Cache /contacts, fix map blink, make mode optional

- Add contacts_inserted_at_desc_id_desc_idx so /contacts list runs as an
  Index Scan (~0.4ms) instead of a Seq Scan + top-N heapsort (~77ms on
  58k rows)
- Add Microwaveprop.Cache: tiny ETS-backed TTL cache for memoizing
  expensive-but-stale-tolerant values
- Cache total_entries for unsearched /contacts page loads (30s TTL,
  invalidated on insert)
- Cache the entire /contacts/map payload (pre-encoded JSON + band list),
  moving load_contacts into Radio.contact_map_payload; invalidated on
  new contact insert. Mount goes from ~150-300ms to ~5ms.
- Fix /map overlay blinking on load: reuse the Leaflet GridLayer across
  renderScores calls and just redraw() against the updated ScoreGrid,
  instead of removeLayer + new layer which flashed between tile regens
- Make mode optional on submission: schema change (null: true),
  submission_changeset no longer requires it, blank strings normalise to
  nil, CSV import accepts 6-column (no mode) or 7-column layouts
- core_components .input adds a red asterisk to labels when required,
  giving users a visual cue for which fields must be filled on /submit

assets/js/propagation_map_hook.ts

@@ -979,10 +979,14 @@ export const PropagationMap: Record<string, unknown> & {
 
   renderScores(this: PropagationMapHook, scores: ScorePoint[]) {
     this.scores = scores
-    if (this.scoreOverlay) {
-      this.map.removeLayer(this.scoreOverlay)
+
+    if (scores.length === 0) {
+      if (this.scoreOverlay) {
+        this.map.removeLayer(this.scoreOverlay)
+        this.scoreOverlay = null
+      }
+      return
     }
-    if (scores.length === 0) return
 
     if (!this.scoreGrid) {
       this.scoreGrid = new ScoreGrid()
@@ -991,7 +995,15 @@ export const PropagationMap: Record<string, unknown> & {
     }
     scores.forEach((s) => this.scoreGrid.put(s.lat, s.lon, s.score))
 
-    // Pre-calculate RGBA strings for scores 0-100
+    if (this.scoreOverlay) {
+      // Layer already on the map — just redraw existing tiles against the
+      // updated grid data. Avoids the remove/add flash that caused the
+      // overlay to blink during the initial load pipeline.
+      this.scoreOverlay.redraw()
+      return
+    }
+
+    // First render — build the GridLayer once and reuse it for every update.
     const colorCache = new Array<string>(101)
     for (let i = 0; i <= 100; i++) {
       const c = this.scoreColorRGB(i)

config/test.exs

@@ -42,6 +42,8 @@ config :microwaveprop, nexrad_req_options: [plug: {Req.Test, Microwaveprop.Weath
 config :microwaveprop, solar_req_options: [plug: {Req.Test, Microwaveprop.Weather.SolarClient}]
 config :microwaveprop, srtm_req_options: [plug: {Req.Test, Microwaveprop.Terrain.Srtm}, retry: false]
 config :microwaveprop, start_freshness_monitor: false
+config :microwaveprop, cache_contact_count: false
+config :microwaveprop, cache_contact_map: false
 
 # Initialize plugs at runtime for faster test compilation
 config :phoenix, :plug_init_mode, :runtime

lib/microwaveprop/application.ex

@@ -14,6 +14,7 @@ defmodule Microwaveprop.Application do
       Microwaveprop.Repo,
       {Cluster.Supervisor, [topologies, [name: Microwaveprop.ClusterSupervisor]]},
       {Phoenix.PubSub, name: Microwaveprop.PubSub},
+      Microwaveprop.Cache,
       Microwaveprop.Propagation.ScoreCache,
       Microwaveprop.Weather.NexradCache,
       {Oban, Application.fetch_env!(:microwaveprop, Oban)},

