# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD 3-Clause license found in the
# LICENSE file in the root directory of this source tree.
from typing import List, Optional, Tuple

import torch
from torch.utils._python_dispatch import return_and_correct_aliasing

from torchao.kernel.bsr_triton_ops import broadcast_batch_dims, bsr_dense_addmm
from torchao.ops import register_custom_op, register_custom_op_impl
from torchao.utils import TorchAOBaseTensor

aten = torch.ops.aten


# quantization support
@register_custom_op_impl("blocksparse::bsr_to_dense")
def bsr_to_dense(
    crow_indices: torch.Tensor,
    col_indices: torch.Tensor,
    values: torch.Tensor,
    M: int,
    K: int,
) -> torch.Tensor:
    return torch.sparse_bsr_tensor(
        crow_indices=crow_indices, col_indices=col_indices, values=values, size=(M, K)
    ).to_dense()


@register_custom_op("blocksparse::bsr_to_dense")
def bsr_to_dense_abstract(
    crow_indices: torch.Tensor,
    col_indices: torch.Tensor,
    values: torch.Tensor,
    M: int,
    K: int,
) -> torch.Tensor:
    return torch.empty((M, K), dtype=values.dtype, device=values.device)


@register_custom_op_impl("blocksparse::int_addmm")
def blocksparse_int_addmm(
    crow_indices: torch.Tensor,
    col_indices: torch.Tensor,
    values: torch.Tensor,
    A: torch.Tensor,
    left_alpha: torch.Tensor,
    right_alpha: torch.Tensor,
) -> torch.Tensor:
    assert values.dtype == torch.int8
    M = left_alpha.shape[-1]
    K = A.shape[-2]
    N = A.shape[-1]
    weight_bsr = torch.sparse_bsr_tensor(crow_indices, col_indices, values, size=(M, K))
    original_batch_dims_broadcasted = broadcast_batch_dims(
        blocksparse_int_addmm, weight_bsr, A
    )
    out = A.new_empty(original_batch_dims_broadcasted + (M, N), dtype=torch.bfloat16)
    return bsr_dense_addmm(
        out,
        weight_bsr,
        A,
        alpha=1,
        beta=0,
        out=out,
        left_alpha=left_alpha,
        right_alpha=right_alpha,
    ).t()


@register_custom_op("blocksparse::int_addmm")
def blocksparse_int_addmm_abstract(
    crow_indices: torch.Tensor,
    col_indices: torch.Tensor,
    values: torch.Tensor,
    A: torch.Tensor,
    left_alpha: torch.Tensor,
    right_alpha: torch.Tensor,
) -> torch.Tensor:
    N = A.shape[-1]
    M = left_alpha.shape[-1]
    # to have the same strides as the transposed result
    return torch.empty((M, N), dtype=torch.bfloat16, device=A.device).t()


@register_custom_op_impl("blocksparse::addmm")
def blocksparse_addmm(
    x_padded: torch.Tensor,
    crow_indices: torch.Tensor,
    col_indices: torch.Tensor,
    values: torch.Tensor,
    M: int,
    K: int,
    bias: torch.Tensor,
) -> torch.Tensor:
    assert bias is None
    bsr = torch.sparse_bsr_tensor(crow_indices, col_indices, values, size=(M, K))
    N_padded = x_padded.shape[1]
    out = x_padded.new_empty((M, N_padded))
    bsr_dense_addmm(
        out,
        bsr,
        x_padded,
        alpha=1,
        beta=0,
        out=out,
    )
    return out


@register_custom_op("blocksparse::addmm")
def blocksparse_addmm_abstract(
    x_padded: torch.Tensor,
    crow_indices: torch.Tensor,
    col_indices: torch.Tensor,
    values: torch.Tensor,
    M: int,
    K: int,
    bias: torch.Tensor,
) -> torch.Tensor:
    N_padded = x_padded.shape[1]
    return x_padded.new_empty((M, N_padded))


# Subclass definition
class BlockSparseTensor(TorchAOBaseTensor):
    bsr_crow_indices: Optional[torch.Tensor]
    bsr_col_indices: Optional[torch.Tensor]
    bsr_values: Optional[torch.Tensor]
    blocksize: int

    __slots__ = ["bsr_crow_indices", "bsr_col_indices", "bsr_values"]

    @staticmethod
    def __new__(  # noqa: PYI034
        cls,
        shape: torch.Size,
        blocksize: int,
        bsr_crow_indices: Optional[torch.Tensor],
        bsr_col_indices: Optional[torch.Tensor],
        bsr_values: Optional[torch.Tensor],
        requires_grad: bool = False,
    ):
        if bsr_values is None:
            raise ValueError(
                "No values passed to BlockSparseTensor: bsr_values must be provided!"
            )
        else:
            previous_tensor = bsr_values

        kwargs = {
            "device": previous_tensor.device,
            "dtype": previous_tensor.dtype,
            "layout": previous_tensor.layout,
            "requires_grad": requires_grad,
        }
        tensor = torch.Tensor._make_wrapper_subclass(cls, shape, **kwargs)  # type: ignore[attr-defined]
        tensor.blocksize = blocksize
        tensor.bsr_crow_indices = bsr_crow_indices
        tensor.bsr_values = bsr_values
        tensor.bsr_col_indices = bsr_col_indices
        return tensor

    def __repr__(self) -> str:  # type: ignore[override]
        assert hasattr(self, "shape")
        return f"{self.__class__.__name__}(shape={self.shape})"

    def __tensor_flatten__(self) -> Tuple[List[str], Tuple[torch.Size, bool, int]]:
        inner_tensors = list(
            filter(lambda x: getattr(self, x) is not None, self.__slots__)
        )
        tensor_meta = (self.shape, self.requires_grad, self.blocksize)
        return inner_tensors, tensor_meta

