#include "board.h"
#include "checkouts.h"
#include "comp.h"
#include "match.h"

#include <math.h>
#include <stdbool.h>
#include <stdlib.h>

double horizontal_stdev = 16, vertical_stdev = 16;

#define NUM_DIFF_PRESETS (sizeof(DIFF_PRESETS) / sizeof(*DIFF_PRESETS))
static struct { int diff; double stdev; } DIFF_PRESETS[] = {
	{ 0, 66.80}, // 10
	{ 8, 40.24}, // 20
	{16, 28.14}, // 30
	{24, 21.35}, // 40
	{32, 17.20}, // 50
	{40, 14.34}, // 60
	{48, 12.15}, // 70
	{56, 10.36}, // 80
	{64,  8.83}, // 90
	{72,  7.48}, // 100
	{80,  6.32}, // 110
	{88,  5.34}, // 120
	{99,  0.00}, // 167
};

// optional function to set stdevs using precomputed 0-99 difficulty values.
// fixed-step interpolation is done between presets.
void comp_set_difficulty(int diff)
{
	if (diff < DIFF_PRESETS[0].diff)
		diff = DIFF_PRESETS[0].diff;
	else if (diff > DIFF_PRESETS[NUM_DIFF_PRESETS - 1].diff)
		diff = DIFF_PRESETS[NUM_DIFF_PRESETS - 1].diff;

	size_t ind = 1;
	while (ind < NUM_DIFF_PRESETS - 1 && DIFF_PRESETS[ind].diff <= diff)
		ind++;

	double step = (DIFF_PRESETS[ind - 1].stdev - DIFF_PRESETS[ind].stdev) /
		(DIFF_PRESETS[ind].diff - DIFF_PRESETS[ind - 1].diff);
	horizontal_stdev = vertical_stdev = DIFF_PRESETS[ind - 1].stdev -
		((diff - DIFF_PRESETS[ind - 1].diff) * step);
}

static double drand()
{
	return (double)rand() / RAND_MAX;
}

static double gauss(double mean, double stdev)
{
	static bool have_next;
	static double next;
	double curr;

	if (have_next) {
		curr = next;
	} else {
		double theta = 2 * M_PI * drand();
		double r = sqrt(-2 * log(1 - drand()));

		curr = r * cos(theta);
		next = r * sin(theta);
	}

	have_next = !have_next;
	return mean + (curr * stdev);
}

static struct ccoords gauss_offset()
{
	return (struct ccoords){ .x = gauss(0, horizontal_stdev),
		.y = gauss(0, vertical_stdev) };
}

struct pcoords throw_dart(struct pcoords target, struct ccoords *cc)
{
	struct ccoords tc = pol_to_cart(target);
	struct ccoords offset = gauss_offset();

	cc->x = tc.x + offset.x;
	cc->y = tc.y + offset.y;

	return cart_to_pol(*cc);
}

static struct segment next_dart(int rem, int darts_in_hand)
{
	char *c = NULL;
	if (rem <= NUM_CHECKOUTS)
		c = CHECKOUTS[darts_in_hand - 1][rem - 1];
	if (!c && rem <= NUM_SETUP_SHOTS)
		c = SETUP_SHOTS[rem - 1];
	if (!c)
		c = "T20";

	return segment_from_name(c);
}

void comp_visit(struct leg *l)
{
	struct visit *v = leg_visit(l);
	v->darts = calloc(3, sizeof(*v->darts));
	v->ccoords = calloc(3, sizeof(*v->ccoords));

	for (int i = 0; i < 3; ++i) {
		struct segment ts = next_dart(l->rem - v->points, 3 - i);
		struct pcoords tc = segment_centre(ts);

		struct ccoords dcart;
		struct pcoords dc = throw_dart(tc, &dcart);
		struct segment ds = segment_from_pcoords(dc);

		v->ccoords[v->n_darts] = dcart;
		v->darts[v->n_darts++] = ds;
		v->points += segment_points(ds);

		if (l->rem - v->points == 0 && segment_is_double(ds))
			break;

		if (l->rem - v->points <= 1) {
			v->points = 0;
			break;
		}
	}

	l->rem -= v->points;
	v->rem = l->rem;
}