// Copyright 2021 Google LLC
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Per-target
#if defined(HIGHWAY_HWY_CONTRIB_SORT_TRAITS128_TOGGLE) == \
    defined(HWY_TARGET_TOGGLE)
#ifdef HIGHWAY_HWY_CONTRIB_SORT_TRAITS128_TOGGLE
#undef HIGHWAY_HWY_CONTRIB_SORT_TRAITS128_TOGGLE
#else
#define HIGHWAY_HWY_CONTRIB_SORT_TRAITS128_TOGGLE
#endif

#include <string>

#include "hwy/contrib/sort/shared-inl.h"
#include "hwy/contrib/sort/vqsort.h"  // SortDescending
#include "hwy/highway.h"

HWY_BEFORE_NAMESPACE();
namespace hwy {
namespace HWY_NAMESPACE {
namespace detail {

#if VQSORT_ENABLED || HWY_IDE

// Highway does not provide a lane type for 128-bit keys, so we use uint64_t
// along with an abstraction layer for single-lane vs. lane-pair, which is
// independent of the order.
struct KeyAny128 {
  static constexpr bool Is128() { return true; }
  constexpr size_t LanesPerKey() const { return 2; }

  // What type bench_sort should allocate for generating inputs.
  using LaneType = uint64_t;
  // KeyType and KeyString are defined by derived classes.

  HWY_INLINE void Swap(LaneType* a, LaneType* b) const {
    const FixedTag<LaneType, 2> d;
    const auto temp = LoadU(d, a);
    StoreU(LoadU(d, b), d, a);
    StoreU(temp, d, b);
  }

  template <class V, class M>
  HWY_INLINE V CompressKeys(V keys, M mask) const {
    return CompressBlocksNot(keys, mask);
  }

  template <class D>
  HWY_INLINE Vec<D> SetKey(D d, const TFromD<D>* key) const {
    return LoadDup128(d, key);
  }

  template <class D>
  HWY_INLINE Vec<D> ReverseKeys(D d, Vec<D> v) const {
    return ReverseBlocks(d, v);
  }

  template <class D>
  HWY_INLINE Vec<D> ReverseKeys2(D /* tag */, const Vec<D> v) const {
    return SwapAdjacentBlocks(v);
  }

  // Only called for 4 keys because we do not support >512-bit vectors.
  template <class D>
  HWY_INLINE Vec<D> ReverseKeys4(D d, const Vec<D> v) const {
    HWY_DASSERT(Lanes(d) <= 64 / sizeof(TFromD<D>));
    return ReverseKeys(d, v);
  }

  // Only called for 4 keys because we do not support >512-bit vectors.
  template <class D>
  HWY_INLINE Vec<D> OddEvenPairs(D d, const Vec<D> odd,
                                 const Vec<D> even) const {
    HWY_DASSERT(Lanes(d) <= 64 / sizeof(TFromD<D>));
    return ConcatUpperLower(d, odd, even);
  }

  template <class V>
  HWY_INLINE V OddEvenKeys(const V odd, const V even) const {
    return OddEvenBlocks(odd, even);
  }

  template <class D>
  HWY_INLINE Vec<D> ReverseKeys8(D, Vec<D>) const {
    HWY_ASSERT(0);  // not supported: would require 1024-bit vectors
  }

  template <class D>
  HWY_INLINE Vec<D> ReverseKeys16(D, Vec<D>) const {
    HWY_ASSERT(0);  // not supported: would require 2048-bit vectors
  }

  // This is only called for 8/16 col networks (not supported).
  template <class D>
  HWY_INLINE Vec<D> SwapAdjacentPairs(D, Vec<D>) const {
    HWY_ASSERT(0);
  }

  // This is only called for 16 col networks (not supported).
  template <class D>
  HWY_INLINE Vec<D> SwapAdjacentQuads(D, Vec<D>) const {
    HWY_ASSERT(0);
  }

