/*
    Copyright (C) 2003 by Anders Stenberg

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#ifndef __CS_IUTIL_STRINGSET_H__
#define __CS_IUTIL_STRINGSET_H__

/**\file
 * Stringset interface
 */
/**\addtogroup util
 * @{ */
#include "csutil/scf_interface.h"

/**
 * An identifier for a string. This identifier is equivalent to the contents
 * of a string: If two strings have the same content, they have get the same
 * identifier. If they have different content, they get different identifiers.
 */
typedef unsigned long csStringID;
/// An \e invalid csStringID.
csStringID const csInvalidStringID = (csStringID) ~0;


/**
 * The string set is a collection of unique strings. Each string has an ID
 * number. The most important operation is to request a string, which means to
 * return the ID for the string, adding it to the collection if not already
 * present.  This is useful when you need to work with strings but want the
 * performance characteristics of simple numeric comparisons.  Rather than
 * performing string comparisons, you instead compare the numeric string ID's.
 *
 * As a convenience, the csInitializer class creates a string set at
 * application initialization time and inserts it into the global object
 * registry (iObjectRegistry).  To obtain a reference this shared string set
 * (which may be desirable when modules need to share string ID's), use a code
 * snippet similar to the following:
 *
 * \code
 * iObjectRegistry* object_reg = ...;
 * csRef<iStringSet> strings = CS_QUERY_REGISTRY_TAG_INTERFACE(
 *   object_reg, "crystalspace.shared.stringset", iStringSet);
 * \endcode
 *
 * \sa csStringHash
 * \sa csStringSet
 */
struct iStringSet : public virtual iBase
{
  SCF_INTERFACE(iStringSet, 2,0,0);
  /**
   * Request the numeric ID for the given string.
   * \return The ID of the string.
   * \remarks Creates a new ID if the string is not yet present in the set,
   *   else returns the previously assigned ID.
   */
  virtual csStringID Request(const char*) = 0;

  /**
   * Request the string corresponding to the given ID.
   * \return Null if the string * has not been requested (yet), else the string
   *   corresponding to the ID.
   */
  virtual const char* Request(csStringID) const = 0;

  /**
   * Check if the set contains a particular string.
   */
  virtual bool Contains(char const*) const = 0;

  /**
   * Check if the set contains a string with a particular ID.
   * \remarks This is rigidly equivalent to
   *   <tt>return Request(id) != NULL</tt>, but more idomatic.
   */
  virtual bool Contains(csStringID) const = 0;

  /**
   * Remove specified string.
   * \return True if a matching string was in thet set; else false.
   */
  virtual bool Delete(char const*) = 0;

  /**
   * Remove a string with the specified ID.
   * \return True if a matching string was in the set; else false.
   */
  virtual bool Delete(csStringID) = 0;

  /**
   * Remove all stored strings. When new strings are registered again, new
   * ID values will be used; the old ID's will not be re-used.
   */
  virtual void Empty() = 0;

  /**
   * Remove all stored strings.
   * \deprecated Use Empty() instead.
   */
  /*CS_DEPRECATED_METHOD_MSG("Use Empty() instead.")*/
  virtual void Clear() = 0;

  /// Get the number of elements in the hash.
  virtual size_t GetSize () const = 0;

  /**
   * Return true if the hash is empty.
   * \remarks Rigidly equivalent to <tt>return GetSize() == 0</tt>, but more
   *   idiomatic.
   */
  virtual bool IsEmpty() const = 0;
};

/** @} */

#endif // __CS_IUTIL_STRINGSET_H__
