/*
 * $Header: /cvshome/build/org.osgi.framework/src/org/osgi/framework/ServicePermission.java,v 1.15 2007/02/20 00:06:02 hargrave Exp $
 * 
 * Copyright (c) OSGi Alliance (2000, 2007). All Rights Reserved.
 * 
 * Licensed 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 org.osgi.framework;

import java.io.IOException;
import java.security.*;
import java.util.Enumeration;
import java.util.Hashtable;

/**
 * A bundle's authority to register or get a service.
 * <ul>
 * <li>The <code>ServicePermission.REGISTER</code> action allows a bundle to
 * register a service on the specified names.
 * <li>The <code>ServicePermission.GET</code> action allows a bundle to
 * detect a service and get it.
 * </ul>
 * Permission to get a service is required in order to detect events regarding
 * the service. Untrusted bundles should not be able to detect the presence of
 * certain services unless they have the appropriate
 * <code>ServicePermission</code> to get the specific service.
 * 
 * @version $Revision: 1.15 $
 */

final public class ServicePermission extends BasicPermission {
	static final long			serialVersionUID	= -7662148639076511574L;
	/**
	 * The action string <code>get</code> (Value is "get").
	 */
	public final static String	GET					= "get";
	/**
	 * The action string <code>register</code> (Value is "register").
	 */
	public final static String	REGISTER			= "register";

	private final static int	ACTION_GET			= 0x00000001;
	private final static int	ACTION_REGISTER		= 0x00000002;
	private final static int	ACTION_ALL			= ACTION_GET
															| ACTION_REGISTER;
	private final static int	ACTION_NONE			= 0;
	/**
	 * The actions mask.
	 */
	private transient int		action_mask			= ACTION_NONE;

	/**
	 * The actions in canonical form.
	 * 
	 * @serial
	 */
	private String				actions				= null;

	/**
	 * Create a new ServicePermission.
	 * 
	 * <p>
	 * The name of the service is specified as a fully qualified class name.
	 * 
	 * <pre>
	 * ClassName ::= &lt;class name&gt; | &lt;class name ending in &quot;.*&quot;&gt;
	 * </pre>
	 * 
	 * Examples:
	 * 
	 * <pre>
	 * org.osgi.service.http.HttpService
	 * org.osgi.service.http.*
	 * org.osgi.service.snmp.*
	 * </pre>
	 * 
	 * <p>
	 * There are two possible actions: <code>get</code> and
	 * <code>register</code>. The <code>get</code> permission allows the
	 * owner of this permission to obtain a service with this name. The
	 * <code>register</code> permission allows the bundle to register a
	 * service under that name.
	 * 
	 * @param name class name
	 * @param actions <code>get</code>,<code>register</code> (canonical
	 *        order)
	 */

	public ServicePermission(String name, String actions) {
		this(name, getMask(actions));
	}

	/**
	 * Package private constructor used by ServicePermissionCollection.
	 * 
	 * @param name class name
	 * @param mask action mask
	 */
	ServicePermission(String name, int mask) {
		super(name);

		init(mask);
	}

	/**
	 * Called by constructors and when deserialized.
	 * 
	 * @param mask action mask
	 */
	private void init(int mask) {
		if ((mask == ACTION_NONE) || ((mask & ACTION_ALL) != mask)) {
			throw new IllegalArgumentException("invalid action string");
		}

		action_mask = mask;
	}

	/**
	 * Parse action string into action mask.
	 * 
	 * @param actions Action string.
	 * @return action mask.
	 */
	private static int getMask(String actions) {
		boolean seencomma = false;

		int mask = ACTION_NONE;

		if (actions == null) {
			return mask;
		}

		char[] a = actions.toCharArray();

		int i = a.length - 1;
		if (i < 0)
			return mask;

		while (i != -1) {
			char c;

			// skip whitespace
			while ((i != -1)
					&& ((c = a[i]) == ' ' || c == '\r' || c == '\n'
							|| c == '\f' || c == '\t'))
				i--;

			// check for the known strings
			int matchlen;

			if (i >= 2 && (a[i - 2] == 'g' || a[i - 2] == 'G')
					&& (a[i - 1] == 'e' || a[i - 1] == 'E')
					&& (a[i] == 't' || a[i] == 'T')) {
				matchlen = 3;
				mask |= ACTION_GET;

