spaceship/enemies/EnemySpawner.gd

extends Node2D

# The wave director (#100 / #97). Keeps its old node name on purpose: it is
# still "the thing that puts enemies in the world", and every test that
# wanted a quiet world already says
# `main.get_node("EnemySpawner").set_process(false)`. Renaming it would have
# changed 88 test files to say the same thing differently.
#
# What it no longer does is trickle. It used to spawn one enemy every 3-6
# seconds for ever, so there was no rhythm to the danger and nothing to
# prepare for. Now the CLOCK lives in GameState (which survives the trip to
# a planet surface) and this node only reacts to it: when a wave turns
# active, it puts the wave in the world; when the wave is dead, it says so
# and the quiet starts again.

@export var spawn_margin: float = 150.0
# Waves arrive as a ring around the fleet rather than from one bearing: a
# wave that all came from the left would be dodged by flying right.
@export var wave_spread: float = 0.55

@onready var fleet: Node2D = get_node("../Fleet")

var enemy_scene: PackedScene = preload("res://enemies/Enemy.tscn")
# The enemies this director launched, so "the wave is dead" is a question
# about THIS wave and not about every enemy on the map - a planet garrison
# or an enemy mothership's own spawns must not hold the next wave back.
var wave_enemies: Array = []


# Seconds between one hull of a wave landing and the next.
const ARRIVAL_INTERVAL: float = 0.45

# Hulls of the current wave that have not landed yet, with the position each
# was assigned when the wave was aimed.
var arriving: Array = []
var arrival_timer: float = 0.0


func _process(delta: float) -> void:
	wave_enemies = wave_enemies.filter(func(e): return is_instance_valid(e))
	if GameState.wave_pending:
		_launch_wave()
		return
	_land_arrivals(delta)
	# `arriving` as well as `wave_enemies`: between the first hull landing and
	# the last, the field can legitimately be empty of live enemies, and
	# clearing the wave there would end it before it had finished arriving.
	if GameState.wave_phase == GameState.WAVE_PHASE_ACTIVE \
			and wave_enemies.is_empty() and arriving.is_empty():
		GameState.wave_cleared()


# Forgejo #233: a wave used to appear entirely within one frame, as a closed
# ring around the fleet. That reads as a wall rather than as an attack, and
# it was the "arrive at the same time" half of the complaint - the other half
# being how many there were, which wave_composition now limits.
#
# The first hull still lands immediately, so a wave never feels delayed; the
# rest follow at ARRIVAL_INTERVAL. Same enemies, same bearing, same total -
# they just do not all exist at once.
func _land_arrivals(delta: float) -> void:
	if arriving.is_empty():
		return
	arrival_timer -= delta
	while arrival_timer <= 0.0 and not arriving.is_empty():
		_spawn_arrival(arriving.pop_front())
		arrival_timer += ARRIVAL_INTERVAL


func _spawn_arrival(entry: Dictionary) -> void:
	var enemy: Node2D = enemy_scene.instantiate()
	# Before add_child: Enemy._ready() resolves enemy_id into a definition.
	enemy.enemy_id = String(entry.id)
	# #113: a wave is an attack on what the player has built. It converges
	# on the nearest structure from wherever it spawned rather than
	# waiting to be flown near.
	enemy.relentless = true
	enemy.position = entry.at
	get_parent().add_child(enemy)
	wave_enemies.append(enemy)


# Public so a test can put a wave in the world without waiting out the peace.
func _launch_wave() -> void:
	if fleet == null or fleet.ships.is_empty():
		# Nothing to attack. Leave it pending rather than spending the wave
		# on an empty map - the fleet-wipe safety net rebuilds within a frame
		# and the wave arrives then.
		return
	GameState.wave_pending = false
	var composition: PackedStringArray = GameState.wave_composition(fleet.ships.size())
	var visible_rect: Rect2 = ViewUtils.get_visible_world_rect(self)
	var radius: float = visible_rect.size.length() / 2.0 + spawn_margin
	var centre: Vector2 = fleet.get_centroid()
	var bearing: float = randf() * TAU
	# Positions are settled now, while the fleet is where the wave was aimed
	# at - not as each hull lands, or a moving fleet would drag the later
	# arrivals around behind it and the ring would smear.
	arriving.clear()
	for i in range(composition.size()):
		# Spread around one bearing rather than scattered at random: a wave
		# should read as an attack arriving, not as the map filling up.
		var angle: float = bearing + randf_range(-wave_spread, wave_spread) \
			+ TAU * float(i) / float(maxi(composition.size(), 1)) * wave_spread
		arriving.append({
			"id": composition[i],
			"at": centre + Vector2(cos(angle), sin(angle)) * radius,
		})
	# The first lands at once, so a wave is never felt as late.
	if not arriving.is_empty():
		_spawn_arrival(arriving.pop_front())
	arrival_timer = ARRIVAL_INTERVAL