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#ifndef __BODY_H__
#define __BODY_H__
#include "color.h"
#include "list.h"
#include "vector.h"
/**
* A rigid body constrained to the plane.
* Implemented as a polygon with uniform density.
*/
typedef struct body body_t;
/**
* Allocates memory for a body with the given parameters.
* The body is initially at rest.
* Asserts that the required memory is allocated.
*
* @param shape a list of vectors describing the initial shape of the body
* @param mass the mass of the body (if INFINITY, stops the body from moving).
* For now, the mass is unused. It will be needed next week for accelerations.
* @param color the color of the body, used to draw it on the screen
* @return a pointer to the newly allocated body
*/
body_t *body_init(list_t *shape, double mass, rgb_color_t color);
/**
* Releases the memory allocated for a body.
*
* @param body a pointer to a body returned from body_init()
*/
void body_free(body_t *body);
/**
* Gets the current shape of a body.
* Returns a newly allocated vector list, which must be list_free()d.
*
* @param body a pointer to a body returned from body_init()
* @return the polygon describing the body's current position
*/
list_t *body_get_shape(body_t *body);
/**
* Gets the current center of mass of a body.
* While this could be calculated with polygon_centroid(), that becomes too slow
* when this function is called thousands of times every tick.
* Instead, the body should store its current centroid.
*
* @param body a pointer to a body returned from body_init()
* @return the body's center of mass
*/
vector_t body_get_centroid(body_t *body);
/**
* Gets the current velocity of a body.
*
* @param body a pointer to a body returned from body_init()
* @return the body's velocity vector
*/
vector_t body_get_velocity(body_t *body);
/**
* Gets the display color of a body.
*
* @param body a pointer to a body returned from body_init()
* @return the body's color, as an (R, G, B) tuple
*/
rgb_color_t body_get_color(body_t *body);
/**
* Translates a body to a new position.
* The position is specified by the position of the body's center of mass.
*
* @param body a pointer to a body returned from body_init()
* @param x the body's new centroid
*/
void body_set_centroid(body_t *body, vector_t x);
/**
* Changes a body's velocity (the time-derivative of its position).
*
* @param body a pointer to a body returned from body_init()
* @param v the body's new velocity
*/
void body_set_velocity(body_t *body, vector_t v);
/**
* Changes a body's orientation in the plane.
* The body is rotated about its center of mass.
* Note that the angle is *absolute*, not relative to the current orientation.
*
* @param body a pointer to a body returned from body_init()
* @param angle the body's new angle in radians. Positive is counterclockwise.
*/
void body_set_rotation(body_t *body, double angle);
/**
* Moves a body at its current velocity over a given time interval.
* Next week, this will take forces and impulses on the body into account.
*
* @param body the body to tick
* @param dt the number of seconds elapsed since the last tick
*/
void body_tick(body_t *body, double dt);
#endif // #ifndef __BODY_H__