# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.

import argparse
import math
from collections.abc import Iterable

import torch
import torch.nn as nn
from examples.speech_recognition.data.data_utils import lengths_to_encoder_padding_mask
from fairseq import utils
from fairseq.models import (
    FairseqEncoder,
    FairseqEncoderDecoderModel,
    FairseqEncoderModel,
    FairseqIncrementalDecoder,
    register_model,
    register_model_architecture,
)
from fairseq.modules import (
    LinearizedConvolution,
    TransformerDecoderLayer,
    TransformerEncoderLayer,
    VGGBlock,
)


@register_model("asr_vggtransformer")
class VGGTransformerModel(FairseqEncoderDecoderModel):
    """
    Transformers with convolutional context for ASR
    https://arxiv.org/abs/1904.11660
    """

    def __init__(self, encoder, decoder):
        super().__init__(encoder, decoder)

    @staticmethod
    def add_args(parser):
        """Add model-specific arguments to the parser."""
        parser.add_argument(
            "--input-feat-per-channel",
            type=int,
            metavar="N",
            help="encoder input dimension per input channel",
        )
        parser.add_argument(
            "--vggblock-enc-config",
            type=str,
            metavar="EXPR",
            help="""
    an array of tuples each containing the configuration of one vggblock:
    [(out_channels,
      conv_kernel_size,
      pooling_kernel_size,
      num_conv_layers,
      use_layer_norm), ...])
            """,
        )
        parser.add_argument(
            "--transformer-enc-config",
            type=str,
            metavar="EXPR",
            help=""""
    a tuple containing the configuration of the encoder transformer layers
    configurations:
    [(input_dim,
      num_heads,
      ffn_dim,
      normalize_before,
      dropout,
      attention_dropout,
      relu_dropout), ...]')
            """,
        )
        parser.add_argument(
            "--enc-output-dim",
            type=int,
            metavar="N",
            help="""
    encoder output dimension, can be None. If specified, projecting the
    transformer output to the specified dimension""",
        )
        parser.add_argument(
            "--in-channels",
            type=int,
            metavar="N",
            help="number of encoder input channels",
        )
        parser.add_argument(
            "--tgt-embed-dim",
            type=int,
            metavar="N",
            help="embedding dimension of the decoder target tokens",
        )
        parser.add_argument(
            "--transformer-dec-config",
            type=str,
            metavar="EXPR",
            help="""
    a tuple containing the configuration of the decoder transformer layers
    configurations:
    [(input_dim,
      num_heads,
      ffn_dim,
      normalize_before,
      dropout,
      attention_dropout,
      relu_dropout), ...]
            """,
        )
        parser.add_argument(
            "--conv-dec-config",
            type=str,
            metavar="EXPR",
            help="""
    an array of tuples for the decoder 1-D convolution config
        [(out_channels, conv_kernel_size, use_layer_norm), ...]""",
        )

    @classmethod
    def build_encoder(cls, args, task):
        return VGGTransformerEncoder(
            input_feat_per_channel=args.input_feat_per_channel,
            vggblock_config=eval(args.vggblock_enc_config),
            transformer_config=eval(args.transformer_enc_config),
            encoder_output_dim=args.enc_output_dim,
            in_channels=args.in_channels,
        )

    @classmethod
    def build_decoder(cls, args, task):
        return TransformerDecoder(
            dictionary=task.target_dictionary,
            embed_dim=args.tgt_embed_dim,
            transformer_config=eval(args.transformer_dec_config),
            conv_config=eval(args.conv_dec_config),
            encoder_output_dim=args.enc_output_dim,
        )

    @classmethod
    def build_model(cls, args, task):
        """Build a new model instance."""
        # make sure that all args are properly defaulted
        # (in case there are any new ones)
        base_architecture(args)

        encoder = cls.build_encoder(args, task)
        decoder = cls.build_decoder(args, task)
        return cls(encoder, decoder)

    def get_normalized_probs(self, net_output, log_probs, sample=None):
        # net_output['encoder_out'] is a (B, T, D) tensor
        lprobs = super().get_normalized_probs(net_output, log_probs, sample)
        lprobs.batch_first = True
        return lprobs


