feat(ts/detours): add activated_at when detour is activated

assets/src/models/createDetourMachine.ts

@@ -36,6 +36,8 @@ export const createDetourMachine = setup({
 
       selectedDuration?: string
       selectedReason?: string
+
+      activatedAt?: Date
     },
 
     input: {} as
@@ -624,6 +626,11 @@ export const createDetourMachine = setup({
                     },
                     "detour.share.activate-modal.activate": {
                       target: "Done",
+                      actions: assign({
+                        // Record current time, should be done on the backend,
+                        // but that requires a larger refactor of the state machine
+                        activatedAt: new Date()
+                      })
                     },
                   },
                 },

priv/repo/async_migrations/20241218135700_backfill_detour_activated_at.exs

@@ -0,0 +1,49 @@
+defmodule Skate.Repo.Migrations.BackfillDetourActivatedAt do
+  # https://fly.io/phoenix-files/backfilling-data/
+
+
+  import Ecto.Query
+  use Ecto.Migration
+
+  @disable_ddl_transaction true
+  @disable_migration_lock true
+
+  def up do
+    # The 'backfilling-data' blog post suggests using a "throttle" function
+    # so that we don't update too many at once, but we currently have less than
+    # 1000 detours, so I think this will be negligable and not worth the
+    # complexity cost at _this_ time.
+    repo().update_all(
+      from(
+        r in Skate.Repo.Migrations.BackfillDetourActivatedAt.MigratingSchema,
+        select: r.id,
+        where: not is_nil(r.state["value"]["Detour Drawing"]["Active"]) and is_nil(r.activated_at),
+        update: [set: [activated_at: r.updated_at]]
+      ),
+      [],
+      log: :info
+    )
+   end
+
+  def down, do: :ok
+end
+
+defmodule Skate.Repo.Migrations.BackfillDetourActivatedAt.MigratingSchema do
+  @moduledoc """
+  Detours database table schema frozen at this point in time.
+  """
+
+  use Skate.Schema
+
+  alias Skate.Settings.Db.User
+
+  typed_schema "detours" do
+    field :state, :map
+    belongs_to :author, User
+
+    # When this detour was activated
+    field :activated_at, :utc_datetime_usec
+
+    timestamps()
+  end
+end