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 // SPDX-License-Identifier: MIT
 // Copyright (c) 2018-2024, Advanced Micro Devices, Inc. All rights reserved.
  
 #pragma once
  
 #include "ck_tile/core.hpp"
 #include "ck_tile/core/tensor/tile_window.hpp"
  
 namespace ck_tile {
  
 // assume that we have only 1 page-block/tensor view
 template <typename TensorView>
 struct TrivialPageBlockNavigator
 {
     using DataType     = typename TensorView::DataType;
     using WindowOrigin = multi_index<2>;
  
     CK_TILE_HOST_DEVICE constexpr TrivialPageBlockNavigator(const TensorView& tensor_view_)
         : tensor_view(tensor_view_)
     {
     }
  
     template <typename WindowLengths>
     CK_TILE_HOST_DEVICE constexpr auto make_tile_window(const WindowLengths& window_lengths,
                                                         const WindowOrigin& window_origin) const
     {
         return make_tuple(/*block_index=*/0,
                           ck_tile::make_tile_window(tensor_view, window_lengths, window_origin));
     }
  
     template <typename WindowLengths, typename TileDistribution>
     CK_TILE_HOST_DEVICE constexpr auto
     make_tile_window(const WindowLengths& window_lengths,
                      const WindowOrigin& window_origin,
                      const TileDistribution& tile_distribution) const
     {
         return make_tuple(
             /*block_index=*/0,
             ck_tile::make_tile_window(
                 tensor_view, window_lengths, window_origin, tile_distribution));
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE static index_t
     move_tile_window(index_t /*block_index*/,
                      TileWindow& tile_window,
                      const typename remove_cvref_t<TileWindow>::BottomTensorIndex& step)
     {
         ck_tile::move_tile_window(tile_window, step);
  
         return /*block_index=*/0;
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE index_t
     move_tile_window(index_t /*block_index*/,
                      TileWindow& tile_window,
                      const typename remove_cvref_t<TileWindow>::BottomTensorIndex& step,
                      index_t /*id*/) const
     {
  
         ck_tile::move_tile_window(tile_window, step);
         return 0;
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE index_t
     prefetch_table_id(index_t /*block_index*/,
                       TileWindow /*tile_window*/,
                       const typename remove_cvref_t<TileWindow>::BottomTensorIndex& /*step*/) const
     {
         return -1;
     }
  
     CK_TILE_HOST_DEVICE static constexpr WindowOrigin
     to_local_window_origin(const WindowOrigin& global_window_origin)
     {
         return global_window_origin;
     }
  
     CK_TILE_HOST_DEVICE static constexpr WindowOrigin
     to_global_window_origin(index_t /*block_index*/, const WindowOrigin& local_window_origin)
     {
         return local_window_origin;
     }
  
     private:
     TensorView tensor_view;
 };
  
 // default page-block navigator, assume that tensor view size is same as page-block size or smaller
 // if tile window on last page-block
 template <typename DataType_, index_t VirtualDim, typename TensorView>
 struct PageBlockNavigator
 {
     using DataType = DataType_;
     static_assert(std::is_same_v<DataType, typename TensorView::DataType>);
     static_assert(VirtualDim == 0 || VirtualDim == 1, "only support 2d tile window");
     using WindowOrigin = multi_index<2>;
  
     CK_TILE_HOST_DEVICE constexpr PageBlockNavigator(copy_const_t<DataType, void>* physical_blocks_,
                                                      long_index_t block_stride_,
                                                      long_index_t fixed_offset_,
                                                      const int32_t* physical_block_indices_,
                                                      index_t num_blocks_,
                                                      index_t page_block_size_,
                                                      const TensorView& complete_view_,
                                                      const TensorView& last_view_)
         : physical_blocks(reinterpret_cast<DataType*>(physical_blocks_)),
           block_stride(block_stride_),
           fixed_offset(fixed_offset_),
           physical_block_indices(physical_block_indices_),
           num_blocks(num_blocks_),
           page_block_size(page_block_size_),
           complete_view(complete_view_),
           last_view(last_view_)
     {
     }
  
