feat(SiteWeb.Router): add /charlie/* redirects (#1782)

* feat(SiteWeb.WwwRedirector): support optional host

* feat(SiteWeb.WwwRedirector): use conn.path_params

* feat(SiteWeb.Router): add /charlie/* redirect

apps/site/lib/site_web/router.ex

@@ -62,6 +62,11 @@ defmodule SiteWeb.Router do
     get("/*path", WwwRedirector, [])
   end
 
+  # redirect 'mbta.com/charlie/*'  to 'charlie.mbta.com/*'
+  scope "/charlie", SiteWeb do
+    get("/*path", WwwRedirector, host: "https://charlie.mbta.com")
+  end
+
   scope "/", SiteWeb do
     pipe_through([:secure, :browser])
 

apps/site/lib/site_web/www_redirector.ex

@@ -6,10 +6,13 @@ defmodule SiteWeb.WwwRedirector do
   alias Plug.Conn
 
   @impl true
-  def init([]), do: []
+  def init(options), do: options
 
   @impl true
-  def call(conn, _options), do: site_redirect(SiteWeb.Endpoint.url(), conn)
+  def call(conn, options) do
+    url = Keyword.get(options, :host, SiteWeb.Endpoint.url())
+    site_redirect(url, conn)
+  end
 
   @spec site_redirect(String.t(), Conn.t()) :: Plug.Conn.t()
   def site_redirect(site_url, conn) do
@@ -21,12 +24,22 @@ defmodule SiteWeb.WwwRedirector do
     |> halt()
   end
 
-  defp redirect_url(site_url, %Conn{request_path: path, query_string: query})
+  # If path_params are matched via SiteWeb.Router, use that to determine path
+  defp redirect_url(site_url, %Conn{path_params: %{"path" => path}, query_string: query}) do
+    revised_path = "/" <> Enum.join(path, "/")
+    do_redirect_url(site_url, revised_path, query)
+  end
+
+  defp redirect_url(site_url, %Conn{request_path: path, query_string: query}) do
+    do_redirect_url(site_url, path, query)
+  end
+
+  defp do_redirect_url(site_url, path, query)
        when is_binary(query) and query != "" do
     "#{site_url}#{path}?#{query}"
   end
 
-  defp redirect_url(site_url, %Conn{request_path: path}) do
+  defp do_redirect_url(site_url, path, _) do
     "#{site_url}#{path}"
   end
 end

apps/site/test/site/lib/www_redirector_test.exs

@@ -9,6 +9,28 @@ defmodule SiteWeb.WwwRedirectorTest do
     assert_conn_redirected_halted(conn, SiteWeb.Endpoint.url() <> "/news")
   end
 
+  test "call with host option", %{conn: conn} do
+    conn = WwwRedirector.call(%{conn | request_path: "/news"}, host: "https://myfakedomain.xyz")
+    assert_conn_redirected_halted(conn, "https://myfakedomain.xyz/news")
+  end
+
+  @doc "Use case: The path_params are populated in the router, and if they're part of a scoped route, the redirected URL should not include the path prefix."
+  test "omits scoped route path prefix", %{conn: conn} do
+    request_path = "/charlie/page/one/two"
+
+    conn = %{
+      conn
+      | request_path: request_path,
+        query_string: nil,
+        path_params: %{"path" => ["page", "one", "two"]}
+    }
+
+    conn = WwwRedirector.call(conn, host: "https://myfakedomain.xyz")
+
+    refute redirected_to(conn, :moved_permanently) == "https://myfakedomain.xyz#{request_path}"
+    assert_conn_redirected_halted(conn, "https://myfakedomain.xyz/page/one/two")
+  end
+
   describe "redirect" do
     test "top level redirected", %{conn: conn} do
       check_redirect_to_www_mbta(conn, "/", nil, "https://www.mbta.com/")