    @classmethod
    def __tensor_unflatten__(
        cls,
        inner_tensors,
        tensor_meta: Tuple[torch.Size, bool, int],
        outer_size,
        outer_stride,
    ) -> torch.Tensor:
        shape, requires_grad, blocksize = tensor_meta
        # print("unflatten", outer_size, outer_stride)
        return cls(
            shape=shape,
            blocksize=blocksize,
            bsr_crow_indices=inner_tensors.get("bsr_crow_indices", None),
            bsr_col_indices=inner_tensors.get("bsr_col_indices", None),
            bsr_values=inner_tensors.get("bsr_values", None),
            requires_grad=requires_grad,
        )

    @classmethod
    def from_dense(cls, dense_tensor, blocksize):
        bsr_tensor = dense_tensor.to_sparse_bsr(blocksize)
        # bsr_tensor_t = dense_tensor.t().contiguous().to_sparse_bsr(blocksize)
        return cls(
            shape=dense_tensor.shape,
            blocksize=blocksize,
            bsr_crow_indices=bsr_tensor.crow_indices(),
            bsr_col_indices=bsr_tensor.col_indices(),
            bsr_values=bsr_tensor.values(),
            requires_grad=False,
        )

    def apply_fn_to_shard(self, func):
        return BlockSparseTensor(
            shape=self.shape,
            blocksize=self.blocksize,
            bsr_crow_indices=func(self.bsr_crow_indices),
            bsr_col_indices=func(self.bsr_col_indices),
            bsr_values=func(self.bsr_values),
            requires_grad=self.requires_grad,
        )


# Subclass op dispatch registration
implements = BlockSparseTensor.implements
implements_torch_function = BlockSparseTensor.implements_torch_function


@implements(aten.detach.default)
def block_sparse_detach(func, types, args, kwargs):
    return return_and_correct_aliasing(
        func, args, kwargs, args[0].apply_fn_to_shard(torch.detach)
    )


@implements(aten.unsqueeze.default)
def block_sparse_unsqueeze(func, types, args, kwargs):
    assert len(args) == 2
    assert len(kwargs) == 0
    assert args[-1] == 2
    bsr = args[0]
    assert bsr.dim() == 2
    assert not bsr.requires_grad
    return BlockSparseTensor(
        bsr.shape + (1,),
        bsr.blocksize,
        bsr.crow_indices(),
        bsr.col_indices(),
        bsr.values().unsqueeze(-1),
        requires_grad=False,
    )


@implements(aten.mul.Tensor)
def block_sparse_mul(func, types, args, kwargs):
    assert len(args) == 2
    assert len(kwargs) == 0
    bsr, t = args

    def my_mul(bsr, t):
        assert isinstance(bsr, BlockSparseTensor)
        assert isinstance(t, torch.Tensor)
        assert bsr.dim() == 3
        assert t.dim() == 3
        assert not bsr.requires_grad
        assert t.size(0) == 1
        t_blocked = t.view(t.size(0), t.size(1) // bsr.blocksize, bsr.blocksize, 1)
        masked_t = t_blocked.transpose(0, 1).index_select(0, bsr.col_indices())
        new_values = bsr.values() * masked_t
        return BlockSparseTensor(
            bsr.shape, bsr.blocksize, bsr.crow_indices(), bsr.col_indices(), new_values
        )

    if isinstance(bsr, torch.Tensor) and isinstance(t, BlockSparseTensor):
        return my_mul(t, bsr)
    return my_mul(bsr, t)


@implements(aten.sum.dim_IntList)
def block_sparse_sum(func, types, args, kwargs):
    bsr, dim = args
    assert type(dim) == list
    assert len(dim) == 1
    dim = dim[0]
    assert dim == 1
    return torch.ops.blocksparse.sum(bsr.values(), bsr.crow_indices(), bsr.shape[0])


@implements(aten.values.default)
def block_sparse_values(func, types, args, kwargs):
    return args[0].bsr_values.detach()


@implements(aten.crow_indices.default)
def block_sparse_crow_indices(func, types, args, kwargs):
    return args[0].bsr_crow_indices.detach()


@implements(aten.col_indices.default)
def block_sparse_col_indices(func, types, args, kwargs):
    return args[0].bsr_col_indices.detach()


@implements(aten._nnz.default)
def block_sparse__nnz(func, types, args, kwargs):
    return args[0].bsr_values.shape[0]


@implements_torch_function(torch.nn.functional.linear)
def block_sparse_linear(func, types, args, kwargs):
    x_orig, w, bias = args
    x = x_orig.reshape(-1, x_orig.size(-1)).t()
    M = w.shape[0]
    K = w.shape[1]

    out = torch.ops.blocksparse.addmm(
        x,
        w.crow_indices(),
        w.col_indices(),
        w.values(),
        M,
        K,
        None,
    )
    out_orig = out.t()
    if bias is None:
        return out_orig

    return out_orig + bias