update redirects plug for custom prefixes

Path normalisation respects custom URL prefixes:
- Orders only lowercase prefix, preserving case-sensitive order numbers
- Distinguishes static shop routes from dynamic prefixed routes
- Uses R module for prefix detection

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/berrypod_web/plugs/redirects.ex

@@ -8,14 +8,17 @@ defmodule BerrypodWeb.Plugs.Redirects do
   3. Custom redirect lookup from the redirects table (ETS-cached)
 
   All redirects preserve query params.
+
+  Note: Order URLs only have their prefix lowercased, not the order number,
+  since order numbers contain uppercase hex characters (e.g. SS-260331-5D1A).
   """
 
   import Plug.Conn
   alias Berrypod.Redirects
+  alias BerrypodWeb.R
 
-  # Only case-normalise paths under these prefixes (SEO-relevant shop routes).
+  # Static prefixes that should always have the full path lowercased (page slugs)
-  # Paths with tokens, API keys, or other case-sensitive segments are excluded.
+  @static_lowercase_prefixes ~w(/about /delivery /privacy /terms /search /cart /contact /checkout)
-  @lowercase_prefixes ~w(/products /collections /about /delivery /privacy /terms /search /cart /contact)
 
   def init(opts), do: opts
 
@@ -28,9 +31,9 @@ defmodule BerrypodWeb.Plugs.Redirects do
       stripped != path ->
         redirect_to(conn, stripped, 301)
 
-      # Case mismatch on a shop path — redirect to lowercase
+      # Case mismatch on a shop path — redirect to normalised form
-      lowercase_path?(path) and String.downcase(path) != path ->
+      (normalised = normalise_path(path)) != nil and normalised != path ->
-        redirect_to(conn, String.downcase(path), 301)
+        redirect_to(conn, normalised, 301)
 
       # Check redirect table (ETS-cached)
       :else ->
@@ -45,10 +48,51 @@ defmodule BerrypodWeb.Plugs.Redirects do
     end
   end
 
-  defp lowercase_path?(path) do
+  # Normalise path case. Returns the normalised path or nil if no normalisation needed.
-    Enum.any?(@lowercase_prefixes, &String.starts_with?(String.downcase(path), &1))
+  # For order routes, only the prefix is lowercased (order numbers preserve case).
+  # For other routes, the entire path is lowercased.
+  defp normalise_path(path) do
+    lowered = String.downcase(path)
+
+    # Check static prefixes (full path lowercase)
+    if Enum.any?(@static_lowercase_prefixes, &String.starts_with?(lowered, &1)) do
+      lowered
+    else
+      # Check dynamic route prefixes
+      segments = path |> String.trim_leading("/") |> String.split("/")
+      first_segment = List.first(segments) || ""
+      prefix_type = R.prefix_type_from_segment(String.downcase(first_segment))
+
+      case prefix_type do
+        nil ->
+          # Not a dynamic route
+          nil
+
+        :orders ->
+          # Order routes: only lowercase the prefix, preserve order number case
+          normalise_order_path(segments)
+
+        _ ->
+          # Products/collections: lowercase entire path (slugs are always lowercase)
+          lowered
+      end
+    end
   end
 
+  # For order routes, only lowercase the first segment (the prefix)
+  defp normalise_order_path([prefix | rest]) do
+    lowered_prefix = String.downcase(prefix)
+
+    if lowered_prefix == prefix do
+      # Prefix already lowercase, no change needed
+      nil
+    else
+      "/" <> Enum.join([lowered_prefix | rest], "/")
+    end
+  end
+
+  defp normalise_order_path([]), do: nil
+
   defp redirect_to(conn, target, status_code) do
     location = append_query(target, conn.query_string)