lib/microwaveprop/cache.ex

@@ -0,0 +1,71 @@
+defmodule Microwaveprop.Cache do
+  @moduledoc """
+  Tiny ETS-backed TTL cache for values that are expensive to compute but
+  tolerate short staleness. Used for things like `Repo.aggregate` counts that
+  would otherwise run on every page load.
+
+  Not a replacement for `Microwaveprop.Propagation.ScoreCache` or
+  `Microwaveprop.Weather.NexradCache` — those have bespoke invalidation logic
+  driven by PubSub. This module is for generic time-boxed memoization.
+  """
+  use GenServer
+
+  @table :microwaveprop_cache
+
+  @spec start_link(keyword()) :: GenServer.on_start()
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  @doc """
+  Return the cached value for `key` if it's still fresh, otherwise invoke
+  `fun`, store the result with `ttl_ms` lifetime, and return it.
+  """
+  @spec fetch_or_store(term(), non_neg_integer(), (-> value)) :: value when value: term()
+  def fetch_or_store(key, ttl_ms, fun) when is_function(fun, 0) do
+    now = System.monotonic_time(:millisecond)
+
+    case :ets.lookup(@table, key) do
+      [{_, value, expires_at}] when expires_at > now ->
+        value
+
+      _ ->
+        value = fun.()
+        :ets.insert(@table, {key, value, now + ttl_ms})
+        value
+    end
+  end
+
+  @doc "Insert `value` directly, overwriting any existing entry for `key`."
+  @spec put(term(), term(), integer()) :: :ok
+  def put(key, value, ttl_ms) do
+    :ets.insert(@table, {key, value, System.monotonic_time(:millisecond) + ttl_ms})
+    :ok
+  end
+
+  @doc "Remove `key` from the cache, forcing the next fetch to recompute."
+  @spec invalidate(term()) :: :ok
+  def invalidate(key) do
+    :ets.delete(@table, key)
+    :ok
+  end
+
+  @spec clear() :: :ok
+  def clear do
+    :ets.delete_all_objects(@table)
+    :ok
+  end
+
+  @impl true
+  def init(_opts) do
+    :ets.new(@table, [
+      :set,
+      :named_table,
+      :public,
+      read_concurrency: true,
+      write_concurrency: true
+    ])
+
+    {:ok, %{}}
+  end
+end

lib/microwaveprop/radio.ex

@@ -4,6 +4,7 @@ defmodule Microwaveprop.Radio do
   import Ecto.Query
 
   alias Microwaveprop.Accounts.User
+  alias Microwaveprop.Cache
   alias Microwaveprop.Radio.Contact
   alias Microwaveprop.Radio.ContactEdit
   alias Microwaveprop.Radio.Maidenhead
@@ -11,6 +12,10 @@ defmodule Microwaveprop.Radio do
 
   @per_page 20
   @sortable_fields ~w(station1 station2 band mode distance_km qso_timestamp inserted_at)a
+  @count_cache_key {__MODULE__, :total_contact_count}
+  @count_cache_ttl_ms 30_000
+  @map_payload_cache_key {__MODULE__, :contact_map_payload}
+  @map_payload_ttl_ms 10 * 60 * 1_000
 
   @type contact_page :: %{
           entries: [Contact.t()],
@@ -20,6 +25,95 @@ defmodule Microwaveprop.Radio do
           total_entries: non_neg_integer()
         }
 
