import importlib.metadata
import inspect
import warnings
from copy import deepcopy
from inspect import signature

from packaging import version

from ..utils import (
    get_available_devices,
    is_accelerate_available,
    is_bitsandbytes_available,
    is_bitsandbytes_multi_backend_available,
    is_torch_available,
    logging,
)


if is_bitsandbytes_available():
    import bitsandbytes as bnb
    import torch
    import torch.nn as nn

    from ..pytorch_utils import Conv1D

if is_accelerate_available():
    import accelerate
    from accelerate import init_empty_weights
    from accelerate.hooks import add_hook_to_module, remove_hook_from_module
    from accelerate.utils import find_tied_parameters

logger = logging.get_logger(__name__)


def set_module_quantized_tensor_to_device(module, tensor_name, device, value=None, quantized_stats=None):
    """
    A helper function to set a given tensor (parameter of buffer) of a module on a specific device (note that doing
    `param.to(device)` creates a new tensor not linked to the parameter, which is why we need this function). The
    function is adapted from `set_module_tensor_to_device` function from accelerate that is adapted to support the
    class `Int8Params` from `bitsandbytes`.

    Args:
        module (`torch.nn.Module`):
            The module in which the tensor we want to move lives.
        tensor_name (`str`):
            The full name of the parameter/buffer.
        device (`int`, `str` or `torch.device`):
            The device on which to set the tensor.
        value (`torch.Tensor`, *optional*):
            The value of the tensor (useful when going from the meta device to any other device).
        quantized_stats (`dict[str, Any]`, *optional*):
            Dict with items for either 4-bit or 8-bit serialization
    """
    # Recurse if needed
    if "." in tensor_name:
        splits = tensor_name.split(".")
        for split in splits[:-1]:
            new_module = getattr(module, split)
            if new_module is None:
                raise ValueError(f"{module} has no attribute {split}.")
            module = new_module
        tensor_name = splits[-1]

    if tensor_name not in module._parameters and tensor_name not in module._buffers:
        raise ValueError(f"{module} does not have a parameter or a buffer named {tensor_name}.")
    is_buffer = tensor_name in module._buffers
    old_value = getattr(module, tensor_name)

    if old_value.device == torch.device("meta") and device not in ["meta", torch.device("meta")] and value is None:
        raise ValueError(f"{tensor_name} is on the meta device, we need a `value` to put in on {device}.")

    prequantized_loading = quantized_stats is not None
    if is_buffer or not is_bitsandbytes_available():
        is_8bit = False
        is_4bit = False
    else:
        is_4bit = hasattr(bnb.nn, "Params4bit") and isinstance(module._parameters[tensor_name], bnb.nn.Params4bit)
        is_8bit = isinstance(module._parameters[tensor_name], bnb.nn.Int8Params)

    if is_8bit or is_4bit:
        param = module._parameters[tensor_name]
        if param.device.type != "cuda":
            if value is None:
                new_value = old_value.to(device)
            elif isinstance(value, torch.Tensor):
                new_value = value.to("cpu")
            else:
                new_value = torch.tensor(value, device="cpu")

            # Support models using `Conv1D` in place of `nn.Linear` (e.g. openai-community/gpt2) by transposing the weight matrix prior to quantization.
            # Since weights are saved in the correct "orientation", we skip transposing when loading.
            if issubclass(module.source_cls, Conv1D) and not prequantized_loading:
                new_value = new_value.T

            kwargs = old_value.__dict__

            if prequantized_loading != (new_value.dtype in (torch.int8, torch.uint8)):
                raise ValueError(
                    f"Value dtype `{new_value.dtype}` is not compatible with parameter quantization status."
                )

