class_name ConditionalSpawnGroup extends DeferredSpawnGroup

var condition: String
var dynamic := false

@onready var _exprobj := Expression.new()

func _ready() -> void:
	super()
	_build_expr()
	_try_spawn_or_despawn()

func _physics_process(_delta: float) -> void:
	if dynamic:
		_try_spawn_or_despawn()

func _build_expr() -> void:
	if _exprobj.parse(condition) != OK:
		push_error((
			"Couldn't parse condition `%s` " +
			"for conditional spawn group %s: %s"
		) % [
			condition, self, _exprobj.get_error_text()
		])
		dissolve()

func _try_spawn_or_despawn() -> void:
	var belongs: bool = not not _exprobj.execute([], Storyboard.save_data)
	if _exprobj.has_execute_failed():
		push_error((
			"Couldn't evaluate condition `%s` " +
			"for conditional spawn group %s: %s"
		) % [
			condition, self, _exprobj.get_error_text()
		])
		queue_free()
	elif belongs: spawn()
	elif not belongs: despawn()
	if not dynamic: dissolve()