spaceship/Ship.gd

extends Area2D

signal destroyed

# Deliberately faster than Fleet.cruise_speed: the fleet as a whole travels
# at the cruise rate, and this headroom is what lets an individual ship
# close on its formation slot - so a pivot mid-flight resolves quickly
# instead of the ship having no speed budget left over for it.
@export var max_speed: float = 460.0
@export var acceleration: float = 450.0
@export var rotation_speed: float = 8.0
@export var arrive_radius: float = 6.0

@export var fire_range: float = 320.0
@export var fire_cooldown: float = 0.5
# How long to wait before looking for targets again after finding none.
@export var idle_rescan_interval: float = 0.25
@export var projectile_damage: int = 1

# Which kind of vessel this is (GameState.VESSEL_*). Drives both its
# researched statistics and whether it carries a shield (#5).
@export var vessel_type: String = "interceptor"

# --- shield (#5) ----------------------------------------------------------
const SHIELD_COLOR: Color = Color(0.45, 0.8, 1.0)
const SHIELD_RADIUS: float = 30.0

# A shield vessel survives a hit that would destroy any other ship, and is
# then defenceless until it cycles back up. Personal, not a bubble: it
# protects the vessel carrying it and nothing else.
var shield_charges: int = 0
var shield_recharge_left: float = 0.0
var _shield_ring: Node2D = null

# Neon colours, assigned by Fleet on spawn so a scene can tint its fleet.
# The lunar surface is a bright grey, where the default near-white core all
# but vanishes - PlanetSurface.tscn passes a dark core there. See NeonDraw.
var glow_color: Color = Color(0.25, 0.85, 1.0)
var core_color: Color = Color(1.0, 1.0, 1.0)

var velocity: Vector2 = Vector2.ZERO
# The fleet's own velocity, supplied by Fleet as CONTEXT rather than as a
# facing command - the ship works out where to point from it.
#
# It is needed because `velocity` below is not the ship's true motion while
# it is holding formation: the slot it chases sits inside arrive_radius, so
# the ship snaps onto it and reports zero velocity even though it is being
# carried along at cruise speed. Facing derived from `velocity` alone
# therefore froze at whatever heading the ship last happened to travel.
# Adding the two gives the ship's ACTUAL motion through the world, which is
# the honest thing to point along in every case: it equals the fleet's
# heading when station-keeping, the ship's own heading when manoeuvring
# alone, and the true blend of both while strafing into a new slot.
var fleet_velocity: Vector2 = Vector2.ZERO
var move_target: Vector2
var fire_timer: float = 0.0
var projectile_scene: PackedScene = preload("res://Projectile.tscn")


func _ready() -> void:
	move_target = position
	add_to_group("player_ships")
	area_entered.connect(_on_area_entered)
	if vessel_type == GameState.VESSEL_SHIELD:
		_build_shield_ring()
		shield_charges = GameState.shield_max_charges()
	apply_vessel_stats()
	queue_redraw()


func set_move_target(world_pos: Vector2) -> void:
	move_target = world_pos


func apply_vessel_stats() -> void:
	# Read from GameState rather than baked in at spawn, so researching an
	# upgrade improves the ships already flying and not just the next one
	# built. Fleet calls this on every vessel when something is bought.
	max_speed = GameState.ship_max_speed(vessel_type)
	acceleration = GameState.ship_acceleration(vessel_type)
	fire_range = GameState.ship_fire_range(vessel_type)
	fire_cooldown = GameState.ship_fire_cooldown(vessel_type)
	projectile_damage = GameState.ship_damage(vessel_type)
	if vessel_type == GameState.VESSEL_SHIELD:
		# Topping up a live shield with researched capacity, without
		# refilling one that is currently down and cycling.
		var was_up: bool = shield_charges > 0
		shield_charges = GameState.shield_max_charges() if was_up else shield_charges
	_update_shield_visual()


func has_shield() -> bool:
	return vessel_type == GameState.VESSEL_SHIELD and shield_charges > 0


func _update_shield_visual() -> void:
	if _shield_ring == null:
		return
	# visible only - per #10 the ring is rasterised once and never redrawn to
	# turn it on and off.
	_shield_ring.visible = has_shield()


func _tick_shield(delta: float) -> void:
	if vessel_type != GameState.VESSEL_SHIELD:
		return
	if shield_charges >= GameState.shield_max_charges():
		return
	shield_recharge_left -= delta
	if shield_recharge_left <= 0.0:
		shield_charges += 1
		shield_recharge_left = GameState.shield_recharge_time()
		_update_shield_visual()


