extends SceneTree

# Headless gameplay test: run with
#   godot --headless -s res://tests/test_shot_reach.gd
# Forgejo #86: the default gun shoots faster and further. #87: the ship that
# fires throws sparks, so a shot is visibly attached to the vessel it came
# from.
#
# The interesting part is not the numbers, it is that a bolt now stops where
# the gun's range ends. It used to fly speed * lifetime - 750 units - while
# the aim guide drew fire_range, 320. The guide was a promise the shot did not
# keep, in the direction that matters: shots landed on things well past the
# line saying where they would stop.
#
# Covers:
#   A. a bolt's travel distance IS the gun's range, whatever either is set to
#   B. the aim guide draws that same range, so the line and the shot agree
#   C. firing throws sparks from the firing ship, and they clear themselves up

const PICKUP_TOLERANCE: float = 60.0

var game_state: Node
var main: Node
var fleet: Node
var controller: Node
var weapon: Node
var shooter: Node2D
var stage: int = 0
var elapsed: float = 0.0
var bolt: Node2D
var launch_point: Vector2 = Vector2.ZERO
var furthest: float = 0.0


func _initialize() -> void:
	game_state = root.get_node("GameState")
	game_state.buildings.clear()
	game_state.extractors.clear()
	game_state.reset_progression()
	main = load("res://world/Main.tscn").instantiate()
	root.add_child(main)
	current_scene = main
	fleet = main.get_node("Fleet")
	controller = main.get_node("FireStickController")


func _sparks() -> Array:
	var found: Array = []
	for node in root.get_children():
		if node.get_script() != null and String(node.get_script().resource_path).ends_with("MuzzleSparkVFX.gd"):
			found.append(node)
	return found


func _process(delta: float) -> bool:
	elapsed += delta
	match stage:
		0:
			if elapsed < 0.3:
				return false
			main.get_node("EnemySpawner").set_process(false)
			main.get_node("AsteroidField").set_process(false)
			for hazard in get_nodes_in_group("asteroids") + get_nodes_in_group("enemies") \
					+ get_nodes_in_group("player_projectiles"):
				if is_instance_valid(hazard):
					hazard.free()
			fleet.spawn_ships(1, Vector2.ZERO, PackedStringArray([GameState.VESSEL_INTERCEPTOR]))
			shooter = fleet.ships[0]
			weapon = shooter.get_component("weapon")
			if weapon == null:
				return _fail("the default vessel has no weapon component")

			# --- B. the guide draws the gun's own range --------------------
			controller.aim(Vector2(1.0, 0.0))
			if not is_equal_approx(controller.guide_range(), weapon.fire_range):
				return _fail("the aim guide reaches %.0f but the gun's range is %.0f" \
					% [controller.guide_range(), weapon.fire_range])
			print("aim guide and gun range agree at %.0f" % weapon.fire_range)

			launch_point = shooter.global_position
			weapon.fire_timer = 0.0
			weapon.tick(0.0)
			var bolts: Array = get_nodes_in_group("player_projectiles")
			if bolts.is_empty():
				return _fail("the gun fired nothing")
			bolt = bolts[0]

			# --- C. sparks at the muzzle -----------------------------------
			var sparks: Array = _sparks()
			if sparks.is_empty():
				return _fail("firing threw no sparks")
			if sparks[0].global_position.distance_to(shooter.global_position) > PICKUP_TOLERANCE:
				return _fail("the sparks appeared %.0f from the ship that fired" \
					% sparks[0].global_position.distance_to(shooter.global_position))
			print("firing threw sparks at the firing ship")
			stage = 1
			elapsed = 0.0
			return false
		1:
			# --- A. the bolt stops where the range ends --------------------
			if is_instance_valid(bolt) and not bolt.is_queued_for_deletion():
				furthest = maxf(furthest, launch_point.distance_to(bolt.global_position))
				return false
			var reach: float = weapon.fire_range
			# One physics step of slack either way: the bolt is freed on the
			# tick its age passes the limit, so it lands just short of or just
			# past the exact figure.
			var slack: float = bolt_step()
			if absf(furthest - reach) > slack:
				return _fail("the bolt travelled %.0f but the gun's range is %.0f (slack %.0f)" \
					% [furthest, reach, slack])
			print("bolt stopped at %.0f against a range of %.0f" % [furthest, reach])

			if not _sparks().is_empty():
				return _fail("%d spark burst(s) still alive long after firing" % _sparks().size())
			print("sparks cleared themselves up")

			print("TEST_SHOT_REACH: PASS")
			quit(0)
			return true
	return false


func bolt_step() -> float:
	# How far a bolt moves in a single physics tick, which is the granularity
	# its lifetime can be enforced at.
	var speed: float = 850.0
	var probe: Node2D = load("res://vessels/Projectile.tscn").instantiate()
	speed = float(probe.speed)
	probe.free()
	return speed / float(Engine.physics_ticks_per_second) * 1.5


func _fail(message: String) -> bool:
	print("TEST_SHOT_REACH: FAIL (%s)" % message)
	quit(1)
	return true