+  @doc """
+  Pre-encoded JSON payload for `/contacts/map`. Computing this requires loading
+  every contact with coordinates, deriving formatted rows, deduplicating
+  reciprocals, and JSON-encoding ~58k rows — ~150-300ms of work that would
+  otherwise run on every page mount. Cached for 10 minutes, invalidated when
+  a new contact is inserted.
+  """
+  @spec contact_map_payload() :: %{
+          json: iodata(),
+          count: non_neg_integer(),
+          bands: [integer()]
+        }
+  def contact_map_payload do
+    if Application.get_env(:microwaveprop, :cache_contact_map, true) do
+      Cache.fetch_or_store(@map_payload_cache_key, @map_payload_ttl_ms, fn ->
+        build_contact_map_payload()
+      end)
+    else
+      build_contact_map_payload()
+    end
+  end
+
+  defp build_contact_map_payload do
+    contacts = load_contacts_for_map()
+    bands = contacts |> Enum.map(fn [_, _, _, _, band | _] -> band end) |> Enum.uniq() |> Enum.sort()
+    %{json: Jason.encode_to_iodata!(contacts), count: length(contacts), bands: bands}
+  end
+
+  defp load_contacts_for_map do
+    from(c in Contact,
+      where: not is_nil(c.pos1) and not is_nil(c.pos2),
+      select: %{
+        id: c.id,
+        pos1: c.pos1,
+        pos2: c.pos2,
+        band: c.band,
+        station1: c.station1,
+        station2: c.station2,
+        mode: c.mode,
+        distance_km: c.distance_km,
+        qso_timestamp: c.qso_timestamp
+      }
+    )
+    |> Repo.all()
+    |> Enum.map(&format_map_contact/1)
+    |> Enum.reject(&is_nil/1)
+    |> dedup_map_reciprocals()
+  end
+
+  defp format_map_contact(c) do
+    lat1 = c.pos1["lat"]
+    lon1 = c.pos1["lon"] || c.pos1["lng"]
+    lat2 = c.pos2["lat"]
+    lon2 = c.pos2["lon"] || c.pos2["lng"]
+
+    if lat1 && lon1 && lat2 && lon2 do
+      [
+        lat1,
+        lon1,
+        lat2,
+        lon2,
+        format_map_band(c.band),
+        c.station1,
+        c.station2,
+        c.mode,
+        format_map_distance(c.distance_km),
+        format_map_timestamp(c.qso_timestamp),
+        c.id
+      ]
+    end
+  end
+
+  defp format_map_band(nil), do: 0
+  defp format_map_band(band), do: Decimal.to_integer(band)
+
+  defp format_map_distance(nil), do: nil
+  defp format_map_distance(d), do: Decimal.to_float(d)
+
+  defp format_map_timestamp(nil), do: nil
+  defp format_map_timestamp(ts), do: Calendar.strftime(ts, "%Y-%m-%d %H:%M")
+
+  defp dedup_map_reciprocals(contacts) do
+    Enum.uniq_by(contacts, fn [_lat1, _lon1, _lat2, _lon2, band, s1, s2, _mode, _dist, ts, _id] ->
+      stations = Enum.sort([s1 || "", s2 || ""])
+      hour = if ts, do: String.slice(ts, 0..12), else: ""
+      {stations, band, hour}
+    end)
+  end
+
   @spec list_contacts(keyword()) :: contact_page()
   def list_contacts(opts \\ []) do
     page = max(Keyword.get(opts, :page, 1), 1)
@@ -30,7 +124,7 @@ defmodule Microwaveprop.Radio do
 
     base_query = maybe_search(Contact, search)
 
-    total_entries = Repo.aggregate(base_query, :count)
+    total_entries = total_entries_for(search, base_query)
     total_pages = max(ceil(total_entries / @per_page), 1)
 
     entries =
@@ -95,6 +189,18 @@ defmodule Microwaveprop.Radio do
       t2 |> NaiveDateTime.truncate(:second) |> Map.take([:year, :month, :day, :hour])
   end
 
+  defp total_entries_for(search, query) when search in [nil, ""] do
+    if Application.get_env(:microwaveprop, :cache_contact_count, true) do
+      Cache.fetch_or_store(@count_cache_key, @count_cache_ttl_ms, fn ->
+        Repo.aggregate(query, :count)
+      end)
+    else
+      Repo.aggregate(query, :count)
+    end
+  end
+
+  defp total_entries_for(_search, query), do: Repo.aggregate(query, :count)
+
   defp maybe_search(query, nil), do: query
   defp maybe_search(query, ""), do: query
 
