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/*! \file
    \brief Templates implementing loading of tiles from pitch-linear rank=2 tensors. 

    This iterator uses masks to guard out-of-bounds accesses and visits the last "residue" tile
    first, with the objective of minimizing predicate mask updates during steady-state operation.

    A precomputed "Params" object minimizes the amount of state that must be stored in registers,
    and integer addition is used to advance the pointer through memory.
*/

#pragma once

#include "cutlass/cutlass.h"
#include "cutlass/tensor_ref.h"
#include "cutlass/layout/matrix.h"
#include "cutlass/layout/pitch_linear.h"

#include "regular_tile_iterator.h"

/////////////////////////////////////////////////////////////////////////////////////////////////

namespace cutlass {
namespace transform {
namespace threadblock {

/////////////////////////////////////////////////////////////////////////////////////////////////

/// Regular tile iterator specialized for pitch-linear.  This one is used by 2-stage SIMT kernels
/// and sparse tensor core meta data.
template <
  typename Shape_,
  typename Element_,
  int AdvanceRank,
  typename ThreadMap_,
  int Alignment
>
class RegularTileIterator<Shape_, Element_, layout::PitchLinear, AdvanceRank, ThreadMap_, Alignment> {
public:

  using Shape = Shape_;
  using Element = Element_;
  using Layout = layout::PitchLinear;
  static int const kAdvanceRank = AdvanceRank;
  using ThreadMap = ThreadMap_;
  static int const kAlignment = Alignment;

  using Index = typename Layout::Index;
  using LongIndex = typename Layout::LongIndex;
  using StrideIndex = typename Layout::Stride::Index;

  using TensorRef = TensorRef<Element, Layout>;
  using TensorCoord = typename Layout::TensorCoord;

  using Fragment = Array<Element, ThreadMap::Iterations::kCount * ThreadMap::kElementsPerAccess>;
  
  using AccessType = AlignedArray<Element, ThreadMap::kElementsPerAccess, kAlignment>;

  static_assert(kAdvanceRank == 0 || kAdvanceRank == 1, 
    "Advance rank may only be along the contiguous or strided dimensions.");

private:

  //
  // Types
  //

  //
  // Data members
  //

  /// Pointer to memory
  uint8_t *pointer_;

  /// Stride quantity
  StrideIndex stride_;

  /// Amount to increment pointer along strided dimension
  Index increment_strided_;

  /// Amount to advance pointer between tiles
  Index increment_advance_;

public:

  CUTLASS_DEVICE
  RegularTileIterator(): pointer_(nullptr), increment_strided_(0), increment_advance_(0) { }

  CUTLASS_DEVICE
  RegularTileIterator(
    TensorRef const &ref, 
    int thread_idx
  ): 
    pointer_(reinterpret_cast<uint8_t *>(ref.data()) + (ref.offset(ThreadMap::initial_offset(thread_idx)) * sizeof_bits<Element>::value / 8)) {
    
    stride_ = ref.stride()[0];
    increment_strided_ = (ref.stride()[0] * sizeof_bits<Element>::value) * ThreadMap::Delta::kStrided / 8;
    
    increment_advance_ = 
      (kAdvanceRank == 0 ? 
        Shape::kContiguous * sizeof_bits<Element>::value / 8 : 
        Shape::kStrided * (ref.stride()[0] * sizeof_bits<Element>::value / 8));
  }

  /// Loads a fragment
  CUTLASS_DEVICE
  void load_with_pointer_offset(Fragment &frag, Index pointer_offset) {

    AccessType *frag_ptr = reinterpret_cast<AccessType *>(&frag);
    uint8_t const *byte_pointer = pointer_ + pointer_offset * sizeof_bits<Element>::value / 8;

    CUTLASS_PRAGMA_UNROLL
    for (int s = 0; s < ThreadMap::Iterations::kStrided; ++s) {

      AccessType const *access_ptr = reinterpret_cast<AccessType const *>(byte_pointer);

