from typing import Tuple

import torch

from .nets_utils import make_pad_mask


class UtteranceMVN(torch.nn.Module):
    def __init__(
        self, norm_means: bool = True, norm_vars: bool = False, eps: float = 1.0e-20,
    ):
        super().__init__()
        self.norm_means = norm_means
        self.norm_vars = norm_vars
        self.eps = eps

    def extra_repr(self):
        return f"norm_means={self.norm_means}, norm_vars={self.norm_vars}"

    def forward(
        self, x: torch.Tensor, ilens: torch.Tensor = None
    ) -> Tuple[torch.Tensor, torch.Tensor]:
        """Forward function

        Args:
            x: (B, L, ...)
            ilens: (B,)

        """
        return utterance_mvn(
            x,
            ilens,
            norm_means=self.norm_means,
            norm_vars=self.norm_vars,
            eps=self.eps,
        )


def utterance_mvn(
    x: torch.Tensor,
    ilens: torch.Tensor = None,
    norm_means: bool = True,
    norm_vars: bool = False,
    eps: float = 1.0e-20,
) -> Tuple[torch.Tensor, torch.Tensor]:
    """Apply utterance mean and variance normalization

    Args:
        x: (B, T, D), assumed zero padded
        ilens: (B,)
        norm_means:
        norm_vars:
        eps:

    """
    if ilens is None:
        ilens = x.new_full([x.size(0)], x.size(1))
    ilens_ = ilens.to(x.device, x.dtype).view(-1, *[1 for _ in range(x.dim() - 1)])
    # Zero padding
    if x.requires_grad:
        x = x.masked_fill(make_pad_mask(ilens, x, 1), 0.0)
    else:
        x.masked_fill_(make_pad_mask(ilens, x, 1), 0.0)
    # mean: (B, 1, D)
    mean = x.sum(dim=1, keepdim=True) / ilens_

    if norm_means:
        x -= mean

        if norm_vars:
            var = x.pow(2).sum(dim=1, keepdim=True) / ilens_
            std = torch.clamp(var.sqrt(), min=eps)
            x = x / std.sqrt()
        return x, ilens
    else:
        if norm_vars:
            y = x - mean
            y.masked_fill_(make_pad_mask(ilens, y, 1), 0.0)
            var = y.pow(2).sum(dim=1, keepdim=True) / ilens_
            std = torch.clamp(var.sqrt(), min=eps)
            x /= std
        return x, ilens