# Taken from https://github.com/pytorch/audio/blob/master/torchaudio/models/wav2letter.py
# So that we don't need torchaudio to be installed

import torch
from torch import Tensor
from torch import nn
import torch.nn.functional as F

import math
from collections import OrderedDict
from typing import Tuple, Optional

__all__ = ["Wav2Letter"]


class Wav2Letter(nn.Module):
    r"""Wav2Letter model architecture from the `"Wav2Letter: an End-to-End ConvNet-based Speech Recognition System"
     <https://arxiv.org/abs/1609.03193>`_ paper.
     :math:`\text{padding} = \frac{\text{ceil}(\text{kernel} - \text{stride})}{2}`
    Args:
        num_classes (int, optional): Number of classes to be classified. (Default: ``40``)
        input_type (str, optional): Wav2Letter can use as input: ``waveform``, ``power_spectrum``
         or ``mfcc`` (Default: ``waveform``).
        num_features (int, optional): Number of input features that the network will receive (Default: ``1``).
    """

    def __init__(self, num_classes: int = 40,
                 input_type: str = "waveform",
                 num_features: int = 1) -> None:
        super(Wav2Letter, self).__init__()

        acoustic_num_features = 250 if input_type == "waveform" else num_features
        acoustic_model = nn.Sequential(
            nn.Conv1d(in_channels=acoustic_num_features, out_channels=250, kernel_size=48, stride=2, padding=23),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=250, kernel_size=7, stride=1, padding=3),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=250, out_channels=2000, kernel_size=32, stride=1, padding=16),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=2000, out_channels=2000, kernel_size=1, stride=1, padding=0),
            nn.ReLU(inplace=True),
            nn.Conv1d(in_channels=2000, out_channels=num_classes, kernel_size=1, stride=1, padding=0),
            nn.ReLU(inplace=True)
        )

        if input_type == "waveform":
            waveform_model = nn.Sequential(
                nn.Conv1d(in_channels=num_features, out_channels=250, kernel_size=250, stride=160, padding=45),
                nn.ReLU(inplace=True)
            )
            self.acoustic_model = nn.Sequential(waveform_model, acoustic_model)

        if input_type in ["power_spectrum", "mfcc"]:
            self.acoustic_model = acoustic_model

    def forward(self, x: Tensor) -> Tensor:
        r"""
        Args:
            x (Tensor): Tensor of dimension (batch_size, num_features, input_length).
        Returns:
            Tensor: Predictor tensor of dimension (batch_size, number_of_classes, input_length).
        """

        x = self.acoustic_model(x)
        x = nn.functional.log_softmax(x, dim=1)
        return x

# Taken from  https://github.com/SeanNaren/deepspeech.pytorch with modifications
class SequenceWise(nn.Module):
    def __init__(self, module):
        """
        Collapses input of dim T*N*H to (T*N)*H, and applies to a module.
        Allows handling of variable sequence lengths and minibatch sizes.
        :param module: Module to apply input to.
        """
        super(SequenceWise, self).__init__()
        self.module = module

    def forward(self, x):
        t, n = x.size(0), x.size(1)
        x = x.view(t * n, -1)
        x = self.module(x)
        x = x.view(t, n, -1)
        return x

    def __repr__(self):
        tmpstr = self.__class__.__name__ + ' (\n'
        tmpstr += self.module.__repr__()
        tmpstr += ')'
        return tmpstr


class MaskConv(nn.Module):
    def __init__(self, seq_module):
        """
        Adds padding to the output of the module based on the given lengths. This is to ensure that the
        results of the model do not change when batch sizes change during inference.
        Input needs to be in the shape of (BxCxDxT)
        :param seq_module: The sequential module containing the conv stack.
        """
        super(MaskConv, self).__init__()
        self.seq_module = seq_module

