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