/*
 * Copyright (C) 2020 Weber Yann
 * 
 * This file is part of pyrpn.
 * 
 * pyrpn 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 3 of the License, or
 * any later version.
 * 
 * pyrpn 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.
 * 
 * You should have received a copy of the GNU General Public License
 * along with pyrpn.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef __rpn_ifs__h__
#define __rpn_ifs__h__

#include "config.h"

#include <assert.h>
#include <string.h>

#include "rpn_jit.h"
#include "rpn_if.h"

/**@file rpn_ifs.h
 * @brief IFS header
 * @ingroup ifs
 */

/**@defgroup ifs Iterated function system
 * @brief IFS implementation with RPN expressions
 *
 * IFS are basically a list of @ref ifs_if associated with a probability
 * of evaluation.
 *
 * This implementation aims to :
 * - optimize @ref ifs_if calls
 * - optimize random number generation and IF random calls
 * 
 * @note It aims to provide an API close to @ref ifs_if API, in order to
 * be able to use both IFS and IF almost tansparently via Python API.
 */

/**@brief struct @ref rpn_ifs_s shortcut */
typedef struct rpn_ifs_s rpn_ifs_t;

/**@brief Stores IFS informations */
struct rpn_ifs_s
{
	/**@brief Parameters shared by all IF of the system */
	rpn_if_param_t params;

	/**@brief Memory map shared by all iterated functions */
	rpn_value_t *mem;
	/**@brief If 1 the mem has to be munmap at free time */
	short self_mem;

	/**@brief Pointers on iterated function structures */
	rpn_if_t **rpn_if;
	/**@brief Number of iterated functions in the system */
	size_t if_sz;

	/**@brief Current position in memory map */
	size_t pos;

	/**@brief Stores the original chance of choosing corresponding IF */
	unsigned int *weight;
	/** @brief Stores an array of 256 pointers on IF allowing fast
	 * random choice.*/
	rpn_if_t *if_proba[256];

	/**@brief Stores the RPN expressions pointer of the IF contained in
	 * the system */
	rpn_expr_t **flat_rpn;
	/**Number of rpn expression in the system */
	size_t flat_sz;
};

/**@brief Initialize a new IFS struct given params
 * @param params Individual, but shared, parameters for iteraed functions
 * in the system
 * @param memmap A suitable memory map or NULL
 * @return NULL if error and set errno
 * @note Initialized system is empty. Use @ref rpn_ifs_add_if to add an iterated
 * function to the system
 */
rpn_ifs_t* rpn_ifs_new(rpn_if_param_t *params, rpn_value_t *memmap);

/**@brief Free ressources of an iterated function system
 * @param rifs The iterated function system to free
 */
void rpn_ifs_free(rpn_ifs_t *rifs);

/**@brief Set the number and weights of functions in the system
 * @note Do not re-init existing function
 * @param rifs The iterated function system
 * @param count The number of functions in the system
 * @param weights The function's weight
 * @return The number of function in the system
 */
size_t rpn_ifs_set_if_count(rpn_ifs_t *rifs, size_t count, unsigned int *weights);

/**@brief Add a new iterated function to the system
 * @param rifs The iterated function system
 * @param weight The new expression weight
 * @return 0 on error, else returns the new @ref rpn_if_s index
 * @note if epxrs is NULL empty RPN expressions are used
 * @todo change the exprs argument when if init will be updated
 */
size_t rpn_ifs_add_if(rpn_ifs_t *rifs, unsigned int weight);

/**@brief Delete an iterated function from the system given its index
 * @param rifs The iterated function system
 * @param if_idx The iterated function index in the system
 * @return -1 if error else 0
 * @note Update sizes but do not calls realloc
 */
int rpn_ifs_del_if(rpn_ifs_t *rifs, size_t if_idx);

/**@brief Call IFS n times
 * @note Make n random choices and call corresponding IF
 * @param rifs The iterated function system
 * @param n consecutive IFS calls
 * @param seed prepopulated array of random bytes (if NULL one is generated)
 * @return -1 if error else 0
 */
int rpn_ifs_run(rpn_ifs_t *rifs, size_t n, unsigned char *rnd);

/**@brief Updates the @ref rpn_ifs_s.if_proba array using
 * @ref rpn_ifs_s.if_proba values
 * @param rifs The iterated function system
 * @return -1 if error else 0
 */
int rpn_ifs_weight_update(rpn_ifs_t *rifs);

/**@brief Returns an array of pointer on all RPN expressions contained in the
 * system, allowing to recompile/update them
 * @param rifs The IF system
 * @returns An array of pointer on @ref rpn_expr_s
 */
rpn_expr_t **rpn_ifs_flat_rpn(rpn_ifs_t *rifs);

/**@brief Randomly choose an IF and make a step updating ifs current posisition
 * @param rifs The IF system
 * @param seed A random byte
 * @return -1 on error else 0
 */
int rpn_ifs_step(rpn_ifs_t *rifs, unsigned char rnd);

#endif