/*
 * Copyright ©️ 2024 Mario Forzanini <mf@marioforzanini.com>
 *
 * This file is part of my exercises for LSN.
 *
 * My exercises for LSN are free software: you can redistribute them
 * and/or modify them under the terms of the GNU General Public License
 * as published by the Free Software Foundation, either version 3 of
 * the License, or (at your option) any later version.
 *
 * My exercises for LSN are distributed in the hope that they 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 my exercises for LSN. If not, see
 * <https://www.gnu.org/licenses/>.
 *
 */

#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "random.h"
#include "std.h"

#define NREALIZATIONS 10000
#define LAMBDA 1.0
#define MEAN 0.0
#define GAMMA 1.0
#define STANDARD_NAME "STANDARD"
#define EXP_NAME "EXPONENTIAL"
#define LORENTZ_NAME "LORENTZ"

enum method {
	METHOD_UNKNOWN,
	METHOD_STD,
	METHOD_EXP,
	METHOD_LORENTZ,
};

void
usage(char *argv0)
{
	fprintf(stderr,
	        "USAGE: %s METHOD N\n"
	        "\tMETHOD is one of " STANDARD_NAME ", " EXP_NAME
	        ", " LORENTZ_NAME "\n",
	        argv0);
	exit(1);
}

int
main(int argc, char *argv[])
{
	enum method method = METHOD_UNKNOWN;
	long N = -1;
	FILE *primes, *input;
	Random rnd = { 0 };
	if (!(primes = fopen("Primes", "r"))) {
		STD_ERROR("Error opening Primes: %s\n", strerror(errno));
		return 1;
	} else if (!(input = fopen("seed.in", "r"))) {
		STD_ERROR("Error opening seed.in: %s\n", strerror(errno));
		return 1;
	}
	if (!random_init(&rnd, primes, input)) {
		return 1;
	}
	if (argc < 3) {
		usage(argv[0]);
	} else {
		char *endptr = NULL;
		if (strcmp(argv[1], STANDARD_NAME) == 0) {
			method = METHOD_STD;
		} else if (strcmp(argv[1], EXP_NAME) == 0) {
			method = METHOD_EXP;
		} else if (strcmp(argv[1], LORENTZ_NAME) == 0) {
			method = METHOD_LORENTZ;
		} else {
			usage(argv[0]);
		}
		N = strtol(argv[2], &endptr, 10);
		if (N <= 0) {
			if (errno != 0) {
				STD_ERROR("Errors parsing N: %s\n",
				        strerror(errno));
			} else if (argv[2] == endptr) {
				STD_ERROR("Errors parsing N: Expected a "
				          "number, got %s\n",
				        argv[2]);
			} else {
				STD_ERROR("N must be a positive number%s",
				        "\n");
			}
			usage(argv[0]);
		}
	}
	double sum = 0.0;
	switch (method) {
	case METHOD_STD: {
		for (int i = 0; i < NREALIZATIONS; i++) {
			for (int n = 0; n < N; n++) {
				sum += random_rannyu(&rnd);
			}
			printf("%lf\n", sum / (double)N);
			sum = 0.0;
		}
	} break;
	case METHOD_EXP: {
		for (int i = 0; i < NREALIZATIONS; i++) {
			for (int n = 0; n < N; n++) {
				sum += random_exp(&rnd, LAMBDA);
			}
			printf("%lf\n", sum / (double)N);
			sum = 0.0;
		}
	} break;
	case METHOD_LORENTZ: {
		for (int i = 0; i < NREALIZATIONS; i++) {
			for (int n = 0; n < N; n++) {
				sum += random_lorentz(&rnd, MEAN, GAMMA);
			}
			printf("%lf\n", sum / (double)N);
			sum = 0.0;
		}
	} break;
	default:
		__builtin_unreachable();
	}
	random_save_seed(&rnd, "seed.out");
	return 0;
}