/********************************************************************\
 * qofid.h -- QOF entity type identification system                 *
 *                                                                  *
 * This program is free software; you can redistribute it and/or    *
 * modify it under the terms of the GNU General Public License as   *
 * published by the Free Software Foundation; either version 2 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 General Public License for more details.                     *
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 * You should have received a copy of the GNU General Public License*
 * along with this program; if not, contact:                        *
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 * Free Software Foundation           Voice:  +1-617-542-5942       *
 * 51 Franklin Street, Fifth Floor    Fax:    +1-617-542-2652       *
 * Boston, MA  02110-1301,  USA       gnu@gnu.org                   *
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\********************************************************************/

#ifndef QOF_ID_H
#define QOF_ID_H

/** @addtogroup Entity
    @{ */
/** @addtogroup Entities

    This file defines an API that adds types to the GncGUID's.
    GncGUID's with types can be used to identify and reference
    typed entities.

    The idea here is that a GncGUID can be used to uniquely identify
    some thing.  By adding a type, one can then talk about the
    type of thing identified.  By adding a collection, one can
    then work with a handle to a collection of things of a given
    type, each uniquely identified by a given ID.  QOF Entities
    can be used independently of any other part of the system.
    In particular, Entities can be useful even if one is not using
    the Query and Object parts of the QOF system.

    Identifiers are globally-unique and permanent, i.e., once
    an entity has been assigned an identifier, it retains that same
    identifier for its lifetime.
    Identifiers can be encoded as hex strings.

    GncGUID Identifiers are 'typed' with strings.  The native ids used
    by QOF are defined below.
	-# An id with type QOF_ID_NONE does not
    refer to any entity.
	-# An id with type QOF_ID_NULL does not refer
	to any entity, and will never refer to any entity.
	=# An identifier with any other type may refer to an
    actual entity, but that is not guaranteed as that entity does
	not have to exist within the current book. (See ::PARTIAL_QOFBOOK).
	Also, creating a new entity from a data source involves creating
	a temporary GncGUID and then setting the value from the data source.
	If an id does refer to an entity, the type of the entity will match
	the type of the identifier.

    If you have a type name, and you want to have a way of finding
    a collection that is associated with that type, then you must use
    Books.

	Entities can refer to other entities as well as to the basic
	QOF types, using the qofclass parameters.

 @{ */
/** @file qofid.h
    @brief QOF entity type identification system
    @author Copyright (C) 2000 Dave Peticolas <peticola@cs.ucdavis.edu>
    @author Copyright (C) 2003 Linas Vepstas <linas@linas.org>
*/

#include <string.h>
#include "guid.h"

/** QofIdType declaration */
typedef const gchar * QofIdType;
/** QofIdTypeConst declaration */
typedef const gchar * QofIdTypeConst;

typedef struct QofCollection_s QofCollection;

#include "qofinstance.h"

#ifdef __cplusplus
extern "C"
{
#endif

#define QOF_ID_NONE           NULL
#define QOF_ID_NULL           "null"

#define QOF_ID_BOOK           "Book"
#define QOF_ID_SESSION        "Session"

#define QSTRCMP g_strcmp0

/** return TRUE if object is of the given type */
#define QOF_CHECK_TYPE(obj,type) (((obj) != NULL) && \
  (0 == QSTRCMP((type),(((QofInstance *)(obj))->e_type))))

/** cast object to the indicated type,
print error message if its bad  */
#define QOF_CHECK_CAST(obj,e_type,c_type) (                   \
  QOF_CHECK_TYPE((obj),(e_type)) ?                            \
  (c_type *) (obj) :                                          \
  (c_type *) ({                                               \
     g_log (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,               \
       "Error: Bad QofInstance at %s:%d", __FILE__, __LINE__);  \
     (obj);                                                   \
  }))


/** QofCollection declaration

@param e_type QofIdType
@param is_dirty gboolean
@param hash_of_entities GHashTable
@param data gpointer, place where object class can hang arbitrary data

*/

/** @name Collections of Entities
 @{ */

/** create a new collection of entities of type */
QofCollection * qof_collection_new (QofIdType type);

/** return the number of entities in the collection. */
guint qof_collection_count (const QofCollection *col);

/** destroy the collection */
void qof_collection_destroy (QofCollection *col);

/** return the type that the collection stores */
QofIdType qof_collection_get_type (const QofCollection *);

/** Find the entity going only from its guid */
/*@ dependent @*/
QofInstance * qof_collection_lookup_entity (const QofCollection *, const GncGUID *);

/** Callback type for qof_collection_foreach */
typedef void (*QofInstanceForeachCB) (QofInstance *, gpointer user_data);

/** Call the callback for each entity in the collection. */
void qof_collection_foreach (const QofCollection *, QofInstanceForeachCB,
                             gpointer user_data);

/** Store and retrieve arbitrary object-defined data
 *
 * XXX We need to add a callback for when the collection is being
 * destroyed, so that the user has a chance to clean up anything
 * that was put in the 'data' member here.
 */
gpointer qof_collection_get_data (const QofCollection *col);
void qof_collection_set_data (QofCollection *col, gpointer user_data);

/** Return value of 'dirty' flag on collection */
gboolean qof_collection_is_dirty (const QofCollection *col);

/** @name QOF_TYPE_COLLECT: Linking one entity to many of one type

\note These are \b NOT the same as the main collections in the book.

QOF_TYPE_COLLECT is a secondary collection, used to select entities
of one object type as references of another entity.
\sa QOF_TYPE_CHOICE.

@{
*/
/** \brief Add an entity to a QOF_TYPE_COLLECT.

\note These are \b NOT the same as the main collections in the book.

Entities can be
freely added and merged across these secondary collections, they
will not be removed from the original collection as they would
by using ::qof_instance_insert_entity or ::qof_instance_remove_entity.

*/
gboolean
qof_collection_add_entity (QofCollection *coll, QofInstance *ent);

void qof_collection_remove_entity (QofInstance *ent);

/** \brief Compare two secondary collections.

Performs a deep comparison of the collections. Each QofInstance in
each collection is looked up in the other collection, via the GncGUID.

\return 0 if the collections are identical or both are NULL
otherwise -1 if target is NULL or either collection contains an entity with an invalid
GncGUID or if the types of the two collections do not match,
or +1 if merge is NULL or if any entity exists in one collection but
not in the other.
*/
gint
qof_collection_compare (QofCollection *target, QofCollection *merge);

/** \brief Create a secondary collection from a GList

@param type The QofIdType of the QofCollection \b and of
	\b all entities in the GList.
@param glist GList of entities of the same QofIdType.

@return NULL if any of the entities fail to match the
	QofCollection type, else a pointer to the collection
	on success.
*/
QofCollection*
qof_collection_from_glist (QofIdType type, const GList *glist);

/** @} */
/** @} */

#ifdef __cplusplus
}
#endif

#endif /* QOF_ID_H */
/** @} */
/** @} */
