# Copyright 2020 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ============================================================================

import torch
from common.layers import STFT


class Denoiser(torch.nn.Module):
    """ Removes model bias from audio produced with waveglow """

    def __init__(self, waveglow, filter_length=1024, n_overlap=4,
                 win_length=1024, mode='zeros'):
        super(Denoiser, self).__init__()
        device = waveglow.upsample.weight.device
        dtype = waveglow.upsample.weight.dtype
        self.stft = STFT(filter_length=filter_length,
                         hop_length=int(filter_length/n_overlap),
                         win_length=win_length).to(device)
        if mode == 'zeros':
            mel_input = torch.zeros((1, 80, 88), dtype=dtype, device=device)
        elif mode == 'normal':
            mel_input = torch.randn((1, 80, 88), dtype=dtype, device=device)
        else:
            raise Exception("Mode {} if not supported".format(mode))

        with torch.no_grad():
            bias_audio = waveglow.infer(mel_input, sigma=0.0).float()
            bias_spec, _ = self.stft.transform(bias_audio)

        self.register_buffer('bias_spec', bias_spec[:, :, 0][:, :, None])

    def forward(self, audio, strength=0.1):
        audio_spec, audio_angles = self.stft.transform(audio)
        audio_spec_denoised = audio_spec - self.bias_spec * strength
        audio_spec_denoised = torch.clamp(audio_spec_denoised, 0.0)
        audio_denoised = self.stft.inverse(audio_spec_denoised, audio_angles)
        return audio_denoised