import warnings
from typing import Any, Optional

import torch
import torch.nn as nn
from torch import Tensor
from torch.nn import functional as F
from torchvision.models.googlenet import GoogLeNetOutputs, BasicConv2d, Inception, InceptionAux, GoogLeNet, model_urls

from ..._internally_replaced_utils import load_state_dict_from_url
from .utils import _fuse_modules, _replace_relu, quantize_model


__all__ = ["QuantizableGoogLeNet", "googlenet"]

quant_model_urls = {
    # fp32 GoogLeNet ported from TensorFlow, with weights quantized in PyTorch
    "googlenet_fbgemm": "https://download.pytorch.org/models/quantized/googlenet_fbgemm-c00238cf.pth",
}


class QuantizableBasicConv2d(BasicConv2d):
    def __init__(self, *args: Any, **kwargs: Any) -> None:
        super().__init__(*args, **kwargs)
        self.relu = nn.ReLU()

    def forward(self, x: Tensor) -> Tensor:
        x = self.conv(x)
        x = self.bn(x)
        x = self.relu(x)
        return x

    def fuse_model(self, is_qat: Optional[bool] = None) -> None:
        _fuse_modules(self, ["conv", "bn", "relu"], is_qat, inplace=True)


class QuantizableInception(Inception):
    def __init__(self, *args: Any, **kwargs: Any) -> None:
        super().__init__(conv_block=QuantizableBasicConv2d, *args, **kwargs)  # type: ignore[misc]
        self.cat = nn.quantized.FloatFunctional()

    def forward(self, x: Tensor) -> Tensor:
        outputs = self._forward(x)
        return self.cat.cat(outputs, 1)


class QuantizableInceptionAux(InceptionAux):
    # TODO https://github.com/pytorch/vision/pull/4232#pullrequestreview-730461659
    def __init__(self, *args: Any, **kwargs: Any) -> None:
        super().__init__(conv_block=QuantizableBasicConv2d, *args, **kwargs)  # type: ignore[misc]
        self.relu = nn.ReLU()

    def forward(self, x: Tensor) -> Tensor:
        # aux1: N x 512 x 14 x 14, aux2: N x 528 x 14 x 14
        x = F.adaptive_avg_pool2d(x, (4, 4))
        # aux1: N x 512 x 4 x 4, aux2: N x 528 x 4 x 4
        x = self.conv(x)
        # N x 128 x 4 x 4
        x = torch.flatten(x, 1)
        # N x 2048
        x = self.relu(self.fc1(x))
        # N x 1024
        x = self.dropout(x)
        # N x 1024
        x = self.fc2(x)
        # N x 1000 (num_classes)

        return x


class QuantizableGoogLeNet(GoogLeNet):
    # TODO https://github.com/pytorch/vision/pull/4232#pullrequestreview-730461659
    def __init__(self, *args: Any, **kwargs: Any) -> None:
        super().__init__(  # type: ignore[misc]
            blocks=[QuantizableBasicConv2d, QuantizableInception, QuantizableInceptionAux], *args, **kwargs
        )
        self.quant = torch.ao.quantization.QuantStub()
        self.dequant = torch.ao.quantization.DeQuantStub()

    def forward(self, x: Tensor) -> GoogLeNetOutputs:
        x = self._transform_input(x)
        x = self.quant(x)
        x, aux1, aux2 = self._forward(x)
        x = self.dequant(x)
        aux_defined = self.training and self.aux_logits
        if torch.jit.is_scripting():
            if not aux_defined:
                warnings.warn("Scripted QuantizableGoogleNet always returns GoogleNetOutputs Tuple")
            return GoogLeNetOutputs(x, aux2, aux1)
        else:
            return self.eager_outputs(x, aux2, aux1)

    def fuse_model(self, is_qat: Optional[bool] = None) -> None:
        r"""Fuse conv/bn/relu modules in googlenet model

        Fuse conv+bn+relu/ conv+relu/conv+bn modules to prepare for quantization.
        Model is modified in place.  Note that this operation does not change numerics
        and the model after modification is in floating point
        """

        for m in self.modules():
            if type(m) is QuantizableBasicConv2d:
                m.fuse_model(is_qat)


def googlenet(
    pretrained: bool = False,
    progress: bool = True,
    quantize: bool = False,
    **kwargs: Any,
) -> QuantizableGoogLeNet:
    r"""GoogLeNet (Inception v1) model architecture from
    `"Going Deeper with Convolutions" <http://arxiv.org/abs/1409.4842>`_.

    Note that quantize = True returns a quantized model with 8 bit
    weights. Quantized models only support inference and run on CPUs.
    GPU inference is not yet supported

    Args:
        pretrained (bool): If True, returns a model pre-trained on ImageNet
        progress (bool): If True, displays a progress bar of the download to stderr
        quantize (bool): If True, return a quantized version of the model
        aux_logits (bool): If True, adds two auxiliary branches that can improve training.
            Default: *False* when pretrained is True otherwise *True*
        transform_input (bool): If True, preprocesses the input according to the method with which it
            was trained on ImageNet. Default: True if ``pretrained=True``, else False.
    """
    if pretrained:
        if "transform_input" not in kwargs:
            kwargs["transform_input"] = True
        if "aux_logits" not in kwargs:
            kwargs["aux_logits"] = False
        if kwargs["aux_logits"]:
            warnings.warn(
                "auxiliary heads in the pretrained googlenet model are NOT pretrained, so make sure to train them"
            )
        original_aux_logits = kwargs["aux_logits"]
        kwargs["aux_logits"] = True
        kwargs["init_weights"] = False

    model = QuantizableGoogLeNet(**kwargs)
    _replace_relu(model)

    if quantize:
        # TODO use pretrained as a string to specify the backend
        backend = "fbgemm"
        quantize_model(model, backend)
    else:
        assert pretrained in [True, False]

    if pretrained:
        if quantize:
            model_url = quant_model_urls["googlenet_" + backend]
        else:
            model_url = model_urls["googlenet"]

        state_dict = load_state_dict_from_url(model_url, progress=progress)

        model.load_state_dict(state_dict)

        if not original_aux_logits:
            model.aux_logits = False
            model.aux1 = None  # type: ignore[assignment]
            model.aux2 = None  # type: ignore[assignment]
    return model