      CUTLASS_PRAGMA_UNROLL
      for (int c = 0; c < ThreadMap::Iterations::kContiguous; ++c) {

        int idx = c + s * ThreadMap::Iterations::kContiguous;
        frag_ptr[idx] = access_ptr[c * ThreadMap::Delta::kContiguous /
                                   ThreadMap::kElementsPerAccess];
      }

      if (s + 1 < ThreadMap::Iterations::kStrided) {
        byte_pointer += increment_strided_;
      }
    }
  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load(Fragment &frag, TensorCoord const & tile_offset) {
    load_with_pointer_offset(
      frag, 
      tile_offset.contiguous() * Shape::kContiguous / ThreadMap::kElementsPerAccess + 
        tile_offset.strided() * Shape::kStrided * stride_
    );
  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load(Fragment &frag) {
    load_with_pointer_offset(frag, 0);
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store_with_pointer_offset(Fragment const &frag, Index pointer_offset) {

    AccessType const *frag_ptr = reinterpret_cast<AccessType const*>(&frag);
    uint8_t *byte_pointer = pointer_ + pointer_offset * sizeof_bits<Element>::value / 8;

    CUTLASS_PRAGMA_UNROLL
    for (int s = 0; s < ThreadMap::Iterations::kStrided; ++s) {

      AccessType *access_ptr = reinterpret_cast<AccessType *>(byte_pointer);

      CUTLASS_PRAGMA_UNROLL
      for (int c = 0; c < ThreadMap::Iterations::kContiguous; ++c) {

        int idx = c + s * ThreadMap::Iterations::kContiguous;
        access_ptr[c * ThreadMap::Delta::kContiguous /
                   ThreadMap::kElementsPerAccess] = frag_ptr[idx];
      }

      if (s + 1 < ThreadMap::Iterations::kStrided) {
        byte_pointer += increment_strided_;
      }
    }
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store(Fragment const &frag, TensorCoord const & tile_offset) {
    store_with_pointer_offset(
      frag,
      tile_offset.contiguous() * Shape::kContiguous + tile_offset.strided() * Shape::kStrided * stride_
    );
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store(Fragment const &frag) {
    store_with_pointer_offset(frag, 0);
  }

  /// Advances the pointer
  CUTLASS_HOST_DEVICE
  RegularTileIterator &operator++() {
    pointer_ += increment_advance_;
    return *this;
  }

  /// Advances the pointer
  CUTLASS_HOST_DEVICE
  RegularTileIterator &operator--() {
    pointer_ -= increment_advance_;
    return *this;
  }

  /// Adds a pointer offset in units of Element
  CUTLASS_HOST_DEVICE
  void add_pointer_offset(LongIndex pointer_offset) {
    pointer_ += pointer_offset;
  }

  /// Adds a tile offset in the unit of tile.
  /// In GEMM/Conv implementation, this is used to move in the k dimension in the shared memory.
  /// Below layouts are the shared memory layouts.  Current SM50 SIMT kernels only use col major A and row major B.
  ///   For row major A operand, k dimension is contiguous dimension;
  ///   For col major A operand, k dimension is strided dimension;
  ///   For row major B operand, k dimension is strided dimension;
  ///   For col major B operand, k dimension is contiguous dimension.
  /// Below two classes map col/row major to the pitch linear coordinates used
  /// in this base class.
  CUTLASS_DEVICE
  void add_tile_offset(TensorCoord const &coord) {
    int offset = sizeof_bits<Element>::value *
        (coord.contiguous() * Shape::kContiguous + coord.strided() * Shape::kStrided * stride_) / 8;
    add_pointer_offset(offset);
  }

  /// Overrides the internal iteration index
  CUTLASS_HOST_DEVICE
  void set_iteration_index(int index) {
  }

