/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.io;

import java.security.Permission;
import java.security.PermissionCollection;
import java.util.Enumeration;
import java.util.Vector;

/**
 * Collects {@link FilePermission} objects and allows to query whether a
 * particular permission is implied by it.
 * 
 * @since Android 1.0
 */
final class FilePermissionCollection extends PermissionCollection implements
        Serializable {

    private static final long serialVersionUID = 2202956749081564585L;

    Vector<Permission> permissions = new Vector<Permission>();

    /**
     * Construct a new FilePermissionCollection
     */
    public FilePermissionCollection() {
        super();
    }

    /**
     * Add a permission object to the permission collection.
     * 
     * @param permission
     *            the FilePermission object to add to the collection.
     * @throws IllegalArgumentException
     *             if {@code permission} is not an instance of
     *             {@code FilePermission}.
     * @throws IllegalStateException
     *             if this collection is read-only.
     * @see java.security.PermissionCollection#add(java.security.Permission)
     */
    @Override
    public void add(Permission permission) {
        if (isReadOnly()) {
            throw new IllegalStateException();
        }
        if (permission instanceof FilePermission) {
            permissions.addElement(permission);
        } else {
            throw new IllegalArgumentException(permission.toString());
        }
    }

    /**
     * Returns an enumeration for the collection of permissions.
     * 
     * @return a permission enumeration for this permission collection.
     * @see java.security.PermissionCollection#elements()
     */
    @Override
    public Enumeration<Permission> elements() {
        return permissions.elements();
    }

    /**
     * Indicates whether this permissions collection implies a specific
     * {@code permission}.
     * 
     * @param permission
     *            the permission to check.
     * @see java.security.PermissionCollection#implies(java.security.Permission)
     */
    @Override
    public boolean implies(Permission permission) {
        if (permission instanceof FilePermission) {
            FilePermission fp = (FilePermission) permission;
            int matchedMask = 0;
            int i = 0;
            while (i < permissions.size()
                    && ((matchedMask & fp.mask) != fp.mask)) {
                // Cast will not fail since we added it
                matchedMask |= ((FilePermission) permissions.elementAt(i))
                        .impliesMask(permission);
                i++;
            }
            return ((matchedMask & fp.mask) == fp.mask);
        }
        return false;
    }
}
