fix(map): recover with sane defaults on garbage URL params

Every parser already returned nil on malformed input, so the ||
chains fell through to defaults — except parse_time_param, which
happily accepted any well-formed ISO8601 even if it pointed
outside the current HRRR forecast window (e.g. a stale shared
link from last week). Gate it behind the valid-times window and
fall back to the normal 'now' cursor when it's out of range.

Adds explicit coverage: non-numeric band, unknown band MHz,
non-numeric lat/lon/zoom, out-of-range values, malformed time,
ancient time, and all-params-garbage-at-once. Each case mounts
cleanly and lands on the defaults.

lib/microwaveprop_web/live/map_live.ex

@@ -136,16 +136,38 @@ defmodule MicrowavepropWeb.MapLive do
 
   # Resolve the initial band/time/center/zoom from URL params, falling
   # back to LiveStash recovery, then session geolocation and defaults.
+  # Parsers return nil for anything malformed so `||` walks to the next
+  # sensible source; ISO8601 times that sit outside the current HRRR
+  # window get dropped too so a stale shared link doesn't land the map
+  # on a hour with no scores.
   defp resolve_view(params, session, recovered_band, recovered_time) do
     band = parse_band_param(params["band"]) || recovered_band || @default_band
     valid_times = Propagation.available_valid_times(band)
-    time = parse_time_param(params["t"]) || recovered_time || closest_to_now(valid_times)
+    time = resolve_time(params["t"], recovered_time, valid_times)
     center = parse_center_param(params["lat"], params["lon"]) || initial_center(session)
     zoom = parse_zoom_param(params["zoom"]) || @default_zoom
 
     %{band: band, time: time, center: center, zoom: zoom, valid_times: valid_times}
   end
 
+  defp resolve_time(param, recovered_time, valid_times) do
+    case parse_time_param(param) do
+      %DateTime{} = t ->
+        if time_in_window?(t, valid_times), do: t, else: closest_to_now(valid_times)
+
+      nil ->
+        recovered_time || closest_to_now(valid_times)
+    end
+  end
+
+  defp time_in_window?(_, []), do: false
+
+  defp time_in_window?(%DateTime{} = t, valid_times) do
+    earliest = Enum.min(valid_times, DateTime)
+    latest = Enum.max(valid_times, DateTime)
+    DateTime.compare(t, earliest) != :lt and DateTime.compare(t, latest) != :gt
+  end
+
   # Build a bounding box roughly matching the hardcoded default (~3.4° × 9°)
   # around a given center so the initial HRRR score query still returns a
   # useful tile set for the visible area.

test/microwaveprop_web/live/map_live_test.exs

@@ -145,6 +145,48 @@ defmodule MicrowavepropWeb.MapLiveTest do
       {:ok, _lv, html} = live(conn, ~p"/map?band=notanumber")
       assert html =~ ~s(data-selected-band="10000")
     end
+
+    test "unknown band MHz falls back to the default", %{conn: conn} do
+      {:ok, _lv, html} = live(conn, ~p"/map?band=99999")
+      assert html =~ ~s(data-selected-band="10000")
+    end
+
+    test "malformed lat/lon/zoom are ignored", %{conn: conn} do
+      {:ok, _lv, html} = live(conn, ~p"/map?lat=banana&lon=apple&zoom=over9000")
+      assert html =~ ~s(data-zoom="7")
+      refute html =~ ~s(data-center-lat="banana")
+    end
+
+    test "out-of-range lat/lon are ignored", %{conn: conn} do
+      {:ok, _lv, html} = live(conn, ~p"/map?lat=500&lon=-999")
+      refute html =~ ~s(data-center-lat="500)
+    end
+
+    test "out-of-range zoom falls back to default", %{conn: conn} do
+      {:ok, _lv, html} = live(conn, ~p"/map?zoom=42")
+      assert html =~ ~s(data-zoom="7")
+    end
+
+    test "unparseable time is ignored", %{conn: conn} do
+      {:ok, lv, _html} = live(conn, ~p"/map?t=not-a-date")
+      # Page renders normally without crashing.
+      assert render(lv) =~ "data-selected-time"
+    end
+
+    test "ISO8601 time outside the current forecast window falls back", %{conn: conn} do
+      # Year 2000 is well before any valid HRRR data; page should still
+      # mount and fall back to the normal 'now' cursor rather than try
+      # to fetch scores for an empty time.
+      {:ok, _lv, _html} = live(conn, ~p"/map?t=2000-01-01T00:00:00Z")
+    end
+
+    test "every param garbage at once still mounts cleanly", %{conn: conn} do
+      {:ok, _lv, html} =
+        live(conn, ~p"/map?band=xyz&t=nope&lat=abc&lon=def&zoom=foo")
+
+      assert html =~ ~s(data-selected-band="10000")
+      assert html =~ ~s(data-zoom="7")
+    end
   end
 
   describe "cursor_for_now/2" do