    /// Returns a pointer
  CUTLASS_HOST_DEVICE
  AccessType *get() const {
#if 0
    AccessType *access_ptr = pointer_[iteration_strided_ & 1];
    int stride_idx = (iteration_strided_ & ~1);

    int access_offset = stride_idx * ThreadMap::Delta::kStrided * stride_ +
                        iteration_contiguous_ * ThreadMap::Delta::kContiguous /
                            ThreadMap::kElementsPerAccess;

    char *access_byte_ptr =
        reinterpret_cast<char *>(access_ptr + access_offset);
    return reinterpret_cast<AccessType *>(access_byte_ptr + byte_offset_);
#endif
    return reinterpret_cast<AccessType *>(pointer_);
  }

};

/////////////////////////////////////////////////////////////////////////////////////////////////

/// Regular tile iterator specialized for row major 
template <
  typename Shape_,
  typename Element_,
  int AdvanceRank,
  typename ThreadMap_,
  int Alignment
>
class RegularTileIterator<Shape_, Element_, layout::RowMajor, AdvanceRank, ThreadMap_, Alignment> {
public:

  using Shape = Shape_;
  using Element = Element_;
  using Layout = layout::RowMajor;
  static int const kAdvanceRank = AdvanceRank;
  using ThreadMap = ThreadMap_;
  static int const kAlignment = Alignment;

  using Index = typename Layout::Index;
  using LongIndex = typename Layout::LongIndex;

  using TensorRef = TensorRef<Element, Layout>;
  using TensorCoord = typename Layout::TensorCoord;

  using Fragment = Array<Element, ThreadMap::Iterations::kCount * ThreadMap::kElementsPerAccess>;

  using Underlying = RegularTileIterator<
    layout::PitchLinearShape<Shape::kColumn, Shape::kRow>,
    Element,
    layout::PitchLinear,
    (kAdvanceRank == 0 ? 1 : 0),
    ThreadMap,
    kAlignment
  >;

  using AccessType = typename Underlying::AccessType;

  static_assert(kAdvanceRank == 0 || kAdvanceRank == 1, 
    "Advance rank may only be along the row or column dimensions.");

private:

  Underlying iterator_;

public:

  CUTLASS_DEVICE
  RegularTileIterator() { }

  CUTLASS_DEVICE
  RegularTileIterator(
    TensorRef const &ref, 
    int thread_idx
  ):
    iterator_({ref.data(), ref.stride()}, thread_idx) {

  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load_with_pointer_offset(Fragment &frag, Index pointer_offset) {
    iterator_.load_with_pointer_offset(frag, pointer_offset);
  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load(Fragment &frag, TensorCoord const & tile_offset) {
    iterator_.load_with_pointer_offset(frag, {tile_offset.column(), tile_offset.row()});
  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load(Fragment &frag) {
    iterator_.load_with_pointer_offset(frag, 0);
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store_with_pointer_offset(Fragment const &frag, Index pointer_offset) {
    iterator_.store_with_pointer_offset(frag, pointer_offset);
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store(Fragment const &frag, TensorCoord const & tile_offset) {
    iterator_.store_with_pointer_offset(frag, {tile_offset.column(), tile_offset.row()});
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store(Fragment const &frag) {
    iterator_.store_with_pointer_offset(frag, 0);
  }

  /// Advances the pointer
  CUTLASS_HOST_DEVICE
  RegularTileIterator &operator++() {
    ++iterator_;
    return *this;
  }

  /// Advances the pointer
  CUTLASS_HOST_DEVICE
  RegularTileIterator &operator--() {
    --iterator_;
    return *this;
  }

  /// Adds a pointer offset in units of Element
  CUTLASS_HOST_DEVICE
  void add_pointer_offset(LongIndex pointer_offset) {
    iterator_.add_pointer_offset(pointer_offset);
  }

  /// Adds a tile offset
  CUTLASS_DEVICE
  void add_tile_offset(TensorCoord const &coord) {
    iterator_.add_tile_offset({coord.column(), coord.row()});
  }

  /// Overrides the internal iteration index
  CUTLASS_HOST_DEVICE
  void set_iteration_index(int index) {
  }