DEFAULT_ENC_VGGBLOCK_CONFIG = ((32, 3, 2, 2, False),) * 2
DEFAULT_ENC_TRANSFORMER_CONFIG = ((256, 4, 1024, True, 0.2, 0.2, 0.2),) * 2
# 256: embedding dimension
# 4: number of heads
# 1024: FFN
# True: apply layerNorm before (dropout + resiaul) instead of after
# 0.2 (dropout): dropout after MultiheadAttention and second FC
# 0.2 (attention_dropout): dropout in MultiheadAttention
# 0.2 (relu_dropout): dropout after ReLu
DEFAULT_DEC_TRANSFORMER_CONFIG = ((256, 2, 1024, True, 0.2, 0.2, 0.2),) * 2
DEFAULT_DEC_CONV_CONFIG = ((256, 3, True),) * 2


# TODO: repace transformer encoder config from one liner
# to explicit args to get rid of this transformation
def prepare_transformer_encoder_params(
    input_dim,
    num_heads,
    ffn_dim,
    normalize_before,
    dropout,
    attention_dropout,
    relu_dropout,
):
    args = argparse.Namespace()
    args.encoder_embed_dim = input_dim
    args.encoder_attention_heads = num_heads
    args.attention_dropout = attention_dropout
    args.dropout = dropout
    args.activation_dropout = relu_dropout
    args.encoder_normalize_before = normalize_before
    args.encoder_ffn_embed_dim = ffn_dim
    return args


def prepare_transformer_decoder_params(
    input_dim,
    num_heads,
    ffn_dim,
    normalize_before,
    dropout,
    attention_dropout,
    relu_dropout,
):
    args = argparse.Namespace()
    args.decoder_embed_dim = input_dim
    args.decoder_attention_heads = num_heads
    args.attention_dropout = attention_dropout
    args.dropout = dropout
    args.activation_dropout = relu_dropout
    args.decoder_normalize_before = normalize_before
    args.decoder_ffn_embed_dim = ffn_dim
    return args


class VGGTransformerEncoder(FairseqEncoder):
    """VGG + Transformer encoder"""

    def __init__(
        self,
        input_feat_per_channel,
        vggblock_config=DEFAULT_ENC_VGGBLOCK_CONFIG,
        transformer_config=DEFAULT_ENC_TRANSFORMER_CONFIG,
        encoder_output_dim=512,
        in_channels=1,
        transformer_context=None,
        transformer_sampling=None,
    ):
        """constructor for VGGTransformerEncoder

        Args:
            - input_feat_per_channel: feature dim (not including stacked,
              just base feature)
            - in_channel: # input channels (e.g., if stack 8 feature vector
                together, this is 8)
            - vggblock_config: configuration of vggblock, see comments on
                DEFAULT_ENC_VGGBLOCK_CONFIG
            - transformer_config: configuration of transformer layer, see comments
                on DEFAULT_ENC_TRANSFORMER_CONFIG
            - encoder_output_dim: final transformer output embedding dimension
            - transformer_context: (left, right) if set, self-attention will be focused
              on (t-left, t+right)
            - transformer_sampling: an iterable of int, must match with
              len(transformer_config), transformer_sampling[i] indicates sampling
              factor for i-th transformer layer, after multihead att and feedfoward
              part
        """
        super().__init__(None)

        self.num_vggblocks = 0
        if vggblock_config is not None:
            if not isinstance(vggblock_config, Iterable):
                raise ValueError("vggblock_config is not iterable")
            self.num_vggblocks = len(vggblock_config)

        self.conv_layers = nn.ModuleList()
        self.in_channels = in_channels
        self.input_dim = input_feat_per_channel
        self.pooling_kernel_sizes = []

        if vggblock_config is not None:
            for _, config in enumerate(vggblock_config):
                (
                    out_channels,
                    conv_kernel_size,
                    pooling_kernel_size,
                    num_conv_layers,
                    layer_norm,
                ) = config
                self.conv_layers.append(
                    VGGBlock(
                        in_channels,
                        out_channels,
                        conv_kernel_size,
                        pooling_kernel_size,
                        num_conv_layers,
                        input_dim=input_feat_per_channel,
                        layer_norm=layer_norm,
                    )
                )
                self.pooling_kernel_sizes.append(pooling_kernel_size)
                in_channels = out_channels
                input_feat_per_channel = self.conv_layers[-1].output_dim

        transformer_input_dim = self.infer_conv_output_dim(
            self.in_channels, self.input_dim
        )
        # transformer_input_dim is the output dimension of VGG part

        self.validate_transformer_config(transformer_config)
        self.transformer_context = self.parse_transformer_context(transformer_context)
        self.transformer_sampling = self.parse_transformer_sampling(
            transformer_sampling, len(transformer_config)
        )