@@ -421,12 +527,20 @@ defmodule Microwaveprop.Radio do
       {{:ok, {lat1, lon1}}, {:ok, {lat2, lon2}}} ->
         distance = lat1 |> haversine_km(lon1, lat2, lon2) |> round() |> Decimal.new()
 
-        changeset
-        |> Ecto.Changeset.put_change(:pos1, %{"lat" => lat1, "lon" => lon1})
-        |> Ecto.Changeset.put_change(:pos2, %{"lat" => lat2, "lon" => lon2})
-        |> Ecto.Changeset.put_change(:distance_km, distance)
-        |> Ecto.Changeset.put_change(:user_submitted, true)
-        |> Repo.insert()
+        result =
+          changeset
+          |> Ecto.Changeset.put_change(:pos1, %{"lat" => lat1, "lon" => lon1})
+          |> Ecto.Changeset.put_change(:pos2, %{"lat" => lat2, "lon" => lon2})
+          |> Ecto.Changeset.put_change(:distance_km, distance)
+          |> Ecto.Changeset.put_change(:user_submitted, true)
+          |> Repo.insert()
+
+        with {:ok, _} <- result do
+          Cache.invalidate(@count_cache_key)
+          Cache.invalidate(@map_payload_cache_key)
+        end
+
+        result
 
       _ ->
         changeset = Ecto.Changeset.add_error(changeset, :grid1, "could not resolve grid to coordinates")

lib/microwaveprop/radio/contact.ex

@@ -49,8 +49,8 @@ defmodule Microwaveprop.Radio.Contact do
 
   @type t :: %__MODULE__{}
 
-  @required_fields ~w(station1 station2 qso_timestamp mode band)a
-  @optional_fields ~w(grid1 grid2 pos1 pos2 distance_km user_id)a
+  @required_fields ~w(station1 station2 qso_timestamp band)a
+  @optional_fields ~w(grid1 grid2 pos1 pos2 distance_km user_id mode)a
 
   @spec changeset(t() | Ecto.Changeset.t(), map()) :: Ecto.Changeset.t()
   def changeset(contact, attrs) do
@@ -60,7 +60,7 @@ defmodule Microwaveprop.Radio.Contact do
   end
 
   @submission_fields ~w(station1 station2 qso_timestamp mode band grid1 grid2 submitter_email)a
-  @submission_required ~w(station1 station2 qso_timestamp mode band grid1 grid2)a
+  @submission_required ~w(station1 station2 qso_timestamp band grid1 grid2)a
   @allowed_modes ~w(CW SSB FM FT8 FT4 Q65)
   @allowed_bands Enum.map(~w(1296 2304 3456 5760 10000 24000 47000 68000 75000 122000 134000 241000), &Decimal.new/1)
 
@@ -74,6 +74,7 @@ defmodule Microwaveprop.Radio.Contact do
     |> sanitize_callsign(:station2)
     |> sanitize_grid(:grid1)
     |> sanitize_grid(:grid2)
+    |> normalize_blank_mode()
     |> validate_callsign(:station1)
     |> validate_callsign(:station2)
     |> validate_grid_format(:grid1)
@@ -86,6 +87,22 @@ defmodule Microwaveprop.Radio.Contact do
     |> validate_length(:station2, max: 20)
   end
 
