import logging
import six

import numpy as np
import torch
import torch.nn.functional as F
from torch.nn.utils.rnn import pack_padded_sequence
from torch.nn.utils.rnn import pad_packed_sequence

from espnet.nets.e2e_asr_common import get_vgg2l_odim
from espnet.nets.pytorch_backend.nets_utils import make_pad_mask
from espnet.nets.pytorch_backend.nets_utils import to_device


class RNNP(torch.nn.Module):
    """RNN with projection layer module

    :param int idim: dimension of inputs
    :param int elayers: number of encoder layers
    :param int cdim: number of rnn units (resulted in cdim * 2 if bidirectional)
    :param int hdim: number of projection units
    :param np.ndarray subsample: list of subsampling numbers
    :param float dropout: dropout rate
    :param str typ: The RNN type
    """

    def __init__(self, idim, elayers, cdim, hdim, subsample, dropout, typ="blstm"):
        super(RNNP, self).__init__()
        bidir = typ[0] == "b"
        for i in six.moves.range(elayers):
            if i == 0:
                inputdim = idim
            else:
                inputdim = hdim

            RNN = torch.nn.LSTM if "lstm" in typ else torch.nn.GRU
            rnn = RNN(
                inputdim, cdim, num_layers=1, bidirectional=bidir, batch_first=True
            )

            setattr(self, "%s%d" % ("birnn" if bidir else "rnn", i), rnn)

            # bottleneck layer to merge
            if bidir:
                setattr(self, "bt%d" % i, torch.nn.Linear(2 * cdim, hdim))
            else:
                setattr(self, "bt%d" % i, torch.nn.Linear(cdim, hdim))

        self.elayers = elayers
        self.cdim = cdim
        self.subsample = subsample
        self.typ = typ
        self.bidir = bidir
        self.dropout = dropout

    def forward(self, xs_pad, ilens, prev_state=None):
        """RNNP forward

        :param torch.Tensor xs_pad: batch of padded input sequences (B, Tmax, idim)
        :param torch.Tensor ilens: batch of lengths of input sequences (B)
        :param torch.Tensor prev_state: batch of previous RNN states
        :return: batch of hidden state sequences (B, Tmax, hdim)
        :rtype: torch.Tensor
        """
        logging.debug(self.__class__.__name__ + " input lengths: " + str(ilens))
        elayer_states = []
        for layer in six.moves.range(self.elayers):
            if not isinstance(ilens, torch.Tensor):
                ilens = torch.tensor(ilens)
            xs_pack = pack_padded_sequence(xs_pad, ilens.cpu(), batch_first=True)
            rnn = getattr(self, ("birnn" if self.bidir else "rnn") + str(layer))
            rnn.flatten_parameters()
            if prev_state is not None and rnn.bidirectional:
                prev_state = reset_backward_rnn_state(prev_state)
            ys, states = rnn(
                xs_pack, hx=None if prev_state is None else prev_state[layer]
            )
            elayer_states.append(states)
            # ys: utt list of frame x cdim x 2 (2: means bidirectional)
            ys_pad, ilens = pad_packed_sequence(ys, batch_first=True)
            sub = self.subsample[layer + 1]
            if sub > 1:
                ys_pad = ys_pad[:, ::sub]
                ilens = torch.tensor([int(i + 1) // sub for i in ilens])
            # (sum _utt frame_utt) x dim
            projection_layer = getattr(self, "bt%d" % layer)
            projected = projection_layer(ys_pad.contiguous().view(-1, ys_pad.size(2)))
            xs_pad = projected.view(ys_pad.size(0), ys_pad.size(1), -1)
            if layer < self.elayers - 1:
                xs_pad = torch.tanh(F.dropout(xs_pad, p=self.dropout))

        return xs_pad, ilens, elayer_states  # x: utt list of frame x dim


class RNN(torch.nn.Module):
    """RNN module

    :param int idim: dimension of inputs
    :param int elayers: number of encoder layers
    :param int cdim: number of rnn units (resulted in cdim * 2 if bidirectional)
    :param int hdim: number of final projection units
    :param float dropout: dropout rate
    :param str typ: The RNN type
    """

    def __init__(self, idim, elayers, cdim, hdim, dropout, typ="blstm"):
        super(RNN, self).__init__()
        bidir = typ[0] == "b"
        self.nbrnn = (
            torch.nn.LSTM(
                idim,
                cdim,
                elayers,
                batch_first=True,
                dropout=dropout,
                bidirectional=bidir,
            )
            if "lstm" in typ
            else torch.nn.GRU(
                idim,
                cdim,
                elayers,
                batch_first=True,
                dropout=dropout,
                bidirectional=bidir,
            )
        )
        if bidir:
            self.l_last = torch.nn.Linear(cdim * 2, hdim)
        else:
            self.l_last = torch.nn.Linear(cdim, hdim)
        self.typ = typ