    def forward(self, x, lengths):
        """
        :param x: The input of size BxCxDxT
        :param lengths: The actual length of each sequence in the batch
        :return: Masked output from the module
        """
        for module in self.seq_module:
            x = module(x)
            mask = torch.BoolTensor(x.size()).fill_(0)
            if x.is_cuda:
                mask = mask.cuda()
            for i, length in enumerate(lengths):
                length = length.item()
                if (mask[i].size(2) - length) > 0:
                    mask[i].narrow(2, length, mask[i].size(2) - length).fill_(1)
            x = x.masked_fill(mask, 0)
        return x, lengths


class InferenceBatchSoftmax(nn.Module):
    def forward(self, input_):
        if not self.training:
            return F.softmax(input_, dim=-1)
        else:
            return input_


class BatchRNN(nn.Module):
    def __init__(self, input_size, hidden_size, rnn_type=nn.LSTM, bidirectional=False, batch_norm=True):
        super(BatchRNN, self).__init__()
        self.input_size = input_size
        self.hidden_size = hidden_size
        self.bidirectional = bidirectional
        self.batch_norm = SequenceWise(nn.BatchNorm1d(input_size)) if batch_norm else None
        self.rnn = rnn_type(input_size=input_size, hidden_size=hidden_size,
                            bidirectional=bidirectional, bias=True)
        self.num_directions = 2 if bidirectional else 1

    def flatten_parameters(self):
        self.rnn.flatten_parameters()

    def forward(self, x, output_lengths):
        if self.batch_norm is not None:
            x = self.batch_norm(x)
        x = nn.utils.rnn.pack_padded_sequence(x, output_lengths, enforce_sorted=False)
        x, h = self.rnn(x)
        x, _ = nn.utils.rnn.pad_packed_sequence(x)
        if self.bidirectional:
            x = x.view(x.size(0), x.size(1), 2, -1).sum(2).view(x.size(0), x.size(1), -1)  # (TxNxH*2) -> (TxNxH) by sum
        return x


class Lookahead(nn.Module):
    # Wang et al 2016 - Lookahead Convolution Layer for Unidirectional Recurrent Neural Networks
    # input shape - sequence, batch, feature - TxNxH
    # output shape - same as input
    def __init__(self, n_features, context):
        super(Lookahead, self).__init__()
        assert context > 0
        self.context = context
        self.n_features = n_features
        self.pad = (0, self.context - 1)
        self.conv = nn.Conv1d(self.n_features, self.n_features, kernel_size=self.context, stride=1,
                              groups=self.n_features, padding=0, bias=None)

    def forward(self, x):
        x = x.transpose(0, 1).transpose(1, 2)
        x = F.pad(x, pad=self.pad, value=0)
        x = self.conv(x)
        x = x.transpose(1, 2).transpose(0, 1).contiguous()
        return x

    def __repr__(self):
        return self.__class__.__name__ + '(' \
            + 'n_features=' + str(self.n_features) \
            + ', context=' + str(self.context) + ')'

class DeepSpeech(nn.Module):
    def __init__(self, rnn_type, labels, rnn_hidden_size, nb_layers, audio_conf,
                 bidirectional, context=20):
        super(DeepSpeech, self).__init__()

        self.hidden_size = rnn_hidden_size
        self.hidden_layers = nb_layers
        self.rnn_type = rnn_type
        self.audio_conf = audio_conf
        self.labels = labels
        self.bidirectional = bidirectional

        sample_rate = self.audio_conf["sample_rate"]
        window_size = self.audio_conf["window_size"]
        num_classes = len(self.labels)

        self.conv = MaskConv(nn.Sequential(
            nn.Conv2d(1, 32, kernel_size=(41, 11), stride=(2, 2), padding=(20, 5)),
            nn.BatchNorm2d(32),
            nn.Hardtanh(0, 20, inplace=True),
            nn.Conv2d(32, 32, kernel_size=(21, 11), stride=(2, 1), padding=(10, 5)),
            nn.BatchNorm2d(32),
            nn.Hardtanh(0, 20, inplace=True)
        ))
        # Based on above convolutions and spectrogram size using conv formula (W - F + 2P)/ S+1
        rnn_input_size = int(math.floor((sample_rate * window_size) / 2) + 1)
        rnn_input_size = int(math.floor(rnn_input_size + 2 * 20 - 41) / 2 + 1)
        rnn_input_size = int(math.floor(rnn_input_size + 2 * 10 - 21) / 2 + 1)
        rnn_input_size *= 32