        self.transformer_layers = nn.ModuleList()

        if transformer_input_dim != transformer_config[0][0]:
            self.transformer_layers.append(
                Linear(transformer_input_dim, transformer_config[0][0])
            )
        self.transformer_layers.append(
            TransformerEncoderLayer(
                prepare_transformer_encoder_params(*transformer_config[0])
            )
        )

        for i in range(1, len(transformer_config)):
            if transformer_config[i - 1][0] != transformer_config[i][0]:
                self.transformer_layers.append(
                    Linear(transformer_config[i - 1][0], transformer_config[i][0])
                )
            self.transformer_layers.append(
                TransformerEncoderLayer(
                    prepare_transformer_encoder_params(*transformer_config[i])
                )
            )

        self.encoder_output_dim = encoder_output_dim
        self.transformer_layers.extend(
            [
                Linear(transformer_config[-1][0], encoder_output_dim),
                LayerNorm(encoder_output_dim),
            ]
        )

    def forward(self, src_tokens, src_lengths, **kwargs):
        """
        src_tokens: padded tensor (B, T, C * feat)
        src_lengths: tensor of original lengths of input utterances (B,)
        """
        bsz, max_seq_len, _ = src_tokens.size()
        x = src_tokens.view(bsz, max_seq_len, self.in_channels, self.input_dim)
        x = x.transpose(1, 2).contiguous()
        # (B, C, T, feat)

        for layer_idx in range(len(self.conv_layers)):
            x = self.conv_layers[layer_idx](x)

        bsz, _, output_seq_len, _ = x.size()

        # (B, C, T, feat) -> (B, T, C, feat) -> (T, B, C, feat) -> (T, B, C * feat)
        x = x.transpose(1, 2).transpose(0, 1)
        x = x.contiguous().view(output_seq_len, bsz, -1)

        input_lengths = src_lengths.clone()
        for s in self.pooling_kernel_sizes:
            input_lengths = (input_lengths.float() / s).ceil().long()

        encoder_padding_mask, _ = lengths_to_encoder_padding_mask(
            input_lengths, batch_first=True
        )
        if not encoder_padding_mask.any():
            encoder_padding_mask = None

        subsampling_factor = int(max_seq_len * 1.0 / output_seq_len + 0.5)
        attn_mask = self.lengths_to_attn_mask(input_lengths, subsampling_factor)

        transformer_layer_idx = 0

        for layer_idx in range(len(self.transformer_layers)):

            if isinstance(self.transformer_layers[layer_idx], TransformerEncoderLayer):
                x = self.transformer_layers[layer_idx](
                    x, encoder_padding_mask, attn_mask
                )

                if self.transformer_sampling[transformer_layer_idx] != 1:
                    sampling_factor = self.transformer_sampling[transformer_layer_idx]
                    x, encoder_padding_mask, attn_mask = self.slice(
                        x, encoder_padding_mask, attn_mask, sampling_factor
                    )

                transformer_layer_idx += 1

            else:
                x = self.transformer_layers[layer_idx](x)

        # encoder_padding_maks is a (T x B) tensor, its [t, b] elements indicate
        # whether encoder_output[t, b] is valid or not (valid=0, invalid=1)

        return {
            "encoder_out": x,  # (T, B, C)
            "encoder_padding_mask": encoder_padding_mask.t()
            if encoder_padding_mask is not None
            else None,
            # (B, T) --> (T, B)
        }

    def infer_conv_output_dim(self, in_channels, input_dim):
        sample_seq_len = 200
        sample_bsz = 10
        x = torch.randn(sample_bsz, in_channels, sample_seq_len, input_dim)
        for i, _ in enumerate(self.conv_layers):
            x = self.conv_layers[i](x)
        x = x.transpose(1, 2)
        mb, seq = x.size()[:2]
        return x.contiguous().view(mb, seq, -1).size(-1)

    def validate_transformer_config(self, transformer_config):
        for config in transformer_config:
            input_dim, num_heads = config[:2]
            if input_dim % num_heads != 0:
                msg = (
                    "ERROR in transformer config {}: ".format(config)
                    + "input dimension {} ".format(input_dim)
                    + "not dividable by number of heads {}".format(num_heads)
                )
                raise ValueError(msg)

