Add comment describing the overpass queries we use

[rails.git] / app / assets / javascripts / index / query.js

diff --git a/app/assets/javascripts/index/query.js b/app/assets/javascripts/index/query.js
index d9906407d11ead6a476d1187025d14c874640922..01a8a1f69e2ed212d4e3383504c6a81b3fbd6669 100644 (file)
--- a/app/assets/javascripts/index/query.js
+++ b/app/assets/javascripts/index/query.js
@@ -198,16 +198,48 @@ OSM.Query = function(map) {
             .text(I18n.t("javascripts.query.nothing_found"))
             .appendTo($ul);
         }
+      },
+      error: function(xhr, status, error) {
+        $section.find(".loader").stopTime("loading").hide();
+
+        $("<li>")
+          .text(I18n.t("javascripts.query." + status, { server: OSM.OVERPASS_URL, error: error }))
+          .appendTo($ul);
       }
     }));
   }
 
+  /*
+   * To find nearby objects we ask overpass for the union of the
+   * following sets:
+   *
+   *   node(around:<radius>,<lat>,lng>)
+   *   way(around:<radius>,<lat>,lng>)
+   *   node(w)
+   *   relation(around:<radius>,<lat>,lng>)
+   *
+   * to find enclosing objects we first find all the enclosing areas:
+   *
+   *   is_in(<lat>,<lng>)->.a
+   *
+   * and then return the union of the following sets:
+   *
+   *   relation(pivot.a)
+   *   way(pivot.a)
+   *   node(w)
+   *
+   * In order to avoid overly large responses we don't currently
+   * attempt to complete any relations and instead just show those
+   * ways and nodes which are returned for other reasons.
+   */
   function queryOverpass(lat, lng) {
     var latlng = L.latLng(lat, lng),
       radius = 10 * Math.pow(1.5, 19 - map.getZoom()),
       around = "around:" + radius + "," + lat + "," + lng,
-      features = "(node(" + around + ");way(" + around + ");relation(" + around + "))",
-      nearby = "((" + features + ";way(bn));node(w));out;",
+      nodes = "node(" + around + ")",
+      ways = "way(" + around + ");node(w)",
+      relations = "relation(" + around + ")",
+      nearby = "(" + nodes + ";" + ways + ";" + relations + ");out;",
       isin = "is_in(" + lat + "," + lng + ")->.a;(relation(pivot.a);way(pivot.a);node(w));out;";
 
     $("#sidebar_content .query-intro")