[WIP] POC for using ETag to verify screens config version (#234)

* Fix default config bug

* Start returning etag when getting config and add put operation

* Add and delete logic

* credo

* Update lib/screenplay/config/config.ex

Co-authored-by: Christian Maddox <[email protected]>

* Remove edit action

* Return more specific error messages

---------

Co-authored-by: Christian Maddox <[email protected]>

config/runtime.exs

@@ -19,7 +19,7 @@ sftp_client_module =
     _ -> Screenplay.Outfront.FakeSFTPClient
   end
 
-env = System.get_env("ENVIRONMENT_NAME")
+env = System.get_env("ENVIRONMENT_NAME", "dev")
 
 config :screenplay,
   alerts_s3_path: "screenplay/" <> System.get_env("ALERTS_S3_FILENAME", ""),

lib/screenplay/config/config.ex

@@ -1,12 +1,45 @@
 defmodule Screenplay.Config.PermanentConfig do
   @moduledoc false
+  alias Screenplay.Config.S3Fetch
 
-  def add_new_screen do
+  @spec add_new_screen(binary(), map(), binary()) ::
+          {:error, :etag_mismatch | :config_not_fetched | :config_not_written} | :ok
+  def add_new_screen(screen_id, screen, etag) do
+    case get_current_config(etag) do
+      {:ok, config} ->
+        config
+        |> Map.put(screen_id, Jason.decode!(screen))
+        |> S3Fetch.put_screens_config()
+
+      error ->
+        error
+    end
   end
 
-  def edit_screen do
+  @spec delete_screen(binary(), binary()) ::
+          {:error, :etag_mismatch | :config_not_fetched | :config_not_written} | :ok
+  def delete_screen(screen_id, etag) do
+    case get_current_config(etag) do
+      {:ok, config} ->
+        config
+        |> Map.delete(screen_id)
+        |> S3Fetch.put_screens_config()
+
+      error ->
+        error
+    end
   end
 
-  def delete_screen do
+  defp get_current_config(etag) do
+    case S3Fetch.get_screens_config() do
+      {:ok, config, ^etag} ->
+        {:ok, config}
+
+      :error ->
+        {:error, :config_not_fetched}
+
+      _ ->
+        {:error, :etag_mismatch}
+    end
   end
 end

lib/screenplay/config/s3_fetch.ex

@@ -6,9 +6,9 @@ defmodule Screenplay.Config.S3Fetch do
   @behaviour Screenplay.Config.Fetch
 
   def get_config do
-    with {:ok, config_contents} <- do_get(:config),
-         {:ok, location_contents} <- do_get(:screen_locations),
-         {:ok, place_description_contents} <- do_get(:place_descriptions),
+    with {:ok, config_contents, _} <- do_get(:config),
+         {:ok, location_contents, _} <- do_get(:screen_locations),
+         {:ok, place_description_contents, _} <- do_get(:place_descriptions),
          {:ok, config_json} <- Jason.decode(config_contents),
          {:ok, location_json} <- Jason.decode(location_contents),
          {:ok, place_description_json} <- Jason.decode(place_description_contents) do
@@ -18,15 +18,29 @@ defmodule Screenplay.Config.S3Fetch do
     end
   end
 
+  def get_screens_config do
+    with {:ok, screens_contents, etag} <- do_get(:screens),
+         {:ok, screens_json} <- Jason.decode(screens_contents) do
+      {:ok, screens_json, etag}
+    else
+      _ -> :error
+    end
+  end
+
   defp do_get(file_spec) do
     bucket = Application.get_env(:screenplay, :config_s3_bucket)
     path = config_path_for_environment(file_spec)
 
     get_operation = ExAws.S3.get_object(bucket, path)
 
     case ExAws.request(get_operation) do
-      {:ok, %{body: body, status_code: 200}} ->
-        {:ok, body}
+      {:ok, %{body: body, headers: headers, status_code: 200}} ->
+        etag =
+          headers
+          |> Enum.into(%{})
+          |> Map.get("ETag")
+
+        {:ok, body, etag}
 
       {:error, err} ->
         Logger.error(err)
@@ -35,12 +49,35 @@ defmodule Screenplay.Config.S3Fetch do
   end
 
   defp config_path_for_environment(file_spec) do
-    base_path = "screenplay/#{Application.get_env(:screenplay, :environment_name, "dev")}"
+    base_path = "screenplay/#{Application.get_env(:screenplay, :environment_name)}"
 
     case file_spec do
-      :config -> "#{base_path}/places_and_screens.json"
-      :screen_locations -> "#{base_path}/screen_locations.json"
-      :place_descriptions -> "#{base_path}/place_descriptions.json"
+      :config ->
+        "#{base_path}/places_and_screens.json"
+
+      :screen_locations ->
+        "#{base_path}/screen_locations.json"
+
+      :place_descriptions ->
+        "#{base_path}/place_descriptions.json"
+
+      :screens ->
+        "screens/screens-#{Application.get_env(:screenplay, :environment_name)}.json"
+    end
+  end
+
+  def put_screens_config(config) do
+    bucket = Application.get_env(:screenplay, :config_s3_bucket)
+    path = config_path_for_environment(:screens)
+
+    put_operation = ExAws.S3.put_object(bucket, path, Jason.encode!(config, pretty: true))
+
+    case ExAws.request(put_operation) do
+      {:ok, %{status_code: 200}} ->
+        :ok
+
+      _ ->
+        {:error, :config_not_written}
     end
   end
 end

lib/screenplay_web/controllers/config_controller.ex

@@ -3,22 +3,35 @@ defmodule ScreenplayWeb.ConfigController do
 
   alias Screenplay.Config.PermanentConfig
 
-  def index(conn, _params) do
-    render(conn, "index.html")
-  end
+  def add(conn, %{"screen_id" => screen_id, "screen" => screen, "etag" => etag}) do
+    case PermanentConfig.add_new_screen(screen_id, screen, etag) do
+      :ok ->
+        send_resp(conn, 200, "OK")
 
-  def add(conn, _params) do
-    PermanentConfig.add_new_screen()
-    conn
-  end
+      {:error, :etag_mismatch} ->
+        send_resp(conn, 400, "Config version mismatch")
+
+      {:error, :config_not_fetched} ->
+        send_resp(conn, 400, "S3 Operation Failed: Get")
 
-  def edit(conn, _params) do
-    PermanentConfig.edit_screen()
-    conn
+      {:error, :config_not_written} ->
+        send_resp(conn, 400, "S3 Operation Failed: Put")
+    end
   end
 
-  def delete(conn, _params) do
-    PermanentConfig.delete_screen()
-    conn
+  def delete(conn, %{"screen_id" => screen_id, "etag" => etag}) do
+    case PermanentConfig.delete_screen(screen_id, etag) do
+      :ok ->
+        send_resp(conn, 200, "OK")
+
+      {:error, :etag_mismatch} ->
+        send_resp(conn, 400, "Config version mismatch")
+
+      {:error, :config_not_fetched} ->
+        send_resp(conn, 400, "S3 Operation Failed: Get")
+
+      {:error, :config_not_written} ->
+        send_resp(conn, 400, "S3 Operation Failed: Put")
+    end
   end
 end

lib/screenplay_web/router.ex

@@ -108,7 +108,6 @@ defmodule ScreenplayWeb.Router do
     ])
 
     post("/add", ConfigController, :add)
-    post("/edit", ConfigController, :edit)
     post("/delete", ConfigController, :delete)
   end