     template <typename WindowLengths>
     CK_TILE_HOST_DEVICE auto make_tile_window(const WindowLengths& window_lengths,
                                               const WindowOrigin& window_origin) const
     {
         const index_t block_index              = get_block_index(window_origin);
         const WindowOrigin local_window_origin = to_local_window_origin(window_origin);
  
         auto new_tile_window =
             ck_tile::make_tile_window(is_last_block(block_index) ? last_view : complete_view,
                                       window_lengths,
                                       local_window_origin);
         new_tile_window.set_bottom_tensor_view_data_ptr(get_block_ptr(block_index));
  
         return make_tuple(block_index, new_tile_window);
     }
  
     template <typename WindowLengths, typename TileDistribution>
     CK_TILE_HOST_DEVICE auto make_tile_window(const WindowLengths& window_lengths,
                                               const WindowOrigin& window_origin,
                                               const TileDistribution& tile_distribution) const
     {
         const index_t block_index              = get_block_index(window_origin);
         const WindowOrigin local_window_origin = to_local_window_origin(window_origin);
  
         auto new_tile_window =
             ck_tile::make_tile_window(is_last_block(block_index) ? last_view : complete_view,
                                       window_lengths,
                                       local_window_origin,
                                       tile_distribution);
         new_tile_window.set_bottom_tensor_view_data_ptr(get_block_ptr(block_index));
  
         return make_tuple(block_index, new_tile_window);
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE index_t
     move_tile_window(index_t block_index,
                      TileWindow& tile_window,
                      const typename remove_cvref_t<TileWindow>::BottomTensorIndex& step) const
     {
  
         ck_tile::move_tile_window(tile_window, step);
  
         const WindowOrigin global_window_origin =
             to_global_window_origin(block_index, tile_window.get_window_origin());
         const WindowOrigin local_window_origin = to_local_window_origin(global_window_origin);
  
         const index_t new_block_index = get_block_index(global_window_origin);
         tile_window.bottom_tensor_view_.desc_ =
             (is_last_block(new_block_index) ? last_view : complete_view).get_tensor_descriptor();
         tile_window.set_window_origin(local_window_origin);
         tile_window.set_bottom_tensor_view_data_ptr(get_block_ptr(new_block_index));
  
         return new_block_index;
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE index_t
     move_tile_window(index_t block_index,
                      TileWindow& tile_window,
                      const typename remove_cvref_t<TileWindow>::BottomTensorIndex& step,
                      index_t id) const
     {
         ck_tile::move_tile_window(tile_window, step);
  
         const WindowOrigin global_window_origin =
             to_global_window_origin(block_index, tile_window.get_window_origin());
         const WindowOrigin local_window_origin = to_local_window_origin(global_window_origin);
  
         const index_t new_block_index = get_block_index(global_window_origin);
         tile_window.bottom_tensor_view_.desc_ =
             (is_last_block(new_block_index) ? last_view : complete_view).get_tensor_descriptor();
         tile_window.set_window_origin(local_window_origin);
         if(id >= 0)
             tile_window.set_bottom_tensor_view_data_ptr(physical_blocks + id * block_stride +
                                                         fixed_offset);
         else
             tile_window.set_bottom_tensor_view_data_ptr(nullptr);
  
         return new_block_index;
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE index_t
     prefetch_table_id(index_t block_index,
                       TileWindow& tile_window,
                       const typename remove_cvref_t<TileWindow>::BottomTensorIndex& step) const
     {
         auto local_tile_window = tile_window; // not affect origin window
         ck_tile::move_tile_window(local_tile_window, step);
  
         const WindowOrigin global_window_origin =
             to_global_window_origin(block_index, local_tile_window.get_window_origin());
         const index_t new_block_index = get_block_index(global_window_origin);
  
         if(new_block_index < num_blocks)
         {
             return physical_block_indices[new_block_index];
         }
         else
         {
             return -1;
         }
     }
  
