# Source: https://github.com/SeanNaren/deepspeech.pytorch

import math

import torch
import torch.nn as nn
import torch.nn.functional as F
from torchaudio.functional import magphase

from data.audio.unsupervised_audio_dataset import load_audio
from models.deepspeech.decoder import GreedyDecoder
from trainer.networks import register_model


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)
        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=False
        )

    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,
                 hidden_size: int = 1024,
                 hidden_layers: int = 5,
                 lookahead_context: int = 20,
                 bidirectional: bool = True,
                 sample_rate: int = 16000,
                 window_size: int = .02,
                 window_stride: int = .01
                 ):
        super().__init__()
        self.bidirectional = bidirectional
        self.sample_rate = sample_rate
        self.window_size = window_size
        self.window_stride = window_stride

        self.labels = [ "_", "'", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q",
                        "R", "S", "T", "U", "V", "W", "X", "Y", "Z", " " ]
        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

        self.rnns = nn.Sequential(
            BatchRNN(
                input_size=rnn_input_size,
                hidden_size=hidden_size,
                rnn_type=nn.LSTM,
                bidirectional=self.bidirectional,
                batch_norm=False
            ),
            *(
                BatchRNN(
                    input_size=hidden_size,
                    hidden_size=hidden_size,
                    rnn_type=nn.LSTM,
                    bidirectional=self.bidirectional
                ) for x in range(hidden_layers - 1)
            )
        )

        self.lookahead = nn.Sequential(
            # consider adding batch norm?
            Lookahead(hidden_size, context=lookahead_context),
            nn.Hardtanh(0, 20, inplace=True)
        ) if not self.bidirectional else None

        fully_connected = nn.Sequential(
            nn.BatchNorm1d(hidden_size),
            nn.Linear(hidden_size, num_classes, bias=False)
        )
        self.fc = nn.Sequential(
            SequenceWise(fully_connected),
        )
        self.inference_softmax = InferenceBatchSoftmax()
        self.evaluation_decoder = GreedyDecoder(self.labels)  # Decoder used for inference.

    def forward(self, wav, lengths=None):
        if lengths is None:
            lengths = torch.tensor([wav.shape[-1] for _ in range(wav.shape[0])], dtype=torch.int32, device=wav.device)

        x = self.audio_to_spectrogram(wav)

        lengths = (lengths // math.ceil(wav.shape[-1] / x.shape[-1])).cpu().int()  # 160 is the spectrogram compression
        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)
        #x = self.inference_softmax(x)  <-- doesn't work?
        return x, output_lengths

    def infer(self, inputs, lengths=None):
        out, output_sizes = self(inputs, lengths)
        decoded_output, _ = self.evaluation_decoder.decode(out, output_sizes)
        return decoded_output

    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) // m.stride[1] + 1)
        return seq_len.int()

    def audio_to_spectrogram(self, y):
        if len(y.shape) == 3:
            assert y.shape[1] == 1
            y = y.squeeze(1)
        n_fft = int(self.sample_rate * self.window_size)
        win_length = n_fft
        hop_length = int(self.sample_rate * self.window_stride)
        # STFT
        D = torch.stft(y, n_fft=n_fft, hop_length=hop_length,
                         win_length=win_length, window=torch.hamming_window(win_length, device=y.device))
        spect, phase = magphase(D)
        # S = log(S+1)
        spect = torch.log1p(spect)

        return spect.unsqueeze(1)  # Deepspeech operates in a 2D spectrogram regime.


@register_model
def register_deepspeech(opt_net, opt):
    return DeepSpeech(**opt_net['kwargs'])


# Test for ~4 second audio clip at 22050Hz
if __name__ == '__main__':
    clip = load_audio('D:\\data\\audio\\libritts\\test-clean\\1089\\134686\\1089_134686_000008_000000.wav', 16000).cuda()
    model = DeepSpeech().cuda()
    model.eval()
    sd = torch.load('\\\\192.168.5.3\\rtx3080_drv\\deepspeech.pytorch\\checkpoint_sd.pth')
    with torch.no_grad():
        model.load_state_dict(sd)
        print(model(clip)[0].shape)
        print(model.infer(clip))