PO Box detection → hide Express, show only Standard

{% liquid
  # If the destination looks like a PO Box, DO NOT offer Express—only Standard.

  # --- editable settings ---
  assign currency = "USD"

  # Standard
  assign std_service_name = "Standard Shipping"
  assign std_service_code = "STANDARD"
  assign std_description = "Ground service"
  assign std_price = 899                        # cents

  # Express
  assign exp_service_name = "Express Shipping"
  assign exp_service_code = "EXPRESS"
  assign exp_description = "2-day service"
  assign exp_price = 1999                       # cents

  # --- logic ---
  assign addr1 = shopify_rate_check.destination.address1 | downcase
  assign is_po_box = false
  if addr1 contains "po box" or addr1 contains "p.o. box" or addr1 contains "p o box" or addr1 contains "po-box"
    assign is_po_box = true
  endif

  # Always offer Standard
  assign rate = rate | merge: "currency", currency
  assign rate = rate | merge: "service_name", std_service_name
  assign rate = rate | merge: "service_code", std_service_code
  assign rate = rate | merge: "total_price", std_price
  assign rate = rate | merge: "description", std_description
  assign rates = rates | array_append: rate

  # Offer Express only if NOT a PO Box
  unless is_po_box
    assign rate = nil
    assign rate = rate | merge: "currency", currency
    assign rate = rate | merge: "service_name", exp_service_name
    assign rate = rate | merge: "service_code", exp_service_code
    assign rate = rate | merge: "total_price", exp_price
    assign rate = rate | merge: "description", exp_description
    assign rates = rates | array_append: rate
  endunless
%}
{
  "rates": {{ rates | array_wrap | json }}
}