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#include <mapbox/geojson.hpp>
#include <mapbox/geometry.hpp>
#include <mbgl/style/conversion_impl.hpp>
#include <mbgl/style/expression/within.hpp>
#include <mbgl/tile/geometry_tile_data.hpp>
#include <mbgl/util/string.hpp>
namespace {
double isLeft(mbgl::Point<double> P0, mbgl::Point<double> P1, mbgl::Point<double> P2) {
return ((P1.x - P0.x) * (P2.y - P0.y) - (P2.x - P0.x) * (P1.y - P0.y));
}
// winding number algorithm for checking if point inside a ploygon or not.
// http://geomalgorithms.com/a03-_inclusion.html#wn_PnPoly()
bool pointWithinPoly(mbgl::Point<double> point, const mapbox::geometry::polygon<double>& polys) {
// wn = the winding number (=0 only when point is outside)
int wn = 0;
for (auto poly : polys) {
auto size = poly.size();
auto i = size;
// loop through every edge of the polygon
for (i = 0; i < size - 1; ++i) {
if (poly[i].y <= point.y) {
if (poly[i + 1].y > point.y) { // upward horizontal crossing from point to edge E(poly[i], poly[i+1])
if (isLeft(poly[i], poly[i + 1], point) > 0) {
++wn;
}
}
} else {
if (poly[i + 1].y <= point.y) { // downward crossing
if (isLeft(poly[i], poly[i + 1], point) < 0) {
--wn;
}
}
}
}
if (wn != 0) {
return true;
}
}
return wn != 0;
}
bool pointsWithinPoly(const mbgl::GeometryTileFeature& feature,
const mbgl::CanonicalTileID& canonical,
const mbgl::GeoJSON& geoJson) {
bool result = false;
geoJson.match(
[&](const mapbox::geometry::geometry<double>& geometrySet) {
geometrySet.match(
[&](const mapbox::geometry::polygon<double>& polygons) {
convertGeometry(feature, canonical)
.match(
[&](const mapbox::geometry::point<double>& point) {
result = pointWithinPoly(point, polygons);
},
[&](const mapbox::geometry::multi_point<double>& points) {
for (const auto& p : points) {
result = pointWithinPoly(p, polygons);
if (!result) {
return;
}
}
},
[&](const auto&) { return; });
},
[&](const auto&) { return; });
},
[&](const auto&) { return; });
return result;
}
mbgl::optional<mbgl::GeoJSON> parseValue(const mbgl::style::conversion::Convertible& value_,
mbgl::style::expression::ParsingContext& ctx) {
if (isObject(value_)) {
const auto geometryType = objectMember(value_, "type");
if (geometryType) {
const auto type = toString(*geometryType);
if (type && *type == "Polygon") {
mbgl::style::conversion::Error error;
auto geojson = toGeoJSON(value_, error);
if (geojson && error.message.empty()) {
return geojson;
}
ctx.error(error.message);
}
}
}
ctx.error("'Within' expression requires valid geojson source that contains polygon geometry type.");
return mbgl::optional<mbgl::GeoJSON>();
}
} // namespace
namespace mbgl {
namespace style {
namespace expression {
using namespace mbgl::style::conversion;
EvaluationResult Within::evaluate(const EvaluationContext& params) const {
if (!params.feature || !params.canonical) {
return false;
}
auto geometryType = params.feature->getType();
// Currently only support Point/Points in polygon
if (geometryType == FeatureType::Point) {
return pointsWithinPoly(*params.feature, *params.canonical, geoJSONSource);
}
return false;
}
ParseResult Within::parse(const Convertible& value, ParsingContext& ctx) {
if (isArray(value)) {
// object value, quoted with ["Within", value]
if (arrayLength(value) != 2) {
ctx.error("'Within' expression requires exactly one argument, but found " +
util::toString(arrayLength(value) - 1) + " instead.");
return ParseResult();
}
auto parsedValue = parseValue(arrayMember(value, 1), ctx);
if (!parsedValue) {
return ParseResult();
}
return ParseResult(std::make_unique<Within>(*parsedValue));
}
return ParseResult();
}
mbgl::Value Within::serialize() const {
return std::vector<mbgl::Value>{{getOperator()}, {mapbox::geojson::stringify(geoJSONSource)}};
}
} // namespace expression
} // namespace style
} // namespace mbgl
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