spaceship/world/Asteroid.gd

extends Area2D

const COMBAT_TARGET = preload("res://core/CombatTarget.gd")

# A drifting rock that can be shot apart for the ore inside it.
#
# Asteroids used to be pure hazard: they could only ever cost you a ship. Now
# they are also the one resource you can reach without conquering anything,
# which is what the fleet's guns are for out in open space.
#
# Two ways to destroy one, and they are deliberately NOT the same:
#   - shot apart, which yields the ore
#   - flown into, which does not. The rock shatters against a hull instead of
#     being mined, and you have just lost a ship (or a shield charge) for it.
#     Without that split, a shield vessel could farm asteroids by ramming.

const ROCK_SCENE: PackedScene = preload("res://surface/Rock.tscn")
# Shots needed to crack one open. Low enough that a single vessel clears one
# in a couple of bursts, high enough that a stray shot in passing does not.
const HIT_POINTS: int = 2
# How long the dropped ore survives if nobody comes for it. Surface rocks live
# forever because a planet surface is bounded and hand-authored; open space is
# not, and an asteroid field shot up and left behind would otherwise leak
# nodes for the rest of the session.
const DROP_LIFETIME: float = 60.0

var velocity: Vector2 = Vector2.ZERO
var rotation_speed: float = 0.0
var hp: int = HIT_POINTS

var shape_points: PackedVector2Array = PackedVector2Array()


func _ready() -> void:
	randomize()
	add_to_group("asteroids")
	COMBAT_TARGET.register(self, COMBAT_TARGET.RESOURCE_PRIORITY)
	area_entered.connect(_on_area_entered)

	var point_count: int = 7
	for i in range(point_count):
		var angle: float = (float(i) / point_count) * TAU
		var radius: float = randf_range(14.0, 22.0)
		shape_points.append(Vector2(cos(angle), sin(angle)) * radius)
	queue_redraw()


func _process(delta: float) -> void:
	# Deliberately no queue_redraw() here. position and rotation are node
	# TRANSFORM properties - Godot applies them when rendering, and the
	# polygon built in _ready() is in local space, so it never changes.
	# Redrawing each frame re-tessellated four antialiased polylines per
	# asteroid for an identical result; with ~150 asteroids on screen that
	# was the single largest source of stutter.
	position += velocity * delta
	rotation += rotation_speed * delta


# Same contract as Enemy.take_damage, so every weapon that already knows how
# to hurt an enemy can hurt an asteroid without learning a second protocol.
func take_damage(amount: int) -> bool:
	hp -= maxi(amount, 1)
	if hp > 0:
		return false
	shatter(true)
	return true


func shatter(drop_ore: bool) -> void:
	AsteroidExplosionVFX.spawn(get_tree().root, position)
	if drop_ore:
		_drop_ore()
	queue_free()


func _drop_ore() -> void:
	var rock: Node2D = ROCK_SCENE.instantiate()
	rock.build_shape(randi())
	rock.position = position
	rock.lifetime = DROP_LIFETIME
	# Inherits the asteroid's drift, so the ore carries on along the path the
	# rock it came from was already travelling instead of stopping dead in
	# space - which reads as debris rather than as a spawned pickup.
	rock.velocity = velocity
	# Deferred: this runs from inside an area_entered signal, where the
	# physics server is mid-flush and refuses a direct add_child.
	get_parent().add_child.call_deferred(rock)


func _on_area_entered(area: Area2D) -> void:
	if area.is_in_group("player_ships"):
		# No ore: see the note at the top of this file.
		shatter(false)


func _draw() -> void:
	NeonDraw.draw_glowing_polygon(self, shape_points, Color(0.65, 0.5, 0.35), 1.0)