#include "FunctionsConsistentHashing.h"
#include <Functions/FunctionFactory.h>

#include <consistent_hashing.h>

namespace DB
{

/// An O(1) time and space consistent hash algorithm by Konstantin Oblakov
struct YandexConsistentHashImpl
{
    static constexpr auto name = "yandexConsistentHash";

    using HashType = UInt64;
    /// Actually it supports UInt64, but it is efficient only if n <= 32768
    using ResultType = UInt16;
    using BucketsType = ResultType;
    static constexpr auto max_buckets = 32768;

    static inline ResultType apply(UInt64 hash, BucketsType n)
    {
        return ConsistentHashing(hash, n);
    }
};

using FunctionYandexConsistentHash = FunctionConsistentHashImpl<YandexConsistentHashImpl>;

void registerFunctionYandexConsistentHash(FunctionFactory & factory)
{
    factory.registerFunction<FunctionYandexConsistentHash>();
}

}