    def parse_transformer_context(self, transformer_context):
        """
        transformer_context can be the following:
        -   None; indicates no context is used, i.e.,
            transformer can access full context
        -   a tuple/list of two int; indicates left and right context,
            any number <0 indicates infinite context
                * e.g., (5, 6) indicates that for query at x_t, transformer can
                access [t-5, t+6] (inclusive)
                * e.g., (-1, 6) indicates that for query at x_t, transformer can
                access [0, t+6] (inclusive)
        """
        if transformer_context is None:
            return None

        if not isinstance(transformer_context, Iterable):
            raise ValueError("transformer context must be Iterable if it is not None")

        if len(transformer_context) != 2:
            raise ValueError("transformer context must have length 2")

        left_context = transformer_context[0]
        if left_context < 0:
            left_context = None

        right_context = transformer_context[1]
        if right_context < 0:
            right_context = None

        if left_context is None and right_context is None:
            return None

        return (left_context, right_context)

    def parse_transformer_sampling(self, transformer_sampling, num_layers):
        """
        parsing transformer sampling configuration

        Args:
            - transformer_sampling, accepted input:
                * None, indicating no sampling
                * an Iterable with int (>0) as element
            - num_layers, expected number of transformer layers, must match with
              the length of transformer_sampling if it is not None

        Returns:
            - A tuple with length num_layers
        """
        if transformer_sampling is None:
            return (1,) * num_layers

        if not isinstance(transformer_sampling, Iterable):
            raise ValueError(
                "transformer_sampling must be an iterable if it is not None"
            )

        if len(transformer_sampling) != num_layers:
            raise ValueError(
                "transformer_sampling {} does not match with the number "
                "of layers {}".format(transformer_sampling, num_layers)
            )

        for layer, value in enumerate(transformer_sampling):
            if not isinstance(value, int):
                raise ValueError("Invalid value in transformer_sampling: ")
            if value < 1:
                raise ValueError(
                    "{} layer's subsampling is {}.".format(layer, value)
                    + " This is not allowed! "
                )
        return transformer_sampling

    def slice(self, embedding, padding_mask, attn_mask, sampling_factor):
        """
        embedding is a (T, B, D) tensor
        padding_mask is a (B, T) tensor or None
        attn_mask is a (T, T) tensor or None
        """
        embedding = embedding[::sampling_factor, :, :]
        if padding_mask is not None:
            padding_mask = padding_mask[:, ::sampling_factor]
        if attn_mask is not None:
            attn_mask = attn_mask[::sampling_factor, ::sampling_factor]

        return embedding, padding_mask, attn_mask

    def lengths_to_attn_mask(self, input_lengths, subsampling_factor=1):
        """
        create attention mask according to sequence lengths and transformer
        context

        Args:
            - input_lengths: (B, )-shape Int/Long tensor; input_lengths[b] is
              the length of b-th sequence
            - subsampling_factor: int
                * Note that the left_context and right_context is specified in
                  the input frame-level while input to transformer may already
                  go through subsampling (e.g., the use of striding in vggblock)
                  we use subsampling_factor to scale the left/right context

        Return:
            - a (T, T) binary tensor or None, where T is max(input_lengths)
                * if self.transformer_context is None, None
                * if left_context is None,
                    * attn_mask[t, t + right_context + 1:] = 1
                    * others = 0
                * if right_context is None,
                    * attn_mask[t, 0:t - left_context] = 1
                    * others = 0
                * elsif
                    * attn_mask[t, t - left_context: t + right_context + 1] = 0
                    * others = 1
        """
        if self.transformer_context is None:
            return None

        maxT = torch.max(input_lengths).item()
        attn_mask = torch.zeros(maxT, maxT)

        left_context = self.transformer_context[0]
        right_context = self.transformer_context[1]
        if left_context is not None:
            left_context = math.ceil(self.transformer_context[0] / subsampling_factor)
        if right_context is not None:
            right_context = math.ceil(self.transformer_context[1] / subsampling_factor)

        for t in range(maxT):
            if left_context is not None:
                st = 0
                en = max(st, t - left_context)
                attn_mask[t, st:en] = 1
            if right_context is not None:
                st = t + right_context + 1
                st = min(st, maxT - 1)
                attn_mask[t, st:] = 1

        return attn_mask.to(input_lengths.device)

    def reorder_encoder_out(self, encoder_out, new_order):
        encoder_out["encoder_out"] = encoder_out["encoder_out"].index_select(
            1, new_order
        )
        if encoder_out["encoder_padding_mask"] is not None:
            encoder_out["encoder_padding_mask"] = encoder_out[
                "encoder_padding_mask"
            ].index_select(1, new_order)
        return encoder_out


