extends Node
## Save/load skeleton — version field, file IO, save-between-ticks contract.
##
## Saves only happen between sim ticks (Sim owns the loop). JobRunner mid-toil
## state must round-trip from day one — see docs/architecture.md.
##
## Phase 0: file-IO smoke test only. Phase 3 expands to real entity state.
## Phase 16 closes coverage of every system.

const SAVE_VERSION: int = 1
const SAVE_PATH: String = "user://save_slot.json"


func write_save() -> bool:
	# Smoke-test payload. Phase 3 expands this.
	var payload := {
		"version": SAVE_VERSION,
		"sim_tick": Sim.tick,
		"game_state": GameState.save_dict(),
	}
	var f := FileAccess.open(SAVE_PATH, FileAccess.WRITE)
	if f == null:
		push_error("SaveSystem.write_save: cannot open %s" % SAVE_PATH)
		return false
	f.store_string(JSON.stringify(payload))
	return true


func read_save() -> Dictionary:
	if not FileAccess.file_exists(SAVE_PATH):
		return {}
	var f := FileAccess.open(SAVE_PATH, FileAccess.READ)
	if f == null:
		return {}
	var raw := f.get_as_text()
	var parsed: Variant = JSON.parse_string(raw)
	if typeof(parsed) != TYPE_DICTIONARY:
		push_error("SaveSystem.read_save: corrupt save")
		return {}
	if int(parsed.get("version", 0)) != SAVE_VERSION:
		push_warning(
			"SaveSystem.read_save: version mismatch (%s vs %s)" %
			[parsed.get("version", "?"), SAVE_VERSION]
		)
	return parsed