			}
			else
				if (i >= 7 && (a[i - 7] == 'r' || a[i - 7] == 'R')
						&& (a[i - 6] == 'e' || a[i - 6] == 'E')
						&& (a[i - 5] == 'g' || a[i - 5] == 'G')
						&& (a[i - 4] == 'i' || a[i - 4] == 'I')
						&& (a[i - 3] == 's' || a[i - 3] == 'S')
						&& (a[i - 2] == 't' || a[i - 2] == 'T')
						&& (a[i - 1] == 'e' || a[i - 1] == 'E')
						&& (a[i] == 'r' || a[i] == 'R')) {
					matchlen = 8;
					mask |= ACTION_REGISTER;

				}
				else {
					// parse error
					throw new IllegalArgumentException("invalid permission: "
							+ actions);
				}

			// make sure we didn't just match the tail of a word
			// like "ackbarfregister". Also, skip to the comma.
			seencomma = false;
			while (i >= matchlen && !seencomma) {
				switch (a[i - matchlen]) {
					case ',' :
						seencomma = true;
					/* FALLTHROUGH */
					case ' ' :
					case '\r' :
					case '\n' :
					case '\f' :
					case '\t' :
						break;
					default :
						throw new IllegalArgumentException(
								"invalid permission: " + actions);
				}
				i--;
			}

			// point i at the location of the comma minus one (or -1).
			i -= matchlen;
		}

		if (seencomma) {
			throw new IllegalArgumentException("invalid permission: " + actions);
		}

		return mask;
	}

	/**
	 * Determines if a <code>ServicePermission</code> object "implies" the
	 * specified permission.
	 * 
	 * @param p The target permission to check.
	 * @return <code>true</code> if the specified permission is implied by
	 *         this object; <code>false</code> otherwise.
	 */

	public boolean implies(Permission p) {
		if (p instanceof ServicePermission) {
			ServicePermission target = (ServicePermission) p;

			return (((action_mask & target.action_mask) == target.action_mask) && super
					.implies(p));
		}

		return (false);
	}

	/**
	 * Returns the canonical string representation of the actions. Always
	 * returns present actions in the following order: <code>get</code>,
	 * <code>register</code>.
	 * 
	 * @return The canonical string representation of the actions.
	 */
	public String getActions() {
		if (actions == null) {
			StringBuffer sb = new StringBuffer();
			boolean comma = false;

			if ((action_mask & ACTION_GET) == ACTION_GET) {
				sb.append(GET);
				comma = true;
			}

			if ((action_mask & ACTION_REGISTER) == ACTION_REGISTER) {
				if (comma)
					sb.append(',');
				sb.append(REGISTER);
			}

			actions = sb.toString();
		}

		return (actions);
	}

	/**
	 * Returns a new <code>PermissionCollection</code> object for storing
	 * <code>ServicePermission<code> objects.
	 *
	 * @return A new <code>PermissionCollection</code> object suitable for storing
	 * <code>ServicePermission</code> objects.
	 */
	public PermissionCollection newPermissionCollection() {
		return (new ServicePermissionCollection());
	}

	/**
	 * Determines the equalty of two ServicePermission objects.
	 * 
	 * Checks that specified object has the same class name and action as this
	 * <code>ServicePermission</code>.
	 * 
	 * @param obj The object to test for equality.
	 * @return true if obj is a <code>ServicePermission</code>, and has the
	 *         same class name and actions as this
	 *         <code>ServicePermission</code> object; <code>false</code>
	 *         otherwise.
	 */
	public boolean equals(Object obj) {
		if (obj == this) {
			return (true);
		}

		if (!(obj instanceof ServicePermission)) {
			return (false);
		}

		ServicePermission p = (ServicePermission) obj;

		return ((action_mask == p.action_mask) && getName().equals(p.getName()));
	}

	/**
	 * Returns the hash code value for this object.
	 * 
	 * @return Hash code value for this object.
	 */

	public int hashCode() {
		return (getName().hashCode() ^ getActions().hashCode());
	}

	/**
	 * Returns the current action mask. Used by the ServicePermissionCollection
	 * object.
	 * 
	 * @return The actions mask.
	 */
	int getMask() {
		return (action_mask);
	}

	/**
	 * WriteObject is called to save the state of this permission to a stream.
	 * The actions are serialized, and the superclass takes care of the name.
	 */

	private synchronized void writeObject(java.io.ObjectOutputStream s)
			throws IOException {
		// Write out the actions. The superclass takes care of the name
		// call getActions to make sure actions field is initialized
		if (actions == null)
			getActions();
		s.defaultWriteObject();
	}

