager.getUserNames());
          }
  
          return PagerFactory.getPager(pagers);
      }
  
      /**
       * @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 foundUser = null;
  
          for (UserManager userManager : userManagers)
          {
              foundUser = userManager.getUser(username);
  
              if (foundUser != null)
                  break;
          }
  
          return foundUser;
      }
  
      /**
       * @return the created user
       * @throws com.atlassian.user.EntityException If user cannot be created in any user managers.
       */
      public User createUser(String username) throws EntityException
      {
          User preexistingUser;
          try
          {
              preexistingUser = getUser(username);
          }
          catch (EntityException e)
          {
              throw new EntityException("Couldn't check whether user already exists", e);
          }
  
          if (preexistingUser != null)
              throw new DuplicateEntityException("User [" + username + "] already exists in " + getRepository(preexistingUser).getName());
  
  
          User createdUser = null;
  
          for (UserManager userManager : userManagers)
         {
 
             if (userManager.isCreative())
                 createdUser = userManager.createUser(username);
 
             if (createdUser != null)
                 break;
         }
 
         if (createdUser == null)
             throw new EntityException("Could not create user: " + username + ". " +
                 "Ensure you have a read-write repository configured.");
 
         return createdUser;
     }
 
     /**
      * Encrypts the plain password, sets it on the user, and saves the user.
      */
     public void alterPassword(User user, String plainTextPass) throws EntityException
     {
         UserManager userManager = getMatchingUserManager(user);
 
         if (userManager != null)
             userManager.alterPassword(user, plainTextPass);
         else
             throw new EntityException("Cannot find a userManager responsible for user [" + user.getName() + "]");
     }
 
     public void saveUser(User user) throws EntityException
     {
         UserManager userManager = getMatchingUserManager(user);
 
         if (userManager != null)
             userManager.saveUser(user);
         else
             throw new EntityException("Cannot find a userManager responsible for user [" + user.getName() + "]");
     }
 
     public void removeUser(User user) throws EntityException
     {
         UserManager userManager = getMatchingUserManager(user);
 
         if (userManager != null)
             userManager.removeUser(user);
         else
             throw new IllegalArgumentException("Cannot find a userManager responsible for user [" + 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}.
      * @throws com.atlassian.user.EntityException
      *
      */
     public boolean isReadOnly(User user) throws EntityException
     {
         UserManager userManager = getMatchingUserManager(user);
 
         if (userManager != null)
             return userManager.isReadOnly(user);
         else
             throw new EntityException("Cannot find a userManager responsible for user [" + user.getName() + "]");
     }
 
     /**
      * @return the {@link com.atlassian.user.repository.RepositoryIdentifier} which is managed by this instance.
      */
     public RepositoryIdentifier getIdentifier()
     {
         Iterator iter = userManagers.iterator();
         ArrayList<RepositoryIdentifier> repositories = new ArrayList<RepositoryIdentifier>();
 
         while (iter.hasNext())
         {
             UserManager userManager = (UserManager) iter.next();
             repositories.add(userManager.getIdentifier());
         }
 
         return new DelegatingRepository(repositories);
     }
 
     /**
      * @return the {@link com.atlassian.user.repository.RepositoryIdentifier} in which the entity is stored, otherwise null.
      * @throws com.atlassian.user.EntityException
      *
      */
     public RepositoryIdentifier getRepository(Entity entity) throws EntityException
     {
 
         for (UserManager userManager : userManagers)
         {
             RepositoryIdentifier repo = userManager.getRepository(entity);
 
             if (repo != null)
                 return repo;
         }
 
         return null;
     }
 
     /**
      * 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()
     {
         for (UserManager userManager : userManagers)
         {
             if (userManager.isCreative())
                 return true;
         }
 
         return false;
     }
 
     /**
      * Helper method to locate the first userManager responsible for the given user, in the delegation.
      */
     protected UserManager getMatchingUserManager(User user) throws EntityException
     {
         Assert.notNull(user, "User must not be null");
 
         for (UserManager userManager : userManagers)
         {
             User foundUser = userManager.getUser(user.getName());
 
             if (foundUser != null)
                 return userManager;
         }
 
         return null;
     }
 
     /**
      * @return an unmodifiable list of {@link UserManager}s which this manager delegates to,
      * in the order of delegation.
      */
     public List getUserManagers()
     {
         return Collections.unmodifiableList(userManagers);
     }
 }