/*
Copyright (c) 1998-2019, Enno Rehling <enno@eressea.de>
Katja Zedel <katze@felidae.kn-bremen.de
Christian Schlittchen <corwin@amber.kn-bremen.de>

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
**/

#include <platform.h>
#include "rand.h"
#include "mtrand.h"
#include "rng.h"

#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <float.h>
#include <ctype.h>

/* do not use M_PI, use one of these instead: */
#define PI_F 3.1415926535897932384626433832795F
#define PI_D 3.1415926535897932384626433832795
#define PI_L 3.1415926535897932384626433832795L

int lovar(double xpct_x2)
{
    int n = (int)(xpct_x2 * 500) + 1;
    if (n == 0)
        return 0;
    return (rng_int() % n + rng_int() % n) / 1000;
}

/* gaussian distribution
 * taken from http://c-faq.com/lib/gaussian.html
 */

double normalvariate(double mu, double sigma)
{
    static double U, V;
    static int phase = 0;
    double Z;

    if (phase == 0) {
        U = (rng_int() + 1.) / (RNG_RAND_MAX + 2.);
        V = rng_int() / (RNG_RAND_MAX + 1.);
        Z = sqrt(-2 * log(U)) * sin(2 * PI_D * V);
    }
    else {
        Z = sqrt(-2 * log(U)) * cos(2 * PI_D * V);
    }
    phase = 1 - phase;

    return mu + Z *sigma;
}

int ntimespprob(int n, double p, double mod)
{
    int count = 0;
    int i;

    for (i = 0; i < n && p > 0; i++) {
        if (rng_double() < p) {
            count++;
            p += mod;
        }
    }
    return count;
}

bool chance(double x)
{
    if (x >= 1.0)
        return true;
    return (1-rng_double()) < x;
}

typedef struct random_source {
    double (*double_source) (void);
} random_source;

random_source *r_source = 0;

double rng_injectable_double(void) {
    if (r_source)
        return r_source->double_source();
    return genrand_real2();
}

static double constant_value;

static double constant_source (void) {
    return constant_value;
}

struct random_source constant_provider = {
    constant_source
};

void random_source_inject_constant(double value) {
    constant_value = value;
    r_source = &constant_provider;
}

static double *values;
static int value_size;
static int value_index;

static double array_source (void) {
    assert(value_index<value_size);
    return values[value_index++];
}

struct random_source array_provider = {
    array_source
};

void random_source_inject_array(double inject[], int size) {
    int i;
    assert(size > 0);
    value_size = size;
    if (values)
        free(values);
    values = malloc(sizeof(double) * size);
    if (!values) abort();
    for (i=0; i < size; ++i) {
        values[i] = inject[i];
    }
    value_index = 0;
    r_source = &array_provider;
}

void random_source_reset(void) {
    if (values)
        free(values);
    values = NULL;
    r_source = NULL;
}