spaceship/surface/RockField.gd

extends Node2D

# Scatters gatherable rocks across a planet's surface around the fleet, and
# tops them back up as they are collected, so there is always something to
# mine wherever the player flies.
#
# Unlike AsteroidField/PlanetField this is deliberately NOT deterministic
# per chunk: rocks are consumable, and a chunk-seeded layout would respawn
# the very same rock in the very same spot the moment the player flew back,
# making them infinite and free. Tracking every collected rock forever would
# grow without bound, so they are simply scattered at random within a ring
# around the fleet and despawned once left far behind.

@export var target_count: int = 14
@export var spawn_radius: float = 1400.0
@export var min_spawn_distance: float = 320.0
@export var despawn_radius: float = 2600.0
@export var check_interval: float = 0.5

@export var fleet_path: NodePath = NodePath("../Fleet")
@onready var fleet: Node2D = get_node(fleet_path)

var rock_scene: PackedScene = preload("res://surface/Rock.tscn")
var rocks: Array = []
var timer: float = 0.0
var rng: RandomNumberGenerator = RandomNumberGenerator.new()


func _ready() -> void:
	rng.randomize()
	# Populate immediately rather than waiting out the first interval, so
	# the surface isn't visibly empty for half a second on arrival.
	update_rocks()


func _process(delta: float) -> void:
	timer += delta
	if timer < check_interval:
		return
	timer = 0.0
	update_rocks()


func update_rocks() -> void:
	var centre: Vector2 = fleet.get_centroid()

	var surviving: Array = []
	for rock in rocks:
		if not is_instance_valid(rock):
			continue
		if rock.position.distance_to(centre) > despawn_radius:
			rock.queue_free()
			continue
		surviving.append(rock)
	rocks = surviving

	while rocks.size() < target_count:
		_spawn_rock(centre)


func _spawn_rock(centre: Vector2) -> void:
	# Ring, not disc: spawning right on top of the fleet would hand the
	# player free rocks without flying anywhere.
	var angle: float = rng.randf() * TAU
	var distance: float = rng.randf_range(min_spawn_distance, spawn_radius)
	var rock: Area2D = rock_scene.instantiate()
	rock.position = centre + Vector2(cos(angle), sin(angle)) * distance
	rock.build_shape(rng.randi())
	# Keep pickups under this field so its visibility and lifecycle really
	# own them. Deferred is still required because this can run from _ready().
	add_child.call_deferred(rock)
	rocks.append(rock)