MapLibreParticleLab/src/mbgl/style/sources/geojson_source_impl.cpp

#include <mbgl/style/sources/geojson_source_impl.hpp>
#include <mbgl/tile/tile_id.hpp>
#include <mbgl/util/constants.hpp>
#include <mbgl/util/feature.hpp>
#include <mbgl/util/string.hpp>

#include <mapbox/geojsonvt.hpp>
#include <supercluster.hpp>

#include <cmath>

namespace mbgl {
namespace style {

class GeoJSONVTData : public GeoJSONData {
public:
    GeoJSONVTData(const GeoJSON& geoJSON, const mapbox::geojsonvt::Options& options)
        : impl(geoJSON, options) {
    }

    mapbox::feature::feature_collection<int16_t> getTile(const CanonicalTileID& tileID) final {
        return impl.getTile(tileID.z, tileID.x, tileID.y).features;
    }

    mapbox::feature::feature_collection<double> getChildren(const std::uint32_t) final {
        return {};
    }

    mapbox::feature::feature_collection<double>
    getLeaves(const std::uint32_t, const std::uint32_t, const std::uint32_t) final {
        return {};
    }

    std::uint8_t getClusterExpansionZoom(std::uint32_t) final {
        return 0;
    }

private:
    mapbox::geojsonvt::GeoJSONVT impl;
};

class SuperclusterData : public GeoJSONData {
public:
    SuperclusterData(const mapbox::feature::feature_collection<double>& features,
                     const mapbox::supercluster::Options& options)
        : impl(features, options) {
    }

    mapbox::feature::feature_collection<int16_t> getTile(const CanonicalTileID& tileID) final {
        return impl.getTile(tileID.z, tileID.x, tileID.y);
    }

    mapbox::feature::feature_collection<double> getChildren(const std::uint32_t cluster_id) final {
        return impl.getChildren(cluster_id);
    }

    mapbox::feature::feature_collection<double> getLeaves(const std::uint32_t cluster_id,
                                                          const std::uint32_t limit,
                                                          const std::uint32_t offset) final {
        return impl.getLeaves(cluster_id, limit, offset);
    }

    std::uint8_t getClusterExpansionZoom(std::uint32_t cluster_id) final {
        return impl.getClusterExpansionZoom(cluster_id);
    }

private:
    mapbox::supercluster::Supercluster impl;
};

template <class T>
T evaluateFeature(const mapbox::feature::feature<double>& f,
                  const std::shared_ptr<expression::Expression>& expression,
                  optional<T> accumulated = nullopt) {
    const expression::EvaluationResult result = expression->evaluate(accumulated, f);
    if (result) {
        optional<T> typed = expression::fromExpressionValue<T>(*result);
        if (typed) {
            return std::move(*typed);
        }
    }
    return T();
}

GeoJSONSource::Impl::Impl(std::string id_, optional<GeoJSONOptions> options_)
    : Source::Impl(SourceType::GeoJSON, std::move(id_)) {
    options = options_ ? std::move(*options_) : GeoJSONOptions{};
}

GeoJSONSource::Impl::Impl(const Impl& other, const GeoJSON& geoJSON)
    : Source::Impl(other), options(other.options) {
    constexpr double scale = util::EXTENT / util::tileSize;
    if (options.cluster && geoJSON.is<mapbox::feature::feature_collection<double>>() &&
        !geoJSON.get<mapbox::feature::feature_collection<double>>().empty()) {
        mapbox::supercluster::Options clusterOptions;
        clusterOptions.maxZoom = options.clusterMaxZoom;
        clusterOptions.extent = util::EXTENT;
        clusterOptions.radius = ::round(scale * options.clusterRadius);
        Feature feature;
        clusterOptions.map = [&](const PropertyMap& properties) -> PropertyMap {
            PropertyMap ret{};
            if (properties.empty()) return ret;
            for (const auto& p : options.clusterProperties) {
                feature.properties = properties;
                ret[p.first] = evaluateFeature<Value>(feature, p.second.first);
            }
            return ret;
        };
        clusterOptions.reduce = [&](PropertyMap& toReturn, const PropertyMap& toFill) {
            for (const auto& p : options.clusterProperties) {
                if (toFill.count(p.first) == 0) {
                    continue;
                }
                feature.properties = toFill;
                optional<Value> accumulated(toReturn[p.first]);
                toReturn[p.first] = evaluateFeature<Value>(feature, p.second.second, accumulated);
            }
        };
        data = std::make_shared<SuperclusterData>(
            geoJSON.get<mapbox::feature::feature_collection<double>>(), clusterOptions);
    } else {
        mapbox::geojsonvt::Options vtOptions;
        vtOptions.maxZoom = options.maxzoom;
        vtOptions.extent = util::EXTENT;
        vtOptions.buffer = ::round(scale * options.buffer);
        vtOptions.tolerance = scale * options.tolerance;
        vtOptions.lineMetrics = options.lineMetrics;
        data = std::make_shared<GeoJSONVTData>(geoJSON, vtOptions);
    }
}

GeoJSONSource::Impl::~Impl() = default;

Range<uint8_t> GeoJSONSource::Impl::getZoomRange() const {
    return { options.minzoom, options.maxzoom };
}

std::weak_ptr<GeoJSONData> GeoJSONSource::Impl::getData() const {
    return data;
}

optional<std::string> GeoJSONSource::Impl::getAttribution() const {
    return {};
}

} // namespace style
} // namespace mbgl