add dynamic routes plug and simplify router

Dynamic prefix rewriting for custom URL prefixes:
- DynamicRoutes plug rewrites /p/123 to /products/123
- 301 redirects from canonical to custom prefix
- Router simplified to 3 catch-all routes
- LiveSandboxHook for test process ownership

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

lib/berrypod_web/endpoint.ex

@@ -13,8 +13,8 @@ defmodule BerrypodWeb.Endpoint do
   ]
 
   socket "/live", Phoenix.LiveView.Socket,
-    websocket: [connect_info: [session: @session_options]],
+    websocket: [connect_info: [:user_agent, session: @session_options]],
-    longpoll: [connect_info: [session: @session_options]]
+    longpoll: [connect_info: [:user_agent, session: @session_options]]
 
   # In prod, image variants and mockups live on the persistent volume
   # rather than inside the ephemeral release directory.
@@ -50,6 +50,11 @@ defmodule BerrypodWeb.Endpoint do
     plug Tidewave, allow_remote_access: true
   end
 
+  # Enable sandbox for LiveView tests (allows LV processes to share test DB connection)
+  if Application.compile_env(:berrypod, :env) == :test do
+    plug Phoenix.Ecto.SQL.Sandbox
+  end
+
   # Code reloading can be explicitly enabled under the
   # :code_reloader configuration of your endpoint.
   if code_reloading? do
@@ -76,5 +81,6 @@ defmodule BerrypodWeb.Endpoint do
   plug Plug.Head
   plug Plug.Session, @session_options
   plug BerrypodWeb.Plugs.Redirects
+  plug BerrypodWeb.Plugs.DynamicRoutes
   plug BerrypodWeb.Plugs.BrokenUrlTracker, router: BerrypodWeb.Router
 end

lib/berrypod_web/live_sandbox_hook.ex

@@ -0,0 +1,24 @@
+defmodule BerrypodWeb.LiveSandboxHook do
+  @moduledoc """
+  On-mount hook that allows LiveView processes to use the Ecto SQL sandbox.
+  Only active in test environment.
+  """
+
+  import Phoenix.LiveView
+  import Phoenix.Component
+
+  def on_mount(:default, _params, _session, socket) do
+    socket =
+      assign_new(socket, :phoenix_ecto_sandbox, fn ->
+        if connected?(socket), do: get_connect_info(socket, :user_agent)
+      end)
+
+    metadata = socket.assigns.phoenix_ecto_sandbox
+
+    if metadata do
+      Phoenix.Ecto.SQL.Sandbox.allow(metadata, Ecto.Adapters.SQL.Sandbox)
+    end
+
+    {:cont, socket}
+  end
+end

