gfolf2/src/equipment/balls/physics_ball/game_ball.gd

class_name GameBall extends RigidBody3D
## Base class for all gfolf balls

## Fired as soon as this ball enters a water hazard
signal entered_water

## Types of game balls
enum Type {
	NONE,
	BASIC,
	PLASMA,
}

const TERRAIN_DAMPING_EPSILON := 1e-6
const MAGNUS_EPSILON := 1e-3
const IRON_DAMPING := 9999.0

## Angular damping while in air
@export var air_damping := 0.0
## Angular damping while in collision with rough terrain
@export var rough_damping := 8.0
## Angular damping for iron balls
@export var iron_damping := 9999.0

#@export var fluid_density := 1.225
#@export var lift_coefficient := 0.05
#@export var radius := 0.05
## Coefficient of angular velocity influence on linear velocity
## This is approximately 1/2 * rho * C_L * pi * r^2
## where `rho` is the fluid density of the medium, or 1.225 for air at sea level,
## and `C_L` is the lift coefficient which for our purposes is 0.05,
## and `r` is the radius of the ball, which is 5cm.
@export var magnus_coefficient := 0.00024

## Causes the ball to act more like a brick
@export var iron_ball := false:
	set(value):
		if value:
			physics_material_override = iron_physics
		else:
			physics_material_override = normal_physics
		iron_ball = value

## Base damage inflicted on impact with a player
@export var base_damage := 15.0

var _last_contact_normal: Vector3 = Vector3.UP
var _position_on_last_wake: Vector3
var _awake := false
var _zones: Array[BallZone] = []

@onready var normal_physics: PhysicsMaterial = preload(
	"res://src/equipment/balls/physics_ball/normal_physics.tres"
)
@onready var iron_physics: PhysicsMaterial = preload(
	"res://src/equipment/balls/physics_ball/iron_physics.tres"
)

@onready var _debug_draw: Control = %DebugDraw


## Called by a water area when this ball enters it
func enter_water() -> void:
	entered_water.emit()


func _total_terrain_angular_damping() -> float:
	return _zones.reduce(
		func(a: float, b: BallZone) -> float: return a + b.terrain_angular_damping, 0.0
	)


func _magnus_force() -> Vector3:
	return magnus_coefficient * angular_velocity.cross(linear_velocity)


func _integrate_forces(state: PhysicsDirectBodyState3D) -> void:
	if not _awake:
		# Triggered on first frame after waking
		_awake = true
		_position_on_last_wake = global_position
		_last_contact_normal = Vector3.UP
		# TODO something's fucky here... I think this gets called once after the ball sleeps

	var damping := air_damping
	if state.get_contact_count():
		constant_force = Vector3.ZERO

		# We want the contact normal which minimizes the angle to the up vector
		var min_dot := -1.0
		for i: int in range(state.get_contact_count()):
			var norm := state.get_contact_local_normal(i)
			var dot := norm.dot(Vector3.UP)
			if dot > min_dot:
				min_dot = dot
				_last_contact_normal = norm

		damping = _total_terrain_angular_damping()
		if damping <= TERRAIN_DAMPING_EPSILON:
			damping = rough_damping
	if iron_ball:
		damping = iron_damping
	angular_damp = damping


func _physics_process(_delta: float) -> void:
	# Simulate magnus effect
	var magnus := _magnus_force()
	if magnus.length_squared() > MAGNUS_EPSILON:
		apply_central_force(magnus)


func enter_zone(zone: BallZone) -> void:
	_zones.push_back(zone)

	if zone.water_hazard:
		entered_water.emit()


func exit_zone(zone: BallZone) -> void:
	_zones.erase(zone)


func get_reoriented_basis() -> Basis:
	var up := _last_contact_normal.normalized()
	var forward := (_position_on_last_wake - global_position).normalized()
	var right := up.cross(forward).normalized()
	forward = right.cross(up)  # orthonormalize
	return Basis(right, up, forward)


func _on_sleeping_state_changed() -> void:
	print("SLEEPING STATE: ", sleeping)
	if sleeping:
		# Trigger to reassign on wake
		_awake = false