import torch
from torch import nn

from TTS.tts.layers.generic.normalization import ActNorm
from TTS.tts.layers.glow_tts.glow import CouplingBlock, InvConvNear


def squeeze(x, x_mask=None, num_sqz=2):
    """GlowTTS squeeze operation
    Increase number of channels and reduce number of time steps
    by the same factor.

    Note:
        each 's' is a n-dimensional vector.
        ``[s1,s2,s3,s4,s5,s6] --> [[s1, s3, s5], [s2, s4, s6]]``
    """
    b, c, t = x.size()

    t = (t // num_sqz) * num_sqz
    x = x[:, :, :t]
    x_sqz = x.view(b, c, t // num_sqz, num_sqz)
    x_sqz = x_sqz.permute(0, 3, 1, 2).contiguous().view(b, c * num_sqz, t // num_sqz)

    if x_mask is not None:
        x_mask = x_mask[:, :, num_sqz - 1 :: num_sqz]
    else:
        x_mask = torch.ones(b, 1, t // num_sqz).to(device=x.device, dtype=x.dtype)
    return x_sqz * x_mask, x_mask


def unsqueeze(x, x_mask=None, num_sqz=2):
    """GlowTTS unsqueeze operation (revert the squeeze)

    Note:
        each 's' is a n-dimensional vector.
        ``[[s1, s3, s5], [s2, s4, s6]] --> [[s1, s3, s5, s2, s4, s6]]``
    """
    b, c, t = x.size()

    x_unsqz = x.view(b, num_sqz, c // num_sqz, t)
    x_unsqz = x_unsqz.permute(0, 2, 3, 1).contiguous().view(b, c // num_sqz, t * num_sqz)

    if x_mask is not None:
        x_mask = x_mask.unsqueeze(-1).repeat(1, 1, 1, num_sqz).view(b, 1, t * num_sqz)
    else:
        x_mask = torch.ones(b, 1, t * num_sqz).to(device=x.device, dtype=x.dtype)
    return x_unsqz * x_mask, x_mask


class Decoder(nn.Module):
    """Stack of Glow Decoder Modules.

    ::

        Squeeze -> ActNorm -> InvertibleConv1x1 -> AffineCoupling -> Unsqueeze

    Args:
        in_channels (int): channels of input tensor.
        hidden_channels (int): hidden decoder channels.
        kernel_size (int): Coupling block kernel size. (Wavenet filter kernel size.)
        dilation_rate (int): rate to increase dilation by each layer in a decoder block.
        num_flow_blocks (int): number of decoder blocks.
        num_coupling_layers (int): number coupling layers. (number of wavenet layers.)
        dropout_p (float): wavenet dropout rate.
        sigmoid_scale (bool): enable/disable sigmoid scaling in coupling layer.
    """

    def __init__(
        self,
        in_channels,
        hidden_channels,
        kernel_size,
        dilation_rate,
        num_flow_blocks,
        num_coupling_layers,
        dropout_p=0.0,
        num_splits=4,
        num_squeeze=2,
        sigmoid_scale=False,
        c_in_channels=0,
    ):
        super().__init__()

        self.in_channels = in_channels
        self.hidden_channels = hidden_channels
        self.kernel_size = kernel_size
        self.dilation_rate = dilation_rate
        self.num_flow_blocks = num_flow_blocks
        self.num_coupling_layers = num_coupling_layers
        self.dropout_p = dropout_p
        self.num_splits = num_splits
        self.num_squeeze = num_squeeze
        self.sigmoid_scale = sigmoid_scale
        self.c_in_channels = c_in_channels

        self.flows = nn.ModuleList()
        for _ in range(num_flow_blocks):
            self.flows.append(ActNorm(channels=in_channels * num_squeeze))
            self.flows.append(InvConvNear(channels=in_channels * num_squeeze, num_splits=num_splits))
            self.flows.append(
                CouplingBlock(
                    in_channels * num_squeeze,
                    hidden_channels,
                    kernel_size=kernel_size,
                    dilation_rate=dilation_rate,
                    num_layers=num_coupling_layers,
                    c_in_channels=c_in_channels,
                    dropout_p=dropout_p,
                    sigmoid_scale=sigmoid_scale,
                )
            )

    def forward(self, x, x_mask, g=None, reverse=False):
        """
        Shapes:
            - x:  :math:`[B, C, T]`
            - x_mask: :math:`[B, 1 ,T]`
            - g: :math:`[B, C]`
        """
        if not reverse:
            flows = self.flows
            logdet_tot = 0
        else:
            flows = reversed(self.flows)
            logdet_tot = None

        if self.num_squeeze > 1:
            x, x_mask = squeeze(x, x_mask, self.num_squeeze)
        for f in flows:
            if not reverse:
                x, logdet = f(x, x_mask, g=g, reverse=reverse)
                logdet_tot += logdet
            else:
                x, logdet = f(x, x_mask, g=g, reverse=reverse)
        if self.num_squeeze > 1:
            x, x_mask = unsqueeze(x, x_mask, self.num_squeeze)
        return x, logdet_tot

    def store_inverse(self):
        for f in self.flows:
            f.store_inverse()