Remote-area surcharge by postal-code prefixes

{% liquid
  # Add a surcharge if the destination postal code starts with any of the configured prefixes.

  # --- editable settings ---
  assign service_name = "Remote Area Shipping"
  assign service_code = "REMOTE_AREA"
  assign currency = "USD"
  assign description = "Base + remote area surcharge if applicable"
  assign base_price = 1200                      # cents
  assign remote_surcharge = 800                 # cents
  assign postal_prefixes_raw = "99950|99951|H0H"  # pipe-separated; case-insensitive

  # --- logic ---
  assign postal = shopify_rate_check.destination.postal_code | upcase
  assign prefixes = postal_prefixes_raw | upcase | split: "|"
  assign is_remote = false

  for p in prefixes
    assign p_len = p | size
    assign test = postal | slice: 0, p_len
    if test == p and p_len > 0
      assign is_remote = true
      break
    endif
  endfor

  assign shipping_price = base_price
  if is_remote
    assign shipping_price = shipping_price | plus: remote_surcharge
  endif

  assign rate = rate | merge: "currency", currency
  assign rate = rate | merge: "service_name", service_name
  assign rate = rate | merge: "service_code", service_code
  assign rate = rate | merge: "total_price", shipping_price
  assign rate = rate | merge: "description", description

  assign rates = rates | array_append: rate
%}
{
  "rates": {{ rates | array_wrap | json }}
}