// Copyright © 2024 Apple Inc.

#pragma once

#include "mlx/backend/metal/kernels/steel/utils.h"

#include "mlx/backend/metal/kernels/steel/conv/params.h"

///////////////////////////////////////////////////////////////////////////////
// Loading helper
///////////////////////////////////////////////////////////////////////////////

namespace mlx {
namespace steel {

template <short n_channels_>
struct ChannelHelper {
  STEEL_CONST short n_channels = n_channels_;
  STEEL_CONST short vec_size = n_channels_ <= 4 ? 4 : 8;
  STEEL_CONST short excess = vec_size - n_channels_;
};

template <>
struct ChannelHelper<1> {
  STEEL_CONST short n_channels = 1;
  STEEL_CONST short vec_size = 1;
  STEEL_CONST short excess = 0;
};

template <>
struct ChannelHelper<2> {
  STEEL_CONST short n_channels = 2;
  STEEL_CONST short vec_size = 2;
  STEEL_CONST short excess = 0;
};

template <>
struct ChannelHelper<3> {
  STEEL_CONST short n_channels = 3;
  STEEL_CONST short vec_size = 4;
  STEEL_CONST short excess = 1;
};

template <>
struct ChannelHelper<4> {
  STEEL_CONST short n_channels = 4;
  STEEL_CONST short vec_size = 4;
  STEEL_CONST short excess = 0;
};

template <
    typename T,
    short BM,
    short BN,
    short BK,
    short tgp_size,
    short n_channels,
    short tgp_padding = 0>
struct Conv2DInputBlockLoaderSmallChannels {
  // Destination dimensions
  STEEL_CONST short BROWS = BM;
  STEEL_CONST short BCOLS = BK;

  // Read dimensions
  STEEL_CONST short dst_ld = BCOLS + tgp_padding;
  STEEL_CONST short vec_size = ChannelHelper<n_channels>::vec_size;

  // Thread read shape
  STEEL_CONST short TCOLS = BCOLS / vec_size;
  STEEL_CONST short TROWS = tgp_size / TCOLS;

  // Rows / strided reads within the block
  STEEL_CONST short n_rows = BROWS / TROWS;

  // Thread location indices
  const short thread_idx;
  const short bi;
  const short bj;

  // threadgroup and device memory
  threadgroup T* dst;

  const constant MLXConvParams<2>* params;
  const constant ImplicitGemmConv2DParams* gemm_params;

  short weight_hw;

  const device T* src[n_rows];

  int read_n[n_rows];
  int read_ih[n_rows];
  int read_iw[n_rows];

  /* Constructor */
  METAL_FUNC Conv2DInputBlockLoaderSmallChannels(
      const device T* src_,
      threadgroup T* dst_,
      const int2 offsets,
      const constant MLXConvParams<2>* params_,
      const constant ImplicitGemmConv2DParams* gemm_params_,
      uint simd_group_id [[simdgroup_index_in_threadgroup]],
      uint simd_lane_id [[thread_index_in_simdgroup]])
      : thread_idx(simd_group_id * 32 + simd_lane_id),
        bi(thread_idx / TCOLS),
        bj(vec_size * (thread_idx % TCOLS)),
        dst(dst_ + bi * dst_ld + bj),
        params(params_),
        gemm_params(gemm_params_),
        weight_hw(thread_idx % TCOLS) {
    int out_n_pixels = params->oS[0] * params->oS[1];

    STEEL_PRAGMA_UNROLL
    for (short i = 0; i < n_rows; ++i) {
      int offset_nhw = offsets.y + bi + i * TROWS;
      int n = offset_nhw / out_n_pixels;
      int hw = offset_nhw % out_n_pixels;
      int oh = hw / params->oS[1];
      int ow = hw % params->oS[1];

      int ih = oh * params->str[0] - params->pad[0];
      int iw = ow * params->str[1] - params->pad[1];

      // Read from input if in bounds
      src[i] = src_ + n * params->in_strides[0] + ih * params->in_strides[1] +
          iw * params->in_strides[2];

      read_n[i] = n;
      read_ih[i] = ih;
      read_iw[i] = iw;
    }
  }

  /* Load from device memory into threadgroup memory - without bound checking */
  METAL_FUNC void load_unsafe() const {
    if (weight_hw >= params->wS[1] * params->wS[0]) {
      STEEL_PRAGMA_UNROLL
      for (short i = 0; i < BROWS; i += TROWS) {
        STEEL_PRAGMA_UNROLL
        for (short j = 0; j < vec_size; j++) {
          dst[i * dst_ld + j] = T(0);
        }
      }
      return;
    }

    int wh = (weight_hw / params->wS[1]);
    int ww = (weight_hw % params->wS[1]);

    int flip_h = params->flip ? params->wS[0] - wh - 1 : wh;
    int flip_w = params->flip ? params->wS[1] - ww - 1 : ww;

    int weight_h = flip_h * params->kdil[0];
    int weight_w = flip_w * params->kdil[1];