     CK_TILE_HOST_DEVICE bool is_last_block(index_t block_index) const
     {
         return block_index == num_blocks - 1;
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE bool is_cross_block(index_t block_index,
                                             const TileWindow& tile_window) const
     {
         const index_t origin = tile_window.get_window_origin().at(number<VirtualDim>{});
         const index_t length = tile_window.get_window_lengths().at(number<VirtualDim>{});
         return (block_index < num_blocks - 1) && (page_block_size < origin + length);
     }
  
     template <typename TileWindow>
     CK_TILE_HOST_DEVICE void
     move_to_block(index_t block_index, TileWindow& tile_window, index_t new_block_index) const
     {
         const multi_index<2> step = [&]() {
             const index_t origin_diff = (block_index - new_block_index) * page_block_size;
             if constexpr(VirtualDim == 0)
             {
                 return make_multi_index(origin_diff, 0);
             }
             else
             {
                 return make_multi_index(0, origin_diff);
             }
         }();
  
         tile_window.bottom_tensor_view_.desc_ =
             (is_last_block(new_block_index) ? last_view : complete_view).get_tensor_descriptor();
         tile_window.set_window_origin(tile_window.get_window_origin() + step);
         tile_window.set_bottom_tensor_view_data_ptr(get_block_ptr(new_block_index));
     }
  
     CK_TILE_HOST_DEVICE WindowOrigin
     to_local_window_origin(const WindowOrigin& global_window_origin) const
     {
         if constexpr(VirtualDim == 0)
         {
             const index_t length              = global_window_origin.at(number<0>{});
             const index_t num_complete_blocks = integer_divide_floor(length, page_block_size);
             return make_multi_index(length - page_block_size * num_complete_blocks,
                                     global_window_origin.at(number<1>{}));
         }
         else
         {
             const index_t length              = global_window_origin.at(number<1>{});
             const index_t num_complete_blocks = integer_divide_floor(length, page_block_size);
             return make_multi_index(global_window_origin.at(number<0>{}),
                                     length - page_block_size * num_complete_blocks);
         }
     }
  
     CK_TILE_HOST_DEVICE WindowOrigin
     to_global_window_origin(index_t block_index, const WindowOrigin& local_window_origin) const
     {
         if constexpr(VirtualDim == 0)
         {
             return make_multi_index(block_index * page_block_size +
                                         local_window_origin.at(number<0>{}),
                                     local_window_origin.at(number<1>{}));
         }
         else
         {
             return make_multi_index(local_window_origin.at(number<0>{}),
                                     block_index * page_block_size +
                                         local_window_origin.at(number<1>{}));
         }
     }
  
     private:
     CK_TILE_HOST_DEVICE
     DataType* get_block_ptr(index_t block_index) const
     {
         if(block_index < num_blocks)
         {
             return physical_blocks + physical_block_indices[block_index] * block_stride +
                    fixed_offset;
         }
         else
         {
             return nullptr;
         }
     }
  
     CK_TILE_HOST_DEVICE int32_t get_block_index(const WindowOrigin& global_window_origin) const
     {
         return integer_divide_floor(global_window_origin.at(number<VirtualDim>{}), page_block_size);
     }
  
     DataType* physical_blocks;
     long_index_t block_stride;
     long_index_t fixed_offset;
  
     const int32_t* physical_block_indices;
     index_t num_blocks;
     index_t page_block_size;
  
     TensorView complete_view;
     TensorView last_view;
 };
  
 template <typename TensorView>
 CK_TILE_HOST_DEVICE auto make_page_block_navigator(const TensorView& tensor_view)
 {
     return TrivialPageBlockNavigator<TensorView>(tensor_view);
 }
  
 template <typename DataType, index_t VirtualDim, typename TensorView>
 CK_TILE_HOST_DEVICE auto make_page_block_navigator(copy_const_t<DataType, void>* physical_blocks,
                                                    long_index_t block_stride,
                                                    long_index_t fixed_offset,
                                                    const int32_t* physical_block_indices,
                                                    index_t num_blocks,
                                                    index_t page_block_size,
                                                    const TensorView& complete_view,
                                                    const TensorView& last_view)
 {
     return PageBlockNavigator<DataType, VirtualDim, TensorView>(physical_blocks,
                                                                 block_stride,
                                                                 fixed_offset,
                                                                 physical_block_indices,
                                                                 num_blocks,
                                                                 page_block_size,
                                                                 complete_view,
                                                                 last_view);
 }
  
 } // namespace ck_tile