        rnns = []
        rnn = BatchRNN(input_size=rnn_input_size, hidden_size=rnn_hidden_size, rnn_type=rnn_type,
                       bidirectional=bidirectional, batch_norm=False)
        rnns.append(('0', rnn))
        for x in range(nb_layers - 1):
            rnn = BatchRNN(input_size=rnn_hidden_size, hidden_size=rnn_hidden_size, rnn_type=rnn_type,
                           bidirectional=bidirectional)
            rnns.append(('%d' % (x + 1), rnn))
        self.rnns = nn.Sequential(OrderedDict(rnns))
        self.lookahead = nn.Sequential(
            # consider adding batch norm?
            Lookahead(rnn_hidden_size, context=context),
            nn.Hardtanh(0, 20, inplace=True)
        ) if not bidirectional else None

        fully_connected = nn.Sequential(
            nn.BatchNorm1d(rnn_hidden_size),
            nn.Linear(rnn_hidden_size, num_classes, bias=False)
        )
        self.fc = nn.Sequential(
            SequenceWise(fully_connected),
        )
        self.inference_softmax = InferenceBatchSoftmax()

    def forward(self, x, lengths):
        lengths = lengths.cpu().int()
        output_lengths = self.get_seq_lens(lengths)
        x, _ = self.conv(x, output_lengths)

        sizes = x.size()
        x = x.view(sizes[0], sizes[1] * sizes[2], sizes[3])  # Collapse feature dimension
        x = x.transpose(1, 2).transpose(0, 1).contiguous()  # TxNxH

        for rnn in self.rnns:
            x = rnn(x, output_lengths)

        if not self.bidirectional:  # no need for lookahead layer in bidirectional
            x = self.lookahead(x)

        x = self.fc(x)
        x = x.transpose(0, 1)
        # identity in training mode, softmax in eval mode
        x = self.inference_softmax(x)
        return x, output_lengths

    def get_seq_lens(self, input_length):
        """
        Given a 1D Tensor or Variable containing integer sequence lengths, return a 1D tensor or variable
        containing the size sequences that will be output by the network.
        :param input_length: 1D Tensor
        :return: 1D Tensor scaled by model
        """
        seq_len = input_length
        for m in self.conv.modules():
            if type(m) == nn.modules.conv.Conv2d:
                seq_len = seq_len + 2 * m.padding[1] - m.dilation[1] * (m.kernel_size[1] - 1) - 1
                seq_len = seq_len.true_divide(m.stride[1]) + 1
        return seq_len.int()

# Taken from https://github.com/pytorch/examples/blob/master/word_language_model/model.py#L108-L152
class PositionalEncoding(nn.Module):
    r"""Inject some information about the relative or absolute position of the tokens
        in the sequence. The positional encodings have the same dimension as
        the embeddings, so that the two can be summed. Here, we use sine and cosine
        functions of different frequencies.
    .. math::
        \text{PosEncoder}(pos, 2i) = sin(pos/10000^(2i/d_model))
        \text{PosEncoder}(pos, 2i+1) = cos(pos/10000^(2i/d_model))
        \text{where pos is the word position and i is the embed idx)
    Args:
        d_model: the embed dim (required).
        dropout: the dropout value (default=0.1).
        max_len: the max. length of the incoming sequence (default=5000).
    Examples:
        >>> pos_encoder = PositionalEncoding(d_model)
    """

    def __init__(self, d_model, dropout=0.1, max_len=5000):
        super(PositionalEncoding, self).__init__()
        self.dropout = nn.Dropout(p=dropout)

