From 8425edbdc40447937dbd6696eed13c42736dd318 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sat, 11 Apr 2026 09:37:25 -0500
Subject: [PATCH] Add comma separators to MHz frequencies on beacon pages

Formats frequencies like 10368.1 as "10,368.1" on both the
beacon list table and detail page (subtitle, map label, stat field).
---
 lib/microwaveprop/beacons/beacon.ex           | 26 +++++++++++++++++++
 .../live/beacon_live/index.ex                 |  4 +--
 .../live/beacon_live/show.ex                  |  6 ++---
 .../live/beacon_live_test.exs                 |  2 +-
 4 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/lib/microwaveprop/beacons/beacon.ex b/lib/microwaveprop/beacons/beacon.ex
index 1de2056c..247ea003 100644
--- a/lib/microwaveprop/beacons/beacon.ex
+++ b/lib/microwaveprop/beacons/beacon.ex
@@ -62,6 +62,32 @@ defmodule Microwaveprop.Beacons.Beacon do
 
   def format_mw(mw), do: to_string(mw)
 
+  @doc "Formats a frequency in MHz with comma separators (e.g. 10368 → \"10,368\")."
+  def format_freq(nil), do: ""
+
+  def format_freq(mhz) when is_number(mhz) do
+    int_part = trunc(mhz)
+    frac = mhz - int_part
+
+    formatted_int =
+      int_part
+      |> Integer.to_string()
+      |> String.reverse()
+      |> String.replace(~r/.{3}/, "\\0,")
+      |> String.trim_trailing(",")
+      |> String.reverse()
+
+    if frac == 0.0 do
+      formatted_int
+    else
+      decimal = mhz |> :erlang.float_to_binary(decimals: 3) |> trim_trailing_zeros()
+      [_int, frac_part] = String.split(decimal, ".")
+      "#{formatted_int}.#{frac_part}"
+    end
+  end
+
+  def format_freq(mhz), do: to_string(mhz)
+
   defp trim_trailing_zeros(str) do
     if String.contains?(str, ".") do
       str |> String.trim_trailing("0") |> String.trim_trailing(".")
diff --git a/lib/microwaveprop_web/live/beacon_live/index.ex b/lib/microwaveprop_web/live/beacon_live/index.ex
index 27b38939..2c9bea74 100644
--- a/lib/microwaveprop_web/live/beacon_live/index.ex
+++ b/lib/microwaveprop_web/live/beacon_live/index.ex
@@ -24,7 +24,7 @@ defmodule MicrowavepropWeb.BeaconLive.Index do
         rows={@streams.beacons}
         row_click={fn {_id, beacon} -> JS.navigate(~p"/beacons/#{beacon}") end}
       >
-        <:col :let={{_id, beacon}} label="Frequency (MHz)">{beacon.frequency_mhz}</:col>
+        <:col :let={{_id, beacon}} label="Frequency (MHz)">{Beacon.format_freq(beacon.frequency_mhz)}</:col>
         <:col :let={{_id, beacon}} label="Call">{beacon.callsign}</:col>
         <:col :let={{_id, beacon}} label="Grid">{beacon.grid}</:col>
         <:col :let={{_id, beacon}} label="Lat">{beacon.lat}</:col>
@@ -65,7 +65,7 @@ defmodule MicrowavepropWeb.BeaconLive.Index do
           rows={@streams.pending}
           row_click={fn {_id, beacon} -> JS.navigate(~p"/beacons/#{beacon}") end}
         >
-          <:col :let={{_id, beacon}} label="Frequency (MHz)">{beacon.frequency_mhz}</:col>
+          <:col :let={{_id, beacon}} label="Frequency (MHz)">{Beacon.format_freq(beacon.frequency_mhz)}</:col>
           <:col :let={{_id, beacon}} label="Call">{beacon.callsign}</:col>
           <:col :let={{_id, beacon}} label="Grid">{beacon.grid}</:col>
           <:col :let={{_id, beacon}} label="EIRP (mW)">{Beacon.format_mw(beacon.power_mw)}</:col>
diff --git a/lib/microwaveprop_web/live/beacon_live/show.ex b/lib/microwaveprop_web/live/beacon_live/show.ex
index f5a4f214..e285524a 100644
--- a/lib/microwaveprop_web/live/beacon_live/show.ex
+++ b/lib/microwaveprop_web/live/beacon_live/show.ex
@@ -13,7 +13,7 @@ defmodule MicrowavepropWeb.BeaconLive.Show do
       <.header>
         {@beacon.callsign}
         <:subtitle>
-          {@beacon.frequency_mhz} MHz &middot; {@beacon.grid}
+          {Beacon.format_freq(@beacon.frequency_mhz)} MHz &middot; {@beacon.grid}
           <span :if={not @beacon.approved} class="badge badge-warning badge-sm ml-2">
             Pending approval
           </span>
@@ -46,7 +46,7 @@ defmodule MicrowavepropWeb.BeaconLive.Show do
         class="h-96 w-full rounded-lg border border-base-300 mb-2"
         data-lat={@beacon.lat}
         data-lon={@beacon.lon}
-        data-label={"#{@beacon.callsign} · #{@beacon.frequency_mhz} MHz"}
+        data-label={"#{@beacon.callsign} · #{Beacon.format_freq(@beacon.frequency_mhz)} MHz"}
         data-on-the-air={to_string(@beacon.on_the_air)}
         data-grid-step={@estimate.grid_step}
         data-cells={Jason.encode!(@estimate.cells)}
@@ -101,7 +101,7 @@ defmodule MicrowavepropWeb.BeaconLive.Show do
 
       <div class="rounded-lg border border-base-300 bg-base-200/40 p-3 text-sm">
         <dl class="grid grid-cols-2 sm:grid-cols-3 md:grid-cols-4 gap-x-4 gap-y-2">
-          <.stat_field label="Frequency">{@beacon.frequency_mhz} MHz</.stat_field>
+          <.stat_field label="Frequency">{Beacon.format_freq(@beacon.frequency_mhz)} MHz</.stat_field>
           <.stat_field label="Callsign">{@beacon.callsign}</.stat_field>
           <.stat_field label="Keying">{Beacon.keying_label(@beacon.keying)}</.stat_field>
           <.stat_field label="On the air">
diff --git a/test/microwaveprop_web/live/beacon_live_test.exs b/test/microwaveprop_web/live/beacon_live_test.exs
index 474333ee..ba198d7d 100644
--- a/test/microwaveprop_web/live/beacon_live_test.exs
+++ b/test/microwaveprop_web/live/beacon_live_test.exs
@@ -84,7 +84,7 @@ defmodule MicrowavepropWeb.BeaconLiveTest do
       beacon = approved_beacon_fixture(user_fixture())
       {:ok, _view, html} = live(conn, ~p"/beacons/#{beacon}")
       assert html =~ beacon.callsign
-      assert html =~ "#{beacon.frequency_mhz}"
+      assert html =~ "10,368.1"
     end
 
     test "shows pending badge on unapproved beacons", %{conn: conn} do