RogueLife/src/entities.h

//---
// entities: Objects that move around the map
//---

#pragma once

#include "geometry.h"

/* Entity types */
enum {
	ENTITY_AGENT,
	ENTITY_PARTICLE,
};

typedef struct {
	/* Entity type */
	uint16_t type;

	/* Coordinates of the entity's hitbox center on the map */
	fixed_t x, y;

	union {
		/* ENTITY_AGENT */
		struct {
			/* Entity's hitbox */
			shape_t hitbox;
			/* Facing */
			uint8_t facing;
		} agent;

		/* ENTITY_PARTICLE */
		struct {
			fixed_t z;
			fixed_t vx, vy, vz;
		} part;
	};

} entity_t;

/* Move an entity in the map space, assumes no collisions. */
void entity_move(entity_t *e, fixed_t dx, fixed_t dy);

/* Distance quared between two entities */
fixed_t entity_distance2(entity_t const *e1, entity_t const *e2);

/* Unit vector in the direction the agent is facing */
fpoint_t entity_facing(entity_t const *e);