extends RefCounted

## Compare actual guest/staff access queries on two isolated Runtime states.
## Reachability alone is not a relocation or in-flight transport migration.
static func inspect(before: Variant, after: Variant, facility_id: StringName) -> Dictionary:
	var result := {&"ok": false, &"errors": [], &"guest_replans": [], &"checked_routes": 0}
	var old_room: FacilityInstance = before.facility_service.get_instance(facility_id)
	var new_room: FacilityInstance = after.facility_service.get_instance(facility_id)
	if old_room == null or new_room == null:
		result[&"errors"].append(&"FACILITY_REQUIRED")
		return result
	_check(result, before.get_facility_access_report(facility_id), after.get_facility_access_report(facility_id), &"ENTRANCE_ACCESS_LOST", &"")
	for guest: GuestRuntime in before.guest_service.get_guests():
		if guest.target_facility_id != facility_id: continue
		var restored: GuestRuntime = after.guest_service.get_guest(guest.guest_id)
		if restored == null:
			result[&"errors"].append({&"code": &"GUEST_MISSING", &"id": guest.guest_id})
			continue
		var old_route: Dictionary = before._find_facility_access_path(guest.current_cell, old_room)
		var new_route: Dictionary = after._find_facility_access_path(restored.current_cell, new_room)
		_check(result, old_route, new_route, &"GUEST_ACCESS_LOST", guest.guest_id)
		if restored.state == GuestRuntime.State.MOVING and new_route[&"reachable"]:
			var target: Vector3i = after._path_handle_target(restored.path_handle, restored.current_cell)
			# A new best destination must be applied explicitly to the saved route.
			if target != new_route[&"target_cell"]:
				result[&"guest_replans"].append({&"id": guest.guest_id, &"old_target": target, &"target": new_route[&"target_cell"]})
	for worker: StaffRuntime in before.staff_service.get_staff_members():
		var assignment: Dictionary = before.staff_service.get_work_assignment(worker.staff_id)
		var rest: Dictionary = before.get_staff_rest_report(worker.staff_id)
		var resting_here := StringName(rest.get(&"facility_id", &"")) == facility_id
		if worker.assigned_facility_id != facility_id and StringName(assignment.get(&"facility_id", &"")) != facility_id and not resting_here: continue
		var restored: StaffRuntime = after.staff_service.get_staff(worker.staff_id)
		if restored == null:
			result[&"errors"].append({&"code": &"STAFF_MISSING", &"id": worker.staff_id})
			continue
		_check(result, before.staff_commute.find_facility_access_path(worker.current_cell, old_room), after.staff_commute.find_facility_access_path(restored.current_cell, new_room), &"STAFF_ACCESS_LOST", worker.staff_id)
	var access_cells := {}
	for cell: Vector3i in new_room.occupied_cells:
		for offset: Vector3i in [Vector3i.ZERO, Vector3i.LEFT, Vector3i.RIGHT]: access_cells[cell + offset] = true
	for task: StaffTask in before.staff_service.get_tasks():
		if task.is_terminal() or (task.target_entity_id != facility_id and task.rescue_facility_id != facility_id): continue
		var restored: StaffTask = after.staff_service.get_task(task.task_id)
		if restored == null or restored.create_snapshot() != task.create_snapshot():
			result[&"errors"].append({&"code": &"TASK_STATE_CHANGED", &"id": task.task_id})
			continue
		if not access_cells.has(task.target_cell):
			result[&"errors"].append({&"code": &"TASK_DESTINATION_CHANGED", &"id": task.task_id})
			continue
		if task.assigned_staff_id.is_empty(): continue
		var old_worker: StaffRuntime = before.staff_service.get_staff(task.assigned_staff_id)
		var new_worker: StaffRuntime = after.staff_service.get_staff(task.assigned_staff_id)
		if old_worker == null or new_worker == null:
			result[&"errors"].append({&"code": &"STAFF_MISSING", &"id": task.assigned_staff_id})
			continue
		_check(result, {&"reachable":_task_reachable(before, old_worker, task)}, {&"reachable":_task_reachable(after, new_worker, restored)}, &"TASK_ACCESS_LOST", task.task_id)
	result[&"ok"] = result[&"errors"].is_empty() and result[&"guest_replans"].is_empty()
	return result

static func _check(result: Dictionary, old_route: Dictionary, new_route: Dictionary, code: StringName, actor_id: StringName) -> void:
	result[&"checked_routes"] += 1
	if old_route.get(&"reachable", false) and not new_route.get(&"reachable", false):
		result[&"errors"].append({&"code": code, &"id": actor_id})

## Apply only to an isolated candidate. Validate the entire batch before changes.
## Position, movement credit, service request, wallet and transport stay intact.
static func retarget_guests(candidate: Variant, report: Dictionary) -> Dictionary:
	var result := {&"ok": false, &"errors": [], &"changed": []}
	if not report.get(&"errors", []).is_empty():
		result[&"errors"].append(&"ACCESS_LOSS")
		return result
	var updates: Array = []
	var seen := {}
	for plan: Dictionary in report.get(&"guest_replans", []):
		var id := StringName(plan.get(&"id", &""))
		var guest: GuestRuntime = candidate.guest_service.get_guest(id)
		if guest == null or seen.has(id) or guest.state != GuestRuntime.State.MOVING or not guest.path_handle is Dictionary or not plan.get(&"target") is Vector3i:
			result[&"errors"].append(&"INVALID_REPLAN")
			return result
		seen[id] = true
		if candidate._path_handle_target(guest.path_handle, guest.current_cell) != plan.get(&"old_target"):
			result[&"errors"].append(&"STALE_REPLAN")
			return result
		if not candidate.elevators.get_actor_trip(candidate._guest_path_actor_id(id)).is_empty():
			result[&"errors"].append(&"TRANSPORT_REPLAN_REQUIRED")
			return result
		if candidate.path_service.find_path(guest.current_cell, plan[&"target"]).is_empty():
			result[&"errors"].append(&"TARGET_UNREACHABLE")
			return result
		updates.append({&"guest": guest, &"target": plan[&"target"]})
	for update: Dictionary in updates:
		var guest: GuestRuntime = update[&"guest"]
		var handle: Dictionary = guest.path_handle.duplicate(true)
		handle[&"target_cell"] = update[&"target"]
		handle[&"graph_revision"] = candidate.path_service.graph_revision
		guest.path_handle = handle
		result[&"changed"].append(guest.guest_id)
	result[&"ok"] = true
	return result

static func _task_reachable(runtime: Variant, worker: StaffRuntime, task: StaffTask) -> bool:
	if task.task_type in [&"rescue_pickup", &"rescue_transport"]:
		return not runtime.path_service.find_backyard_path(worker.current_cell, task.target_cell, true).is_empty()
	return not runtime.path_service.find_path(worker.current_cell, task.target_cell, [WorldService.LAYER_FRONT, WorldService.LAYER_BACK], [&"staff"]).is_empty()