ClickHouse/src/Functions/h3EdgeLengthKm.cpp

#include "config_functions.h"

#if USE_H3

#include <Columns/ColumnsNumber.h>
#include <DataTypes/DataTypesNumber.h>
#include <Functions/FunctionFactory.h>
#include <Functions/IFunction.h>
#include <IO/WriteHelpers.h>
#include <Common/typeid_cast.h>
#include <base/range.h>

#include <constants.h>
#include <h3api.h>


namespace DB
{
namespace ErrorCodes
{
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
extern const int ARGUMENT_OUT_OF_BOUND;
extern const int ILLEGAL_COLUMN;
}

namespace
{

class FunctionH3EdgeLengthKm : public IFunction
{
public:
    static constexpr auto name = "h3EdgeLengthKm";

    static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionH3EdgeLengthKm>(); }

    std::string getName() const override { return name; }

    size_t getNumberOfArguments() const override { return 1; }
    bool useDefaultImplementationForConstants() const override { return true; }
    bool isSuitableForShortCircuitArgumentsExecution(const DataTypesWithConstInfo & /*arguments*/) const override { return false; }

    DataTypePtr getReturnTypeImpl(const DataTypes & arguments) const override
    {
        const auto * arg = arguments[0].get();
        if (!WhichDataType(arg).isUInt8())
            throw Exception(
                ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
                "Illegal type {} of argument {} of function {}. Must be UInt8",
                arg->getName(), 1, getName());

        return std::make_shared<DataTypeFloat64>();
    }

    ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t input_rows_count) const override
    {
        auto non_const_arguments = arguments;
        for (auto & argument : non_const_arguments)
            argument.column = argument.column->convertToFullColumnIfConst();

        const auto * column = checkAndGetColumn<ColumnUInt8>(non_const_arguments[0].column.get());
        if (!column)
            throw Exception(
                ErrorCodes::ILLEGAL_COLUMN,
                "Illegal type {} of argument {} of function {}. Must be UInt8",
                arguments[0].type->getName(),
                1,
                getName());

        const auto & data = column->getData();

        auto dst = ColumnVector<Float64>::create();
        auto & dst_data = dst->getData();
        dst_data.resize(input_rows_count);

        for (size_t row = 0; row < input_rows_count; ++row)
        {
            const UInt8 resolution = data[row];
            if (resolution > MAX_H3_RES)
                throw Exception(
                    ErrorCodes::ARGUMENT_OUT_OF_BOUND,
                    "The argument 'resolution' ({}) of function {} is out of bounds because the maximum resolution in H3 library is ",
                    toString(resolution),
                    getName(),
                    MAX_H3_RES);
            Float64 res = getHexagonEdgeLengthAvgKm(resolution);
            dst_data[row] = res;
        }

        return dst;
    }
};

}

REGISTER_FUNCTION(H3EdgeLengthKm)
{
    factory.registerFunction<FunctionH3EdgeLengthKm>();
}

}

#endif