Enqueue propagation grid worker on startup if scores are stale

On app start, check if latest scores are older than 2 hours. If so,
immediately enqueue a PropagationGridWorker job. Covers app restarts,
deploys, and missed cron ticks.

lib/microwaveprop/application.ex

@@ -5,6 +5,8 @@ defmodule Microwaveprop.Application do
 
   use Application
 
+  require Logger
+
   @impl true
   def start(_type, _args) do
     migrate()
@@ -16,7 +18,8 @@ defmodule Microwaveprop.Application do
       {Phoenix.PubSub, name: Microwaveprop.PubSub},
       {Oban, Application.fetch_env!(:microwaveprop, Oban)},
       # Start to serve requests, typically the last entry
-      MicrowavepropWeb.Endpoint
+      MicrowavepropWeb.Endpoint,
+      {Task, &ensure_fresh_scores/0}
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html
@@ -31,6 +34,26 @@ defmodule Microwaveprop.Application do
     Microwaveprop.Release.migrate()
   end
 
+  # If propagation scores are older than 2 hours, enqueue a grid worker immediately.
+  # Covers app restarts, deploys, and missed cron ticks.
+  defp ensure_fresh_scores do
+    case Microwaveprop.Propagation.latest_valid_time() do
+      nil ->
+        Logger.info("No propagation scores found, enqueuing grid worker")
+        Oban.insert(Microwaveprop.Workers.PropagationGridWorker.new(%{}))
+
+      latest ->
+        age_minutes = DateTime.diff(DateTime.utc_now(), latest, :minute)
+
+        if age_minutes > 120 do
+          Logger.info("Propagation scores are #{age_minutes}m old, enqueuing grid worker")
+          Oban.insert(Microwaveprop.Workers.PropagationGridWorker.new(%{}))
+        else
+          Logger.info("Propagation scores are #{age_minutes}m old, fresh enough")
+        end
+    end
+  end
+
   @impl true
   def config_change(changed, _new, removed) do
     MicrowavepropWeb.Endpoint.config_change(changed, removed)