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 is within beam_half_width takes Ship.take_damage(damage). The
# ordinary mothership beam remains a finite segment; bosses opt into a ray
# with no upper distance bound. Ship.take_damage handles shields itself.

signal finished

@export var charge_time: float = 2.5
@export var beam_range: float = 1200.0
@export var infinite_range: bool = false
@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
const REDRAW_INTERVAL: float = 1.0 / 30.0

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
var redraw_left: 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:
	redraw_left -= delta
	match phase:
		Phase.CHARGING:
			charge_left -= delta
			if charge_left <= 0.0:
				_fire()
			if redraw_left <= 0.0:
				redraw_left = REDRAW_INTERVAL
				queue_redraw()
		Phase.FLASH:
			flash_time -= delta
			if redraw_left <= 0.0:
				redraw_left = REDRAW_INTERVAL
				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
		if reaches_point(ship.global_position):
			ship.take_damage(damage)
	queue_redraw()


func reaches_point(world_point: Vector2) -> bool:
	var offset: Vector2 = world_point - origin
	var along: float = offset.dot(aim_direction)
	if along < 0.0 or (not infinite_range and along > beam_range):
		return false
	return (offset - aim_direction * along).length() <= beam_half_width


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 length: float = _visible_ray_length() if infinite_range else beam_range
	var to: Vector2 = Vector2(length, 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)


func _visible_ray_length() -> float:
	# Collision is mathematically unbounded, but rasterizing a 20,000-unit
	# primitive wastes fill work outside the screen. Reaching beyond the
	# furthest viewport corner looks identical and follows a moving camera.
	var viewport_world_size: Vector2 = get_viewport_rect().size
	var camera: Camera2D = get_viewport().get_camera_2d()
	if camera == null:
		return viewport_world_size.length() + 256.0
	viewport_world_size /= camera.zoom
	return origin.distance_to(camera.global_position) \
		+ viewport_world_size.length() * 0.5 + 256.0