    def forward(self, xs_pad, ilens, prev_state=None):
        """RNN forward

        :param torch.Tensor xs_pad: batch of padded input sequences (B, Tmax, D)
        :param torch.Tensor ilens: batch of lengths of input sequences (B)
        :param torch.Tensor prev_state: batch of previous RNN states
        :return: batch of hidden state sequences (B, Tmax, eprojs)
        :rtype: torch.Tensor
        """
        logging.debug(self.__class__.__name__ + " input lengths: " + str(ilens))
        if not isinstance(ilens, torch.Tensor):
            ilens = torch.tensor(ilens)
        xs_pack = pack_padded_sequence(xs_pad, ilens.cpu(), batch_first=True)
        self.nbrnn.flatten_parameters()
        if prev_state is not None and self.nbrnn.bidirectional:
            # We assume that when previous state is passed,
            # it means that we're streaming the input
            # and therefore cannot propagate backward BRNN state
            # (otherwise it goes in the wrong direction)
            prev_state = reset_backward_rnn_state(prev_state)
        ys, states = self.nbrnn(xs_pack, hx=prev_state)
        # ys: utt list of frame x cdim x 2 (2: means bidirectional)
        ys_pad, ilens = pad_packed_sequence(ys, batch_first=True)
        # (sum _utt frame_utt) x dim
        projected = torch.tanh(
            self.l_last(ys_pad.contiguous().view(-1, ys_pad.size(2)))
        )
        xs_pad = projected.view(ys_pad.size(0), ys_pad.size(1), -1)
        return xs_pad, ilens, states  # x: utt list of frame x dim


def reset_backward_rnn_state(states):
    """Sets backward BRNN states to zeroes

    Useful in processing of sliding windows over the inputs
    """
    if isinstance(states, (list, tuple)):
        for state in states:
            state[1::2] = 0.0
    else:
        states[1::2] = 0.0
    return states


class VGG2L(torch.nn.Module):
    """VGG-like module

    :param int in_channel: number of input channels
    """

    def __init__(self, in_channel=1):
        super(VGG2L, self).__init__()
        # CNN layer (VGG motivated)
        self.conv1_1 = torch.nn.Conv2d(in_channel, 64, 3, stride=1, padding=1)
        self.conv1_2 = torch.nn.Conv2d(64, 64, 3, stride=1, padding=1)
        self.conv2_1 = torch.nn.Conv2d(64, 128, 3, stride=1, padding=1)
        self.conv2_2 = torch.nn.Conv2d(128, 128, 3, stride=1, padding=1)

        self.in_channel = in_channel

    def forward(self, xs_pad, ilens, **kwargs):
        """VGG2L forward

        :param torch.Tensor xs_pad: batch of padded input sequences (B, Tmax, D)
        :param torch.Tensor ilens: batch of lengths of input sequences (B)
        :return: batch of padded hidden state sequences (B, Tmax // 4, 128 * D // 4)
        :rtype: torch.Tensor
        """
        logging.debug(self.__class__.__name__ + " input lengths: " + str(ilens))

        # x: utt x frame x dim
        # xs_pad = F.pad_sequence(xs_pad)

        # x: utt x 1 (input channel num) x frame x dim
        xs_pad = xs_pad.view(
            xs_pad.size(0),
            xs_pad.size(1),
            self.in_channel,
            xs_pad.size(2) // self.in_channel,
        ).transpose(1, 2)

        # NOTE: max_pool1d ?
        xs_pad = F.relu(self.conv1_1(xs_pad))
        xs_pad = F.relu(self.conv1_2(xs_pad))
        xs_pad = F.max_pool2d(xs_pad, 2, stride=2, ceil_mode=True)

        xs_pad = F.relu(self.conv2_1(xs_pad))
        xs_pad = F.relu(self.conv2_2(xs_pad))
        xs_pad = F.max_pool2d(xs_pad, 2, stride=2, ceil_mode=True)
        if torch.is_tensor(ilens):
            ilens = ilens.cpu().numpy()
        else:
            ilens = np.array(ilens, dtype=np.float32)
        ilens = np.array(np.ceil(ilens / 2), dtype=np.int64)
        ilens = np.array(
            np.ceil(np.array(ilens, dtype=np.float32) / 2), dtype=np.int64
        ).tolist()