            if is_8bit:
                is_8bit_serializable = version.parse(importlib.metadata.version("bitsandbytes")) > version.parse(
                    "0.37.2"
                )
                if new_value.dtype in (torch.int8, torch.uint8) and not is_8bit_serializable:
                    raise ValueError(
                        "Detected int8 weights but the version of bitsandbytes is not compatible with int8 serialization. "
                        "Make sure to download the latest `bitsandbytes` version. `pip install --upgrade bitsandbytes`."
                    )
                new_value = bnb.nn.Int8Params(new_value, requires_grad=False, **kwargs).to(device)
                if prequantized_loading:
                    setattr(new_value, "SCB", quantized_stats["SCB"].to(device))
            elif is_4bit:
                if prequantized_loading:
                    is_4bit_serializable = version.parse(importlib.metadata.version("bitsandbytes")) >= version.parse(
                        "0.41.3"
                    )
                    if new_value.dtype in (torch.int8, torch.uint8) and not is_4bit_serializable:
                        raise ValueError(
                            "Detected 4-bit weights but the version of bitsandbytes is not compatible with 4-bit serialization. "
                            "Make sure to download the latest `bitsandbytes` version. `pip install --upgrade bitsandbytes`."
                        )
                    new_value = bnb.nn.Params4bit.from_prequantized(
                        data=new_value,
                        quantized_stats=quantized_stats,
                        requires_grad=False,
                        device=device,
                        **kwargs,
                    )
                else:
                    new_value = bnb.nn.Params4bit(new_value, requires_grad=False, **kwargs).to(device)
            module._parameters[tensor_name] = new_value

    else:
        if value is None:
            new_value = old_value.to(device)
        elif isinstance(value, torch.Tensor):
            new_value = value.to(device)
        else:
            new_value = torch.tensor(value, device=device)

        if is_buffer:
            module._buffers[tensor_name] = new_value
        else:
            new_value = nn.Parameter(new_value, requires_grad=old_value.requires_grad)
            module._parameters[tensor_name] = new_value


def _replace_with_bnb_linear(
    model,
    modules_to_not_convert=None,
    current_key_name=None,
    quantization_config=None,
    has_been_replaced=False,
):
    """
    Private method that wraps the recursion for module replacement.

    Returns the converted model and a boolean that indicates if the conversion has been successful or not.
    """
    for name, module in model.named_children():
        if current_key_name is None:
            current_key_name = []
        current_key_name.append(name)

        if (isinstance(module, (nn.Linear, Conv1D))) and name not in modules_to_not_convert:
            # Check if the current key is not in the `modules_to_not_convert`
            current_key_name_str = ".".join(current_key_name)
            if not any(
                (key + "." in current_key_name_str) or (key == current_key_name_str) for key in modules_to_not_convert
            ):
                with init_empty_weights():
                    if isinstance(module, Conv1D):
                        in_features, out_features = module.weight.shape
                    else:
                        in_features = module.in_features
                        out_features = module.out_features

                    if quantization_config.quantization_method() == "llm_int8":
                        model._modules[name] = bnb.nn.Linear8bitLt(
                            in_features,
                            out_features,
                            module.bias is not None,
                            has_fp16_weights=quantization_config.llm_int8_has_fp16_weight,
                            threshold=quantization_config.llm_int8_threshold,
                        )
                        has_been_replaced = True
                    else:
                        if (
                            quantization_config.llm_int8_skip_modules is not None
                            and name in quantization_config.llm_int8_skip_modules
                        ):
                            pass
                        else:
                            extra_kwargs = (
                                {"quant_storage": quantization_config.bnb_4bit_quant_storage}
                                if "quant_storage" in list(signature(bnb.nn.Linear4bit).parameters)
                                else {}
                            )
                            model._modules[name] = bnb.nn.Linear4bit(
                                in_features,
                                out_features,
                                module.bias is not None,
                                quantization_config.bnb_4bit_compute_dtype,
                                compress_statistics=quantization_config.bnb_4bit_use_double_quant,
                                quant_type=quantization_config.bnb_4bit_quant_type,
                                **extra_kwargs,
                            )
                            has_been_replaced = True
                    # Store the module class in case we need to transpose the weight later
                    model._modules[name].source_cls = type(module)
                    # Force requires grad to False to avoid unexpected errors
                    model._modules[name].requires_grad_(False)
        if len(list(module.children())) > 0:
            _, has_been_replaced = _replace_with_bnb_linear(
                module,
                modules_to_not_convert,
                current_key_name,
                quantization_config,
                has_been_replaced=has_been_replaced,
            )
        # Remove the last key for recursion
        current_key_name.pop(-1)
    return model, has_been_replaced