  // This is only called for 8 col networks (not supported).
  template <class D>
  HWY_INLINE Vec<D> OddEvenQuads(D, Vec<D>, Vec<D>) const {
    HWY_ASSERT(0);
  }
};

// Base class shared between OrderAscending128, OrderDescending128.
struct Key128 : public KeyAny128 {
  // False indicates the entire key should be compared. KV means key-value.
  static constexpr bool IsKV() { return false; }

  // What type to pass to VQSort.
  using KeyType = hwy::uint128_t;

  const char* KeyString() const { return "U128"; }

  template <class D>
  HWY_INLINE Mask<D> EqualKeys(D d, Vec<D> a, Vec<D> b) const {
    return Eq128(d, a, b);
  }

  template <class D>
  HWY_INLINE Mask<D> NotEqualKeys(D d, Vec<D> a, Vec<D> b) const {
    return Ne128(d, a, b);
  }

  // For keys=entire 128 bits, any difference counts.
  template <class D>
  HWY_INLINE bool NoKeyDifference(D /*tag*/, Vec<D> diff) const {
    // Must avoid floating-point comparisons (for -0)
    const RebindToUnsigned<D> du;
    return AllTrue(du, Eq(BitCast(du, diff), Zero(du)));
  }

  HWY_INLINE bool Equal1(const LaneType* a, const LaneType* b) const {
    return a[0] == b[0] && a[1] == b[1];
  }

  // Returns vector with only the top half of each block valid. This allows
  // fusing the "replicate upper to lower half" step with a subsequent permute.
  template <class Order, class D>
  HWY_INLINE HWY_MAYBE_UNUSED Vec<D> CompareTop(D d, Vec<D> a, Vec<D> b) const {
    const Mask<D> eqHL = Eq(a, b);
    const Vec<D> ltHL = VecFromMask(d, Order().CompareLanes(a, b));
#if HWY_TARGET <= HWY_AVX2  // slightly faster
    const Vec<D> ltLX = ShiftLeftLanes<1>(ltHL);
    return OrAnd(ltHL, VecFromMask(d, eqHL), ltLX);
#else
    return IfThenElse(eqHL, DupEven(ltHL), ltHL);
#endif
  }
};

// Anything order-related depends on the key traits *and* the order (see
// FirstOfLanes). We cannot implement just one Compare function because Lt128
// only compiles if the lane type is u64. Thus we need either overloaded
// functions with a tag type, class specializations, or separate classes.
// We avoid overloaded functions because we want all functions to be callable
// from a SortTraits without per-function wrappers. Specializing would work, but
// we are anyway going to specialize at a higher level.
struct OrderAscending128 : public Key128 {
  using Order = SortAscending;

  HWY_INLINE bool Compare1(const LaneType* a, const LaneType* b) {
    return (a[1] == b[1]) ? a[0] < b[0] : a[1] < b[1];
  }

  template <class D>
  HWY_INLINE Mask<D> Compare(D d, Vec<D> a, Vec<D> b) const {
    return Lt128(d, a, b);
  }

  // Used by CompareTop
  template <class V>
  HWY_INLINE Mask<DFromV<V> > CompareLanes(V a, V b) const {
    return Lt(a, b);
  }

  template <class D>
  HWY_INLINE Vec<D> First(D d, const Vec<D> a, const Vec<D> b) const {
    return Min128(d, a, b);
  }

  template <class D>
  HWY_INLINE Vec<D> Last(D d, const Vec<D> a, const Vec<D> b) const {
    return Max128(d, a, b);
  }