        pe = torch.zeros(max_len, d_model)
        position = torch.arange(0, max_len, dtype=torch.float).unsqueeze(1)
        div_term = torch.exp(torch.arange(0, d_model, 2).float() * (-math.log(10000.0) / d_model))
        pe[:, 0::2] = torch.sin(position * div_term)
        pe[:, 1::2] = torch.cos(position * div_term)
        pe = pe.unsqueeze(0).transpose(0, 1)
        self.register_buffer('pe', pe)

    def forward(self, x):
        r"""Inputs of forward function
        Args:
            x: the sequence fed to the positional encoder model (required).
        Shape:
            x: [sequence length, batch size, embed dim]
            output: [sequence length, batch size, embed dim]
        Examples:
            >>> output = pos_encoder(x)
        """

        x = x + self.pe[:x.size(0), :]
        return self.dropout(x)

class TransformerModel(nn.Module):
    """Container module with an encoder, a recurrent or transformer module, and a decoder."""

    def __init__(self, ntoken, ninp, nhead, nhid, nlayers, dropout=0.5):
        super(TransformerModel, self).__init__()
        try:
            from torch.nn import TransformerEncoder, TransformerEncoderLayer
        except Exception:
            raise ImportError('TransformerEncoder module does not exist in PyTorch 1.1 or lower.')
        self.model_type = 'Transformer'
        self.src_mask = None
        self.pos_encoder = PositionalEncoding(ninp, dropout)
        encoder_layers = TransformerEncoderLayer(ninp, nhead, nhid, dropout)
        self.transformer_encoder = TransformerEncoder(encoder_layers, nlayers)
        self.encoder = nn.Embedding(ntoken, ninp)
        self.ninp = ninp
        self.decoder = nn.Linear(ninp, ntoken)

        self.init_weights()

    def _generate_square_subsequent_mask(self, sz):
        mask = (torch.triu(torch.ones(sz, sz)) == 1).transpose(0, 1)
        mask = mask.float().masked_fill(mask == 0, float('-inf')).masked_fill(mask == 1, float(0.0))
        return mask

    def init_weights(self):
        initrange = 0.1
        nn.init.uniform_(self.encoder.weight, -initrange, initrange)
        # Not sure how this works in the original code
        # nn.init.zeros_(self.decoder)
        nn.init.uniform_(self.decoder.weight, -initrange, initrange)

    def forward(self, src, has_mask=True):
        if has_mask:
            device = src.device
            # This will be created once during warmup
            if self.src_mask is None or self.src_mask.size(0) != len(src):
                mask = self._generate_square_subsequent_mask(len(src)).to(device)
                self.src_mask = mask
        else:
            self.src_mask = None

        src = self.encoder(src) * math.sqrt(self.ninp)
        src = self.pos_encoder(src)
        output = self.transformer_encoder(src, self.src_mask)
        output = self.decoder(output)
        return F.log_softmax(output, dim=-1)

# From https://github.com/pytorch/text/blob/master/torchtext/modules
class MultiheadAttentionContainer(torch.nn.Module):
    def __init__(self, nhead, in_proj_container, attention_layer, out_proj):
        r""" A multi-head attention container
        Args:
            nhead: the number of heads in the multiheadattention model
            in_proj_container: A container of multi-head in-projection linear layers (a.k.a nn.Linear).
            attention_layer: The attention layer.
            out_proj: The multi-head out-projection layer (a.k.a nn.Linear).
        Examples::
            >>> import torch
            >>> embed_dim, num_heads, bsz = 10, 5, 64
            >>> in_proj_container = InProjContainer(torch.nn.Linear(embed_dim, embed_dim),
                                                    torch.nn.Linear(embed_dim, embed_dim),
                                                    torch.nn.Linear(embed_dim, embed_dim))
            >>> MHA = MultiheadAttentionContainer(num_heads,
                                                  in_proj_container,
                                                  ScaledDotProduct(),
                                                  torch.nn.Linear(embed_dim, embed_dim))
            >>> query = torch.rand((21, bsz, embed_dim))
            >>> key = value = torch.rand((16, bsz, embed_dim))
            >>> attn_output, attn_weights = MHA(query, key, value)
            >>> print(attn_output.shape)
            >>> torch.Size([21, 64, 10])
        """
        super(MultiheadAttentionContainer, self).__init__()
        self.nhead = nhead
        self.in_proj_container = in_proj_container
        self.attention_layer = attention_layer
        self.out_proj = out_proj

