init(ex/skate/snapshot_serde): create deserialize function (#2897)

* init(ex/skate/snapshot_serde): create `deserialize` function

* refactor(ex/detours): refactor `update_or_create_detour_for_user` to use Serde module

lib/skate/detours/detours.ex

@@ -193,36 +193,33 @@ defmodule Skate.Detours.Detours do
   end
 
   @doc """
-  Update or create a detour given a user id & detour id.
+  Update or insert a detour given a user id and a XState Snapshot.
   """
-  def update_or_create_detour_for_user(user_id, uuid, attrs \\ %{}) do
-    user = User.get_by_id!(user_id)
-
-    previous_record = uuid != nil && Skate.Repo.get(Detour, uuid)
-
-    detour =
-      case uuid do
-        nil ->
-          create_detour_for_user(user_id, attrs)
-
-        _ ->
-          Repo.insert(
-            Detour.changeset(%Detour{author: user, id: uuid}, attrs),
-            returning: true,
-            conflict_target: [:id],
-            on_conflict: {:replace, [:state, :updated_at]}
-          )
+  def upsert_from_snapshot(author_id, %{} = snapshot) do
+    previous_record =
+      case Skate.Detours.SnapshotSerde.id_from_snapshot(snapshot) do
+        nil -> nil
+        id -> Skate.Repo.get(Detour, id)
       end
 
-    case detour do
+    detour_db_result =
+      author_id
+      |> Skate.Detours.SnapshotSerde.deserialize(snapshot)
+      |> Skate.Repo.insert(
+        returning: true,
+        conflict_target: [:id],
+        on_conflict: {:replace, [:state, :updated_at]}
+      )
+
+    case detour_db_result do
       {:ok, %Detour{} = new_record} ->
-        send_notification(new_record, previous_record, user_id)
+        send_notification(new_record, previous_record, author_id)
 
       _ ->
         nil
     end
 
-    detour
+    detour_db_result
   end
 
   @doc """

lib/skate/detours/snapshot_serde.ex

@@ -3,4 +3,28 @@ defmodule Skate.Detours.SnapshotSerde do
   Deserializes XState JSON Snapshots to Ecto Database Changesets
   Serializes Ecto Database Structs into XState JSON Snapshots
   """
+
+  @doc """
+  Converts a XState JSON Snapshot to Detours Database Changeset
+  """
+  def deserialize(user_id, %{} = snapshot) do
+    Skate.Detours.Db.Detour.changeset(
+      %Skate.Detours.Db.Detour{
+        # `id` is `nil` by default, so a `nil` `id` should be fine
+        id: id_from_snapshot(snapshot),
+        author_id: user_id
+      },
+      %{
+        # Save Snapshot to DB until we've fully transitioned to serializing
+        # snapshots from DB data
+        state: snapshot
+      }
+    )
+  end
+
+  @doc """
+  Extracts the Detour ID from a XState Snapshot
+  """
+  def id_from_snapshot(%{"context" => %{"uuid" => id}}), do: id
+  def id_from_snapshot(%{"context" => %{}}), do: nil
 end

lib/skate_web/controllers/detours_controller.ex

@@ -11,15 +11,11 @@ defmodule SkateWeb.DetoursController do
   alias Util.Location
 
   @spec update_snapshot(Plug.Conn.t(), map()) :: Plug.Conn.t()
-  def update_snapshot(conn, %{"snapshot" => %{"context" => context} = snapshot}) do
-    uuid = Map.get(context, "uuid")
-
+  def update_snapshot(conn, %{"snapshot" => snapshot}) do
     %{id: user_id} = AuthManager.Plug.current_resource(conn)
 
     {:ok, %Skate.Detours.Db.Detour{id: returned_uuid}} =
-      Detours.update_or_create_detour_for_user(user_id, uuid, %{
-        state: snapshot
-      })
+      Detours.upsert_from_snapshot(user_id, snapshot)
 
     json(conn, %{data: returned_uuid})
   end

test/skate_web/controllers/detours_controller_test.exs

@@ -280,23 +280,21 @@ defmodule SkateWeb.DetoursControllerTest do
       other_user = Skate.Settings.User.get_by_email("[email protected]")
 
       # Manually insert a detour by another user
-      Detours.update_or_create_detour_for_user(other_user.id, 10, %{
-        state: %{
-          "context" => %{
-            "route" => %{
-              "name" => "23",
-              "directionNames" => %{
-                "0" => "Outbound",
-                "1" => "Inbound"
-              }
-            },
-            "routePattern" => %{
-              "headsign" => "Headsign",
-              "directionId" => 0
-            },
-            "nearestIntersection" => "Street A & Avenue B",
-            "uuid" => 10
-          }
+      Detours.upsert_from_snapshot(other_user.id, %{
+        "context" => %{
+          "route" => %{
+            "name" => "23",
+            "directionNames" => %{
+              "0" => "Outbound",
+              "1" => "Inbound"
+            }
+          },
+          "routePattern" => %{
+            "headsign" => "Headsign",
+            "directionId" => 0
+          },
+          "nearestIntersection" => "Street A & Avenue B",
+          "uuid" => 10
         }
       })