  // Same as for regular lanes because 128-bit keys are u64.
  template <class D>
  HWY_INLINE Vec<D> FirstValue(D d) const {
    return Set(d, hwy::LowestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> LastValue(D d) const {
    return Set(d, hwy::HighestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> PrevValue(D d, Vec<D> v) const {
    const Vec<D> k0 = Zero(d);
    const Vec<D> k1 = OddEven(k0, Set(d, uint64_t{1}));
    const Mask<D> borrow = Eq(v, k0);  // don't-care, lo == 0
    // lo == 0? 1 : 0, 0
    const Vec<D> adjust = ShiftLeftLanes<1>(IfThenElseZero(borrow, k1));
    return Sub(Sub(v, k1), adjust);
  }
};

struct OrderDescending128 : public Key128 {
  using Order = SortDescending;

  HWY_INLINE bool Compare1(const LaneType* a, const LaneType* b) {
    return (a[1] == b[1]) ? b[0] < a[0] : b[1] < a[1];
  }

  template <class D>
  HWY_INLINE Mask<D> Compare(D d, Vec<D> a, Vec<D> b) const {
    return Lt128(d, b, a);
  }

  // Used by CompareTop
  template <class V>
  HWY_INLINE Mask<DFromV<V> > CompareLanes(V a, V b) const {
    return Lt(b, a);
  }

  template <class D>
  HWY_INLINE Vec<D> First(D d, const Vec<D> a, const Vec<D> b) const {
    return Max128(d, a, b);
  }

  template <class D>
  HWY_INLINE Vec<D> Last(D d, const Vec<D> a, const Vec<D> b) const {
    return Min128(d, a, b);
  }

  // Same as for regular lanes because 128-bit keys are u64.
  template <class D>
  HWY_INLINE Vec<D> FirstValue(D d) const {
    return Set(d, hwy::HighestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> LastValue(D d) const {
    return Set(d, hwy::LowestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> PrevValue(D d, Vec<D> v) const {
    const Vec<D> k1 = OddEven(Zero(d), Set(d, uint64_t{1}));
    const Vec<D> added = Add(v, k1);
    const Mask<D> overflowed = Lt(added, v);  // false, overflowed
    // overflowed? 1 : 0, 0
    const Vec<D> adjust = ShiftLeftLanes<1>(IfThenElseZero(overflowed, k1));
    return Add(added, adjust);
  }
};

// Base class shared between OrderAscendingKV128, OrderDescendingKV128.
struct KeyValue128 : public KeyAny128 {
  // True indicates only part of the key (the more significant lane) should be
  // compared. KV stands for key-value.
  static constexpr bool IsKV() { return true; }

  // What type to pass to VQSort.
  using KeyType = K64V64;

  const char* KeyString() const { return "KV128"; }

  template <class D>
  HWY_INLINE Mask<D> EqualKeys(D d, Vec<D> a, Vec<D> b) const {
    return Eq128Upper(d, a, b);
  }

  template <class D>
  HWY_INLINE Mask<D> NotEqualKeys(D d, Vec<D> a, Vec<D> b) const {
    return Ne128Upper(d, a, b);
  }

  // Only count differences in the actual key, not the value.
  template <class D>
  HWY_INLINE bool NoKeyDifference(D /*tag*/, Vec<D> diff) const {
    // Must avoid floating-point comparisons (for -0)
    const RebindToUnsigned<D> du;
    const Vec<decltype(du)> zero = Zero(du);
    const Vec<decltype(du)> keys = OddEven(diff, zero);  // clear values
    return AllTrue(du, Eq(BitCast(du, keys), zero));
  }

  HWY_INLINE bool Equal1(const LaneType* a, const LaneType* b) const {
    return a[1] == b[1];
  }

  // Returns vector with only the top half of each block valid. This allows
  // fusing the "replicate upper to lower half" step with a subsequent permute.
  template <class Order, class D>
  HWY_INLINE HWY_MAYBE_UNUSED Vec<D> CompareTop(D d, Vec<D> a, Vec<D> b) const {
    // Only the upper lane of each block is a key, and only that lane is
    // required to be valid, so comparing all lanes is sufficient.
    return VecFromMask(d, Order().CompareLanes(a, b));
  }
};

struct OrderAscendingKV128 : public KeyValue128 {
  using Order = SortAscending;

