class_name Ball
extends RigidBody3D

# Physics ball. Floor gravity is untouched (gravity_scale in ball.tscn); this
# only adds the wall/ceiling "surface pull" (see ArenaBoundary.get_surface_pull)
# so the ball can cling near a wall for dribbling or hang against the ceiling
# for ceiling shots, plus a safety speed clamp (the ball previously had none).

@export_group("Surface Pull")
@export var wall_pull_strength = 4.0     # Weaker than the ship's — assist, not adherence
@export var wall_pull_range = 2.0
@export var ceiling_pull_strength = 5.5  # Stays below the ball's effective gravity (0.8 * 9.8)
@export var ceiling_pull_range = 2.0

# Kept close to ship_observations.gd's BALL_SPEED_SCALE (30.0) so this feature
# doesn't push ball velocity further out of the range trained policies expect.
const MAX_SPEED := 32.0

var _boundary: ArenaBoundary
var _trail: GPUParticles3D


func _ready() -> void:
	_boundary = get_tree().get_first_node_in_group("arena_boundary")
	if DisplayServer.get_name() == "headless":
		# _integrate_forces remains active; only the render-side trail updater is
		# disabled across the many parallel RL environments.
		set_physics_process(false)
	else:
		_build_trail()


func _physics_process(_delta: float) -> void:
	if _trail:
		var speed_ratio := clampf(linear_velocity.length() / MAX_SPEED, 0.0, 1.0)
		_trail.emitting = speed_ratio > 0.12
		_trail.amount_ratio = smoothstep(0.12, 1.0, speed_ratio)


func _build_trail() -> void:
	var mat := StandardMaterial3D.new()
	mat.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
	mat.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
	mat.billboard_mode = BaseMaterial3D.BILLBOARD_ENABLED
	mat.albedo_color = Color(0.55, 0.85, 1.0, 0.42)
	mat.emission_enabled = true
	mat.emission = Color(0.35, 0.72, 1.0)
	mat.emission_energy_multiplier = 1.8
	var quad := QuadMesh.new()
	quad.size = Vector2(0.22, 0.22)
	quad.material = mat
	var process := ParticleProcessMaterial.new()
	process.emission_shape = ParticleProcessMaterial.EMISSION_SHAPE_SPHERE
	process.emission_sphere_radius = 0.35
	process.gravity = Vector3.ZERO
	process.scale_min = 0.35
	process.scale_max = 1.0
	_trail = GPUParticles3D.new()
	_trail.name = "BallTrail"
	_trail.amount = 48
	_trail.lifetime = 0.48
	_trail.local_coords = false
	_trail.process_material = process
	_trail.draw_pass_1 = quad
	_trail.visibility_aabb = AABB(Vector3(-18, -18, -18), Vector3(36, 36, 36))
	_trail.emitting = false
	add_child(_trail)


func _integrate_forces(state: PhysicsDirectBodyState3D) -> void:
	if _boundary:
		var pull := _boundary.get_surface_pull(
			global_position, wall_pull_strength, wall_pull_range,
			ceiling_pull_strength, ceiling_pull_range
		)
		state.apply_central_force(pull * mass)

	if state.linear_velocity.length() > MAX_SPEED:
		state.linear_velocity = state.linear_velocity.normalized() * MAX_SPEED