# Copyright 2022 The HuggingFace Team. All rights reserved.
#
# 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.
from __future__ import annotations

import inspect
from collections.abc import Callable
from functools import lru_cache, wraps

import torch
from safetensors.torch import storage_ptr, storage_size
from torch import nn

from .utils import (
    is_torch_greater_or_equal,
    is_torch_xla_available,
    is_torchdynamo_compiling,
    logging,
)


ALL_LAYERNORM_LAYERS = [nn.LayerNorm]

logger = logging.get_logger(__name__)

is_torch_greater_or_equal_than_2_8 = is_torch_greater_or_equal("2.8", accept_dev=True)
is_torch_greater_or_equal_than_2_6 = is_torch_greater_or_equal("2.6", accept_dev=True)

# For backwards compatibility (e.g. some remote codes on Hub using those variables).
is_torch_greater_or_equal_than_2_4 = is_torch_greater_or_equal("2.4", accept_dev=True)
is_torch_greater_or_equal_than_2_3 = is_torch_greater_or_equal("2.3", accept_dev=True)
is_torch_greater_or_equal_than_2_2 = is_torch_greater_or_equal("2.2", accept_dev=True)
is_torch_greater_or_equal_than_2_1 = is_torch_greater_or_equal("2.1", accept_dev=True)
is_torch_greater_or_equal_than_2_0 = is_torch_greater_or_equal("2.0", accept_dev=True)
is_torch_greater_or_equal_than_1_13 = is_torch_greater_or_equal("1.13", accept_dev=True)
is_torch_greater_or_equal_than_1_12 = is_torch_greater_or_equal("1.12", accept_dev=True)

# Cache this result has it's a C FFI call which can be pretty time-consuming
_torch_distributed_available = torch.distributed.is_available()


def softmax_backward_data(parent, grad_output, output):
    """
    A function that calls the internal `_softmax_backward_data` PyTorch method and that adjusts the arguments according
    to the torch version detected.
    """

    from torch import _softmax_backward_data

    return _softmax_backward_data(grad_output, output, parent.dim, output.dtype)


def prune_linear_layer(layer: nn.Linear, index: torch.LongTensor, dim: int = 0) -> nn.Linear:
    """
    Prune a linear layer to keep only entries in index.

    Used to remove heads.

    Args:
        layer (`torch.nn.Linear`): The layer to prune.
        index (`torch.LongTensor`): The indices to keep in the layer.
        dim (`int`, *optional*, defaults to 0): The dimension on which to keep the indices.

    Returns:
        `torch.nn.Linear`: The pruned layer as a new layer with `requires_grad=True`.
    """
    index = index.to(layer.weight.device)
    W = layer.weight.index_select(dim, index).detach().clone()
    if layer.bias is not None:
        if dim == 1:
            b = layer.bias.detach().clone()
        else:
            b = layer.bias[index].detach().clone()
    new_size = list(layer.weight.size())
    new_size[dim] = len(index)
    new_layer = nn.Linear(new_size[1], new_size[0], bias=layer.bias is not None).to(layer.weight.device)
    new_layer.weight.requires_grad = False
    new_layer.weight.copy_(W.contiguous())
    new_layer.weight.requires_grad = True
    if layer.bias is not None:
        new_layer.bias.requires_grad = False
        new_layer.bias.copy_(b.contiguous())
        new_layer.bias.requires_grad = True
    return new_layer


class Conv1D(nn.Module):
    """
    1D-convolutional layer as defined by Radford et al. for OpenAI GPT (and also used in GPT-2).

    Basically works like a linear layer but the weights are transposed.

    Args:
        nf (`int`): The number of output features.
        nx (`int`): The number of input features.
    """

    def __init__(self, nf, nx):
        super().__init__()
        self.nf = nf
        self.nx = nx
        self.weight = nn.Parameter(torch.empty(nx, nf))
        self.bias = nn.Parameter(torch.zeros(nf))
        nn.init.normal_(self.weight, std=0.02)

    def __repr__(self) -> str:
        return "Conv1D(nf={nf}, nx={nx})".format(**self.__dict__)

    def forward(self, x):
        size_out = x.size()[:-1] + (self.nf,)
        x = torch.addmm(self.bias, x.view(-1, x.size(-1)), self.weight)
        x = x.view(size_out)
        return x


def apply_chunking_to_forward(
    forward_fn: Callable[..., torch.Tensor],
    chunk_size: int,
    chunk_dim: int,
    *input_tensors,
) -> torch.Tensor:
    """
    This function chunks the `input_tensors` into smaller input tensor parts of size `chunk_size` over the dimension
    `chunk_dim`. It then applies a layer `forward_fn` to each chunk independently to save memory.

    If the `forward_fn` is independent across the `chunk_dim` this function will yield the same result as directly
    applying `forward_fn` to `input_tensors`.