class TransformerDecoder(FairseqIncrementalDecoder):
    """
    Transformer decoder consisting of *args.decoder_layers* layers. Each layer
    is a :class:`TransformerDecoderLayer`.
    Args:
        args (argparse.Namespace): parsed command-line arguments
        dictionary (~fairseq.data.Dictionary): decoding dictionary
        embed_tokens (torch.nn.Embedding): output embedding
        no_encoder_attn (bool, optional): whether to attend to encoder outputs.
            Default: ``False``
        left_pad (bool, optional): whether the input is left-padded. Default:
            ``False``
    """

    def __init__(
        self,
        dictionary,
        embed_dim=512,
        transformer_config=DEFAULT_ENC_TRANSFORMER_CONFIG,
        conv_config=DEFAULT_DEC_CONV_CONFIG,
        encoder_output_dim=512,
    ):

        super().__init__(dictionary)
        vocab_size = len(dictionary)
        self.padding_idx = dictionary.pad()
        self.embed_tokens = Embedding(vocab_size, embed_dim, self.padding_idx)

        self.conv_layers = nn.ModuleList()
        for i in range(len(conv_config)):
            out_channels, kernel_size, layer_norm = conv_config[i]
            if i == 0:
                conv_layer = LinearizedConv1d(
                    embed_dim, out_channels, kernel_size, padding=kernel_size - 1
                )
            else:
                conv_layer = LinearizedConv1d(
                    conv_config[i - 1][0],
                    out_channels,
                    kernel_size,
                    padding=kernel_size - 1,
                )
            self.conv_layers.append(conv_layer)
            if layer_norm:
                self.conv_layers.append(nn.LayerNorm(out_channels))
            self.conv_layers.append(nn.ReLU())

        self.layers = nn.ModuleList()
        if conv_config[-1][0] != transformer_config[0][0]:
            self.layers.append(Linear(conv_config[-1][0], transformer_config[0][0]))
        self.layers.append(
            TransformerDecoderLayer(
                prepare_transformer_decoder_params(*transformer_config[0])
            )
        )

        for i in range(1, len(transformer_config)):
            if transformer_config[i - 1][0] != transformer_config[i][0]:
                self.layers.append(
                    Linear(transformer_config[i - 1][0], transformer_config[i][0])
                )
            self.layers.append(
                TransformerDecoderLayer(
                    prepare_transformer_decoder_params(*transformer_config[i])
                )
            )
        self.fc_out = Linear(transformer_config[-1][0], vocab_size)

    def forward(self, prev_output_tokens, encoder_out=None, incremental_state=None):
        """
        Args:
            prev_output_tokens (LongTensor): previous decoder outputs of shape
                `(batch, tgt_len)`, for input feeding/teacher forcing
            encoder_out (Tensor, optional): output from the encoder, used for
                encoder-side attention
            incremental_state (dict): dictionary used for storing state during
                :ref:`Incremental decoding`
        Returns:
            tuple:
                - the last decoder layer's output of shape `(batch, tgt_len,
                  vocab)`
                - the last decoder layer's attention weights of shape `(batch,
                  tgt_len, src_len)`
        """
        target_padding_mask = (
            (prev_output_tokens == self.padding_idx).to(prev_output_tokens.device)
            if incremental_state is None
            else None
        )

        if incremental_state is not None:
            prev_output_tokens = prev_output_tokens[:, -1:]

        # embed tokens
        x = self.embed_tokens(prev_output_tokens)

        # B x T x C -> T x B x C
        x = self._transpose_if_training(x, incremental_state)

        for layer in self.conv_layers:
            if isinstance(layer, LinearizedConvolution):
                x = layer(x, incremental_state)
            else:
                x = layer(x)

        # B x T x C -> T x B x C
        x = self._transpose_if_inference(x, incremental_state)

        # decoder layers
        for layer in self.layers:
            if isinstance(layer, TransformerDecoderLayer):
                x, *_ = layer(
                    x,
                    (encoder_out["encoder_out"] if encoder_out is not None else None),
                    (
                        encoder_out["encoder_padding_mask"].t()
                        if encoder_out["encoder_padding_mask"] is not None
                        else None
                    ),
                    incremental_state,
                    self_attn_mask=(
                        self.buffered_future_mask(x)
                        if incremental_state is None
                        else None
                    ),
                    self_attn_padding_mask=(
                        target_padding_mask if incremental_state is None else None
                    ),
                )
            else:
                x = layer(x)