def replace_with_bnb_linear(model, modules_to_not_convert=None, current_key_name=None, quantization_config=None):
    """
    A helper function to replace all `torch.nn.Linear` modules by `bnb.nn.Linear8bit` modules from the `bitsandbytes`
    library. This will enable running your models using mixed int8 precision as described by the paper `LLM.int8():
    8-bit Matrix Multiplication for Transformers at Scale`. Make sure `bitsandbytes` compiled with the correct CUDA
    version of your hardware is installed before running this function. `pip install -i https://test.pypi.org/simple/
    bitsandbytes`

    The function will be run recursively and replace all `torch.nn.Linear` modules except for the `lm_head` that should
    be kept as a `torch.nn.Linear` module. The replacement is done under `init_empty_weights` context manager so no
    CPU/GPU memory is required to run this function. Int8 mixed-precision matrix decomposition works by separating a
    matrix multiplication into two streams: (1) and systematic feature outlier stream matrix multiplied in fp16
    (0.01%), (2) a regular stream of int8 matrix multiplication (99.9%). With this method, int8 inference with no
    predictive degradation is possible for very large models (>=176B parameters).

    Parameters:
        model (`torch.nn.Module`):
            Input model or `torch.nn.Module` as the function is run recursively.
        modules_to_not_convert (`list[`str`]`, *optional*, defaults to `["lm_head"]`):
            Names of the modules to not convert in `Linear8bitLt`. In practice we keep the `lm_head` in full precision
            for numerical stability reasons.
        current_key_name (`list[`str`]`, *optional*):
            An array to track the current key of the recursion. This is used to check whether the current key (part of
            it) is not in the list of modules to not convert (for instances modules that are offloaded to `cpu` or
            `disk`).
        quantization_config ('transformers.utils.quantization_config.BitsAndBytesConfig'):
            To configure and manage settings related to quantization, a technique used to compress neural network models
            by reducing the precision of the weights and activations, thus making models more efficient in terms of both
            storage and computation.
    """
    modules_to_not_convert = ["lm_head"] if modules_to_not_convert is None else modules_to_not_convert
    model, has_been_replaced = _replace_with_bnb_linear(
        model, modules_to_not_convert, current_key_name, quantization_config
    )

    if not has_been_replaced:
        logger.warning(
            "You are loading your model in 8bit or 4bit but no linear modules were found in your model."
            " Please double check your model architecture, or submit an issue on github if you think this is"
            " a bug."
        )

    return model


# For backward compatibility
def replace_8bit_linear(*args, **kwargs):
    warnings.warn(
        "`replace_8bit_linear` will be deprecated in a future version, please use `replace_with_bnb_linear` instead",
        FutureWarning,
    )
    return replace_with_bnb_linear(*args, **kwargs)


# For backward compatibility
def set_module_8bit_tensor_to_device(*args, **kwargs):
    warnings.warn(
        "`set_module_8bit_tensor_to_device` will be deprecated in a future version, please use `set_module_quantized_tensor_to_device` instead",
        FutureWarning,
    )
    return set_module_quantized_tensor_to_device(*args, **kwargs)


def get_keys_to_not_convert(model):
    r"""
    An utility function to get the key of the module to keep in full precision if any For example for CausalLM modules
    we may want to keep the lm_head in full precision for numerical stability reasons. For other architectures, we want
    to keep the tied weights of the model. The function will return a list of the keys of the modules to not convert in
    int8.

