spaceship/ArtilleryShell.gd

class_name ArtilleryShell
extends Node2D

# Self-contained telegraph -> travel -> explode sequence for the artillery
# enemy's attack (see EnemyArtilleryComponent). Lives independently of the
# enemy that fired it once launched - added to the tree root, exactly like
# EnemyProjectile/Projectile - so the shooter dying mid-flight doesn't
# cancel a shot already telegraphed to the player.
#
# Shield interaction: a shield charge absorbs this hit entirely, same
# all-or-nothing semantics as every other damage source in this game
# (VesselShieldComponent.absorb_hit) - _explode() just calls
# Ship.take_damage() like everything else and lets that logic decide.

signal finished

@export var telegraph_time: float = 1.8
@export var shell_speed: float = 180.0
@export var aoe_radius: float = 220.0
@export var damage: int = 3
@export var color: Color = Color(1.0, 0.5, 0.2)

enum Phase { TELEGRAPHING, TRAVELING, EXPLODING }

const EXPLOSION_DURATION: float = 0.8

var phase: int = Phase.TELEGRAPHING
var target: Vector2 = Vector2.ZERO
var shell_pos: Vector2 = Vector2.ZERO
var telegraph_left: float = 0.0
var explosion_time: float = 0.0
var trail: PackedVector2Array = PackedVector2Array()


func _ready() -> void:
	add_to_group("artillery_shells")


func launch(from: Vector2, at: Vector2) -> void:
	target = at
	shell_pos = from
	telegraph_left = telegraph_time
	phase = Phase.TELEGRAPHING
	position = target
	queue_redraw()


func _process(delta: float) -> void:
	match phase:
		Phase.TELEGRAPHING:
			telegraph_left -= delta
			if telegraph_left <= 0.0:
				phase = Phase.TRAVELING
				trail = PackedVector2Array([shell_pos])
			queue_redraw()
		Phase.TRAVELING:
			var to_target: Vector2 = target - shell_pos
			var step: float = shell_speed * delta
			if to_target.length() <= step:
				shell_pos = target
				_explode()
			else:
				shell_pos += to_target.normalized() * step
				trail.append(shell_pos)
				while trail.size() > 14:
					trail.remove_at(0)
			position = shell_pos
			queue_redraw()
		Phase.EXPLODING:
			explosion_time -= delta
			queue_redraw()
			if explosion_time <= 0.0:
				finished.emit()
				queue_free()


func _explode() -> void:
	phase = Phase.EXPLODING
	explosion_time = EXPLOSION_DURATION
	position = target
	for ship in get_tree().get_nodes_in_group("player_ships"):
		if is_instance_valid(ship) and ship.global_position.distance_to(target) <= aoe_radius:
			ship.take_damage(damage)


func _draw() -> void:
	match phase:
		Phase.TELEGRAPHING:
			var progress: float = clampf(1.0 - telegraph_left / maxf(telegraph_time, 0.001), 0.0, 1.0)
			# Growing ring plus a filling countdown arc: the warning reads
			# clearly without needing a number on screen.
			var radius: float = lerpf(24.0, aoe_radius, progress)
			_draw_ring(radius, 0.7)
			draw_arc(Vector2.ZERO, aoe_radius + 14.0, -PI / 2.0, -PI / 2.0 + TAU * progress, 48,
				Color(color, 0.85), 8.0, true)
		Phase.TRAVELING:
			for i in range(1, trail.size()):
				var alpha: float = float(i) / trail.size()
				draw_line(trail[i - 1] - shell_pos, trail[i] - shell_pos, Color(color, alpha * 0.6), 5.0, true)
			draw_circle(Vector2.ZERO, 14.0, Color(color, 0.35))
			NeonDraw.draw_glowing_circle(self, Vector2.ZERO, 8.0, color, 1.0)
		Phase.EXPLODING:
			var eprogress: float = 1.0 - explosion_time / EXPLOSION_DURATION
			var eradius: float = lerpf(30.0, aoe_radius, minf(eprogress * 1.5, 1.0))
			draw_circle(Vector2.ZERO, eradius, Color(color, (1.0 - eprogress) * 0.18))
			_draw_ring(eradius, 1.0 - eprogress)


func _draw_ring(radius: float, alpha: float) -> void:
	draw_arc(Vector2.ZERO, radius, 0.0, TAU, 64, Color(color, 0.16 * alpha), 16.0, true)
	draw_arc(Vector2.ZERO, radius, 0.0, TAU, 64, Color(color, 0.5 * alpha), 6.0, true)
	draw_arc(Vector2.ZERO, radius, 0.0, TAU, 64, Color(1.0, 0.92, 0.86, 0.9 * alpha), 2.0, true)