        # x: utt_list of frame (remove zeropaded frames) x (input channel num x dim)
        xs_pad = xs_pad.transpose(1, 2)
        xs_pad = xs_pad.contiguous().view(
            xs_pad.size(0), xs_pad.size(1), xs_pad.size(2) * xs_pad.size(3)
        )
        return xs_pad, ilens, None  # no state in this layer


class Encoder(torch.nn.Module):
    """Encoder module

    :param str etype: type of encoder network
    :param int idim: number of dimensions of encoder network
    :param int elayers: number of layers of encoder network
    :param int eunits: number of lstm units of encoder network
    :param int eprojs: number of projection units of encoder network
    :param np.ndarray subsample: list of subsampling numbers
    :param float dropout: dropout rate
    :param int in_channel: number of input channels
    """

    def __init__(
        self, etype, idim, elayers, eunits, eprojs, subsample, dropout, in_channel=1
    ):
        super(Encoder, self).__init__()
        typ = etype.lstrip("vgg").rstrip("p")
        if typ not in ["lstm", "gru", "blstm", "bgru"]:
            logging.error("Error: need to specify an appropriate encoder architecture")

        if etype.startswith("vgg"):
            if etype[-1] == "p":
                self.enc = torch.nn.ModuleList(
                    [
                        VGG2L(in_channel),
                        RNNP(
                            get_vgg2l_odim(idim, in_channel=in_channel),
                            elayers,
                            eunits,
                            eprojs,
                            subsample,
                            dropout,
                            typ=typ,
                        ),
                    ]
                )
                logging.info("Use CNN-VGG + " + typ.upper() + "P for encoder")
            else:
                self.enc = torch.nn.ModuleList(
                    [
                        VGG2L(in_channel),
                        RNN(
                            get_vgg2l_odim(idim, in_channel=in_channel),
                            elayers,
                            eunits,
                            eprojs,
                            dropout,
                            typ=typ,
                        ),
                    ]
                )
                logging.info("Use CNN-VGG + " + typ.upper() + " for encoder")
        else:
            if etype[-1] == "p":
                self.enc = torch.nn.ModuleList(
                    [RNNP(idim, elayers, eunits, eprojs, subsample, dropout, typ=typ)]
                )
                logging.info(typ.upper() + " with every-layer projection for encoder")
            else:
                self.enc = torch.nn.ModuleList(
                    [RNN(idim, elayers, eunits, eprojs, dropout, typ=typ)]
                )
                logging.info(typ.upper() + " without projection for encoder")

    def forward(self, xs_pad, ilens, prev_states=None):
        """Encoder forward

        :param torch.Tensor xs_pad: batch of padded input sequences (B, Tmax, D)
        :param torch.Tensor ilens: batch of lengths of input sequences (B)
        :param torch.Tensor prev_state: batch of previous encoder hidden states (?, ...)
        :return: batch of hidden state sequences (B, Tmax, eprojs)
        :rtype: torch.Tensor
        """
        if prev_states is None:
            prev_states = [None] * len(self.enc)
        assert len(prev_states) == len(self.enc)

        current_states = []
        for module, prev_state in zip(self.enc, prev_states):
            xs_pad, ilens, states = module(xs_pad, ilens, prev_state=prev_state)
            current_states.append(states)

        # make mask to remove bias value in padded part
        mask = to_device(xs_pad, make_pad_mask(ilens).unsqueeze(-1))

        return xs_pad.masked_fill(mask, 0.0), ilens, current_states


def encoder_for(args, idim, subsample):
    """Instantiates an encoder module given the program arguments

    :param Namespace args: The arguments
    :param int or List of integer idim: dimension of input, e.g. 83, or
                                        List of dimensions of inputs, e.g. [83,83]
    :param List or List of List subsample: subsample factors, e.g. [1,2,2,1,1], or
                                        List of subsample factors of each encoder.
                                         e.g. [[1,2,2,1,1], [1,2,2,1,1]]
    :rtype torch.nn.Module
    :return: The encoder module
    """
    num_encs = getattr(args, "num_encs", 1)  # use getattr to keep compatibility
    if num_encs == 1:
        # compatible with single encoder asr mode
        return Encoder(
            args.etype,
            idim,
            args.elayers,
            args.eunits,
            args.eprojs,
            subsample,
            args.dropout_rate,
        )
    elif num_encs >= 1:
        enc_list = torch.nn.ModuleList()
        for idx in range(num_encs):
            enc = Encoder(
                args.etype[idx],
                idim[idx],
                args.elayers[idx],
                args.eunits[idx],
                args.eprojs,
                subsample[idx],
                args.dropout_rate[idx],
            )
            enc_list.append(enc)
        return enc_list
    else:
        raise ValueError(
            "Number of encoders needs to be more than one. {}".format(num_encs)
        )