	/**
	 * readObject is called to restore the state of this permission from a
	 * stream.
	 */
	private synchronized void readObject(java.io.ObjectInputStream s)
			throws IOException, ClassNotFoundException {
		// Read in the action, then initialize the rest
		s.defaultReadObject();
		init(getMask(actions));
	}
}

/**
 * Stores a set of ServicePermission permissions.
 * 
 * @see java.security.Permission
 * @see java.security.Permissions
 * @see java.security.PermissionCollection
 */

final class ServicePermissionCollection extends PermissionCollection {
	static final long	serialVersionUID	= 662615640374640621L;
	/**
	 * Table of permissions.
	 * 
	 * @serial
	 */
	private Hashtable<String,Permission>	permissions;

	/**
	 * Boolean saying if "*" is in the collection.
	 * 
	 * @serial
	 */
	private boolean		all_allowed;

	/**
	 * Creates an empty ServicePermissions object.
	 */

	public ServicePermissionCollection() {
		permissions = new Hashtable<String,Permission>();
		all_allowed = false;
	}

	/**
	 * Adds a permission to the <code>ServicePermission</code> objects using
	 * the key for the hash as the name.
	 * 
	 * @param permission The Permission object to add.
	 * 
	 * @throws IllegalArgumentException If the permission is not a
	 *         ServicePermission object.
	 * @throws SecurityException If this
	 *         <code>ServicePermissionCollection</code> object has been marked
	 *         read-only.
	 */

	public void add(Permission permission) {
		if (!(permission instanceof ServicePermission))
			throw new IllegalArgumentException("invalid permission: "
					+ permission);
		if (isReadOnly())
			throw new SecurityException("attempt to add a Permission to a "
					+ "readonly PermissionCollection");

		ServicePermission sp = (ServicePermission) permission;
		String name = sp.getName();

		ServicePermission existing = (ServicePermission) permissions.get(name);

		if (existing != null) {
			int oldMask = existing.getMask();
			int newMask = sp.getMask();
			if (oldMask != newMask) {
				permissions.put(name, new ServicePermission(name, oldMask
						| newMask));
			}
		}
		else {
			permissions.put(name, permission);
		}

		if (!all_allowed) {
			if (name.equals("*"))
				all_allowed = true;
		}
	}

	/**
	 * Determines if a set of permissions implies the permissions expressed in
	 * <code>permission</code>.
	 * 
	 * @param permission The Permission object to compare.
	 * 
	 * @return <code>true</code> if <code>permission</code> is a proper
	 *         subset of a permission in the set; <code>false</code>
	 *         otherwise.
	 */

	public boolean implies(Permission permission) {
		if (!(permission instanceof ServicePermission))
			return (false);

		ServicePermission sp = (ServicePermission) permission;
		ServicePermission x;

		int desired = sp.getMask();
		int effective = 0;

		// short circuit if the "*" Permission was added
		if (all_allowed) {
			x = (ServicePermission) permissions.get("*");
			if (x != null) {
				effective |= x.getMask();
				if ((effective & desired) == desired)
					return (true);
			}
		}

		// strategy:
		// Check for full match first. Then work our way up the
		// name looking for matches on a.b.*

		String name = sp.getName();

		x = (ServicePermission) permissions.get(name);

		if (x != null) {
			// we have a direct hit!
			effective |= x.getMask();
			if ((effective & desired) == desired)
				return (true);
		}

		// work our way up the tree...
		int last, offset;

		offset = name.length() - 1;

		while ((last = name.lastIndexOf(".", offset)) != -1) {

			name = name.substring(0, last + 1) + "*";
			x = (ServicePermission) permissions.get(name);

			if (x != null) {
				effective |= x.getMask();
				if ((effective & desired) == desired)
					return (true);
			}
			offset = last - 1;
		}

		// we don't have to check for "*" as it was already checked
		// at the top (all_allowed), so we just return false
		return (false);
	}

	/**
	 * Returns an enumeration of all the <code>ServicePermission</code>
	 * objects in the container.
	 * 
	 * @return Enumeration of all the ServicePermission objects.
	 */

	public Enumeration<Permission> elements() {
		return (permissions.elements());
	}
}