Minor improvements

core/generator/currency_generator.gd

@@ -154,8 +154,12 @@ func can_buy(amount: int = 1) -> bool:
 	if not is_available_to_player():
 		return false
 
+	var purchase_currency_id: StringName = get_purchase_currency_id()
+	if purchase_currency_id == &"":
+		return false
+
 	var cost: BigNumber = get_cost_for_amount(amount)
-	var current: BigNumber = _get_currency_amount()
+	var current: BigNumber = _get_currency_amount_by_id(purchase_currency_id)
 	return current.is_greater_than(cost) or current.is_equal_to(cost)
 
 ## Attempts to buy `amount` units and emits purchase success/failure signals.
@@ -164,11 +168,14 @@ func buy(amount: int = 1) -> bool:
 		return false
 	if not is_available_to_player():
 		return false
+	var purchase_currency_id: StringName = get_purchase_currency_id()
+	if purchase_currency_id == &"":
+		return false
 
 	var safe_amount: int = maxi(amount, 1)
 	var total_cost: BigNumber = get_cost_for_amount(safe_amount)
-	if not _spend_currency(total_cost):
-		purchase_failed.emit(safe_amount, total_cost, _get_currency_amount())
+	if not _spend_currency_by_id(purchase_currency_id, total_cost):
+		purchase_failed.emit(safe_amount, total_cost, _get_currency_amount_by_id(purchase_currency_id))
 		return false
 
 	owned += safe_amount
@@ -182,8 +189,11 @@ func buy_max() -> int:
 		return 0
 	if not is_available_to_player():
 		return 0
+	var purchase_currency_id: StringName = get_purchase_currency_id()
+	if purchase_currency_id == &"":
+		return 0
 
-	var available_currency: float = _big_number_to_float(_get_currency_amount())
+	var available_currency: float = _big_number_to_float(_get_currency_amount_by_id(purchase_currency_id))
 	var estimated_max: int = data.max_affordable(owned, available_currency)
 	if estimated_max <= 0:
 		return 0
@@ -368,6 +378,13 @@ func get_generator_id() -> StringName:
 func get_currency_id() -> StringName:
 	return GameState.get_currency_id(currency)
 
+func get_purchase_currency_id() -> StringName:
+	var purchase_currency: Currency = _resolve_purchase_currency()
+	if purchase_currency == null:
+		return &""
+
+	return GameState.get_currency_id(purchase_currency)
+
 ## True when the generator is both unlocked and available.
 func is_available_to_player() -> bool:
 	return is_unlocked and is_available
@@ -406,6 +423,12 @@ func _get_currency_amount() -> BigNumber:
 		return BigNumber.from_float(0.0)
 	return GameState.get_currency_amount(currency)
 
+func _get_currency_amount_by_id(currency_id: StringName) -> BigNumber:
+	if currency_id == &"":
+		return BigNumber.from_float(0.0)
+
+	return GameState.get_currency_amount_by_id(currency_id)
+
 ## Safely converts finite float values into BigNumber costs.
 func _float_to_big_number(value: float) -> BigNumber:
 	if value <= 0.0:
@@ -439,6 +462,12 @@ func _resolve_buff_cost_currency_id(buff: GeneratorBuffData) -> StringName:
 
 	return GameState.get_currency_id(cost_currency)
 
+func _resolve_purchase_currency() -> Currency:
+	if data != null and data.purchase_currency != null:
+		return data.purchase_currency
+
+	return currency
+
 func _resolve_buff_target_currency_id(buff: GeneratorBuffData) -> StringName:
 	if buff == null:
 		return &""
@@ -501,7 +530,12 @@ func _ensure_registered() -> void:
 	if _generator_id == &"":
 		return
 
-	GameState.register_generator(_generator_id, _default_unlocked_state(), _default_available_state())
+	GameState.register_generator(
+		_generator_id,
+		_default_unlocked_state(),
+		_default_available_state(),
+		_default_owned_state()
+	)
 	_register_buffs()
 	_is_registered = true
 
@@ -580,6 +614,11 @@ func _default_available_state() -> bool:
 		return false
 	return data.starts_available
 
+func _default_owned_state() -> int:
+	if data == null:
+		return 0
+	return maxi(data.initial_owned, 0)
+
 ## Area2D callback: pointer entered generator interaction region.
 func _on_area_2d_mouse_entered() -> void:
 	_mouse_entered = true