spaceship/enemies/EnemyBigLaserBeam.gd

class_name EnemyBigLaserBeam
extends Node2D

# Self-contained charge -> fire -> flash sequence for the mothership's big
# laser (see EnemyBigLaserComponent). Lives independently of the enemy that
# fired it once launched - added to the tree root, exactly like
# ArtilleryShell/EnemyProjectile - so the mothership dying mid-charge
# doesn't cancel a shot already telegraphed to the player.
#
# The aim direction is locked once, in launch(), and never touched again:
# that is what makes the telegraph dodgeable. Nothing in _process() re-reads
# the fleet's position while charging.
#
# Damage: every ship in group "player_ships" whose perpendicular distance
# to the beam segment is within beam_half_width, AND whose projection along
# the beam falls inside [0, beam_range], takes Ship.take_damage(damage) -
# same all-or-nothing shield semantics as every other damage source in this
# game (Ship.take_damage already handles the absorb_hit check itself).

signal finished

@export var charge_time: float = 2.5
@export var beam_range: float = 1200.0
@export var beam_half_width: float = 35.0
@export var damage: int = 3
@export var color: Color = Color(0.55, 0.05, 0.85)

enum Phase { CHARGING, FLASH }
const FLASH_DURATION: float = 0.25

var phase: int = Phase.CHARGING
var origin: Vector2 = Vector2.ZERO
var aim_direction: Vector2 = Vector2.RIGHT
var charge_left: float = 0.0
var flash_time: float = 0.0


func launch(from: Vector2, toward: Vector2) -> void:
	origin = from
	aim_direction = toward.normalized() if toward.length() > 0.001 else Vector2.RIGHT
	position = origin
	rotation = aim_direction.angle()
	charge_left = charge_time
	phase = Phase.CHARGING
	queue_redraw()


func _process(delta: float) -> void:
	match phase:
		Phase.CHARGING:
			charge_left -= delta
			if charge_left <= 0.0:
				_fire()
			queue_redraw()
		Phase.FLASH:
			flash_time -= delta
			queue_redraw()
			if flash_time <= 0.0:
				finished.emit()
				queue_free()


func _fire() -> void:
	phase = Phase.FLASH
	flash_time = FLASH_DURATION
	for ship in get_tree().get_nodes_in_group("player_ships"):
		if not is_instance_valid(ship):
			continue
		var to_ship: Vector2 = ship.global_position - origin
		var along: float = to_ship.dot(aim_direction)
		if along < 0.0 or along > beam_range:
			continue
		var perpendicular: float = (to_ship - aim_direction * along).length()
		if perpendicular <= beam_half_width:
			ship.take_damage(damage)
	queue_redraw()


func _draw() -> void:
	# Drawn in local space, rotated in launch() so local +X already points
	# along the locked aim_direction - the same reason the beam segment's
	# own math is done in world space up in _fire() (global_position/origin)
	# while _draw() only ever needs the length along that local +X axis.
	match phase:
		Phase.CHARGING:
			var progress: float = clampf(1.0 - charge_left / maxf(charge_time, 0.001), 0.0, 1.0)
			var width: float = lerpf(4.0, beam_half_width * 2.0, progress)
			_draw_beam_line(width, 0.65)
			# Countdown arc at the origin, the same idiom as
			# ArtilleryShell's growing-ring-plus-arc telegraph.
			draw_arc(Vector2.ZERO, 40.0, -PI / 2.0, -PI / 2.0 + TAU * progress, 32,
				Color(color, 0.85), 8.0, true)
		Phase.FLASH:
			var fprogress: float = 1.0 - flash_time / FLASH_DURATION
			var width: float = lerpf(beam_half_width * 2.2, 6.0, fprogress)
			_draw_beam_line(width, 1.0 - fprogress * 0.3)


func _draw_beam_line(width: float, alpha: float) -> void:
	# Three-layer glow along local +X - the same soft-halo / core / bright-
	# hairline structure as ArtilleryShell._draw_ring, adapted from a ring
	# to a straight line.
	var to: Vector2 = Vector2(beam_range, 0.0)
	draw_line(Vector2.ZERO, to, Color(color, 0.16 * alpha), width * 2.6, true)
	draw_line(Vector2.ZERO, to, Color(color, 0.5 * alpha), width, true)
	draw_line(Vector2.ZERO, to, Color(1.0, 0.92, 0.98, 0.9 * alpha), width * 0.35, true)