/*
 * Copyright (C) 2007 Martin Willi
 * Hochschule fuer Technik Rapperswil
 *
 * 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
 *
 * 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.
 *
 * $Id: enumerator.h 3589 2008-03-13 14:14:44Z martin $
 */
 
/**
 * @defgroup enumerator enumerator
 * @{ @ingroup utils
 */

#ifndef ENUMERATOR_H_
#define ENUMERATOR_H_

typedef struct enumerator_t enumerator_t;

#include <library.h>

/**
 * Enumerate is simpler, but more flexible than iterator.
 */
struct enumerator_t {

	/**
	 * Enumerate collection.
	 *
	 * The enumerate function takes a variable argument list containing 
	 * pointers where the enumerated values get written.
	 *
	 * @param ...	variable list of enumerated items, implementation dependant
	 * @return		TRUE if pointers returned
	 */
	bool (*enumerate)(enumerator_t *this, ...);
		
	/**
     * Destroy a enumerator instance.
     */
    void (*destroy)(enumerator_t *this);
};

/**
 * Create an enumerator which enumerates over nothing
 *
 * @return			an enumerator over no values
 */
enumerator_t* enumerator_create_empty();

/**
 * Create an enumerator which enumerates over a single item
 *
 * @param item		item to enumerate
 * @param cleanup	cleanup function called on destroy with the item
 * @return			an enumerator over a single value
 */
enumerator_t *enumerator_create_single(void *item, void (*cleanup)(void *item));

/**
 * Create an enumerator over files/subdirectories in a directory.
 *
 * This enumerator_t.enumerate() function returns a (to the directory) relative
 * filename (as a char*), an absolute filename (as a char*) and a file status
 * (to a struct stat), which all may be NULL. "." and ".." entries are
 * skipped. Example:
 *
 * @code
	char *rel, *abs;
	struct stat st;
	enumerator_t *e;
	
	e = enumerator_create_directory("/tmp");
	if (e)
	{
		while (e->enumerate(e, &rel, &abs, &st))
		{
			if (S_ISDIR(st.st_mode) && *rel != '.')
			{
				printf("%s\n", abs);
			}
		}
		e->destroy(e);
	}
   @endcode
 *
 * @param path		path of the directory
 * @return 			the directory enumerator, NULL on failure
 */
enumerator_t* enumerator_create_directory(char *path);

/**
 * Creates an enumerator which enumerates over enumerated enumerators :-).
 * 
 * The variable argument list of enumeration values is limit to 5.
 *
 * @param outer					outer enumerator
 * @param inner_constructor		constructor to inner enumerator
 * @param data					data to pass to each inner_constructor call
 * @param destroy_data			destructor to pass to data
 * @return						the nested enumerator
 */
enumerator_t *enumerator_create_nested(enumerator_t *outer,
					enumerator_t *(inner_constructor)(void *outer, void *data),
					void *data, void (*destroy_data)(void *data));

/**
 * Creates an enumerator which filters output of another enumerator.
 *
 * The filter function receives the user supplied "data" followed by a
 * unfiltered enumeration item, followed by an output pointer where to write
 * the filtered data. Then the next input/output pair follows.
 * It returns TRUE to deliver the
 * values to the caller of enumerate(), FALSE to filter this enumeration.
 *
 * The variable argument list of enumeration values is limit to 5.
 *
 * @param unfiltered			unfiltered enumerator to wrap, gets destroyed
 * @param filter				filter function
 * @param data					user data to supply to filter
 * @param destructor			destructor function to clean up data after use
 * @return						the filtered enumerator
 */
enumerator_t *enumerator_create_filter(enumerator_t *unfiltered,
					bool (*filter)(void *data, ...),
					void *data, void (*destructor)(void *data));

/**
 * Create an enumerator wrapper which does a cleanup on destroy.
 *
 * @param wrapped				wrapped enumerator
 * @param cleanup				cleanup function called on destroy
 * @param data					user data to supply to cleanup
 * @return						the enumerator with cleanup
 */
enumerator_t *enumerator_create_cleaner(enumerator_t *wrapped,
					void (*cleanup)(void *data), void *data);

#endif /* ENUMERATOR_H_ @} */