    STEEL_PRAGMA_UNROLL
    for (short i = 0, is = 0; i < n_rows; ++i, is += TROWS) {
      // Find bounds
      int n = read_n[i];
      int ih = read_ih[i] + weight_h;
      int iw = read_iw[i] + weight_w;

      // Read from input if in bounds
      if ((n < params->N) && (ih >= 0 && ih < params->iS[0]) &&
          (iw >= 0 && iw < params->iS[1])) {
        const device T* curr_src = src[i] + weight_h * params->in_strides[1] +
            weight_w * params->in_strides[2];

        STEEL_PRAGMA_UNROLL
        for (short j = 0; j < n_channels; ++j) {
          dst[is * dst_ld + j] = curr_src[j];
        }

        STEEL_PRAGMA_UNROLL
        for (short j = n_channels; j < vec_size; ++j) {
          dst[is * dst_ld + j] = T(0);
        }
      }

      // Zero pad otherwise
      else {
        STEEL_PRAGMA_UNROLL
        for (short j = 0; j < vec_size; ++j) {
          dst[is * dst_ld + j] = T(0);
        }
      }
    }
  }

  /* Iteration helper */
  METAL_FUNC void next() {
    weight_hw += TCOLS;
  }
};

template <
    typename T,
    short BM,
    short BN,
    short BK,
    short tgp_size,
    short n_channels,
    short tgp_padding = 0>
struct Conv2DWeightBlockLoaderSmallChannels {
  // Destination dimensions
  STEEL_CONST short BROWS = BN;
  STEEL_CONST short BCOLS = BK;

  // Read dimensions
  STEEL_CONST short dst_ld = BCOLS + tgp_padding;
  STEEL_CONST short vec_size = ChannelHelper<n_channels>::vec_size;

  // Thread read shape
  STEEL_CONST short TCOLS = BCOLS / vec_size;
  STEEL_CONST short TROWS = tgp_size / TCOLS;

  // Rows / strided reads within the block
  STEEL_CONST short n_rows = BROWS / TROWS;

  // Leading dimension for src
  const int src_ld;

  // Thread location indices
  const short thread_idx;
  const short bi;
  const short bj;

  // threadgroup and device memory
  threadgroup T* dst;
  const device T* src;

  const constant MLXConvParams<2>* params;

  int weight_hw;

  const int read_n;
  const bool do_read;

  /* Constructor */
  METAL_FUNC Conv2DWeightBlockLoaderSmallChannels(
      const device T* src_,
      threadgroup T* dst_,
      const int2 offsets,
      const constant MLXConvParams<2>* params_,
      const constant ImplicitGemmConv2DParams* gemm_params_,
      uint simd_group_id [[simdgroup_index_in_threadgroup]],
      uint simd_lane_id [[thread_index_in_simdgroup]])
      : src_ld(params_->wt_strides[0]),
        thread_idx(simd_group_id * 32 + simd_lane_id),
        bi(thread_idx / TCOLS),
        bj(vec_size * (thread_idx % TCOLS)),
        dst(dst_ + bi * dst_ld + bj),
        src(src_ + bi * src_ld),
        params(params_),
        weight_hw(thread_idx % TCOLS),
        read_n(offsets.y + bi),
        do_read(read_n + BN <= gemm_params_->N) {}

  /* Load from device memory into threadgroup memory - without bound checking */
  METAL_FUNC void load_unsafe() const {
    if (bi >= BROWS || bj >= BCOLS)
      return;

    if (read_n >= params->O || weight_hw >= params->wS[1] * params->wS[0]) {
      STEEL_PRAGMA_UNROLL
      for (short i = 0; i < BROWS; i += TROWS) {
        STEEL_PRAGMA_UNROLL
        for (short j = 0; j < vec_size; j++) {
          dst[i * dst_ld + j] = T(0);
        }
      }

      return;
    }

    const device T* curr_src = src + weight_hw * params->wt_strides[2];

    if (BN != 8 || do_read) {
      STEEL_PRAGMA_UNROLL
      for (short i = 0; i < BROWS; i += TROWS) {
        STEEL_PRAGMA_UNROLL
        for (short j = 0; j < n_channels; j++) {
          dst[i * dst_ld + j] = curr_src[i * src_ld + j];
        }

        STEEL_PRAGMA_UNROLL
        for (short j = n_channels; j < vec_size; j++) {
          dst[i * dst_ld + j] = T(0);
        }
      }
    } else {
      for (short i = 0; i < BROWS; i += TROWS) {
        if (((read_n + i) < params->O)) {
          STEEL_PRAGMA_UNROLL
          for (short j = 0; j < n_channels; j++) {
            dst[i * dst_ld + j] = curr_src[i * src_ld + j];
          }

          STEEL_PRAGMA_UNROLL
          for (short j = n_channels; j < vec_size; j++) {
            dst[i * dst_ld + j] = T(0);
          }
        } else {
          STEEL_PRAGMA_UNROLL
          for (short j = 0; j < vec_size; j++) {
            dst[i * dst_ld + j] = T(0);
          }
        }
      }
    }
  }

  /* Iteration helper */
  METAL_FUNC void next() {
    weight_hw += TCOLS;
  }
};

} // namespace steel
} // namespace mlx