+  # Treat empty / whitespace-only mode strings as "not provided" so the column
+  # ends up NULL instead of failing validate_inclusion. Mode is optional on the
+  # submission path.
+  defp normalize_blank_mode(changeset) do
+    case get_change(changeset, :mode) do
+      nil ->
+        changeset
+
+      value ->
+        case String.trim(value) do
+          "" -> put_change(changeset, :mode, nil)
+          trimmed -> put_change(changeset, :mode, trimmed)
+        end
+    end
+  end
+
   # Either a user_id (logged-in submitter) or a submitter_email (anonymous)
   # must be present so we know who submitted the contact.
   defp validate_user_or_email(changeset) do

lib/microwaveprop/radio/csv_import.ex

@@ -29,8 +29,8 @@ defmodule Microwaveprop.Radio.CsvImport do
 
   @dedup_window_seconds 3600
 
-  @expected_columns 7
-  @columns ~w(station1 station2 grid1 grid2 band mode qso_timestamp)
+  @columns_with_mode ~w(station1 station2 grid1 grid2 band mode qso_timestamp)
+  @columns_without_mode ~w(station1 station2 grid1 grid2 band qso_timestamp)
 
   @doc """
   Parse-and-insert in one shot. Kept for backward compatibility — does NOT
@@ -156,19 +156,29 @@ defmodule Microwaveprop.Radio.CsvImport do
   defp parse_row(line, row_num, submitter_email) do
     fields = parse_csv_fields(line)
 
-    if length(fields) == @expected_columns do
-      attrs =
-        @columns
-        |> Enum.zip(fields)
-        |> Map.new()
-        |> Map.put("submitter_email", submitter_email)
+    case columns_for(length(fields)) do
+      nil ->
+        {:invalid,
+         %{
+           row_num: row_num,
+           messages: ["expected 6 columns (no mode) or 7 columns (with mode), got #{length(fields)}"]
+         }}
 
-      parse_row_with_timestamp(attrs, row_num)
-    else
-      {:invalid, %{row_num: row_num, messages: ["expected #{@expected_columns} columns, got #{length(fields)}"]}}
+      columns ->
+        attrs =
+          columns
+          |> Enum.zip(fields)
+          |> Map.new()
+          |> Map.put("submitter_email", submitter_email)
+
+        parse_row_with_timestamp(attrs, row_num)
     end
   end
 
+  defp columns_for(7), do: @columns_with_mode
+  defp columns_for(6), do: @columns_without_mode
+  defp columns_for(_), do: nil
+
   defp parse_row_with_timestamp(attrs, row_num) do
     case normalize_timestamp(attrs["qso_timestamp"]) do
       {:ok, iso_timestamp} ->

lib/microwaveprop_web/components/core_components.ex

@@ -235,7 +235,9 @@ defmodule MicrowavepropWeb.CoreComponents do
     ~H"""
     <div class="fieldset mb-2">
       <label>
-        <span :if={@label} class="label mb-1">{@label}</span>
+        <span :if={@label} class="label mb-1">
+          {@label}<span :if={@rest[:required]} class="text-error ml-0.5" aria-hidden="true">*</span>
+        </span>
         <select
           id={@id}
           name={@name}
@@ -256,7 +258,9 @@ defmodule MicrowavepropWeb.CoreComponents do
     ~H"""
     <div class="fieldset mb-2">
       <label>
-        <span :if={@label} class="label mb-1">{@label}</span>
+        <span :if={@label} class="label mb-1">
+          {@label}<span :if={@rest[:required]} class="text-error ml-0.5" aria-hidden="true">*</span>
+        </span>
         <textarea
           id={@id}
           name={@name}
@@ -277,7 +281,9 @@ defmodule MicrowavepropWeb.CoreComponents do
     ~H"""
     <div class="fieldset mb-2">
       <label>
-        <span :if={@label} class="label mb-1">{@label}</span>
+        <span :if={@label} class="label mb-1">
+          {@label}<span :if={@rest[:required]} class="text-error ml-0.5" aria-hidden="true">*</span>
+        </span>
         <input
           type={@type}
           name={@name}

lib/microwaveprop_web/live/contact_map_live.ex

@@ -2,10 +2,7 @@ defmodule MicrowavepropWeb.ContactMapLive do
   @moduledoc false
   use MicrowavepropWeb, :live_view
 