    Parameters:
    model (`torch.nn.Module`):
        Input model
    """
    # Create a copy of the model and tie the weights, then
    # check if it contains tied weights
    tied_model = deepcopy(model)  # this has 0 cost since it is done inside `init_empty_weights` context manager`
    tied_model.tie_weights()

    tied_params = find_tied_parameters(tied_model)
    # For compatibility with Accelerate < 0.18
    if isinstance(tied_params, dict):
        tied_keys = sum(list(tied_params.values()), []) + list(tied_params.keys())
    else:
        tied_keys = sum(tied_params, [])
    has_tied_params = len(tied_keys) > 0

    # If there is not tied weights, we want to keep the lm_head（output_embedding) in full precision
    if not has_tied_params:
        output_emb = model.get_output_embeddings()
        if output_emb is not None:
            list_last_module = [name for name, module in model.named_modules() if id(module) == id(output_emb)]
            return list_last_module

    # otherwise, no tied weights, no output embedding defined, simply keep the last module in full precision
    list_modules = list(model.named_parameters())
    list_last_module = [list_modules[-1][0]]
    # add last module together with tied weights
    intersection = set(list_last_module) - set(tied_keys)
    list_untouched = list(set(tied_keys)) + list(intersection)

    # remove ".weight" from the keys
    names_to_remove = [".weight", ".bias"]
    filtered_module_names = []
    for name in list_untouched:
        for name_to_remove in names_to_remove:
            if name_to_remove in name:
                name = name.replace(name_to_remove, "")
        filtered_module_names.append(name)

    return filtered_module_names


# Copied from PEFT: https://github.com/huggingface/peft/blob/47b3712898539569c02ec5b3ed4a6c36811331a1/src/peft/utils/integrations.py#L41
def dequantize_bnb_weight(weight: "torch.nn.Parameter", dtype: "torch.dtype", state=None):
    """
    Helper function to dequantize 4bit or 8bit bnb weights.

    If the weight is not a bnb quantized weight, it will be returned as is.
    """
    if not isinstance(weight, torch.nn.Parameter):
        raise TypeError(f"Input weight should be of type nn.Parameter, got {type(weight)} instead")

    cls_name = weight.__class__.__name__
    if cls_name not in ("Params4bit", "Int8Params"):
        return weight

    if cls_name == "Params4bit":
        output_tensor = bnb.functional.dequantize_4bit(weight.data, weight.quant_state)
        logger.warning_once(
            f"The model is going to be dequantized in {output_tensor.dtype} - if you want to upcast it to another dtype, make sure to pass the desired dtype when quantizing the model through `bnb_4bit_quant_type` argument of `BitsAndBytesConfig`"
        )
        return output_tensor.to(dtype)

    if state.SCB is None:
        state.SCB = weight.SCB

    if hasattr(bnb.functional, "int8_vectorwise_dequant"):
        # Use bitsandbytes API if available (requires v0.45.0+)
        dequantized = bnb.functional.int8_vectorwise_dequant(weight.data, state.SCB)
    else:
        # Multiply by (scale/127) to dequantize.
        dequantized = weight.data * state.SCB.view(-1, 1) * 7.874015718698502e-3

    return dequantized.to(dtype)


def _create_accelerate_new_hook(old_hook):
    r"""
    Creates a new hook based on the old hook. Use it only if you know what you are doing !
    This method is a copy of: https://github.com/huggingface/peft/blob/748f7968f3a31ec06a1c2b0328993319ad9a150a/src/peft/utils/other.py#L245
    with some changes
    """
    old_hook_cls = getattr(accelerate.hooks, old_hook.__class__.__name__)
    old_hook_attr = old_hook.__dict__
    filtered_old_hook_attr = {}
    old_hook_init_signature = inspect.signature(old_hook_cls.__init__)
    for k in old_hook_attr:
        if k in old_hook_init_signature.parameters:
            filtered_old_hook_attr[k] = old_hook_attr[k]
    new_hook = old_hook_cls(**filtered_old_hook_attr)
    return new_hook


def _dequantize_and_replace(
    model,
    dtype,
    modules_to_not_convert=None,
    current_key_name=None,
    quantization_config=None,
    has_been_replaced=False,
):
    """
    Converts a quantized model into its dequantized original version. The newly converted model will have
    some performance drop compared to the original model before quantization - use it only for specific usecases
    such as QLoRA adapters merging.