        # T x B x C -> B x T x C
        x = x.transpose(0, 1)

        x = self.fc_out(x)

        return x, None

    def buffered_future_mask(self, tensor):
        dim = tensor.size(0)
        if (
            not hasattr(self, "_future_mask")
            or self._future_mask is None
            or self._future_mask.device != tensor.device
        ):
            self._future_mask = torch.triu(
                utils.fill_with_neg_inf(tensor.new(dim, dim)), 1
            )
        if self._future_mask.size(0) < dim:
            self._future_mask = torch.triu(
                utils.fill_with_neg_inf(self._future_mask.resize_(dim, dim)), 1
            )
        return self._future_mask[:dim, :dim]

    def _transpose_if_training(self, x, incremental_state):
        if incremental_state is None:
            x = x.transpose(0, 1)
        return x

    def _transpose_if_inference(self, x, incremental_state):
        if incremental_state:
            x = x.transpose(0, 1)
        return x


@register_model("asr_vggtransformer_encoder")
class VGGTransformerEncoderModel(FairseqEncoderModel):
    def __init__(self, encoder):
        super().__init__(encoder)

    @staticmethod
    def add_args(parser):
        """Add model-specific arguments to the parser."""
        parser.add_argument(
            "--input-feat-per-channel",
            type=int,
            metavar="N",
            help="encoder input dimension per input channel",
        )
        parser.add_argument(
            "--vggblock-enc-config",
            type=str,
            metavar="EXPR",
            help="""
    an array of tuples each containing the configuration of one vggblock
    [(out_channels, conv_kernel_size, pooling_kernel_size,num_conv_layers), ...]
    """,
        )
        parser.add_argument(
            "--transformer-enc-config",
            type=str,
            metavar="EXPR",
            help="""
    a tuple containing the configuration of the Transformer layers
    configurations:
    [(input_dim,
      num_heads,
      ffn_dim,
      normalize_before,
      dropout,
      attention_dropout,
      relu_dropout), ]""",
        )
        parser.add_argument(
            "--enc-output-dim",
            type=int,
            metavar="N",
            help="encoder output dimension, projecting the LSTM output",
        )
        parser.add_argument(
            "--in-channels",
            type=int,
            metavar="N",
            help="number of encoder input channels",
        )
        parser.add_argument(
            "--transformer-context",
            type=str,
            metavar="EXPR",
            help="""
    either None or a tuple of two ints, indicating left/right context a
    transformer can have access to""",
        )
        parser.add_argument(
            "--transformer-sampling",
            type=str,
            metavar="EXPR",
            help="""
    either None or a tuple of ints, indicating sampling factor in each layer""",
        )

    @classmethod
    def build_model(cls, args, task):
        """Build a new model instance."""
        base_architecture_enconly(args)
        encoder = VGGTransformerEncoderOnly(
            vocab_size=len(task.target_dictionary),
            input_feat_per_channel=args.input_feat_per_channel,
            vggblock_config=eval(args.vggblock_enc_config),
            transformer_config=eval(args.transformer_enc_config),
            encoder_output_dim=args.enc_output_dim,
            in_channels=args.in_channels,
            transformer_context=eval(args.transformer_context),
            transformer_sampling=eval(args.transformer_sampling),
        )
        return cls(encoder)

    def get_normalized_probs(self, net_output, log_probs, sample=None):
        # net_output['encoder_out'] is a (T, B, D) tensor
        lprobs = super().get_normalized_probs(net_output, log_probs, sample)
        # lprobs is a (T, B, D) tensor
        # we need to transoose to get (B, T, D) tensor
        lprobs = lprobs.transpose(0, 1).contiguous()
        lprobs.batch_first = True
        return lprobs


class VGGTransformerEncoderOnly(VGGTransformerEncoder):
    def __init__(
        self,
        vocab_size,
        input_feat_per_channel,
        vggblock_config=DEFAULT_ENC_VGGBLOCK_CONFIG,
        transformer_config=DEFAULT_ENC_TRANSFORMER_CONFIG,
        encoder_output_dim=512,
        in_channels=1,
        transformer_context=None,
        transformer_sampling=None,
    ):
        super().__init__(
            input_feat_per_channel=input_feat_per_channel,
            vggblock_config=vggblock_config,
            transformer_config=transformer_config,
            encoder_output_dim=encoder_output_dim,
            in_channels=in_channels,
            transformer_context=transformer_context,
            transformer_sampling=transformer_sampling,
        )
        self.fc_out = Linear(self.encoder_output_dim, vocab_size)

