Add scenes, static scene-finding mechanism, and scene pool for visual hold/tap notes.

rhythm_game/note/visual/note_pool.gd

@@ -0,0 +1,84 @@
+class_name NotePool extends Node
+
+@export_group("Start")
+## Tap notes to spawn on [method _ready].
+@export var tap_size: int = 30
+
+## Hold notes to spawn on [method _ready].
+@export var hold_size: int = 10
+
+@export_group("Skin")
+## [StringName] of the tap note skin to use.
+@export var tap_skin: StringName = "default"
+
+## [StringName] of the hold note skin to use.
+@export var hold_skin: StringName = "default"
+
+func get_note(type: NoteVisual.TYPE) -> NoteVisual:
+	var note: NoteVisual
+	# TODO: Implement.
+	return note
+
+## Get a tap note. Instantiates one if no free nodes are available.
+func get_tap() -> TapNote:
+	var tap: TapNote = _free_taps.pop_back()
+	if tap == null:
+		tap = _instantiate_tap()
+	_used_taps[tap] = true
+	return tap
+
+## Return a tap note.
+func return_tap(tap: TapNote) -> void:
+	var parent: Node = tap.get_parent()
+	if parent:
+		parent.remove_child(tap)
+		
+	if not _used_taps.erase(tap):
+		push_warning(
+			"Returning tap note ", tap,
+			" that was not spawned by pool ", self, "."
+			)
+	_free_taps.append(tap)
+
+## Get a hold note. Instantiates one if no free nodes are available.
+func get_hold() -> HoldNote:
+	var hold: HoldNote = _free_holds.pop_back()
+	if hold == null:
+		hold = _instantiate_hold()
+	_used_holds[hold] = true
+	return hold
+
+## Return a hold note.
+func return_hold(hold: HoldNote) -> void:
+	var parent: Node = hold.get_parent()
+	if parent:
+		parent.remove_child(hold)
+		
+	if not _used_holds.erase(hold):
+		push_warning(
+			"Returning hold note ", hold,
+			" that was not spawned by pool ", self, "."
+			)
+	_free_holds.append(hold)
+
+## Spawn the given number of notes.
+func reserve(taps: int, holds: int) -> void:
+	for i: int in range(taps):
+		_free_taps.append(_instantiate_tap())
+	
+	for i: int in range(holds):
+		_free_holds.append(_instantiate_hold())
+
+
+# ========= IMPLEMENTATION ========= #
+var _free_taps: Array[TapNote]
+var _used_taps: Dictionary[TapNote, bool]
+
+var _free_holds: Array[HoldNote]
+var _used_holds: Dictionary[HoldNote, bool]
+
+func _instantiate_tap() -> TapNote:
+	return NoteScenes.get_tap(tap_skin).instantiate() as TapNote
+
+func _instantiate_hold() -> HoldNote:
+	return NoteScenes.get_tap(tap_skin).instantiate() as HoldNote