extends SceneTree

# Headless gameplay test: run with
#   godot --headless -s res://tests/test_fleet_formation.gd
# Verifies that issuing a fleet move order makes every ship converge on its
# formation slot (offset preserved) around the ordered point AND actually
# stops there - a regression guard for the arrival-overshoot bug where ships
# oscillated back and forth around the target forever instead of settling.

const CHECKPOINT_TIME: float = 4.0
const TEST_DURATION: float = 7.0
const ARRIVE_TOLERANCE: float = 2.0
const STABLE_TOLERANCE: float = 1.0
const VELOCITY_TOLERANCE: float = 1.0

var main_scene: Node
var fleet: Node
var target: Vector2 = Vector2(600.0, 300.0)
var elapsed: float = 0.0
var started: bool = false
var checkpoint_taken: bool = false
var checkpoint_positions: Array = []


func _initialize() -> void:
	var packed: PackedScene = load("res://Main.tscn")
	main_scene = packed.instantiate()
	root.add_child(main_scene)
	fleet = main_scene.get_node("Fleet")


func _physics_process(delta: float) -> bool:
	if not started:
		# Wait one physics tick so Fleet/Ship _ready() has run and
		# formation_offsets are computed before we issue the order.
		fleet.move_to(target)
		started = true
		return false

	elapsed += delta

	if not checkpoint_taken and elapsed >= CHECKPOINT_TIME:
		checkpoint_taken = true
		for ship in fleet.ships:
			checkpoint_positions.append(ship.position)

	if elapsed >= TEST_DURATION:
		_finish()
		return true
	return false


func _finish() -> void:
	var all_ok: bool = true
	for i in range(fleet.ships.size()):
		var ship: Node = fleet.ships[i]
		var expected: Vector2 = target + fleet.formation_offsets[i]
		var dist: float = ship.position.distance_to(expected)
		var drift_since_checkpoint: float = ship.position.distance_to(checkpoint_positions[i])
		var speed: float = ship.velocity.length()

		var arrived: bool = dist <= ARRIVE_TOLERANCE
		var stable: bool = drift_since_checkpoint <= STABLE_TOLERANCE
		var stopped: bool = speed <= VELOCITY_TOLERANCE
		var ok: bool = arrived and stable and stopped
		all_ok = all_ok and ok

		print("Ship %d expected=%s actual=%s dist=%.3f drift_since_t%.0fs=%.3f speed=%.3f %s" % [
			i, expected, ship.position, dist, CHECKPOINT_TIME, drift_since_checkpoint, speed, "OK" if ok else "FAIL"
		])

	if all_ok:
		print("TEST_FLEET_FORMATION: PASS (ships arrived and settled, no oscillation)")
		quit(0)
	else:
		print("TEST_FLEET_FORMATION: FAIL")
		quit(1)