/* Acl.java -- An access control list
   Copyright (C) 1998 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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package java.security.acl;

import java.security.Principal;
import java.util.Enumeration;

/**
 * A Java access control list (ACL) is a group of individual ACL entries.
 * These entries consist of a <code>Principal</code> and a list of
 * permissions this <code>Principal</code> is either granted or denied.
 * A given <code>Principal</code> can have at most one positive ACL entry
 * (i.e., one that grants permissions) and one negative ACL entry (i.e., one
 * that denies permissions).  If a given permission is both granted and
 * denied, the ACL treats it as if it were never granted or denied.  If
 * both a <code>Principal</code> and a <code>Group</code> to which the
 * <code>Principal</code> belongs have an ACL entry, the permissions for
 * the individual <code>Principal</code> take precedence over the 
 * permissions of the <code>Group</code> if there is a conflict.
 * <p
 * Additionally, the ACL interface extends the <code>Owner</code> interface
 * and so an ACL has owners.  Actions which modify the ACL are restricted
 * to owners.
 *
 * @version 0.0
 *
 * @author Aaron M. Renn (arenn@urbanophile.com)
 */
public interface Acl extends Owner
{

  /**
   * This method returns the name of this ACL.
   *
   * @return The name of this ACL
   */
  public abstract String getName();

  /**
   * This method sets the name of the ACL
   *
   * @param caller The <code>Principal</code> requesting the action.
   * @param name The new name for this ACL.
   *
   * @exception NotOwnerException If the caller is not an owner of this ACL.
   */
  public abstract void setName(Principal caller, String name)
    throws NotOwnerException;

  /**
   * This method adds the specified entry to the ACL
   *
   * @param caller The <code>Principal</code> requesting the addition
   * @param entry The ACL entry to add
   *
   * @return <code>true</code> if the entry was added, <code>false</code> if there is already an entry of the same type for the <code>Principal</code>.
   *
   * @exception NotOwnerException If the caller is not an owner of this ACL.
   */
  public abstract boolean addEntry(Principal caller, AclEntry entry) 
    throws NotOwnerException;

  /**
   * This method delets the specified entry from the ACL
   *
   * @param caller The <code>Principal</code> requesting the deletion.
   * @param entry The ACL entry to delete
   *
   * @return <code>true</code> if the entry was deleted, or <code>false</code> if this entry was not part of the ACL to begin with
   *
   * @exception NotOwnerException If the caller is not an owner of this ACL.
   */
  public abstract boolean removeEntry(Principal caller, AclEntry entry)
    throws NotOwnerException;

  /**
   * This method returns a list of all the entries in the ACL as an
   * <code>Enumeration</code>.
   *
   * @return An enumeration of the ACL entries
   */
  public abstract Enumeration entries();

  /**
   * This method tests whether or not the specified <code>Principal</code>
   * has the specified <code>Permission</code>
   *
   * @param user The <code>Principal</code> to test
   * @param perm The <code>Permission</code> to test for
   *
   * @return <code>true</code> if the user has been granted the permission, <code>false</code> otherwise
   */
  public abstract boolean checkPermission(Principal user, Permission perm);

  /**
   * This method returns a list of <code>Permission</code>'s that are granted
   * to a particular <code>Principal</code>.  This includes any permissions
   * that are granted to <code>Group</code>'s to which the <code>Principal</code>
   * belongs unless they are overridden by a negative ACL.  This permission
   * list is returned as an <code>Enumeration</code>.
   *
   * @param user The <code>Principal</code> to retrieve permissions for.
   *
   * @return A list of permissions for the <code>Principal</code>.
   */
  public abstract Enumeration getPermissions(Principal user);

  /**
   * This method returns the ACL as a <code>String</code>
   *
   * @return A <code>String</code> representation of this ACL
   */
  public abstract String toString();
}