/*
 * @(#)file      AclImpl.java
 * @(#)author    Sun Microsystems, Inc.
 * @(#)version   4.11
 * @(#)date      06/05/03
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 */


package com.sun.jmx.snmp.IPAcl;



import java.security.Principal;
import java.security.acl.Acl; 
import java.security.acl.AclEntry; 
import java.security.acl.NotOwnerException; 

import java.io.Serializable;
import java.util.Vector;
import java.util.Enumeration;


/**
 * Represent an Access Control List (ACL) which is used to guard access to http adaptor.
 * <P>
 * It is a data structure with multiple ACL entries. Each ACL entry, of interface type
 * AclEntry, contains a set of permissions and a set of communities associated with a 
 * particular principal. (A principal represents an entity such as a host or a group of host).
 * Additionally, each ACL entry is specified as being either positive or negative.
 * If positive, the permissions are to be granted to the associated principal.
 * If negative, the permissions are to be denied.
 *
 * @see java.security.acl.Acl
 * @version     4.11     12/19/03
 * @author      Sun Microsystems, Inc
 */

class AclImpl extends OwnerImpl implements Acl, Serializable {
  private Vector entryList = null;
  private String aclName = null;
  
  /**
   * Constructs the ACL with a specified owner
   *
   * @param owner owner of the ACL.
   * @param name  name of this ACL.
   */
  public AclImpl (PrincipalImpl owner, String name) {
	super(owner);
	entryList = new Vector();
	aclName = name;
  }
  
  /**
   * Sets the name of this ACL.
   *
   * @param caller the principal invoking this method. It must be an owner 
   *        of this ACL.
   * @param name the name to be given to this ACL. 
   *
   * @exception NotOwnerException if the caller principal is not an owner 
   *            of this ACL. 
   * @see java.security.Principal
   */
  public void setName(Principal caller, String name)
	throws NotOwnerException {
	  if (!isOwner(caller))
		throw new NotOwnerException();	
	  aclName = name;
  }
  
  /**
   * Returns the name of this ACL. 
   *
   * @return the name of this ACL. 
   */
  public String getName(){
	return aclName;
  }
  
  /**
   * Adds an ACL entry to this ACL. An entry associates a principal (e.g., an individual or a group)
   * with a set of permissions. Each principal can have at most one positive ACL entry
   * (specifying permissions to be granted to the principal) and one negative ACL entry
   * (specifying permissions to be denied). If there is already an ACL entry
   * of the same type (negative or positive) already in the ACL, false is returned. 
   *
   * @param caller the principal invoking this method. It must be an owner 
   *        of this ACL. 
   * @param entry the ACL entry to be added to this ACL. 
   * @return true on success, false if an entry of the same type (positive 
   *       or negative) for the same principal is already present in this ACL. 
   * @exception NotOwnerException if the caller principal is not an owner of 
   *       this ACL. 
   * @see java.security.Principal
   */
  public boolean addEntry(Principal caller, AclEntry entry)
	throws NotOwnerException {
	  if (!isOwner(caller)) 
		throw new NotOwnerException();
	
	  if (entryList.contains(entry))
		return false;
	  /* 
		 for (Enumeration e = entryList.elements();e.hasMoreElements();){
		 AclEntry ent = (AclEntry) e.nextElement();
		 if (ent.getPrincipal().equals(entry.getPrincipal())) 
		 return false;
		 }
		 */
	  
	  entryList.addElement(entry);
	  return true;
  }
  
  /**
   * Removes an ACL entry from this ACL. 
   *
   * @param caller the principal invoking this method. It must be an owner 
   *        of this ACL. 
   * @param entry the ACL entry to be removed from this ACL. 
   * @return true on success, false if the entry is not part of this ACL. 
   * @exception NotOwnerException if the caller principal is not an owner 
   *   of this Acl. 
   * @see java.security.Principal
   * @see java.security.acl.AclEntry
   */
  public boolean removeEntry(Principal caller, AclEntry entry)
	throws NotOwnerException {
	  if (!isOwner(caller))
		throw new NotOwnerException();
	  
	  return (entryList.removeElement(entry));
  }
  
  /**
   * Removes all ACL entries from this ACL.
   *
   * @param caller the principal invoking this method. It must be an owner 
   *        of this ACL. 
   * @exception NotOwnerException if the caller principal is not an owner of 
   *        this Acl. 
   * @see java.security.Principal
   */
  public void removeAll(Principal caller)
	throws NotOwnerException {
	  if (!isOwner(caller))
		throw new NotOwnerException();
	entryList.removeAllElements();
  }
  
