Show a GeoJSON icon next to files with a ready cache

GpxStore#tree now reports a "cached" flag per file (reusing the same
mtime freshness check geojson() already does); the file tree shows a
small curly-braces icon next to any file whose conversion is already
on disk, so it's visible which files will toggle on instantly versus
which still need to parse.

lib/maptool/gpx_store.rb

@@ -22,7 +22,10 @@ module Maptool
     end
 
     # Nested { type:, name:, path:, children: } hash describing every
-    # folder and .gpx/.fit file under the store root.
+    # folder and .gpx/.fit file under the store root. Each file also
+    # carries "cached" — whether its GeoJSON conversion is ready on disk
+    # (see `geojson` below) — so the tree UI can show a file's ready to
+    # view instantly, without a round trip just to find out.
     def tree
       { "type" => "folder", "name" => "root", "path" => "", "children" => list_children(@root, "") }
     end
@@ -112,7 +115,7 @@ module Maptool
       raise Errno::ENOENT, path unless File.file?(path)
 
       cache = geojson_cache_path(path)
-      if !File.file?(cache) || File.mtime(cache) < File.mtime(path)
+      unless geojson_cached?(path)
         data = path.downcase.end_with?(".fit") ? Fit.to_geojson(path) : Gpx.to_geojson(path)
         File.write(cache, JSON.generate(data))
       end
@@ -136,6 +139,11 @@ module Maptool
       "#{path}.geojson"
     end
 
+    def geojson_cached?(path)
+      cache = geojson_cache_path(path)
+      File.file?(cache) && File.mtime(cache) >= File.mtime(path)
+    end
+
     TRACK_EXTENSIONS = %w[.gpx .fit].freeze
 
     def safe_filename(filename)
@@ -165,9 +173,9 @@ module Maptool
         if File.directory?(full)
           { "type" => "folder", "name" => entry, "path" => rel, "children" => list_children(full, rel) }
         elsif entry.downcase.end_with?(".gpx")
-          { "type" => "file", "name" => entry, "path" => rel, "kinds" => Gpx.kinds(full) }
+          { "type" => "file", "name" => entry, "path" => rel, "kinds" => Gpx.kinds(full), "cached" => geojson_cached?(full) }
         elsif entry.downcase.end_with?(".fit")
-          { "type" => "file", "name" => entry, "path" => rel, "kinds" => Fit.kinds(full) }
+          { "type" => "file", "name" => entry, "path" => rel, "kinds" => Fit.kinds(full), "cached" => geojson_cached?(full) }
         end
       end
     end

public/js/gpx.js

@@ -6,6 +6,7 @@ import {
   WAYPOINT_ICON,
   TRACK_ICON,
   ROUTE_ICON,
+  GEOJSON_ICON,
   MAP_MARKER_ICON,
   POI_ICONS,
   PARK4NIGHT_TAGS,
@@ -276,6 +277,7 @@ export class GpxPanelControl {
     name.title = file.name;
     label.appendChild(checkbox);
     (file.kinds || []).forEach((kind) => label.appendChild(this._kindIcon(kind)));
+    if (file.cached) label.appendChild(this._cachedIcon());
     label.appendChild(name);
     row.appendChild(label);
     row.appendChild(this._deleteButton(() => this._deleteFile(file.path)));
@@ -299,6 +301,14 @@ export class GpxPanelControl {
     return icon;
   }
 
+  _cachedIcon() {
+    const icon = document.createElement("span");
+    icon.className = "gpx-tree__kind-icon";
+    icon.innerHTML = GEOJSON_ICON;
+    icon.title = "Ready to view instantly (GeoJSON cached)";
+    return icon;
+  }
+
   _deleteButton(onClick) {
     const button = document.createElement("button");
     button.type = "button";

public/js/icons.js

@@ -54,6 +54,16 @@ export const WAYPOINT_ICON = `
 
 export const TRACK_ICON = GPX_ICON;
 
+// Shown next to a file whose GeoJSON conversion is already cached on disk
+// (GpxStore#geojson) — ready to view instantly instead of paying REXML's
+// parse cost on click. Curly braces read as "structured data ready", the
+// same shorthand most editors/tools use for JSON.
+export const GEOJSON_ICON = `
+<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.6" stroke-linecap="round" stroke-linejoin="round">
+  <path d="M9 4c-1.5 0-2 .8-2 2v3c0 1-.5 1.5-1.5 1.5 1 0 1.5.5 1.5 1.5v3c0 1.2.5 2 2 2"/>
+  <path d="M15 4c1.5 0 2 .8 2 2v3c0 1 .5 1.5 1.5 1.5-1 0-1.5.5-1.5 1.5v3c0 1.2-.5 2-2 2"/>
+</svg>`;
+
 // Same shape as TRACK_ICON, dashed — a route is planned rather than
 // recorded, the same visual convention most map apps use for the
 // distinction.

test/test_gpx_store.rb

@@ -121,6 +121,30 @@ class GpxStoreTest < Minitest::Test
     assert_raises(Errno::ENOENT) { @store.geojson("nope.gpx") }
   end
 
+  def test_tree_reports_cached_true_after_a_successful_save
+    @store.save(folder: "", filename: "ride.gpx", io: StringIO.new(sample_gpx))
+
+    file = @store.tree["children"].find { |c| c["name"] == "ride.gpx" }
+    assert file["cached"]
+  end
+
+  def test_tree_reports_cached_false_for_an_unparseable_file
+    @store.save(folder: "", filename: "bad.gpx", io: StringIO.new("not gpx at all"))
+
+    file = @store.tree["children"].find { |c| c["name"] == "bad.gpx" }
+    refute file["cached"]
+  end
+
+  def test_tree_reports_cached_false_once_the_source_is_resaved
+    path = @store.save(folder: "", filename: "ride.gpx", io: StringIO.new(sample_gpx))
+    FileUtils.touch(@store.resolve_file(path) + ".geojson", mtime: Time.now - 10)
+    File.write(@store.resolve_file(path), sample_gpx)
+    FileUtils.touch(@store.resolve_file(path), mtime: Time.now)
+
+    file = @store.tree["children"].find { |c| c["name"] == "ride.gpx" }
+    refute file["cached"]
+  end
+
   private
 
   def sample_gpx