New cpp folder structure

Signed-off-by: Alexander Borsuk <me@alex.bio>

libs/indexer/data_source_helpers.cpp

@@ -0,0 +1,50 @@
+#include "indexer/data_source_helpers.hpp"
+
+#include "indexer/data_source.hpp"
+#include "indexer/feature_algo.hpp"
+#include "indexer/scales.hpp"
+
+namespace indexer
+{
+using namespace std;
+
+void ForEachFeatureAtPoint(DataSource const & dataSource, function<void(FeatureType &)> && fn,
+                           m2::PointD const & mercator, double toleranceInMeters)
+{
+  double constexpr kSelectRectWidthInMeters = 1.1;
+  double constexpr kMetersToLinearFeature = 3;
+  int constexpr kScale = scales::GetUpperScale();
+  m2::RectD const rect =
+      mercator::RectByCenterXYAndSizeInMeters(mercator, kSelectRectWidthInMeters);
+
+  auto const emitter = [&fn, &rect, &mercator, toleranceInMeters](FeatureType & ft) {
+    switch (ft.GetGeomType())
+    {
+    case feature::GeomType::Point:
+      if (rect.IsPointInside(ft.GetCenter()))
+        fn(ft);
+      break;
+    case feature::GeomType::Line:
+      if (feature::GetMinDistanceMeters(ft, mercator) < kMetersToLinearFeature)
+        fn(ft);
+      break;
+    case feature::GeomType::Area:
+    {
+      auto limitRect = ft.GetLimitRect(kScale);
+      // Be a little more tolerant. When used by editor mercator is given
+      // with some error, so we must extend limit rect a bit.
+      limitRect.Inflate(kMwmPointAccuracy, kMwmPointAccuracy);
+      if (limitRect.IsPointInside(mercator) &&
+          feature::GetMinDistanceMeters(ft, mercator) <= toleranceInMeters)
+      {
+        fn(ft);
+      }
+    }
+    break;
+    case feature::GeomType::Undefined: ASSERT(false, ("case feature::GeomType::Undefined")); break;
+    }
+  };
+
+  dataSource.ForEachInRect(emitter, rect, kScale);
+}
+}  // namespace indexer