[core] Introduce distance expression

Add distance unit choices

Fix cmake and add license

Add support for LineString Features

Add template to geometry helper function

Only support line and point

Rename geometry_within.cpp hpp file to geometry_util.cpp .hpp

Remove incorrect indexFilter, fix pointSetsDistance

Fix distance expression

3 files changed, 40 insertions, 2 deletions

diff --git a/include/mbgl/style/expression/distance.hpp b/include/mbgl/style/expression/distance.hpp
new file mode 100644
index 0000000000..e034b9452f
--- /dev/null
+++ b/include/mbgl/style/expression/distance.hpp
@@ -0,0 +1,38 @@
+#pragma once
+
+#include <mapbox/cheap_ruler.hpp>
+#include <mbgl/style/expression/expression.hpp>
+#include <mbgl/util/geojson.hpp>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+class Distance final : public Expression {
+public:
+    Distance(GeoJSON geoJSONSource_, Feature::geometry_type geometries_, mapbox::cheap_ruler::CheapRuler::Unit unit_);
+
+    ~Distance() override;
+
+    EvaluationResult evaluate(const EvaluationContext&) const override;
+
+    static ParseResult parse(const mbgl::style::conversion::Convertible&, ParsingContext&);
+
+    void eachChild(const std::function<void(const Expression&)>&) const override {}
+
+    bool operator==(const Expression& e) const override;
+
+    std::vector<optional<Value>> possibleOutputs() const override;
+
+    mbgl::Value serialize() const override;
+    std::string getOperator() const override;
+
+private:
+    GeoJSON geoJSONSource;
+    Feature::geometry_type geometries;
+    mapbox::cheap_ruler::CheapRuler::Unit unit;
+};
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl
diff --git a/include/mbgl/style/expression/expression.hpp b/include/mbgl/style/expression/expression.hpp
index e522821185..51cc3b0f15 100644
--- a/include/mbgl/style/expression/expression.hpp
+++ b/include/mbgl/style/expression/expression.hpp
@@ -169,7 +169,8 @@ enum class Kind : int32_t {
     NumberFormat,
     ImageExpression,
     In,
-    Within
+    Within,
+    Distance
 };
 
 class Expression {
diff --git a/include/mbgl/style/expression/within.hpp b/include/mbgl/style/expression/within.hpp
index a8e45f9bf0..37e27f4940 100644
--- a/include/mbgl/style/expression/within.hpp
+++ b/include/mbgl/style/expression/within.hpp
@@ -2,7 +2,6 @@
 
 #include <mbgl/style/expression/expression.hpp>
 #include <mbgl/util/geojson.hpp>
-#include <mbgl/util/geometry_within.hpp>
 #include <mbgl/util/optional.hpp>
 
 namespace mbgl {