  /**
   * Returns an enumeration for the set of allowed permissions for 
   * the specified principal
   * (representing an entity such as an individual or a group).
   * This set of allowed permissions is calculated as follows:
   * <UL>
   * <LI>If there is no entry in this Access Control List for the specified 
   * principal, an empty permission set is returned.</LI>
   * <LI>Otherwise, the principal's group permission sets are determined. 
   * (A principal can belong to one or more groups, where a group is a group 
   * of principals, represented by the Group interface.)</LI>
   * </UL>
   * @param user the principal whose permission set is to be returned. 
   * @return the permission set specifying the permissions the principal 
   *     is allowed. 
   * @see java.security.Principal
   */
  public Enumeration getPermissions(Principal user){
	Vector empty = new Vector();
	for (Enumeration e = entryList.elements();e.hasMoreElements();){
	  AclEntry ent = (AclEntry) e.nextElement();
	  if (ent.getPrincipal().equals(user))
		return ent.permissions();
	}
	return empty.elements();
  }
  
  /**
   * Returns an enumeration of the entries in this ACL. Each element in the
   * enumeration is of type AclEntry. 
   *
   * @return an enumeration of the entries in this ACL. 
   */
  public Enumeration entries(){
	return entryList.elements();
  }
  
  /**
   * Checks whether or not the specified principal has the specified 
   * permission.
   * If it does, true is returned, otherwise false is returned. 
   * More specifically, this method checks whether the passed permission 
   * is a member of the allowed permission set of the specified principal. 
   * The allowed permission set is determined by the same algorithm as is 
   * used by the getPermissions method. 
   *
   * @param user the principal, assumed to be a valid authenticated Principal. 
   * @param perm the permission to be checked for. 
   * @return true if the principal has the specified permission, 
   *         false otherwise. 
   * @see java.security.Principal
   * @see java.security.Permission
   */
  public boolean checkPermission(Principal user, 
				 java.security.acl.Permission perm) {
	for (Enumeration e = entryList.elements();e.hasMoreElements();){
	  AclEntry ent = (AclEntry) e.nextElement();
	  if (ent.getPrincipal().equals(user))
		if (ent.checkPermission(perm)) return true;
	}
	return false;
  }
  
  /**
   * Checks whether or not the specified principal has the specified 
   * permission.
   * If it does, true is returned, otherwise false is returned. 
   * More specifically, this method checks whether the passed permission 
   * is a member of the allowed permission set of the specified principal. 
   * The allowed permission set is determined by the same algorithm as is 
   * used by the getPermissions method. 
   *
   * @param user the principal, assumed to be a valid authenticated Principal. 
   * @param community the community name associated with the principal.
   * @param perm the permission to be checked for. 
   * @return true if the principal has the specified permission, false 
   *        otherwise. 
   * @see java.security.Principal
   * @see java.security.Permission
   */
  public boolean checkPermission(Principal user, String community, 
				 java.security.acl.Permission perm) {
	for (Enumeration e = entryList.elements();e.hasMoreElements();){
	  AclEntryImpl ent = (AclEntryImpl) e.nextElement();
	  if (ent.getPrincipal().equals(user))
		if (ent.checkPermission(perm) && ent.checkCommunity(community)) return true;
	}
	return false;
  }
  
  /**
   * Checks whether or not the specified community string is defined. 
   *
   * @param community the community name associated with the principal.
   *
   * @return true if the specified community string is defined, false 
   *      otherwise. 
   * @see java.security.Principal
   * @see java.security.Permission
   */
  public boolean checkCommunity(String community) {
	for (Enumeration e = entryList.elements();e.hasMoreElements();){
	  AclEntryImpl ent = (AclEntryImpl) e.nextElement();
	  if (ent.checkCommunity(community)) return true;
	}
	return false;
  }
  
  /**
   * Returns a string representation of the ACL contents. 
   *
   * @return a string representation of the ACL contents. 
   */
  public String toString(){
	return ("AclImpl: "+ getName());
  }
}