skeleton of level system

scripts/level/level.gd

@@ -0,0 +1,7 @@
+class_name Level
+extends Node2D
+
+
+@export var title: String
+@export var id: String
+@export_range(0,1,1,"or_greater") var order: int

scripts/level/level_info.gd

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+@tool
+class_name LevelInfo
+extends Resource
+
+
+@export var title: String:
+	set(value):
+		title = value
+		resource_name = title
+@export var id: String
+@export var order: int = 0
+@export_file("*.tscn", "*.scn") var scene_path: String
+
+
+static func from_level(level: Level) -> LevelInfo:
+	var info = LevelInfo.new()
+	info.title = level.title
+	info.id = level.id
+	info.order = level.order
+	return info

scripts/level/level_set.gd

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+@tool
+class_name LevelSet
+extends Resource
+
+
+@export var title: String:
+	set(value):
+		title = value
+		resource_name = title
+@export var id: String
+@export_dir var levels_dir: String:
+	set(value):
+		levels_dir = value
+		if Engine.is_editor_hint():
+			update_levels()
+
+@export var levels: Array[LevelInfo] = []
+
+
+func has_id(id: String) -> bool:
+	for info in levels:
+		if info.id == id:
+			return true
+	return false
+
+
+func has_level(level: Level) -> bool:
+	for info in levels:
+		if info.scene_path == level.scene_file_path:
+			return true
+	return false
+
+
+func update_levels() -> void:
+	levels.clear()
+	var dir = DirAccess.open(levels_dir)
+	if dir:
+		dir.list_dir_begin()
+		var file = dir.get_next()
+		while file != "":
+			if not dir.current_is_dir() and file.ends_with(".tscn") or file.ends_with(".scn"):
+				var scene := load(levels_dir + "/" + file) as PackedScene
+				if scene and scene.can_instantiate():
+					var level = scene.instantiate()
+					if level is Level:
+						if has_id(level.id):
+							_popup_alert("Duplicate level ID: %s" % level.id)
+						else:
+							levels.append(LevelInfo.from_level(level))
+					level.free()
+			file = dir.get_next()
+	# sort levels by level order
+	levels.sort_custom(func(a, b): return a.order < b.order)
+
+
+func _popup_alert(message: String) -> void:
+	var popup = AcceptDialog.new()
+	popup.dialog_text = message
+	EditorInterface.popup_dialog_centered(popup)