Add forecast timeline, shareable URLs, and real-time form updates to /path

- 18-hour propagation forecast bar chart from grid scores at path midpoint
  Shows best/worst score and time, color-coded bars
- URL query params: all form fields reflected in URL, auto-calculates
  when source+destination present. Bookmarkable/shareable links.
- phx-change on form updates assigns in real-time as user types
- Removed LiveStash in favor of URL-based state persistence

lib/microwaveprop_web/live/path_live.ex

@@ -1,8 +1,8 @@
 defmodule MicrowavepropWeb.PathLive do
   @moduledoc false
   use MicrowavepropWeb, :live_view
-  use LiveStash
 
+  alias Microwaveprop.Propagation
   alias Microwaveprop.Propagation.BandConfig
   alias Microwaveprop.Propagation.Scorer
   alias Microwaveprop.Radio.CallsignClient
@@ -22,56 +22,93 @@ defmodule MicrowavepropWeb.PathLive do
     {"241 GHz", "241000"}
   ]
 
-  @stash_fields [
-    :source,
-    :destination,
-    :band,
-    :src_height_ft,
-    :dst_height_ft,
-    :tx_power_dbm,
-    :src_gain_dbi,
-    :dst_gain_dbi
-  ]
+  @url_params ~w(source destination band src_height_ft dst_height_ft tx_power_dbm src_gain_dbi dst_gain_dbi)
+  @defaults %{
+    "source" => "",
+    "destination" => "",
+    "band" => "10000",
+    "src_height_ft" => "30",
+    "dst_height_ft" => "30",
+    "tx_power_dbm" => "20",
+    "src_gain_dbi" => "30",
+    "dst_gain_dbi" => "30"
+  }
 
   @impl true
   def mount(_params, _session, socket) do
-    defaults = %{
-      source: "",
-      destination: "",
-      band: "10000",
-      src_height_ft: "30",
-      dst_height_ft: "30",
-      tx_power_dbm: "20",
-      src_gain_dbi: "30",
-      dst_gain_dbi: "30"
-    }
-
-    recovered =
-      case LiveStash.recover_state(socket) do
-        {:recovered, socket} ->
-          socket.assigns
-          |> Map.take(@stash_fields)
-          |> then(&Map.merge(defaults, &1))
-
-        _ ->
-          defaults
-      end
-
     {:ok,
-     assign(
-       socket,
-       [
-         {:page_title, "Path Calculator"},
-         {:band_options, @band_options},
-         {:result, nil},
-         {:error, nil},
-         {:computing, false}
-       ] ++
-         Map.to_list(recovered)
+     assign(socket,
+       page_title: "Path Calculator",
+       band_options: @band_options,
+       result: nil,
+       error: nil,
+       computing: false,
+       source: "",
+       destination: "",
+       band: "10000",
+       src_height_ft: "30",
+       dst_height_ft: "30",
+       tx_power_dbm: "20",
+       src_gain_dbi: "30",
+       dst_gain_dbi: "30"
      )}
   end
 
   @impl true
+  def handle_params(params, _uri, socket) do
+    p = Map.merge(@defaults, Map.take(params, @url_params))
+
+    socket =
+      assign(socket,
+        source: p["source"],
+        destination: p["destination"],
+        band: p["band"],
+        src_height_ft: p["src_height_ft"],
+        dst_height_ft: p["dst_height_ft"],
+        tx_power_dbm: p["tx_power_dbm"],
+        src_gain_dbi: p["src_gain_dbi"],
+        dst_gain_dbi: p["dst_gain_dbi"]
+      )
+
+    # Auto-calculate if source and destination are in the URL
+    if p["source"] != "" and p["destination"] != "" and not socket.assigns.computing and is_nil(socket.assigns.result) do
+      src_ht = parse_float(p["src_height_ft"], 30.0)
+      dst_ht = parse_float(p["dst_height_ft"], 30.0)
+      tx_dbm = parse_float(p["tx_power_dbm"], 20.0)
+
+      station_params = %{
+        src_height_ft: src_ht,
+        dst_height_ft: dst_ht,
+        src_height_m: src_ht * 0.3048,
+        dst_height_m: dst_ht * 0.3048,
+        tx_power_dbm: tx_dbm,
+        tx_power_mw: :math.pow(10, tx_dbm / 10),
+        src_gain_dbi: parse_float(p["src_gain_dbi"], 30.0),
+        dst_gain_dbi: parse_float(p["dst_gain_dbi"], 30.0)
+      }
+
+      send(self(), {:compute_path, p["source"], p["destination"], String.to_integer(p["band"]), station_params})
+      {:noreply, assign(socket, computing: true)}
+    else
+      {:noreply, socket}
+    end
+  end
+
+  @impl true
+  def handle_event("update_form", params, socket) do
+    {:noreply,
+     assign(socket,
+       source: params["source"] || "",
+       destination: params["destination"] || "",
+       band: params["band"] || "10000",
+       src_height_ft: params["src_height_ft"] || "30",
+       dst_height_ft: params["dst_height_ft"] || "30",
+       tx_power_dbm: params["tx_power_dbm"] || "20",
+       src_gain_dbi: params["src_gain_dbi"] || "30",
+       dst_gain_dbi: params["dst_gain_dbi"] || "30"
+     )}
+  end
+
   def handle_event("calculate", params, socket) do
     src_height_ft = parse_float(params["src_height_ft"], 30.0)
     dst_height_ft = parse_float(params["dst_height_ft"], 30.0)
@@ -110,7 +147,8 @@ defmodule MicrowavepropWeb.PathLive do
       {:compute_path, params["source"], params["destination"], String.to_integer(params["band"]), station_params}
     )
 
