/*
 * $Id$
 *
 * Copyright (C) 2003-2015 JNode.org
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
package org.jnode.vm;

import java.security.AccessControlException;
import java.security.Permission;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.List;

/**
 * Representation of the current access control context.
 *
 * @author Ewout Prangsma (epr@users.sourceforge.net)
 */
public final class VmAccessControlContext {

    private final ProtectionDomain domains[];

    /**
     * Initialize this instance.
     *
     * @param context
     * @param inheritedContext
     */
    public VmAccessControlContext(ProtectionDomain[] context,
                                  VmAccessControlContext inheritedContext) {
        final ArrayList<ProtectionDomain> ctxList = new ArrayList<ProtectionDomain>();
        if (context != null) {
            addUniqueToList(ctxList, context);
        }
        if ((inheritedContext != null) && (inheritedContext.domains != null)) {
            addUniqueToList(ctxList, inheritedContext.domains);
        }
        if (ctxList.isEmpty()) {
            this.domains = null;
        } else {
            this.domains = (ProtectionDomain[]) ctxList
                .toArray(new ProtectionDomain[ctxList.size()]);
        }
    }

    /**
     * Determines whether or not the specific permission is granted depending
     * on the context it is within.
     *
     * @param perm a permission to check
     * @throws AccessControlException if the permssion is not permitted
     */
    public final void checkPermission(Permission perm)
        throws AccessControlException {
        if (domains != null) {
            final int count = domains.length;
            for (int i = 0; i < count; i++) {
                if (!domains[i].implies(perm)) {
                    throw new AccessControlException(
                        "Permission \"" + perm + "\" not granted");
                }
            }
        }
    }

    /**
     * Checks if two AccessControlContexts are equal.
     * <p/>
     * It first checks if obj is an AccessControlContext class, and then checks
     * if each ProtectionDomain matches.
     *
     * @param obj The object to compare this class to
     * @return true if equal, false otherwise
     */
    public final boolean equals(Object obj) {
        if (obj instanceof VmAccessControlContext) {
            final VmAccessControlContext acc = (VmAccessControlContext) obj;
            final int count = (domains == null) ? 0 : domains.length;

            if (acc.domains.length != count) {
                return false;
            }

            for (int i = 0; i < count; i++) {
                if (acc.domains[i] != domains[i]) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    /**
     * Computes a hash code of this class
     *
     * @return a hash code representing this class
     */
    public final int hashCode() {
        int h = 0;
        final int count = (domains == null) ? 0 : domains.length;
        for (int i = 0; i < count; i++) {
            h ^= domains[i].hashCode();
        }
        return h;
    }

    private final void addUniqueToList(List<ProtectionDomain> ctxList,
                                       ProtectionDomain[] context) {
        final int count = context.length;
        for (int i = 0; i < count; i++) {
            final ProtectionDomain pd = context[i];
            if (pd != null) {
                if (!ctxList.contains(pd)) {
                    ctxList.add(pd);
                }
            }
        }
    }
}