-  import Ecto.Query
-
-  alias Microwaveprop.Radio.Contact
-  alias Microwaveprop.Repo
+  alias Microwaveprop.Radio
 
   @band_colors %{
     1296 => "#475569",
@@ -24,23 +21,15 @@ defmodule MicrowavepropWeb.ContactMapLive do
 
   @impl true
   def mount(_params, _session, socket) do
-    contacts = load_contacts()
-
-    bands =
-      contacts
-      |> Enum.map(fn [_, _, _, _, band | _] -> band end)
-      |> Enum.uniq()
-      |> Enum.sort()
-
-    enabled_bands = MapSet.new(bands)
+    %{json: json, count: count, bands: bands} = Radio.contact_map_payload()
 
     {:ok,
      assign(socket,
        page_title: "Contact Map",
-       contacts_json: Jason.encode!(contacts),
-       contact_count: length(contacts),
+       contacts_json: IO.iodata_to_binary(json),
+       contact_count: count,
        all_bands: bands,
-       enabled_bands: enabled_bands,
+       enabled_bands: MapSet.new(bands),
        callsign_filter: ""
      )}
   end
@@ -92,67 +81,6 @@ defmodule MicrowavepropWeb.ContactMapLive do
 
   defp band_color(mhz), do: Map.get(@band_colors, mhz, "#64748b")
 
-  defp load_contacts do
-    from(c in Contact,
-      where: not is_nil(c.pos1) and not is_nil(c.pos2),
-      select: %{
-        id: c.id,
-        pos1: c.pos1,
-        pos2: c.pos2,
-        band: c.band,
-        station1: c.station1,
-        station2: c.station2,
-        mode: c.mode,
-        distance_km: c.distance_km,
-        qso_timestamp: c.qso_timestamp
-      }
-    )
-    |> Repo.all()
-    |> Enum.map(&format_contact/1)
-    |> Enum.reject(&is_nil/1)
-    |> dedup_reciprocals()
-  end
-
-  defp format_contact(c) do
-    lat1 = c.pos1["lat"]
-    lon1 = c.pos1["lon"] || c.pos1["lng"]
-    lat2 = c.pos2["lat"]
-    lon2 = c.pos2["lon"] || c.pos2["lng"]
-
-    if lat1 && lon1 && lat2 && lon2 do
-      [
-        lat1,
-        lon1,
-        lat2,
-        lon2,
-        format_band(c.band),
-        c.station1,
-        c.station2,
-        c.mode,
-        format_distance(c.distance_km),
-        format_timestamp(c.qso_timestamp),
-        c.id
-      ]
-    end
-  end
-
-  defp format_band(nil), do: 0
-  defp format_band(band), do: Decimal.to_integer(band)
-
-  defp format_distance(nil), do: nil
-  defp format_distance(d), do: Decimal.to_float(d)
-
-  defp format_timestamp(nil), do: nil
-  defp format_timestamp(ts), do: Calendar.strftime(ts, "%Y-%m-%d %H:%M")
-
-  # Deduplicate reciprocal contacts (A↔B same band/hour = same contact logged by both sides)
-  defp dedup_reciprocals(contacts) do
-    Enum.uniq_by(contacts, fn [_lat1, _lon1, _lat2, _lon2, band, s1, s2, _mode, _dist, ts, _id] ->
-      stations = Enum.sort([s1 || "", s2 || ""])
-      hour = if ts, do: String.slice(ts, 0..12), else: ""
-      {stations, band, hour}
-    end)
-  end
 