-    {:noreply, LiveStash.stash_assigns(socket, @stash_fields)}
+    url_params = params |> Map.take(@url_params) |> Enum.reject(fn {_k, v} -> v == "" end) |> Map.new()
+    {:noreply, push_patch(socket, to: ~p"/path?#{url_params}", replace: true)}
   end
 
   def handle_event("gps_location", %{"lat" => lat, "lon" => lon}, socket) do
@@ -172,6 +210,9 @@ defmodule MicrowavepropWeb.PathLive do
       loss_budget = compute_loss_budget(dist_km, freq_ghz, band_config, terrain_result, conditions)
       power_budget = compute_power_budget(station_params, loss_budget)
 
+      # 18-hour forecast from propagation grid (midpoint of path)
+      forecast = Propagation.point_forecast(band_mhz, midlat, midlon)
+
       {:ok,
        %{
          source: src,
@@ -187,6 +228,7 @@ defmodule MicrowavepropWeb.PathLive do
          scoring: scoring,
          loss_budget: loss_budget,
          power_budget: power_budget,
+         forecast: forecast,
          hrrr_count: length(hrrr_profiles)
        }}
     end
@@ -399,6 +441,9 @@ defmodule MicrowavepropWeb.PathLive do
   defp format_number(n) when is_float(n), do: :erlang.float_to_binary(n, decimals: 1)
   defp format_number(n), do: to_string(n)
 
+  defp format_utc_hour(%DateTime{} = dt), do: Calendar.strftime(dt, "%H:%M")
+  defp format_utc_hour(_), do: "?"
+
   defp format_mw(mw) when mw >= 1000, do: "#{format_number(mw / 1000)} W"
   defp format_mw(mw) when mw >= 1, do: "#{format_number(mw)} mW"
   defp format_mw(mw), do: "#{format_number(mw * 1000)} uW"
@@ -414,7 +459,7 @@ defmodule MicrowavepropWeb.PathLive do
         <:subtitle>Analyze microwave propagation between two points</:subtitle>
       </.header>
 
-      <form phx-submit="calculate" class="bg-base-200 rounded-box p-4 mb-6">
+      <form phx-submit="calculate" phx-change="update_form" class="bg-base-200 rounded-box p-4 mb-6">
         <div class="grid grid-cols-1 md:grid-cols-4 gap-4 items-end">
           <div class="fieldset">
             <label class="label text-sm font-medium">Source (callsign or grid)</label>
@@ -781,6 +826,50 @@ defmodule MicrowavepropWeb.PathLive do
         </div>
       <% end %>
     </div>
+
+    <%!-- 18-Hour Forecast --%>
+    <%= if @result.forecast != [] do %>
+      <div class="bg-base-200 rounded-box p-4 mb-6">
+        <div class="text-xs opacity-60 mb-3">
+          18-Hour Propagation Forecast &middot; {@result.band_config.label}
+        </div>
+        <div class="flex items-end gap-0.5 h-24">
+          <%= for point <- @result.forecast do %>
+            <% pct = max(point.score, 2) %>
+            <div
+              class="flex-1 rounded-t-sm relative group cursor-default"
+              style={"height: #{pct}%; background-color: #{tier_color(point.score)}; min-width: 4px"}
+              title={"#{format_utc_hour(point.valid_time)} UTC: #{point.score}/100 #{tier_label(point.score)}"}
+            >
+            </div>
+          <% end %>
+        </div>
+        <div class="flex justify-between text-xs opacity-50 mt-1">
+          <%= if length(@result.forecast) > 0 do %>
+            <span>{format_utc_hour(List.first(@result.forecast).valid_time)} UTC</span>
+            <span>{format_utc_hour(List.last(@result.forecast).valid_time)} UTC</span>
+          <% end %>
+        </div>
+        <div class="flex justify-between text-xs mt-2">
+          <% best = Enum.max_by(@result.forecast, & &1.score) %>
+          <span>
+            Best:
+            <span class="font-bold" style={"color: #{tier_color(best.score)}"}>
+              {best.score}
+            </span>
+            at {format_utc_hour(best.valid_time)} UTC
+          </span>
+          <% worst = Enum.min_by(@result.forecast, & &1.score) %>
+          <span>
+            Worst:
+            <span class="font-bold" style={"color: #{tier_color(worst.score)}"}>
+              {worst.score}
+            </span>
+            at {format_utc_hour(worst.valid_time)} UTC
+          </span>
+        </div>
+      </div>
+    <% end %>
     """
   end