    Returns the converted model and a boolean that indicates if the conversion has been successful or not.
    """
    quant_method = quantization_config.quantization_method()

    target_cls = bnb.nn.Linear8bitLt if quant_method == "llm_int8" else bnb.nn.Linear4bit

    for name, module in model.named_children():
        if current_key_name is None:
            current_key_name = []
        current_key_name.append(name)

        if isinstance(module, target_cls) and name not in modules_to_not_convert:
            # Check if the current key is not in the `modules_to_not_convert`
            current_key_name_str = ".".join(current_key_name)

            if not any(
                (key + "." in current_key_name_str) or (key == current_key_name_str) for key in modules_to_not_convert
            ):
                bias = getattr(module, "bias", None)

                device = module.weight.device
                with init_empty_weights():
                    new_module = torch.nn.Linear(module.in_features, module.out_features, bias=bias is not None)

                if quant_method == "llm_int8":
                    state = module.state
                else:
                    state = None

                new_module.weight = torch.nn.Parameter(dequantize_bnb_weight(module.weight, dtype, state))

                if bias is not None:
                    new_module.bias = bias

                # Create a new hook and attach it in case we use accelerate
                if hasattr(module, "_hf_hook"):
                    old_hook = module._hf_hook
                    new_hook = _create_accelerate_new_hook(old_hook)

                    remove_hook_from_module(module)
                    add_hook_to_module(new_module, new_hook)

                new_module.to(device)
                model._modules[name] = new_module
                has_been_replaced = True
        if len(list(module.children())) > 0:
            _, has_been_replaced = _dequantize_and_replace(
                module,
                dtype,
                modules_to_not_convert,
                current_key_name,
                quantization_config,
                has_been_replaced=has_been_replaced,
            )
        # Remove the last key for recursion
        current_key_name.pop(-1)
    return model, has_been_replaced


def dequantize_and_replace(
    model,
    modules_to_not_convert=None,
    quantization_config=None,
):
    model, has_been_replaced = _dequantize_and_replace(
        model,
        model.dtype,
        modules_to_not_convert=modules_to_not_convert,
        quantization_config=quantization_config,
    )

    if not has_been_replaced:
        logger.warning(
            "For some reason the model has not been properly dequantized. You might see unexpected behavior."
        )

    return model


def _validate_bnb_multi_backend_availability(raise_exception):
    import bitsandbytes as bnb

    bnb_supported_devices = getattr(bnb, "supported_torch_devices", set())
    available_devices = set(get_available_devices())

    if not available_devices.intersection(bnb_supported_devices):
        if raise_exception:
            err_msg = (
                f"None of the available devices `available_devices = {available_devices or None}` are supported by the bitsandbytes version you have installed: `bnb_supported_devices = {bnb_supported_devices}`. "
                "Please check the docs to see if the backend you intend to use is available and how to install it: https://huggingface.co/docs/bitsandbytes/main/en/installation"
            )

            logger.error(err_msg)
            raise RuntimeError(err_msg)

        logger.warning("No supported devices found for bitsandbytes multi-backend.")
        return False

    logger.debug("Multi-backend validation successful.")
    return True


def _validate_bnb_cuda_backend_availability(raise_exception):
    if not is_torch_available():
        return False

    import torch

    if not torch.cuda.is_available():
        log_msg = (
            "CUDA is required but not available for bitsandbytes. Please consider installing the multi-platform enabled version of bitsandbytes, which is currently a work in progress. "
            "Please check currently supported platforms and installation instructions at https://huggingface.co/docs/bitsandbytes/main/en/installation#multi-backend"
        )
        if raise_exception:
            logger.error(log_msg)
            raise RuntimeError(log_msg)

        logger.warning(log_msg)
        return False

    logger.debug("CUDA backend validation successful.")
    return True


def validate_bnb_backend_availability(raise_exception=False):
    """
    Validates if the available devices are supported by bitsandbytes, optionally raising an exception if not.
    """
    if not is_bitsandbytes_available():
        if importlib.util.find_spec("bitsandbytes") and version.parse(
            importlib.metadata.version("bitsandbytes")
        ) < version.parse("0.43.1"):
            return _validate_bnb_cuda_backend_availability(raise_exception)
        return False

    if is_bitsandbytes_multi_backend_available():
        return _validate_bnb_multi_backend_availability(raise_exception)
    return _validate_bnb_cuda_backend_availability(raise_exception)
