Find nearest radar site

scwx-qt/source/scwx/qt/config/radar_site.cpp

@@ -8,6 +8,7 @@
 #include <unordered_map>
 
 #include <boost/json.hpp>
+#include <GeographicLib/Geodesic.hpp>
 
 namespace scwx
 {
@@ -30,6 +31,9 @@ static std::unordered_map<std::string, std::shared_ptr<RadarSite>>
 static std::unordered_map<std::string, std::string> siteIdMap_;
 static std::shared_mutex                            siteMutex_;
 
+static GeographicLib::Geodesic geodesic_ {GeographicLib::Constants::WGS84_a(),
+                                          GeographicLib::Constants::WGS84_f()};
+
 static bool ValidateJsonEntry(const boost::json::object& o);
 
 class RadarSiteImpl
@@ -162,6 +166,44 @@ std::vector<std::shared_ptr<RadarSite>> RadarSite::GetAll()
    return radarSites;
 }
 
+std::shared_ptr<RadarSite> RadarSite::FindNearest(
+   double latitude, double longitude, std::optional<std::string> type)
+{
+   std::shared_lock lock(siteMutex_);
+
+   double distanceInMeters;
+
+   std::shared_ptr<RadarSite> nearestRadarSite = nullptr;
+   double                     nearestDistance  = 0.0;
+
+   for (const auto& site : radarSiteMap_)
+   {
+      auto& radarSite = site.second;
+
+      // If the type filter doesn't match, skip
+      if (type.has_value() && radarSite->type() != type)
+      {
+         continue;
+      }
+
+      // Calculate distance to radar site
+      geodesic_.Inverse(latitude,
+                        longitude,
+                        radarSite->latitude(),
+                        radarSite->longitude(),
+                        distanceInMeters);
+
+      // If the radar site is the closer, record it as the closest
+      if (nearestRadarSite == nullptr || distanceInMeters < nearestDistance)
+      {
+         nearestRadarSite = radarSite;
+         nearestDistance  = distanceInMeters;
+      }
+   }
+
+   return nearestRadarSite;
+}
+
 std::string GetRadarIdFromSiteId(const std::string& siteId)
 {
    std::shared_lock lock(siteMutex_);

scwx-qt/source/scwx/qt/config/radar_site.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
@@ -38,6 +39,20 @@ public:
    static std::shared_ptr<RadarSite>              Get(const std::string& id);
    static std::vector<std::shared_ptr<RadarSite>> GetAll();
 
+   /**
+    * Find the nearest radar site to the supplied location.
+    *
+    * @param latitude Latitude in degrees
+    * @param longitude Longitude in degrees
+    * @param type Restrict results to optional radar type
+    *
+    * @return Nearest radar site
+    */
+   static std::shared_ptr<RadarSite>
+   FindNearest(double                     latitude,
+               double                     longitude,
+               std::optional<std::string> type = std::nullopt);
+
    static void   Initialize();
    static size_t ReadConfig(const std::string& path);
 

test/source/scwx/qt/config/radar_site.test.cpp

@@ -12,12 +12,23 @@ namespace config
 static const std::string DEFAULT_RADAR_SITE_FILE =
    ":/res/config/radar_sites.json";
 
-TEST(RadarSite, DefaultConfig)
+class RadarSiteTest : public testing::Test
 {
-   size_t numSites = RadarSite::ReadConfig(DEFAULT_RADAR_SITE_FILE);
+protected:
+   static size_t numSites_;
 
-   ASSERT_GT(numSites, 0);
-   EXPECT_EQ(numSites, 204);
+   static void SetUpTestSuite()
+   {
+      numSites_ = RadarSite::ReadConfig(DEFAULT_RADAR_SITE_FILE);
+   }
+};
+
+size_t RadarSiteTest::numSites_ {0u};
+
+TEST_F(RadarSiteTest, DefaultConfig)
+{
+   ASSERT_GT(numSites_, 0);
+   EXPECT_EQ(numSites_, 204);
 
    std::shared_ptr<RadarSite> radarSite = RadarSite::Get("KLSX");
 
@@ -31,6 +42,25 @@ TEST(RadarSite, DefaultConfig)
    EXPECT_DOUBLE_EQ(radarSite->longitude(), -90.682877);
 }
 
+TEST_F(RadarSiteTest, FindNearest)
+{
+   ASSERT_GT(numSites_, 0);
+
+   std::shared_ptr<RadarSite> nearest1 =
+      RadarSite::FindNearest(46.591111, -112.020278); // Helena, MT
+   std::shared_ptr<RadarSite> nearest2 =
+      RadarSite::FindNearest(28.54, -81.38); // Orlando, FL
+   std::shared_ptr<RadarSite> nearest3 =
+      RadarSite::FindNearest(38.627222, -90.197778, "wsr88d"); // St Louis, MO
+   std::shared_ptr<RadarSite> nearest4 =
+      RadarSite::FindNearest(38.627222, -90.197778, "tdwr"); // St Louis, MO
+
+   EXPECT_EQ(nearest1->id(), "KTFX");
+   EXPECT_EQ(nearest2->id(), "TMCO");
+   EXPECT_EQ(nearest3->id(), "KLSX");
+   EXPECT_EQ(nearest4->id(), "TSTL");
+}
+
 } // namespace config
 } // namespace qt
 } // namespace scwx