/*
 * Copyright (C) 2020,2023 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_mutate__h__
#define __rpn_mutate__h__
#include "config.h"

#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <sys/random.h>

#include "rpn_parse.h"

/**@file rpn_mutate.h
 * @brief Expression mutation headers
 */

/**@brief RPN expression mutation parameters */
typedef struct rpn_mutation_params_s rpn_mutation_params_t;
/**@brief Type of random values used by mutations */
typedef uint16_t rnd_t;

/**@brief maximum value for rnd_t */
extern const rnd_t rnd_t_max;

/**@brief Default values for mutations parameters */
extern rpn_mutation_params_t rpn_mutation_params_default;

/**@brief RPN expression mutation parameters */
struct rpn_mutation_params_s
{
	/**@brief Minimum expression length  */
	size_t min_len;
	/**@brief Weight of adding a token*/
	float w_add;
	/**@brief Weight of deleting a token*/
	float w_del;
	/**@brief Weight of mutating a token*/
	float w_mut;
	/**@brief Weight of mutating a token without type change*/
	float w_mut_soft;
	/**@brief Weight for each token types (op, const, var) when
	 * adding a token*/
	float w_add_elt[3];
	/**@brief Weight for each token types (op, const, var) when
	 * mutating a token*/
	float w_mut_elt[3];

	/**@brief For internal use, set by rpn_mutation_init_params
	 *
	 * weight reported by groups on rnd_t integers
	 * - [0..3] -> weights mutation
	 * - [4..6] -> w_add_elt
	 * - [7..9] -> w_mut_elt
	 *
	 * @note Weights are stored a way allowing fast random choice.
	 * They are kind of ascending threshold until @ref rnd_t max value.
	 */
	rnd_t  _weights[10];
};


/**@brief Initialize mutation parameters 
 *
 * pre-process integers threshold by group
 * @param params
 * @return 0 if no error else -1 and set ERRNO (EINVAL)
 */
int rpn_mutation_init_params(rpn_mutation_params_t *params);

/**@brief Mutate a tokenized rpn expression
 * @param toks The tokenized expression
 * @param params The mutation parameters
 * @return 0 or -1 on error */
int rpn_mutation(rpn_tokenized_t *toks, rpn_mutation_params_t *params);

/**@brief Mutate an expression by adding a token
 * @param toks The tokenized expression
 * @param params The mutation parameters
 * @return 0 or -1 on error */
int rpn_mutation_add(rpn_tokenized_t *toks, rpn_mutation_params_t *params);
/**@brief Mutate an expression by removing a token
 * @param toks The tokenized expression
 * @param params The mutation parameters
 * @return 0 or -1 on error */
int rpn_mutation_del(rpn_tokenized_t *toks, rpn_mutation_params_t *params);
/**@brief Mutate an expression by changing a token
 * @param toks The tokenized expression
 * @param params The mutation parameters
 * @return 0 or -1 on error */
int rpn_mutation_mut(rpn_tokenized_t *toks, rpn_mutation_params_t *params);
/**@brief Mutate an expression by changing a token value (not type)
 * @param toks The tokenized expression
 * @param params The mutation parameters
 * @return 0 or -1 on error */
int rpn_mutation_mut_soft(rpn_tokenized_t *toks, rpn_mutation_params_t *params);

/**@brief Change the "value" of a token randomly not it's type
 * @param tok Point on the token to mutate
 * @param toks The tokenized expression the token tok belongs to
 * @param params The mutation parameters
 * @return 0 or -1 on error */
int rpn_mutation_random_token(rpn_token_t *tok,
		rpn_tokenized_t *toks, rpn_mutation_params_t *params);


/**@brief Choose a random token type
 * @param type Point on result
 * @param weights The weight of each types for the choice
 * @note Weights comes from @ref rpn_mutation_params_s._weights and are
 * processed in a form allowing a fast random choice.
 * @return 0 or -1 on error
 */
int rpn_random_token_type(rpn_token_type_t *type, rnd_t *weights);

/**@brief Generate a random value
 * @param rand Point on result
 * @return -1 on error else 0 */
int rpn_getrandom(rnd_t *rand);

/**@brief Generate a random number between 0 and max (max excluded)
 * @param max Maximum value
 * @param res Will be set to a value between [..max[
 * @return -1 on error else 0 */
int rpn_rand_limit(size_t max, size_t *res);

/**@brief Conver an array of float weights to an array for fast random
 * choices (see @ref _rpn_random_choices() )
 * @param sz The number of items in to choose from
 * @param weights Array of size sz with items weights (positive values)
 * @param fast_weights Array of size sz pointing on result
 * @return -1 on error else 0 */
int rpnifs_fast_rnd_weights(size_t sz, const float *weights,
		rnd_t *fast_weights);

/**
 * @return A float between [-range[1] .. -range[0]] or [range[0] .. range[1]]
 */
int rpnifs_rnd_float(float range[2], float *res);

/**@brief Given a size return an random element with regards to given weights
 * @param sz The given size
 * @param weights Weights coming from @ref rpn_mutation_params_s._weights
 * @param res Points on result
 * @return 0 or -1 on error
 * @todo refactor rename without rpn prefix */
int _rpn_random_choice(size_t sz, rnd_t *weights, size_t *res);

/**@brief Given a size and a (random) value, returns an element with regards
 * to given weights 
 * @param sz The given size
 * @param weights Weights coming from @ref rpn_mutation_params_s._weights
 * @param rand A (random) value
 * @param res Points on result */
void __rpn_random_choice(size_t sz, rnd_t *weights, rnd_t rand, size_t *res);

/**@brief Debugging function that dump mutation params in a human readable format
 * @param fd The file descriptor on wich we should print parameters
 * @param params The mutation parameters to dump */
void _print_params(int fd, rpn_mutation_params_t *params);

#endif