    def forward(self, src_tokens, src_lengths, **kwargs):
        """
        src_tokens: padded tensor (B, T, C * feat)
        src_lengths: tensor of original lengths of input utterances (B,)
        """

        enc_out = super().forward(src_tokens, src_lengths)
        x = self.fc_out(enc_out["encoder_out"])
        # x = F.log_softmax(x, dim=-1)
        # Note: no need this line, because model.get_normalized_prob will call
        # log_softmax
        return {
            "encoder_out": x,  # (T, B, C)
            "encoder_padding_mask": enc_out["encoder_padding_mask"],  # (T, B)
        }

    def max_positions(self):
        """Maximum input length supported by the encoder."""
        return (1e6, 1e6)  # an arbitrary large number


def Embedding(num_embeddings, embedding_dim, padding_idx):
    m = nn.Embedding(num_embeddings, embedding_dim, padding_idx=padding_idx)
    # nn.init.uniform_(m.weight, -0.1, 0.1)
    # nn.init.constant_(m.weight[padding_idx], 0)
    return m


def Linear(in_features, out_features, bias=True, dropout=0):
    """Linear layer (input: N x T x C)"""
    m = nn.Linear(in_features, out_features, bias=bias)
    # m.weight.data.uniform_(-0.1, 0.1)
    # if bias:
    #     m.bias.data.uniform_(-0.1, 0.1)
    return m


def LinearizedConv1d(in_channels, out_channels, kernel_size, dropout=0, **kwargs):
    """Weight-normalized Conv1d layer optimized for decoding"""
    m = LinearizedConvolution(in_channels, out_channels, kernel_size, **kwargs)
    std = math.sqrt((4 * (1.0 - dropout)) / (m.kernel_size[0] * in_channels))
    nn.init.normal_(m.weight, mean=0, std=std)
    nn.init.constant_(m.bias, 0)
    return nn.utils.weight_norm(m, dim=2)


def LayerNorm(embedding_dim):
    m = nn.LayerNorm(embedding_dim)
    return m


# seq2seq models
def base_architecture(args):
    args.input_feat_per_channel = getattr(args, "input_feat_per_channel", 40)
    args.vggblock_enc_config = getattr(
        args, "vggblock_enc_config", DEFAULT_ENC_VGGBLOCK_CONFIG
    )
    args.transformer_enc_config = getattr(
        args, "transformer_enc_config", DEFAULT_ENC_TRANSFORMER_CONFIG
    )
    args.enc_output_dim = getattr(args, "enc_output_dim", 512)
    args.in_channels = getattr(args, "in_channels", 1)
    args.tgt_embed_dim = getattr(args, "tgt_embed_dim", 128)
    args.transformer_dec_config = getattr(
        args, "transformer_dec_config", DEFAULT_ENC_TRANSFORMER_CONFIG
    )
    args.conv_dec_config = getattr(args, "conv_dec_config", DEFAULT_DEC_CONV_CONFIG)
    args.transformer_context = getattr(args, "transformer_context", "None")


@register_model_architecture("asr_vggtransformer", "vggtransformer_1")
def vggtransformer_1(args):
    args.input_feat_per_channel = getattr(args, "input_feat_per_channel", 80)
    args.vggblock_enc_config = getattr(
        args, "vggblock_enc_config", "[(64, 3, 2, 2, True), (128, 3, 2, 2, True)]"
    )
    args.transformer_enc_config = getattr(
        args,
        "transformer_enc_config",
        "((1024, 16, 4096, True, 0.15, 0.15, 0.15),) * 14",
    )
    args.enc_output_dim = getattr(args, "enc_output_dim", 1024)
    args.tgt_embed_dim = getattr(args, "tgt_embed_dim", 128)
    args.conv_dec_config = getattr(args, "conv_dec_config", "((256, 3, True),) * 4")
    args.transformer_dec_config = getattr(
        args,
        "transformer_dec_config",
        "((1024, 16, 4096, True, 0.15, 0.15, 0.15),) * 4",
    )


