#pragma once

#include <city.h>

#include <Common/HashTable/Hash.h>

#if __SSE4_2__
#include <nmmintrin.h>
#endif


namespace DB
{

/// For aggregation by SipHash, UUID type or concatenation of several fields.
struct UInt128
{
/// Suppress gcc7 warnings: 'prev_key.DB::UInt128::low' may be used uninitialized in this function
#if !__clang__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif

    UInt64 low;
    UInt64 high;

    UInt128() = default;
    explicit UInt128(const UInt64 rhs) : low(0), high(rhs) { }
    explicit UInt128(const UInt64 low, const UInt64 high) : low(low), high(high) { }

    bool inline operator== (const UInt128 rhs) const { return std::tie(low, high) == std::tie(rhs.low, rhs.high); }
    bool inline operator!= (const UInt128 rhs) const { return !(*this == rhs); }

    bool inline operator<  (const UInt128 rhs) const { return std::tie(low, high) < std::tie(rhs.low, rhs.high); }
    bool inline operator<= (const UInt128 rhs) const { return !(rhs < *this); }
    bool inline operator>  (const UInt128 rhs) const { return rhs < *this; }
    bool inline operator>= (const UInt128 rhs) const { return !(*this < rhs); }

    /** Type stored in the database will contain no more than 64 bits at the moment, don't need
     *  to check the `high` element 
     */
    template<typename T> bool inline operator== (const T rhs) const { return *this == UInt128(0, rhs); }
    template<typename T> bool inline operator!= (const T rhs) const { return *this != UInt128(0, rhs); }
    template<typename T> bool inline operator>= (const T rhs) const { return *this >= UInt128(0, rhs); }
    template<typename T> bool inline operator>  (const T rhs) const { return *this >  UInt128(0, rhs); }
    template<typename T> bool inline operator<= (const T rhs) const { return *this <= UInt128(0, rhs); }
    template<typename T> bool inline operator<  (const T rhs) const { return *this <  UInt128(0, rhs); }

    template<typename T> explicit operator T() const { return static_cast<T>(high); }

#if !__clang__
#pragma GCC diagnostic pop
#endif

    UInt128 & operator= (const UInt64 rhs) { low = 0; high = rhs; return *this; }
};

template<typename T> bool inline operator== (T a, const UInt128 b) { return b == a; }
template<typename T> bool inline operator!= (T a, const UInt128 b) { return b != a; }
template<typename T> bool inline operator>= (T a, const UInt128 b) { return b.low == 0 && a >= static_cast<T>(b.high); }
template<typename T> bool inline operator>  (T a, const UInt128 b) { return b.low == 0 && a >  static_cast<T>(b.high); }
template<typename T> bool inline operator<= (T a, const UInt128 b) { return b.low != 0 || a <= static_cast<T>(b.high); }
template<typename T> bool inline operator<  (T a, const UInt128 b) { return b.low != 0 || a <  static_cast<T>(b.high); }

struct UInt128Hash
{
    size_t operator()(UInt128 x) const
    {
        return CityHash_v1_0_2::Hash128to64({x.low, x.high});
    }
};

#if __SSE4_2__

struct UInt128HashCRC32
{
    size_t operator()(UInt128 x) const
    {
        UInt64 crc = -1ULL;
        crc = _mm_crc32_u64(crc, x.low);
        crc = _mm_crc32_u64(crc, x.high);
        return crc;
    }
};

#else

/// On other platforms we do not use CRC32. NOTE This can be confusing.
struct UInt128HashCRC32 : public UInt128Hash {};

#endif

struct UInt128TrivialHash
{
    size_t operator()(UInt128 x) const { return x.low; }
};



/** Used for aggregation, for putting a large number of constant-length keys in a hash table.
  */
struct UInt256
{

/// Suppress gcc7 warnings: 'prev_key.DB::UInt256::a' may be used uninitialized in this function
#if !__clang__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
#endif

    UInt64 a;
    UInt64 b;
    UInt64 c;
    UInt64 d;

    bool operator== (const UInt256 rhs) const
    {
        return a == rhs.a && b == rhs.b && c == rhs.c && d == rhs.d;

    /* So it's no better.
        return 0xFFFF == _mm_movemask_epi8(_mm_and_si128(
            _mm_cmpeq_epi8(
                _mm_loadu_si128(reinterpret_cast<const __m128i *>(&a)),
                _mm_loadu_si128(reinterpret_cast<const __m128i *>(&rhs.a))),
            _mm_cmpeq_epi8(
                _mm_loadu_si128(reinterpret_cast<const __m128i *>(&c)),
                _mm_loadu_si128(reinterpret_cast<const __m128i *>(&rhs.c)))));*/
    }

    bool operator!= (const UInt256 rhs) const { return !operator==(rhs); }

    bool operator== (const UInt64 rhs) const { return a == rhs && b == 0 && c == 0 && d == 0; }
    bool operator!= (const UInt64 rhs) const { return !operator==(rhs); }

#if !__clang__
#pragma GCC diagnostic pop
#endif

    UInt256 & operator= (const UInt64 rhs) { a = rhs; b = 0; c = 0; d = 0; return *this; }
};

struct UInt256Hash
{
    size_t operator()(UInt256 x) const
    {
        /// NOTE suboptimal
        return CityHash_v1_0_2::Hash128to64({CityHash_v1_0_2::Hash128to64({x.a, x.b}), CityHash_v1_0_2::Hash128to64({x.c, x.d})});
    }
};

#if __SSE4_2__

struct UInt256HashCRC32
{
    size_t operator()(UInt256 x) const
    {
        UInt64 crc = -1ULL;
        crc = _mm_crc32_u64(crc, x.a);
        crc = _mm_crc32_u64(crc, x.b);
        crc = _mm_crc32_u64(crc, x.c);
        crc = _mm_crc32_u64(crc, x.d);
        return crc;
    }
};

#else

/// We do not need to use CRC32 on other platforms. NOTE This can be confusing.
struct UInt256HashCRC32
{
    DefaultHash<UInt64> hash64;
    size_t operator()(UInt256 x) const
    {
        /// TODO This is not optimal.
        return hash64(hash64(hash64(hash64(x.a) ^ x.b) ^ x.c) ^ x.d);
    }
};

#endif
}

/// Overload hash for type casting
namespace std
{
template <> struct hash<DB::UInt128>
{
    size_t operator()(const DB::UInt128 & u) const
    {
        return CityHash_v1_0_2::Hash128to64({u.low, u.high});
    }
};

template <> struct is_signed<DB::UInt128>
{
    static constexpr bool value = false;
};

template <> struct is_unsigned<DB::UInt128>
{
    static constexpr bool value = true;
};
}