Support source=gps in URL for dynamic GPS-based bookmarks

Bookmarking /path?source=gps&destination=K5TR&band=10000 will use
the viewer's device GPS to resolve the source location on load.
The LocateMe hook handles both button clicks and server-pushed
request_gps events. Once coords are resolved, the URL is updated
with actual lat,lon and calculation runs automatically.

assets/js/locate_me_hook.js

@@ -1,27 +1,32 @@
 export const LocateMe = {
   mounted() {
-    this.el.addEventListener("click", () => {
-      if (!navigator.geolocation) {
-        alert("Geolocation is not supported by this browser")
-        return
-      }
+    this.el.addEventListener("click", () => this.locate())
 
-      this.el.classList.add("loading", "loading-spinner")
+    // Also respond to server-pushed request (for source=gps URLs)
+    this.handleEvent("request_gps", () => this.locate())
+  },
 
-      navigator.geolocation.getCurrentPosition(
-        (pos) => {
-          this.el.classList.remove("loading", "loading-spinner")
-          this.pushEvent("gps_location", {
-            lat: pos.coords.latitude,
-            lon: pos.coords.longitude
-          })
-        },
-        (err) => {
-          this.el.classList.remove("loading", "loading-spinner")
-          alert("Could not get location: " + err.message)
-        },
-        { enableHighAccuracy: true, timeout: 10000 }
-      )
-    })
+  locate() {
+    if (!navigator.geolocation) {
+      alert("Geolocation is not supported by this browser")
+      return
+    }
+
+    this.el.classList.add("loading", "loading-spinner")
+
+    navigator.geolocation.getCurrentPosition(
+      (pos) => {
+        this.el.classList.remove("loading", "loading-spinner")
+        this.pushEvent("gps_location", {
+          lat: pos.coords.latitude,
+          lon: pos.coords.longitude
+        })
+      },
+      (err) => {
+        this.el.classList.remove("loading", "loading-spinner")
+        alert("Could not get location: " + err.message)
+      },
+      { enableHighAccuracy: true, timeout: 10000 }
+    )
   }
 }

lib/microwaveprop_web/live/path_live.ex

@@ -70,8 +70,17 @@ defmodule MicrowavepropWeb.PathLive do
         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
+    # If source=gps, request device location via JS
+    if p["source"] == "gps" and connected?(socket) do
+      {:noreply, push_event(socket, "request_gps", %{})}
+    else
+      auto_calculate(socket, p)
+    end
+  end
+
+  defp auto_calculate(socket, p) do
+    if p["source"] != "" and p["source"] != "gps" 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)
@@ -152,9 +161,26 @@ defmodule MicrowavepropWeb.PathLive do
   end
 
   def handle_event("gps_location", %{"lat" => lat, "lon" => lon}, socket) do
-    # Use coordinate string as source — resolve_location handles lat,lon format
     source = "#{Float.round(lat / 1, 6)},#{Float.round(lon / 1, 6)}"
-    {:noreply, assign(socket, source: source)}
+
+    # Replace gps with actual coords in URL and trigger calculation
+    socket = assign(socket, source: source, result: nil)
+
+    url_params =
+      %{
+        "source" => source,
+        "destination" => socket.assigns.destination,
+        "band" => socket.assigns.band,
+        "src_height_ft" => socket.assigns.src_height_ft,
+        "dst_height_ft" => socket.assigns.dst_height_ft,
+        "tx_power_dbm" => socket.assigns.tx_power_dbm,
+        "src_gain_dbi" => socket.assigns.src_gain_dbi,
+        "dst_gain_dbi" => socket.assigns.dst_gain_dbi
+      }
+      |> Enum.reject(fn {_k, v} -> v == "" end)
+      |> Map.new()
+
+    {:noreply, push_patch(socket, to: ~p"/path?#{url_params}", replace: true)}
   end
 
   @impl true