   @impl true
   def render(assigns) do

lib/microwaveprop_web/live/submit_live.ex

@@ -362,9 +362,8 @@ defmodule MicrowavepropWeb.SubmitLive do
           field={@form[:mode]}
           type="select"
           label="Mode"
-          prompt="Select mode"
+          prompt="Optional"
           options={@mode_options}
-          required
         />
         <.input
           field={@form[:qso_timestamp]}
@@ -405,9 +404,7 @@ defmodule MicrowavepropWeb.SubmitLive do
     <div class="space-y-6">
       <div class="alert text-sm">
         <div>
-          <p class="mb-2">
-            Upload a CSV file with multiple contacts. Required columns:
-          </p>
+          <p class="mb-2">Upload a CSV file with multiple contacts. Columns:</p>
           <code class="text-xs">station1, station2, grid1, grid2, band, mode, qso_timestamp</code>
           <ul class="list-disc list-inside mt-2 space-y-1 text-base-content/60">
             <li>
@@ -417,6 +414,10 @@ defmodule MicrowavepropWeb.SubmitLive do
               Grid squares should be as detailed as possible (8 characters preferred, e.g. EM12kp37)
             </li>
             <li>Band in MHz (e.g. 10000, 24000)</li>
+            <li>
+              Mode is <strong>optional</strong> — omit the <code>mode</code> column entirely
+              (6 columns total) or leave its value blank.
+            </li>
           </ul>
           <p class="mt-2">
             <a href="/downloads/sample_contacts.csv" download class="link link-primary">

priv/repo/migrations/20260412173459_add_contacts_inserted_at_desc_index.exs

@@ -0,0 +1,13 @@
+defmodule Microwaveprop.Repo.Migrations.AddContactsInsertedAtDescIndex do
+  use Ecto.Migration
+
+  # Matches the default sort for `Radio.list_contacts/1` which is
+  # `ORDER BY inserted_at DESC, id DESC`. Without this index Postgres does a
+  # Seq Scan + top-N heapsort over every row on each `/contacts` page load
+  # (measured ~77ms on 58k rows).
+  def change do
+    create index(:contacts, ["inserted_at DESC", "id DESC"],
+             name: :contacts_inserted_at_desc_id_desc_idx
+           )
+  end
+end

priv/repo/migrations/20260412174304_make_contacts_mode_nullable.exs

@@ -0,0 +1,9 @@
+defmodule Microwaveprop.Repo.Migrations.MakeContactsModeNullable do
+  use Ecto.Migration
+
+  def change do
+    alter table(:contacts) do
+      modify :mode, :string, null: true, from: {:string, null: false}
+    end
+  end
+end

test/microwaveprop/cache_test.exs

@@ -0,0 +1,46 @@
+defmodule Microwaveprop.CacheTest do
+  use ExUnit.Case, async: false
+
+  alias Microwaveprop.Cache
+
+  setup do
+    Cache.clear()
+    :ok
+  end
+
+  describe "fetch_or_store/3" do
+    test "invokes the function and returns the value on a cold cache" do
+      assert Cache.fetch_or_store(:the_key, 1_000, fn -> 42 end) == 42
+    end
+
+    test "returns the cached value without invoking the function on a warm hit" do
+      Cache.fetch_or_store(:the_key, 1_000, fn -> 42 end)
+      assert Cache.fetch_or_store(:the_key, 1_000, fn -> raise "should not run" end) == 42
+    end
+
+    test "re-invokes the function once the TTL expires" do
+      Cache.put(:the_key, 1, -1)
+      assert Cache.fetch_or_store(:the_key, 1_000, fn -> 2 end) == 2
+    end
+
+    test "isolates values by key" do
+      assert Cache.fetch_or_store(:a, 1_000, fn -> 1 end) == 1
+      assert Cache.fetch_or_store(:b, 1_000, fn -> 2 end) == 2
+      assert Cache.fetch_or_store(:a, 1_000, fn -> raise "no" end) == 1
+      assert Cache.fetch_or_store(:b, 1_000, fn -> raise "no" end) == 2
+    end
+  end
+
+  describe "put/3 and invalidate/1" do
+    test "put/3 stores a value with the given TTL" do
+      Cache.put(:k, "hello", 1_000)
+      assert Cache.fetch_or_store(:k, 1_000, fn -> "other" end) == "hello"
+    end
+
+    test "invalidate/1 removes an entry, forcing the next fetch to recompute" do
+      Cache.put(:k, "stale", 60_000)
+      Cache.invalidate(:k)
+      assert Cache.fetch_or_store(:k, 1_000, fn -> "fresh" end) == "fresh"
+    end
+  end
+end

test/microwaveprop/radio/contact_submission_test.exs

@@ -20,18 +20,29 @@ defmodule Microwaveprop.Radio.ContactSubmissionTest do
       assert changeset.valid?
     end
 
