// --- BEGIN COPYRIGHT BLOCK ---
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; version 2 of the License.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// (C) 2007 Red Hat, Inc.
// All rights reserved.
// --- END COPYRIGHT BLOCK ---
package netscape.security.acl;

import java.security.Principal;
import java.security.acl.Group;
import java.util.Enumeration;
import java.util.Vector;

/**
 * This class implements a group of principals.
 *
 * @author Satish Dharmaraj
 */
public class GroupImpl implements Group {
    private Vector<Principal> groupMembers = new Vector<Principal>(50, 100);
    private String group;

    /**
     * Constructs a Group object with no members.
     *
     * @param groupName the name of the group
     */
    public GroupImpl(String groupName) {
        this.group = groupName;
    }

    /**
     * adds the specified member to the group.
     *
     * @param user The principal to add to the group.
     * @return true if the member was added - false if the
     *         member could not be added.
     */
    public boolean addMember(Principal user) {
        if (groupMembers.contains(user))
            return false;

        // do not allow groups to be added to itself.
        if (group.equals(user.toString()))
            throw new IllegalArgumentException();

        groupMembers.addElement(user);
        return true;
    }

    /**
     * removes the specified member from the group.
     *
     * @param user The principal to remove from the group.
     * @param true if the principal was removed false if
     *        the principal was not a member
     */
    public boolean removeMember(Principal user) {
        return groupMembers.removeElement(user);
    }

    /**
     * returns the enumeration of the members in the group.
     */
    public Enumeration<Principal> members() {
        return groupMembers.elements();
    }

    /**
     * This function returns true if the group passed matches
     * the group represented in this interface.
     *
     * @param another The group to compare this group to.
     */
    public boolean equals(Group another) {
        return group.equals(another.toString());
    }

    /**
     * Prints a stringified version of the group.
     */
    public String toString() {
        return group;
    }

    /**
     * return a hashcode for the principal.
     */
    public int hashCode() {
        return group.hashCode();
    }

    /**
     * returns true if the passed principal is a member of the group.
     *
     * @param member The principal whose membership must be checked for.
     * @return true if the principal is a member of this group,
     *         false otherwise
     */
    public boolean isMember(Principal member) {

        //
        // if the member is part of the group (common case), return true.
        // if not, recursively search depth first in the group looking for the
        // principal.
        //
        if (groupMembers.contains(member)) {
            return true;
        } else {
            Vector<Group> alreadySeen = new Vector<Group>(10);
            return isMemberRecurse(member, alreadySeen);
        }
    }

    /**
     * return the name of the principal.
     */
    public String getName() {
        return group;
    }

    //
    // This function is the recursive search of groups for this
    // implementation of the Group. The search proceeds building up
    // a vector of already seen groups. Only new groups are considered,
    // thereby avoiding loops.
    //
    boolean isMemberRecurse(Principal member, Vector<Group> alreadySeen) {
        Enumeration<Principal> e = members();
        while (e.hasMoreElements()) {
            boolean mem = false;
            Principal p = e.nextElement();

            // if the member is in this collection, return true
            if (p.equals(member)) {
                return true;
            } else if (p instanceof GroupImpl) {
                //
                // if not recurse if the group has not been checked already.
                // Can call method in this package only if the object is an
                // instance of this class. Otherwise call the method defined
                // in the interface. (This can lead to a loop if a mixture of
                // implementations form a loop, but we live with this improbable
                // case rather than clutter the interface by forcing the
                // implementation of this method.)
                //
                GroupImpl g = (GroupImpl) p;
                alreadySeen.addElement(this);
                if (!alreadySeen.contains(g))
                    mem = g.isMemberRecurse(member, alreadySeen);
            } else if (p instanceof Group) {
                Group g = (Group) p;
                if (!alreadySeen.contains(g))
                    mem = g.isMember(member);
            }

            if (mem)
                return mem;
        }
        return false;
    }
}
