From 9e4ca154ffcaf7196bc297cba01903026a252289 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Wed, 29 Apr 2026 14:03:55 -0500
Subject: [PATCH] fix(weather): drop valid_times older than one hour from the
 timeline
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The HRRR scalar cache can hold a previous run's forecast hours past
their useful life — the timeline was offering "current conditions"
points that were 2-3 hours old, which is more misleading than helpful
on a map labeled "Now".

Filter Weather.available_weather_valid_times() through a `now - 1h`
cutoff in mount, :weather_updated, and :propagation_pipeline_progress
so the timeline only ever shows the most recent analysis hour plus
forecast hours.
---
 .../live/weather_map_live.ex                  | 15 +++++++++---
 .../live/weather_map_live_test.exs            | 24 +++++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/lib/microwaveprop_web/live/weather_map_live.ex b/lib/microwaveprop_web/live/weather_map_live.ex
index 97b4911f..59c99cae 100644
--- a/lib/microwaveprop_web/live/weather_map_live.ex
+++ b/lib/microwaveprop_web/live/weather_map_live.ex
@@ -27,7 +27,7 @@ defmodule MicrowavepropWeb.WeatherMapLive do
     # the LiveView socket join timeout. The client now paints weather
     # through a tile endpoint, so mount only needs the selected layer
     # and valid_time metadata.
-    valid_times = Weather.available_weather_valid_times()
+    valid_times = recent_valid_times(Weather.available_weather_valid_times())
     initial_vt = pick_initial_valid_time(valid_times)
 
     {:ok,
@@ -65,6 +65,15 @@ defmodule MicrowavepropWeb.WeatherMapLive do
     Enum.min_by(valid_times, fn vt -> abs(DateTime.diff(vt, now, :second)) end)
   end
 
+  # Drop valid_times older than one hour ago. The HRRR scalar cache can
+  # hold the previous run's forecast hours past their useful life;
+  # showing 3-hour-old "current conditions" on the map is more
+  # misleading than helpful.
+  defp recent_valid_times(valid_times) do
+    cutoff = DateTime.add(DateTime.utc_now(), -3600, :second)
+    Enum.filter(valid_times, fn vt -> DateTime.compare(vt, cutoff) != :lt end)
+  end
+
   @impl true
   def handle_event("select_layer", %{"layer" => layer_id}, socket) do
     if MapLayers.valid_id?(layer_id) do
@@ -122,7 +131,7 @@ defmodule MicrowavepropWeb.WeatherMapLive do
 
   @impl true
   def handle_info({:weather_updated, _valid_time}, socket) do
-    valid_times = Weather.available_weather_valid_times()
+    valid_times = recent_valid_times(Weather.available_weather_valid_times())
 
     # Keep whatever the user has scrubbed to if it's still available,
     # otherwise fall back to the latest on-disk time (GridCache-backed
@@ -152,7 +161,7 @@ defmodule MicrowavepropWeb.WeatherMapLive do
   # so the timeline picks up the extra hour, but keep the currently
   # selected time where it is.
   def handle_info({:propagation_pipeline_progress, _progress}, socket) do
-    valid_times = Weather.available_weather_valid_times()
+    valid_times = recent_valid_times(Weather.available_weather_valid_times())
 
     if valid_times == socket.assigns.valid_times do
       {:noreply, socket}
diff --git a/test/microwaveprop_web/live/weather_map_live_test.exs b/test/microwaveprop_web/live/weather_map_live_test.exs
index c796d456..37c68e2d 100644
--- a/test/microwaveprop_web/live/weather_map_live_test.exs
+++ b/test/microwaveprop_web/live/weather_map_live_test.exs
@@ -75,6 +75,30 @@ defmodule MicrowavepropWeb.WeatherMapLiveTest do
       end)
     end
 
+    test "mount drops valid_times older than one hour ago", %{conn: conn} do
+      now =
+        DateTime.utc_now()
+        |> DateTime.truncate(:second)
+        |> Map.put(:minute, 0)
+        |> Map.put(:second, 0)
+
+      stale_t = DateTime.add(now, -2 * 3600, :second)
+      recent_t = DateTime.add(now, -30 * 60, :second)
+      future_t = DateTime.add(now, 3 * 3600, :second)
+
+      Enum.each([stale_t, recent_t, future_t], &write_profile(&1, 33.0, -97.0))
+
+      {:ok, _lv, html} = live(conn, ~p"/weather")
+
+      stale_iso = DateTime.to_iso8601(stale_t)
+      recent_iso = DateTime.to_iso8601(recent_t)
+      future_iso = DateTime.to_iso8601(future_t)
+
+      refute html =~ stale_iso, "stale valid_time #{stale_iso} should be filtered out"
+      assert html =~ recent_iso, "recent valid_time #{recent_iso} should be present"
+      assert html =~ future_iso, "future valid_time #{future_iso} should be present"
+    end
+
     test "mount defaults to the valid_time closest to now, not the latest forecast hour",
          %{conn: conn} do
       base =