devato · TECHNOFAB11 · Sep 18, 2023
diff --git a/README.md b/README.md
@@ -58,14 +58,29 @@ Import render_inertia `lib/active_web.ex`
   end
 ```
 
+If you want to use SSR add `InertiaPhoenix.ViewHelper` to `lib/<your app>_web.ex`
+```elixir
+  defp view_helpers do
+    quote do
+      ...
+
+      import InertiaPhoenix.ViewHelper
+
+      ...
+    end
+  end
+```
+
 ## Configuration
 
 Add to `config/config.exs`
 
 ```elixir
 config :inertia_phoenix,
-  assets_version: 1,          # default 1
-  inertia_layout: "app.html"  # default app.html
+  assets_version: 1,                 # default 1
+  inertia_layout: "app.html",        # default app.html
+  ssr_enabled: false,                # default false
+  ssr_url: "http://127.0.0.1:13714"  # default http://127.0.0.1:13714
 ```
 
 - Asset Versioning Docs: https://inertiajs.com/asset-versioning
@@ -96,6 +111,8 @@ An example layout:
 <html lang="en">
   <head>
     ...
+    <!-- add this when using SSR: -->
+    <%= inertia_head(@conn) %>
   </head>
   <body>
     <%= @inner_content %>

diff --git a/lib/inertia_phoenix.ex b/lib/inertia_phoenix.ex
@@ -22,6 +22,14 @@ defmodule InertiaPhoenix do
     |> to_string
   end
 
+  def inertia_ssr_enabled do
+    Application.get_env(:inertia_phoenix, :ssr_enabled, false)
+  end
+
+  def inertia_ssr_url do
+    Application.get_env(:inertia_phoenix, :ssr_url, "http://127.0.0.1:13714")
+  end
+
   def path_with_params(%{request_path: request_path, query_string: ""}), do: request_path
 
   def path_with_params(%{request_path: request_path, query_string: query_string}) do

diff --git a/lib/inertia_phoenix/controller.ex b/lib/inertia_phoenix/controller.ex
@@ -1,12 +1,14 @@
 defmodule InertiaPhoenix.Controller do
   @moduledoc false
   import InertiaPhoenix
+  require Logger
 
   import Plug.Conn,
     only: [
       get_req_header: 2,
       put_resp_header: 3,
-      put_resp_cookie: 4
+      put_resp_cookie: 4,
+      assign: 3
     ]
 
   alias Phoenix.Controller
@@ -26,13 +28,42 @@ defmodule InertiaPhoenix.Controller do
   def render_inertia(conn, component, assigns) do
     assigns = build_assigns(conn, assigns, component)
 
+    %{"body" => body, "head" => raw_head} = fetch_ssr(conn, assigns)
+    assigns = Keyword.put(assigns, :inertia_ssr_body, body)
+    head = Phoenix.HTML.raw(Enum.join(raw_head, "\n"))
+
     conn
     |> Controller.put_view(InertiaPhoenix.View)
     |> Controller.put_layout(html: {InertiaPhoenix.View, :inertia})
     |> put_csrf_cookie
+    |> assign(:inertia_ssr_head, head)
     |> Controller.render("inertia.html", assigns)
   end
 
+  defp fetch_ssr(conn, assigns) do
+    default = %{
+      "head" => [],
+      "body" => ""
+    }
+
+    if inertia_ssr_enabled() do
+      case HTTPoison.post(inertia_ssr_url() <> "/render", Jason.encode!(page_map(conn, assigns)), [{"Content-Type", "application/json"}]) do
+        {:ok, %HTTPoison.Response{status_code: 200, body: body}} ->
+          if body == "" do
+            Logger.warn("Inertia SSR returned empty response, check SSR server logs")
+            default
+          else
+            Jason.decode!(body)
+          end
+        response ->
+          Logger.warn("Inertia SSR request failed: #{inspect(response)}")
+          default
+      end
+    else
+      default
+    end
+  end
+
   defp build_assigns(conn, assigns, component) do
     assigns
     |> filter_partial_data(conn, component)

diff --git a/lib/inertia_phoenix/helper.ex b/lib/inertia_phoenix/helper.ex
@@ -0,0 +1,5 @@
+defmodule InertiaPhoenix.ViewHelper do
+  def inertia_head(conn) do
+    conn.assigns[:inertia_ssr_head]
+  end
+end
diff --git a/lib/inertia_phoenix/view.ex b/lib/inertia_phoenix/view.ex
@@ -4,10 +4,16 @@ defmodule InertiaPhoenix.View do
   alias Phoenix.HTML.Tag
 
   def render("inertia.html", assigns) do
-    Tag.content_tag(:div, "", [
-      {:id, "app"},
-      {:data, [page: page_json(assigns)]}
-    ])
+    { body, assigns } = Map.pop(assigns, :inertia_ssr_body)
+
+    if body != "" do
+      Phoenix.HTML.raw(body)
+    else
+      Tag.content_tag(:div, "", [
+        {:id, "app"},
+        {:data, [page: page_json(assigns)]}
+      ])
+    end
   end
 
   defp page_json(%{conn: conn}) do

diff --git a/mix.exs b/mix.exs
@@ -43,7 +43,9 @@ defmodule InertiaPhoenix.MixProject do
       {:ex_doc, "~> 0.29.4", only: :dev},
       {:plug_cowboy, "~> 2.1", only: [:test]},
       {:excoveralls, "~> 0.16", only: :test},
-      {:doctor, "~> 0.17.0"}
+      {:doctor, "~> 0.17.0"},
+      # needed for SSR
+      {:httpoison, "~> 2.0"}
     ]
   end