  HWY_INLINE bool Compare1(const LaneType* a, const LaneType* b) {
    return a[1] < b[1];
  }

  template <class D>
  HWY_INLINE Mask<D> Compare(D d, Vec<D> a, Vec<D> b) const {
    return Lt128Upper(d, a, b);
  }

  // Used by CompareTop
  template <class V>
  HWY_INLINE Mask<DFromV<V> > CompareLanes(V a, V b) const {
    return Lt(a, b);
  }

  template <class D>
  HWY_INLINE Vec<D> First(D d, const Vec<D> a, const Vec<D> b) const {
    return Min128Upper(d, a, b);
  }

  template <class D>
  HWY_INLINE Vec<D> Last(D d, const Vec<D> a, const Vec<D> b) const {
    return Max128Upper(d, a, b);
  }

  // Same as for regular lanes because 128-bit keys are u64.
  template <class D>
  HWY_INLINE Vec<D> FirstValue(D d) const {
    return Set(d, hwy::LowestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> LastValue(D d) const {
    return Set(d, hwy::HighestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> PrevValue(D d, Vec<D> v) const {
    const Vec<D> k1 = OddEven(Set(d, uint64_t{1}), Zero(d));
    return Sub(v, k1);
  }
};

struct OrderDescendingKV128 : public KeyValue128 {
  using Order = SortDescending;

  HWY_INLINE bool Compare1(const LaneType* a, const LaneType* b) {
    return b[1] < a[1];
  }

  template <class D>
  HWY_INLINE Mask<D> Compare(D d, Vec<D> a, Vec<D> b) const {
    return Lt128Upper(d, b, a);
  }

  // Used by CompareTop
  template <class V>
  HWY_INLINE Mask<DFromV<V> > CompareLanes(V a, V b) const {
    return Lt(b, a);
  }

  template <class D>
  HWY_INLINE Vec<D> First(D d, const Vec<D> a, const Vec<D> b) const {
    return Max128Upper(d, a, b);
  }

  template <class D>
  HWY_INLINE Vec<D> Last(D d, const Vec<D> a, const Vec<D> b) const {
    return Min128Upper(d, a, b);
  }

  // Same as for regular lanes because 128-bit keys are u64.
  template <class D>
  HWY_INLINE Vec<D> FirstValue(D d) const {
    return Set(d, hwy::HighestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> LastValue(D d) const {
    return Set(d, hwy::LowestValue<TFromD<D> >());
  }

  template <class D>
  HWY_INLINE Vec<D> PrevValue(D d, Vec<D> v) const {
    const Vec<D> k1 = OddEven(Set(d, uint64_t{1}), Zero(d));
    return Add(v, k1);
  }
};

// We want to swap 2 u128, i.e. 4 u64 lanes, based on the 0 or FF..FF mask in
// the most-significant of those lanes (the result of CompareTop), so
// replicate it 4x. Only called for >= 256-bit vectors.

#if HWY_TARGET <= HWY_AVX3
template <class V, HWY_IF_V_SIZE_V(V, 64)>
HWY_INLINE V ReplicateTop4x(V v) {
  return V{_mm512_permutex_epi64(v.raw, _MM_SHUFFLE(3, 3, 3, 3))};
}
#endif  // HWY_TARGET <= HWY_AVX3

#if HWY_TARGET <= HWY_AVX2

template <class V, HWY_IF_V_SIZE_V(V, 32)>
HWY_INLINE V ReplicateTop4x(V v) {
  return V{_mm256_permute4x64_epi64(v.raw, _MM_SHUFFLE(3, 3, 3, 3))};
}

#else  // HWY_TARGET > HWY_AVX2

template <class V>
HWY_INLINE V ReplicateTop4x(V v) {
#if HWY_TARGET == HWY_SVE_256
  return svdup_lane_u64(v, 3);
#else
    alignas(64) static constexpr uint64_t kIndices[8] = {3, 3, 3, 3,
                                                         7, 7, 7, 7};
    const ScalableTag<uint64_t> d;
    return TableLookupLanes(v, SetTableIndices(d, kIndices));
#endif
}