    Args:
        forward_fn (`Callable[..., torch.Tensor]`):
            The forward function of the model.
        chunk_size (`int`):
            The chunk size of a chunked tensor: `num_chunks = len(input_tensors[0]) / chunk_size`.
        chunk_dim (`int`):
            The dimension over which the `input_tensors` should be chunked.
        input_tensors (`tuple[torch.Tensor]`):
            The input tensors of `forward_fn` which will be chunked

    Returns:
        `torch.Tensor`: A tensor with the same shape as the `forward_fn` would have given if applied`.


    Examples:

    ```python
    # rename the usual forward() fn to forward_chunk()
    def forward_chunk(self, hidden_states):
        hidden_states = self.decoder(hidden_states)
        return hidden_states


    # implement a chunked forward function
    def forward(self, hidden_states):
        return apply_chunking_to_forward(self.forward_chunk, self.chunk_size_lm_head, self.seq_len_dim, hidden_states)
    ```"""

    assert len(input_tensors) > 0, f"{input_tensors} has to be a tuple/list of tensors"

    # inspect.signature exist since python 3.5 and is a python method -> no problem with backward compatibility
    num_args_in_forward_chunk_fn = len(inspect.signature(forward_fn).parameters)
    if num_args_in_forward_chunk_fn != len(input_tensors):
        raise ValueError(
            f"forward_chunk_fn expects {num_args_in_forward_chunk_fn} arguments, but only {len(input_tensors)} input "
            "tensors are given"
        )

    if chunk_size > 0:
        tensor_shape = input_tensors[0].shape[chunk_dim]
        for input_tensor in input_tensors:
            if input_tensor.shape[chunk_dim] != tensor_shape:
                raise ValueError(
                    f"All input tenors have to be of the same shape: {tensor_shape}, "
                    f"found shape {input_tensor.shape[chunk_dim]}"
                )

        if input_tensors[0].shape[chunk_dim] % chunk_size != 0:
            raise ValueError(
                f"The dimension to be chunked {input_tensors[0].shape[chunk_dim]} has to be a multiple of the chunk "
                f"size {chunk_size}"
            )

        num_chunks = input_tensors[0].shape[chunk_dim] // chunk_size

        # chunk input tensor into tuples
        input_tensors_chunks = tuple(input_tensor.chunk(num_chunks, dim=chunk_dim) for input_tensor in input_tensors)
        # apply forward fn to every tuple
        output_chunks = tuple(forward_fn(*input_tensors_chunk) for input_tensors_chunk in zip(*input_tensors_chunks))
        # concatenate output at same dimension
        return torch.cat(output_chunks, dim=chunk_dim)

    return forward_fn(*input_tensors)


def meshgrid(*tensors: torch.Tensor | list[torch.Tensor], indexing: str | None = None) -> tuple[torch.Tensor, ...]:
    """
    Wrapper around torch.meshgrid to avoid warning messages about the introduced `indexing` argument.

    Reference: https://pytorch.org/docs/1.13/generated/torch.meshgrid.html
    """
    return torch.meshgrid(*tensors, indexing=indexing)


def id_tensor_storage(tensor: torch.Tensor) -> tuple[torch.device, int, int]:
    """
    Unique identifier to a tensor storage. Multiple different tensors can share the same underlying storage. For
    example, "meta" tensors all share the same storage, and thus their identifier will all be equal. This identifier is
    guaranteed to be unique and constant for this tensor's storage during its lifetime. Two tensor storages with
    non-overlapping lifetimes may have the same id.
    """
    if _torch_distributed_available and is_torch_greater_or_equal("2.5"):
        from torch.distributed.tensor import DTensor

        if isinstance(tensor, DTensor):
            local_tensor = tensor.to_local()
            return tensor.device, local_tensor.storage().data_ptr(), tensor.nbytes

    if tensor.device.type == "xla" and is_torch_xla_available():
        # NOTE: xla tensors dont have storage
        # use some other unique id to distinguish.
        # this is a XLA tensor, it must be created using torch_xla's
        # device. So the following import is safe:
        import torch_xla

        unique_id = torch_xla._XLAC._xla_get_tensor_id(tensor)
    else:
        unique_id = storage_ptr(tensor)

    return tensor.device, unique_id, storage_size(tensor)


@wraps(lru_cache)
def compile_compatible_method_lru_cache(*lru_args, **lru_kwargs):
    """
    LRU cache decorator from standard functools library, but with a workaround to disable
    caching when torchdynamo is compiling. Expected to work with class methods.
    """

    def decorator(func):
        func_with_cache = lru_cache(*lru_args, **lru_kwargs)(func)

        @wraps(func)
        def wrapper(*args, **kwargs):
            if is_torchdynamo_compiling():
                return func(*args, **kwargs)
            else:
                return func_with_cache(*args, **kwargs)

        return wrapper

    return decorator