    def forward(self, query: torch.Tensor, key: torch.Tensor, value: torch.Tensor,
                attn_mask: Optional[torch.Tensor] = None,
                bias_k: Optional[torch.Tensor] = None,
                bias_v: Optional[torch.Tensor] = None) -> Tuple[torch.Tensor, torch.Tensor]:
        r"""
        Args:
            query, key, value (Tensor): map a query and a set of key-value pairs to an output.
                See "Attention Is All You Need" for more details.
            attn_mask, bias_k and bias_v (Tensor, optional): keyword arguments passed to the attention layer.
                See the definitions in the attention.
        Shape:
            - Inputs:
            - query: :math:`(L, N, E)`
            - key: :math:`(S, N, E)`
            - value: :math:`(S, N, E)`
            - attn_mask, bias_k and bias_v: same with the shape of the corresponding args in attention layer.
            - Outputs:
            - attn_output: :math:`(L, N, E)`
            - attn_output_weights: :math:`(N * H, L, S)`
            where where L is the target length, S is the sequence length, H is the number of attention heads,
                N is the batch size, and E is the embedding dimension.
        """
        tgt_len, src_len, bsz, embed_dim = query.size(-3), key.size(-3), query.size(-2), query.size(-1)
        q, k, v = self.in_proj_container(query, key, value)
        assert q.size(-1) % self.nhead == 0, "query's embed_dim must be divisible by the number of heads"
        head_dim = q.size(-1) // self.nhead
        q = q.reshape(tgt_len, bsz * self.nhead, head_dim)

        assert k.size(-1) % self.nhead == 0, "key's embed_dim must be divisible by the number of heads"
        head_dim = k.size(-1) // self.nhead
        k = k.reshape(src_len, bsz * self.nhead, head_dim)

        assert v.size(-1) % self.nhead == 0, "value's embed_dim must be divisible by the number of heads"
        head_dim = v.size(-1) // self.nhead
        v = v.reshape(src_len, bsz * self.nhead, head_dim)

        attn_output, attn_output_weights = self.attention_layer(q, k, v, attn_mask=attn_mask,
                                                                bias_k=bias_k, bias_v=bias_v)
        attn_output = attn_output.reshape(tgt_len, bsz, embed_dim)
        attn_output = self.out_proj(attn_output)
        return attn_output, attn_output_weights


class ScaledDotProduct(torch.nn.Module):

    def __init__(self, dropout=0.0):
        r"""Processes a projected query and key-value pair to apply
        scaled dot product attention.
        Args:
            dropout (float): probability of dropping an attention weight.
        Examples::
            >>> SDP = torchtext.models.ScaledDotProduct(0.1)
            >>> q = torch.randn(256, 21, 3)
            >>> k = v = torch.randn(256, 21, 3)
            >>> attn_output, attn_weights = SDP(q, k, v)
            >>> print(attn_output.shape, attn_weights.shape)
            torch.Size([256, 21, 3]) torch.Size([256, 21, 21])
        """
        super(ScaledDotProduct, self).__init__()
        self.dropout = dropout

