# ConcurrentResource.java

    /*
    ** Module   : ConcurrentResourceResource.java
    ** Abstract : plugin to manage access to concurrent resources
    **
    ** Copyright (c) 2020-2023, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ----------------------------Description-----------------------------------
    ** 001 GES 20200130 Created the first version.
    ** 002 HC  20230427 Added support for file system rights.
    */

    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
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    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
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    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.concurrent;

    import com.goldencode.p2j.security.*;
    import com.goldencode.p2j.directory.*;
    import com.goldencode.util.*;

    import java.util.*;

    /**
     * Implements the "ConcurrentResource" resource. Access to such resources have rights which can
     * be represented by a small set of flags:
     * <ul>
     *   <li> create - a runtime instance of the resource can be created
     *   <li> delete - an existing runtime instance can be destroyed
     *   <li> read - the state or data associated with an existing runtime instance can be accessed
     *   <li> write - the state or data associated with an existing runtime instance can be modified
     *   <li> denied - no access is allowed (overrides any other access flags)
     * </ul>
     * <p>
     * Rights objects for this resource are made of one bitfield with 8 bits.  The first four bits
     * correspond to the create, delete, read and write respectively.  There are 3 reserved bits.
     * The last bit is for explicit denial of access. When printed, they are shown as
     * {@code CDRW...N}.
     * <p>
     * Resource names will be namespaced using the subclass' resource type name.  The naming approach
     * is {@code /resource_type_name/instance_name}.  Each different instance of a particular
     * resource type will share the same type name but must have a unique, non-empty instance name.
     */
    public class ConcurrentResource
    extends BitFlagsResource
    {
       /** All valid resource names. */
       private static Set<String> names = new HashSet<String>();

       static
       {
          names.add("event_semaphore");
       }

       /**
        * Default constructor.
        */
       public ConcurrentResource()
       {
       }

       /**
        * Obtains the set of all possible valid resource type names.
        *
        * @return   The set of valid resource type names.
        */
       public Set<String> resourceTypeName()
       {
          return Collections.unmodifiableSet(names);
       }

       /**
        * Returns the plugin resource type name as a string.
        *
        * @return   The plugin resource type name.
        */
       public String getTypeName()
       {
          return "ConcurrentResource";
       }

       /**
        * Instantiates a plugin's class that implements the <code>Rights</code> interface, using
        * the array of objects representing a set of access rights fields.
        *
        * @param    rights
        *           The objects needed to create an access rights instance.
        *
        * @return   The newly created rights instance.
        */
       public Rights getRightsInstance(Object[] rights)
       {
          return new ConcurrentRights(BitSetHelper.fromBitField((BitField)rights[0]));
       }

       /**
        * Checks whether a given string is a valid resource name for this resource type.
        * <p>
        * Valid names are of the form {@code /resource_type_name/instance_name} where instance_name
        * is a non-empty string which has no whitespace and which uniquely identifies a given
        * resource instance and where resource_type_name is shared across all resources of the same
        * type.  Resource names are NOT case sensitive.
        *
        * @param    resource
        *           The possible name to validate.
        *
        * @return   <code>true</code> if the name is syntactically correct
        */
       public boolean isInstanceNameValid(String resource)
       {
          if (resource == null || resource.length() == 0)
             return false;

          Set<String> names = resourceTypeName();

          if (resource.charAt(0) != '/')
             return false;

          int resEnd   = resource.indexOf('/', 1);
          int insBegin = resEnd + 1;

          // no ending slash OR an empty resource name OR an empty instance name
          if (resEnd == -1 || resEnd == 1 || insBegin == resource.length())
             return false;

          String resName = resource.substring(1, resEnd).toLowerCase();

          if (!names.contains(resName))
             return false;

          String iname = resource.substring(insBegin);

          if (StringHelper.containsWhitespace(iname))
             return false;

          return true;
       }
    }