lib/berrypod_web/plugs/dynamic_routes.ex

@@ -0,0 +1,101 @@
+defmodule BerrypodWeb.Plugs.DynamicRoutes do
+  @moduledoc """
+  Plug that enables dynamic route prefixes for products, collections, and orders.
+
+  When a shop owner customises their URL prefixes (e.g., /products → /p), this plug:
+
+  1. **Rewrites incoming paths** - If the URL uses a custom prefix (/p/123), rewrites
+     path_info to the canonical form (/products/123) so the router matches.
+
+  2. **Redirects old prefixes** - If the URL uses the old default prefix when a custom
+     one is set (/products/123 when prefix is "p"), issues a 301 redirect to /p/123.
+
+  This plug must run AFTER the Redirects plug (which handles trailing slashes and
+  explicit redirects) but BEFORE the router.
+
+  ## How it works
+
+  The R module maintains an ETS cache of custom prefixes loaded from Settings.
+  `R.prefix/1` returns the current prefix for a type, and `R.prefix_type_from_segment/1`
+  performs reverse lookups.
+
+  ## Example
+
+      # Settings: url_prefixes = %{"products" => "p", "collections" => "c"}
+
+      GET /p/123           → Rewrite to /products/123, router matches :product
+      GET /products/123    → Redirect 301 to /p/123
+      GET /c/art           → Rewrite to /collections/art, router matches :collection
+      GET /collections/art → Redirect 301 to /c/art
+
+  When no custom prefix is set, paths pass through unchanged.
+  """
+
+  import Plug.Conn
+  alias BerrypodWeb.R
+
+  @default_prefixes %{
+    products: "products",
+    collections: "collections",
+    orders: "orders"
+  }
+
+  def init(opts), do: opts
+
+  def call(conn, _opts) do
+    case conn.path_info do
+      [first_segment | rest] when rest != [] ->
+        handle_prefixed_path(conn, first_segment, rest)
+
+      _ ->
+        conn
+    end
+  end
+
+  defp handle_prefixed_path(conn, segment, rest) do
+    prefix_type = R.prefix_type_from_segment(segment)
+    current_prefix = prefix_type && R.prefix(prefix_type)
+    default_prefix = prefix_type && @default_prefixes[prefix_type]
+
+    cond do
+      # No prefix type matched - not a dynamic route
+      is_nil(prefix_type) ->
+        conn
+
+      # Using the current (possibly custom) prefix - rewrite to default for router
+      segment == current_prefix and current_prefix != default_prefix ->
+        rewrite_path(conn, default_prefix, rest, segment)
+
+      # Using default prefix but custom is set - redirect to custom prefix
+      segment == default_prefix and current_prefix != default_prefix ->
+        redirect_to_custom(conn, current_prefix, rest)
+
+      # Using the default prefix and no custom set, or already canonical
+      true ->
+        conn
+    end
+  end
+
+  # Rewrite path_info so the router's static routes match
+  # Store original path in conn.private for LiveView to use
+  defp rewrite_path(conn, canonical_prefix, rest, original_prefix) do
+    conn
+    |> put_private(:original_prefix, original_prefix)
+    |> put_private(:original_request_path, conn.request_path)
+    |> Map.put(:path_info, [canonical_prefix | rest])
+  end
+
+  # 301 redirect to the canonical custom prefix
+  defp redirect_to_custom(conn, custom_prefix, rest) do
+    path = "/" <> Enum.join([custom_prefix | rest], "/")
+    location = append_query(path, conn.query_string)
+
+    conn
+    |> put_resp_header("location", location)
+    |> send_resp(301, "")
+    |> halt()
+  end
+
+  defp append_query(path, ""), do: path
+  defp append_query(path, qs), do: "#{path}?#{qs}"
+end

lib/berrypod_web/router.ex

@@ -275,21 +275,25 @@ defmodule BerrypodWeb.Router do
         {BerrypodWeb.PageEditorHook, :mount_page_editor},
         {BerrypodWeb.NewsletterHook, :mount_newsletter}
       ] do
-      live "/", Shop.Page, :home
+      # ┌─────────────────────────────────────────────────────────────────────┐
-      live "/about", Shop.Page, :about
+      # │ Dynamic Shop Routes                                                  │
-      live "/delivery", Shop.Page, :delivery
+      # │                                                                       │
-      live "/privacy", Shop.Page, :privacy
+      # │ All shop pages are served by Shop.Page with runtime route resolution │
-      live "/terms", Shop.Page, :terms
+      # │ via BerrypodWeb.R. This enables shop owners to customise URLs.       │
-      live "/contact", Shop.Page, :contact
+      # │                                                                       │
-      live "/collections/:slug", Shop.Page, :collection
+      # │ Single-segment pages (/:slug):                                       │
-      live "/products/:id", Shop.Page, :product
+      # │   /cart, /about, /contact, /search, /delivery, /privacy, /terms,     │
-      live "/cart", Shop.Page, :cart
+      # │   /orders, /checkout/success, plus custom CMS pages                  │
-      live "/search", Shop.Page, :search
+      # │                                                                       │
-      live "/checkout/success", Shop.Page, :checkout_success
+      # │ Two-segment pages (/:prefix/:id_or_slug):                            │
-      live "/orders", Shop.Page, :orders
+      # │   /products/:id, /collections/:slug, /orders/:number                 │
-      live "/orders/:order_number", Shop.Page, :order_detail
+      # │   (prefixes are customisable, e.g. /p/:id, /shop/:slug)              │
+      # │                                                                       │
+      # │ See: R.default_page_type/1, R.default_prefix_type/1, @page_modules   │
+      # └─────────────────────────────────────────────────────────────────────┘
 
-      # Catch-all for custom CMS pages — must be last
+      live "/", Shop.Page, :home
+      live "/:prefix/:id_or_slug", Shop.Page, :dynamic_prefix
       live "/:slug", Shop.Page, :custom_page
     end