#ifndef PHYSICS_H
#define PHYSICS_H

#include "common.h"

typedef enum {
	PHYS_SHAPE_BOX,
	PHYS_SHAPE_SPHERE,
	PHYS_SHAPE_CAPSULE,
	PHYS_SHAPE_CYLINDER,
	PHYS_SHAPE_CONVEX_HULL,
	PHYS_SHAPE_STATIC_TRIMESH,
} PhysicsShapeTag;

typedef enum {
	PHYS_JOINT_SPHERICAL,
	PHYS_JOINT_REVOLUTE,
	PHYS_JOINT_PRISMATIC,
	PHYS_JOINT_WELD,
	PHYS_JOINT_WHEEL,
	PHYS_JOINT_DISTANCE,
} PhysicsJointTag;

typedef enum {
	PHYS_JOINT_LIMIT,
	PHYS_JOINT_SPRING,
	PHYS_JOINT_MOTOR,
} PhysicsJointFlags;

typedef enum {
	PHYS_MODE_STATIC,
	PHYS_MODE_KINEMATIC,
	PHYS_MODE_DYNAMIC,
} PhysicsMode;

typedef enum {
	PHYS_MASK_DEFAULT,
	PHYS_MASK_WORLD,
	PHYS_MASK_PROP,
	PHYS_MASK_PLAYER,
	PHYS_MASK_PARTICLE,

	PHYS_MASK_EDITOR_SELECTABLE,
	PHYS_MASK_EDITOR_RAYCAST,
} PhysicsMask;

typedef struct {
	PhysicsShapeTag tag;
	union {
		struct {
			Vec3 sz;
		} Box;

		struct {
			f32 radius;
		} Sphere;

		struct {
			f32 height, radius;
		} Capsule, Cylinder;

		struct {
			Vec3 *points;
			u32 point_cnt;
		} ConvexHull;

		struct {
			Vec3 *points;
			u32 *indices;
			u32 point_cnt, idx_cnt;
		} TriMesh;
	};

	/* local to body */
	Vec3 pos;
	Quaternion rot;

	f32 density, friction, restitution;
	Flags32 category_bits, mask_bits;
} PhysicsShape;

typedef struct {
	PhysicsShape *shapes;
	u32 shape_cnt;

	/* local to entity */
	Vec3 pos;
	Quaternion rot;

	f32 linear_damping, angular_damping;
	f32 gravity_scale;
	PhysicsMode mode;
	bool enable_sleep;
} PhysicsBody;

/*
	physics joint fields meaning changes depending on their context.

	anchor_a/axis_a are local to body_a.
	anchor_b/axis_b are local to body_b.
	axes should be normalized.

	lower/upper are generic limits
	- revolute: radians
	- prismatic: metres
	- distance: metres
	- wheel: suspension travel

	springs:
	- spring_hz: frequency of the spring response; higher = stiffer/faster
	- spring_damping: damping ratio; controls oscillation

	motors:
		revolute:
		motor_speed = angular velocity
		motor_force = maximum torque

		prismatic:
		motor_speed = linear velocity
		motor_force = maximum force

		wheel:
		motor_speed = wheel angular velocity
		motor_force = maximum drive/braking torque
*/
typedef struct {
	PhysicsJointTag tag;
	u32 body_a, body_b;
	Flags32 flags;

	Vec3 anchor_a, anchor_b;
	Vec3 axis_a, axis_b;

	f32 lower, upper;
	f32 spring_hz, spring_damping;
	f32 motor_speed, motor_force;
} PhysicsJoint;

typedef struct {
	b3BodyId id;
	b3ShapeId *shapes; // count is stored in PhysicsCmp
} PhysicsBodyRuntime;

typedef struct {
	b3WorldDef world_def;
	b3WorldId world_id;
	bool simulate;
} PhysicsInfo;

extern PhysicsInfo physics;

void 		physics_init(void);
void 		physics_exit(void);
void 		physics_update(void);

#endif