@register_model_architecture("asr_vggtransformer", "vggtransformer_2")
def vggtransformer_2(args):
    args.input_feat_per_channel = getattr(args, "input_feat_per_channel", 80)
    args.vggblock_enc_config = getattr(
        args, "vggblock_enc_config", "[(64, 3, 2, 2, True), (128, 3, 2, 2, True)]"
    )
    args.transformer_enc_config = getattr(
        args,
        "transformer_enc_config",
        "((1024, 16, 4096, True, 0.15, 0.15, 0.15),) * 16",
    )
    args.enc_output_dim = getattr(args, "enc_output_dim", 1024)
    args.tgt_embed_dim = getattr(args, "tgt_embed_dim", 512)
    args.conv_dec_config = getattr(args, "conv_dec_config", "((256, 3, True),) * 4")
    args.transformer_dec_config = getattr(
        args,
        "transformer_dec_config",
        "((1024, 16, 4096, True, 0.15, 0.15, 0.15),) * 6",
    )


@register_model_architecture("asr_vggtransformer", "vggtransformer_base")
def vggtransformer_base(args):
    args.input_feat_per_channel = getattr(args, "input_feat_per_channel", 80)
    args.vggblock_enc_config = getattr(
        args, "vggblock_enc_config", "[(64, 3, 2, 2, True), (128, 3, 2, 2, True)]"
    )
    args.transformer_enc_config = getattr(
        args, "transformer_enc_config", "((512, 8, 2048, True, 0.15, 0.15, 0.15),) * 12"
    )

    args.enc_output_dim = getattr(args, "enc_output_dim", 512)
    args.tgt_embed_dim = getattr(args, "tgt_embed_dim", 512)
    args.conv_dec_config = getattr(args, "conv_dec_config", "((256, 3, True),) * 4")
    args.transformer_dec_config = getattr(
        args, "transformer_dec_config", "((512, 8, 2048, True, 0.15, 0.15, 0.15),) * 6"
    )
    # Size estimations:
    # Encoder:
    #   - vggblock param: 64*1*3*3 + 64*64*3*3 + 128*64*3*3  + 128*128*3 = 258K
    #   Transformer:
    #   - input dimension adapter: 2560 x 512 -> 1.31M
    #   - transformer_layers (x12) --> 37.74M
    #       * MultiheadAttention: 512*512*3 (in_proj) + 512*512 (out_proj) = 1.048M
    #       * FFN weight: 512*2048*2 = 2.097M
    #   - output dimension adapter: 512 x 512 -> 0.26 M
    # Decoder:
    #   - LinearizedConv1d: 512 * 256 * 3 + 256 * 256 * 3 * 3
    #   - transformer_layer: (x6) --> 25.16M
    #        * MultiheadAttention (self-attention): 512*512*3 + 512*512 = 1.048M
    #        * MultiheadAttention (encoder-attention): 512*512*3 + 512*512 = 1.048M
    #        * FFN: 512*2048*2 = 2.097M
    # Final FC:
    #   - FC: 512*5000 = 256K (assuming vocab size 5K)
    # In total:
    #       ~65 M


# CTC models
def base_architecture_enconly(args):
    args.input_feat_per_channel = getattr(args, "input_feat_per_channel", 40)
    args.vggblock_enc_config = getattr(
        args, "vggblock_enc_config", "[(32, 3, 2, 2, True)] * 2"
    )
    args.transformer_enc_config = getattr(
        args, "transformer_enc_config", "((256, 4, 1024, True, 0.2, 0.2, 0.2),) * 2"
    )
    args.enc_output_dim = getattr(args, "enc_output_dim", 512)
    args.in_channels = getattr(args, "in_channels", 1)
    args.transformer_context = getattr(args, "transformer_context", "None")
    args.transformer_sampling = getattr(args, "transformer_sampling", "None")


@register_model_architecture("asr_vggtransformer_encoder", "vggtransformer_enc_1")
def vggtransformer_enc_1(args):
    # vggtransformer_1 is the same as vggtransformer_enc_big, except the number
    # of layers is increased to 16
    # keep it here for backward compatiablity purpose
    args.input_feat_per_channel = getattr(args, "input_feat_per_channel", 80)
    args.vggblock_enc_config = getattr(
        args, "vggblock_enc_config", "[(64, 3, 2, 2, True), (128, 3, 2, 2, True)]"
    )
    args.transformer_enc_config = getattr(
        args,
        "transformer_enc_config",
        "((1024, 16, 4096, True, 0.15, 0.15, 0.15),) * 16",
    )
    args.enc_output_dim = getattr(args, "enc_output_dim", 1024)
