#include "ctranslate.h"

#include <math.h>

// TODO remove dublicate pi definitions
#define PI 3.14159265359

void csystem_init(csystem_t *cs, vector_t *up)
{
	cs->up = up;

	// Create new coordinate system where N is up. To do this we need two more vectors for the other axises.
	// Create the 2. by setting x or y to 0
	if (up->x > up->y) {
		vector_set(&cs->ax, up->z, 0, -up->x);
	} else {
		vector_set(&cs->ax, 0, -up->z, up->y);
	}
	// Normalice
	vector_scale_inv(&cs->ax, &cs->ax, vector_len(&cs->ax));

	// Create the 3. axis by taking the cross of the other
	vector_cross(&cs->az, up, &cs->ax);
}

void csystem_calc_real(csystem_t *cs, vector_t *inside, vector_t *real)
{
	vector_set(real, inside->x * cs->ax.x + inside->y * cs->up->x + inside->z * cs->az.x,
			         inside->x * cs->ax.y + inside->y * cs->up->y + inside->z * cs->az.y,
					 inside->x * cs->ax.z + inside->y * cs->up->z + inside->z * cs->az.z);
}

void csystem_hemisphere_random(csystem_t *cs, COORD_T r1, COORD_T r2, vector_t *out)
{
	COORD_T sinTheta = sqrt(1 - r1 * r1);
	COORD_T phi = 2 * PI * r2;

	// Calculate the random direction vector
	vector_set(out, sinTheta * cos(phi), r1, sinTheta * sin(phi));
}