#endif  // HWY_TARGET <= HWY_AVX2

// Shared code that depends on Order.
template <class Base>
struct Traits128 : public Base {
  template <class D>
  HWY_INLINE Vec<D> FirstOfLanes(D d, Vec<D> v,
                                 TFromD<D>* HWY_RESTRICT buf) const {
    const Base* base = static_cast<const Base*>(this);
    const size_t N = Lanes(d);
    Store(v, d, buf);
    v = base->SetKey(d, buf + 0);  // result must be broadcasted
    for (size_t i = base->LanesPerKey(); i < N; i += base->LanesPerKey()) {
      v = base->First(d, v, base->SetKey(d, buf + i));
    }
    return v;
  }

  template <class D>
  HWY_INLINE Vec<D> LastOfLanes(D d, Vec<D> v,
                                TFromD<D>* HWY_RESTRICT buf) const {
    const Base* base = static_cast<const Base*>(this);
    const size_t N = Lanes(d);
    Store(v, d, buf);
    v = base->SetKey(d, buf + 0);  // result must be broadcasted
    for (size_t i = base->LanesPerKey(); i < N; i += base->LanesPerKey()) {
      v = base->Last(d, v, base->SetKey(d, buf + i));
    }
    return v;
  }

  template <class D>
  HWY_INLINE void Sort2(D d, Vec<D>& a, Vec<D>& b) const {
    const Base* base = static_cast<const Base*>(this);

    const Vec<D> a_copy = a;
    const auto lt = base->Compare(d, a, b);
    a = IfThenElse(lt, a, b);
    b = IfThenElse(lt, b, a_copy);
  }

  // Conditionally swaps even-numbered keys with their odd-numbered neighbor.
  template <class D>
  HWY_INLINE Vec<D> SortPairsDistance1(D d, Vec<D> v) const {
    const Base* base = static_cast<const Base*>(this);
    Vec<D> swapped = base->ReverseKeys2(d, v);
    const Vec<D> cmpHx = base->template CompareTop<Base>(d, v, swapped);
    return IfVecThenElse(ReplicateTop4x(cmpHx), swapped, v);
  }

  // Swaps with the vector formed by reversing contiguous groups of four 128-bit
  // keys, which implies 512-bit vectors (we do not support more than that).
  template <class D>
  HWY_INLINE Vec<D> SortPairsReverse4(D d, Vec<D> v) const {
    const Base* base = static_cast<const Base*>(this);
    Vec<D> swapped = base->ReverseKeys4(d, v);

    const Vec<D> cmpHx = base->template CompareTop<Base>(d, v, swapped);
    // Similar to ReplicateTop4x, we want to gang together 2 comparison results
    // (4 lanes). They are not contiguous, so use permute to replicate 4x.
    alignas(64) uint64_t kIndices[8] = {7, 7, 5, 5, 5, 5, 7, 7};
    const Vec<D> select = TableLookupLanes(cmpHx, SetTableIndices(d, kIndices));
    return IfVecThenElse(select, swapped, v);
  }

  // Conditionally swaps lane 0 with 4, 1 with 5 etc.
  template <class D>
  HWY_INLINE Vec<D> SortPairsDistance4(D, Vec<D>) const {
    // Only used by Merge16, which would require 2048 bit vectors (unsupported).
    HWY_ASSERT(0);
  }
};

#endif  // VQSORT_ENABLED

}  // namespace detail
// NOLINTNEXTLINE(google-readability-namespace-comments)
}  // namespace HWY_NAMESPACE
}  // namespace hwy
HWY_AFTER_NAMESPACE();

#endif  // HIGHWAY_HWY_CONTRIB_SORT_TRAITS128_TOGGLE
