Preserve approved pixel tower prototype as development baseline

scripts/core/simulation_snapshot.gd

@@ -0,0 +1,47 @@
+class_name SimulationSnapshot
+extends RefCounted
+
+const SCHEMA_VERSION := 1
+
+static func capture(clock: SimulationKernel, state: Node, extra := {}) -> Dictionary:
+	var snapshot := {
+		&"schema_version": SCHEMA_VERSION,
+		&"clock": clock.clock_snapshot(),
+		&"game_state": state.create_snapshot(),
+	}
+	if extra is Dictionary and not extra.is_empty():
+		snapshot[&"systems"] = extra.duplicate(true)
+	return snapshot
+
+static func validate(snapshot: Dictionary) -> Dictionary:
+	var errors: Array[String] = []
+	if int(snapshot.get(&"schema_version", -1)) != SCHEMA_VERSION:
+		errors.append("unsupported_schema_version")
+	if not snapshot.get(&"clock", null) is Dictionary:
+		errors.append("missing_clock")
+	else:
+		var clock_data: Dictionary = snapshot[&"clock"]
+		if int(clock_data.get(&"absolute_minute", -1)) < 0:
+			errors.append("invalid_absolute_minute")
+		if int(clock_data.get(&"speed", 0)) not in [1, 2, 4]:
+			errors.append("invalid_speed")
+	if not snapshot.get(&"game_state", null) is Dictionary:
+		errors.append("missing_game_state")
+	return {
+		&"ok": errors.is_empty(),
+		&"errors": errors,
+	}
+
+static func restore(snapshot: Dictionary, clock: SimulationKernel, state: Node) -> bool:
+	var validation := validate(snapshot)
+	if not validation[&"ok"]:
+		return false
+	var previous_clock := clock.clock_snapshot()
+	var previous_state: Dictionary = state.create_snapshot()
+	if not clock.restore_clock(snapshot[&"clock"]):
+		return false
+	if not state.restore_snapshot(snapshot[&"game_state"]):
+		clock.restore_clock(previous_clock)
+		state.restore_snapshot(previous_state)
+		return false
+	return true