func _physics_process(delta: float) -> void:
	_tick_shield(delta)
	var to_target: Vector2 = move_target - position
	var distance: float = to_target.length()

	if distance <= arrive_radius:
		# Snap and stop dead - prevents residual float-level jitter that
		# would otherwise keep nudging back and forth around the target.
		position = move_target
		velocity = Vector2.ZERO
	else:
		# Braking-distance formula: the fastest speed we can be going right
		# now and still be able to decelerate to 0 exactly at the target,
		# given our acceleration. Without this the ship approaches at full
		# speed, overshoots (stopping distance = max_speed^2 / (2*accel)),
		# and oscillates back and forth forever instead of settling.
		var braking_speed: float = sqrt(2.0 * acceleration * distance)
		var desired_speed: float = min(max_speed, braking_speed)
		var desired_velocity: Vector2 = to_target.normalized() * desired_speed
		velocity = velocity.move_toward(desired_velocity, acceleration * delta)
		position += velocity * delta

	# One owner, one rule: face the way this ship is actually travelling.
	var motion: Vector2 = velocity + fleet_velocity
	if motion.length() > 8.0:
		var target_angle: float = motion.angle() + PI / 2.0
		rotation = lerp_angle(rotation, target_angle, rotation_speed * delta)

	_update_weapon(delta)


func _update_weapon(delta: float) -> void:
	fire_timer -= delta
	if fire_timer > 0.0:
		return

	var target: Node2D = _find_nearest_enemy()
	if target == null:
		# Back off before scanning again. Without this, fire_timer stays at
		# or below zero and every ship queries the whole "enemies" group and
		# loops it on EVERY physics frame whenever nothing is in range -
		# which is most of the time.
		fire_timer = idle_rescan_interval
		return

	fire_timer = fire_cooldown
	var proj: Node2D = projectile_scene.instantiate()
	proj.position = position
	proj.damage = projectile_damage
	get_tree().root.add_child(proj)
	proj.launch(target.position - position)


func _find_nearest_enemy() -> Node2D:
	var enemies: Array = get_tree().get_nodes_in_group("enemies")
	var nearest: Node2D = null
	var best_dist: float = fire_range

	for e in enemies:
		if not is_instance_valid(e):
			continue
		var d: float = position.distance_to(e.position)
		if d <= best_dist:
			best_dist = d
			nearest = e

	return nearest


func _on_area_entered(area: Area2D) -> void:
	if not (area.is_in_group("enemies") or area.is_in_group("asteroids")):
		return
	if has_shield():
		# Absorbed. The thing that hit it is still destroyed - a shield stops
		# the vessel dying, it does not make the rock harmless - but the
		# vessel survives and is defenceless until the shield cycles back.
		shield_charges -= 1
		shield_recharge_left = GameState.shield_recharge_time()
		_update_shield_visual()
		if area.is_in_group("asteroids") and is_instance_valid(area):
			area.queue_free()
		return
	ShipExplosionVFX.spawn(get_tree().root, position)
	destroyed.emit()
	queue_free()


func _build_shield_ring() -> void:
	# Its own child, drawn once, toggled with `visible` (#10). A shield that
	# came and went by redrawing the ship would re-tessellate the hull every
	# time it cycled.
	_shield_ring = NeonPiece.create(self, Vector2.ZERO, SHIELD_COLOR)
	var points: PackedVector2Array = PackedVector2Array()
	for i in range(14):
		var a: float = (float(i) / 14.0) * TAU
		points.append(Vector2(cos(a), sin(a)) * SHIELD_RADIUS)
	_shield_ring.add_polygon(points, 0.7)
	_shield_ring.queue_redraw()
	_shield_ring.visible = false


func _draw() -> void:
	var nose: Vector2 = Vector2(0, -22)
	var left: Vector2 = Vector2(-14, 16)
	var right: Vector2 = Vector2(14, 16)
	var points: PackedVector2Array = PackedVector2Array([nose, left, right])
	# Constant glow, drawn once. No pulse means nothing changes frame to
	# frame, so the ship never needs redrawing after _ready() - which also
	# removes four antialiased polyline rebuilds per ship per frame.
	NeonDraw.draw_glowing_polygon(self, points, glow_color, 1.0, core_color)