    def forward(self, query: torch.Tensor, key: torch.Tensor, value: torch.Tensor,
                attn_mask: Optional[torch.Tensor] = None,
                bias_k: Optional[torch.Tensor] = None,
                bias_v: Optional[torch.Tensor] = None) -> Tuple[torch.Tensor, torch.Tensor]:
        r"""Uses a scaled dot product with the projected key-value pair to update
        the projected query.
        Args:
            query (Tensor): Projected query
            key (Tensor): Projected key
            value (Tensor): Projected value
            attn_mask (BoolTensor, optional): 3D mask that prevents attention to certain positions.
            bias_k and bias_v: (Tensor, optional): one more key and value sequence to be added at
                sequence dim (dim=-3). Those are used for incremental decoding. Users should provide
                non-None to both arguments in order to activate them.
        Shape:
            - query: :math:`(L, N * H, E / H)`
            - key: :math:`(S, N * H, E / H)`
            - value: :math:`(S, N * H, E / H)`
            - attn_mask: :math:`(N * H, L, S)`, positions with ``True`` are not allowed to attend
                while ``False`` values will be unchanged.
            - bias_k and bias_v:bias: :math:`(1, N * H, E / H)`
            - Output: :math:`(L, N * H, E / H)`, :math:`(N * H, L, S)`
            where L is the target length, S is the source length, H is the number
            of attention heads, N is the batch size, and E is the embedding dimension.
        """
        if bias_k is not None and bias_v is not None:
            assert key.size(-1) == bias_k.size(-1) and key.size(-2) == bias_k.size(-2) and bias_k.size(-3) == 1, \
                "Shape of bias_k is not supported"
            assert value.size(-1) == bias_v.size(-1) and value.size(-2) == bias_v.size(-2) and bias_v.size(-3) == 1, \
                "Shape of bias_v is not supported"
            key = torch.cat([key, bias_k])
            value = torch.cat([value, bias_v])
            if attn_mask is not None:
                _attn_mask = attn_mask
                attn_mask = torch.nn.functional.pad(_attn_mask, [0, 1])

        tgt_len, head_dim = query.size(-3), query.size(-1)
        assert query.size(-1) == key.size(-1) == value.size(-1), "The feature dim of query, key, value must be equal."
        assert key.size() == value.size(), "Shape of key, value must match"
        src_len = key.size(-3)
        batch_heads = max(query.size(-2), key.size(-2))

        # Scale query
        query, key, value = query.transpose(-2, -3), key.transpose(-2, -3), value.transpose(-2, -3)
        query = query * (float(head_dim) ** -0.5)
        if attn_mask is not None:
            if attn_mask.dim() != 3:
                raise RuntimeError('attn_mask must be a 3D tensor.')
            if (attn_mask.size(-1) != src_len) or (attn_mask.size(-2) != tgt_len) or \
               (attn_mask.size(-3) != 1 and attn_mask.size(-3) != batch_heads):
                raise RuntimeError('The size of the attn_mask is not correct.')
            if attn_mask.dtype != torch.bool:
                raise RuntimeError('Only bool tensor is supported for attn_mask')

        # Dot product of q, k
        attn_output_weights = torch.matmul(query, key.transpose(-2, -1))
        if attn_mask is not None:
            attn_output_weights.masked_fill_(attn_mask, -1e8,)
        attn_output_weights = torch.nn.functional.softmax(attn_output_weights, dim=-1)
        attn_output_weights = torch.nn.functional.dropout(attn_output_weights, p=self.dropout, training=self.training)
        attn_output = torch.matmul(attn_output_weights, value)
        return attn_output.transpose(-2, -3), attn_output_weights


class InProjContainer(torch.nn.Module):
    def __init__(self, query_proj, key_proj, value_proj):
        r"""A in-proj container to process inputs.
        Args:
            query_proj: a proj layer for query.
            key_proj: a proj layer for key.
            value_proj: a proj layer for value.
        """

        super(InProjContainer, self).__init__()
        self.query_proj = query_proj
        self.key_proj = key_proj
        self.value_proj = value_proj

    def forward(self,
                query: torch.Tensor,
                key: torch.Tensor,
                value: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
        r"""Projects the input sequences using in-proj layers.
        Args:
            query, key, value (Tensors): sequence to be projected
        Shape:
            - query, key, value: :math:`(S, N, E)`
            - Output: :math:`(S, N, E)`
            where S is the sequence length, N is the batch size, and E is the embedding dimension.
        """
        return self.query_proj(query), self.key_proj(key), self.value_proj(value)