  /// Returns a pointer
  CUTLASS_HOST_DEVICE
  AccessType *get() const {
    return iterator_.get();
  }

};

/////////////////////////////////////////////////////////////////////////////////////////////////

/// Regular tile iterator specialized for pitch-linear
template <
  typename Shape_,
  typename Element_,
  int AdvanceRank,
  typename ThreadMap_,
  int Alignment
>
class RegularTileIterator<Shape_, Element_, layout::ColumnMajor, AdvanceRank, ThreadMap_, Alignment> {
public:

  using Shape = Shape_;
  using Element = Element_;
  using Layout = layout::ColumnMajor;
  static int const kAdvanceRank = AdvanceRank;
  using ThreadMap = ThreadMap_;
  static int const kAlignment = Alignment;

  using Index = typename Layout::Index;
  using LongIndex = typename Layout::LongIndex;

  using TensorRef = TensorRef<Element, Layout>;
  using TensorCoord = typename Layout::TensorCoord;

  using Fragment = Array<Element, ThreadMap::Iterations::kCount * ThreadMap::kElementsPerAccess>;

  using Underlying = RegularTileIterator<
    layout::PitchLinearShape<Shape::kRow, Shape::kColumn>,
    Element,
    layout::PitchLinear,
    (kAdvanceRank == 0 ? 0 : 1),
    ThreadMap
  >;

  using AccessType = typename Underlying::AccessType;

  static_assert(kAdvanceRank == 0 || kAdvanceRank == 1, 
    "Advance rank may only be along the row or column dimensions.");

private:

  Underlying iterator_;

public:

  CUTLASS_DEVICE
  RegularTileIterator() { }

  CUTLASS_DEVICE
  RegularTileIterator(
    TensorRef const &ref, 
    int thread_idx
  ):
    iterator_({ref.data(), ref.stride()}, thread_idx) {

  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load_with_pointer_offset(Fragment &frag, Index pointer_offset) {
    iterator_.load_with_pointer_offset(frag, pointer_offset);
  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load(Fragment &frag, TensorCoord const & tile_offset) {
    iterator_.load_with_pointer_offset(frag, {tile_offset.row(), tile_offset.column()});
  }

  /// Loads a fragment
  CUTLASS_HOST_DEVICE
  void load(Fragment &frag) {
    iterator_.load_with_pointer_offset(frag, 0);
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store_with_pointer_offset(Fragment const &frag, Index pointer_offset) {
    iterator_.store_with_pointer_offset(frag, pointer_offset);
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store(Fragment const &frag, TensorCoord const & tile_offset) {
    iterator_.store_with_pointer_offset(frag, {tile_offset.row(), tile_offset.column()});
  }

  /// Stores a fragment
  CUTLASS_HOST_DEVICE
  void store(Fragment const &frag) {
    iterator_.store_with_pointer_offset(frag, 0);
  }

  /// Advances the pointer
  CUTLASS_HOST_DEVICE
  RegularTileIterator &operator++() {
    ++iterator_;
    return *this;
  }

  /// Advances the pointer
  CUTLASS_HOST_DEVICE
  RegularTileIterator &operator--() {
    --iterator_;
    return *this;
  }

  /// Adds a pointer offset in units of Element
  CUTLASS_HOST_DEVICE
  void add_pointer_offset(LongIndex pointer_offset) {
    iterator_.add_pointer_offset(pointer_offset);
  }

  /// Adds a tile offset
  CUTLASS_DEVICE
  void add_tile_offset(TensorCoord const &coord) {
    iterator_.add_tile_offset({coord.row(), coord.column()});
  }

  /// Overrides the internal iteration index
  CUTLASS_HOST_DEVICE
  void set_iteration_index(int index) {
  }

  /// Returns a pointer
  CUTLASS_HOST_DEVICE
  AccessType *get() const {
    return iterator_.get();
  }

};

/////////////////////////////////////////////////////////////////////////////////////////////////

} // namespace threadblock
} // namespace transform
} // namespace cutlass