-    test "requires station1, station2, qso_timestamp, mode, band, grid1, grid2, submitter_email" do
+    test "requires station1, station2, qso_timestamp, band, grid1, grid2, submitter_email" do
       changeset = Contact.submission_changeset(%Contact{}, %{})
       errors = errors_on(changeset)
 
       assert errors[:station1]
       assert errors[:station2]
       assert errors[:qso_timestamp]
-      assert errors[:mode]
       assert errors[:band]
       assert errors[:grid1]
       assert errors[:grid2]
       assert errors[:submitter_email]
+
+      # Mode is optional on submission
+      refute errors[:mode]
+    end
+
+    test "accepts a blank mode and normalises it to nil" do
+      for blank <- ["", "   ", nil] do
+        attrs = Map.put(@valid_attrs, :mode, blank)
+        changeset = Contact.submission_changeset(%Contact{}, attrs)
+        assert changeset.valid?, "Expected blank mode #{inspect(blank)} to validate"
+        assert Ecto.Changeset.get_field(changeset, :mode) == nil
+      end
     end
 
     test "rejects invalid grid1" do

test/microwaveprop/radio/contact_test.exs

@@ -22,16 +22,15 @@ defmodule Microwaveprop.Radio.ContactTest do
       assert changeset.valid?
     end
 
-    test "requires station1, station2, qso_timestamp, mode, and band" do
+    test "requires station1, station2, qso_timestamp, and band (mode is optional)" do
       changeset = Contact.changeset(%Contact{}, %{})
 
-      assert %{
-               station1: ["can't be blank"],
-               station2: ["can't be blank"],
-               qso_timestamp: ["can't be blank"],
-               mode: ["can't be blank"],
-               band: ["can't be blank"]
-             } = errors_on(changeset)
+      errors = errors_on(changeset)
+      assert errors.station1 == ["can't be blank"]
+      assert errors.station2 == ["can't be blank"]
+      assert errors.qso_timestamp == ["can't be blank"]
+      assert errors.band == ["can't be blank"]
+      refute Map.has_key?(errors, :mode)
     end
 
     test "persists to the database" do

test/microwaveprop/radio/csv_import_test.exs

@@ -122,6 +122,25 @@ defmodule Microwaveprop.Radio.CsvImportTest do
       assert {:ok, _result} = CsvImport.import(csv, @submitter)
       assert Repo.aggregate(Contact, :count) == 1
     end
+
+    test "accepts a 6-column CSV without the mode column" do
+      csv =
+        "station1,station2,grid1,grid2,band,qso_timestamp\n" <>
+          "W5XD,K5TR,EM12,EM00,10000,2026-03-28T18:00:00Z"
+
+      assert {:ok, %{imported: [contact], errors: []}} = CsvImport.import(csv, @submitter)
+      assert contact.station1 == "W5XD"
+      assert contact.mode == nil
+    end
+
+    test "accepts a 7-column CSV with a blank mode value" do
+      csv =
+        "station1,station2,grid1,grid2,band,mode,qso_timestamp\n" <>
+          "W5XD,K5TR,EM12,EM00,10000,,2026-03-28T18:00:00Z"
+
+      assert {:ok, %{imported: [contact], errors: []}} = CsvImport.import(csv, @submitter)
+      assert contact.mode == nil
+    end
   end
 
   describe "import/2 with invalid data" do