# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
# Copyright 2019 Mobvoi Inc. All Rights Reserved.
#
# 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.
# Modified from wenet(https://github.com/wenet-e2e/wenet)
"""Subsampling layer definition."""
from typing import Tuple

import paddle
from paddle import nn

from paddlespeech.s2t.modules.align import Conv2D
from paddlespeech.s2t.modules.align import LayerNorm
from paddlespeech.s2t.modules.align import Linear
from paddlespeech.s2t.modules.embedding import PositionalEncoding
from paddlespeech.s2t.utils.log import Log

logger = Log(__name__).getlog()

__all__ = [
    "LinearNoSubsampling", "Conv2dSubsampling4", "Conv2dSubsampling6",
    "Conv2dSubsampling8"
]


class BaseSubsampling(nn.Layer):
    def __init__(self, pos_enc_class: nn.Layer=PositionalEncoding):
        super().__init__()
        self.pos_enc = pos_enc_class
        # window size = (1 + right_context) + (chunk_size -1) * subsampling_rate
        self.right_context = 0
        # stride = subsampling_rate * chunk_size
        self.subsampling_rate = 1

    def position_encoding(self, offset: int, size: int) -> paddle.Tensor:
        return self.pos_enc.position_encoding(offset, size)


class LinearNoSubsampling(BaseSubsampling):
    """Linear transform the input without subsampling."""

    def __init__(self,
                 idim: int,
                 odim: int,
                 dropout_rate: float,
                 pos_enc_class: nn.Layer=PositionalEncoding):
        """Construct an linear object.
        Args:
            idim (int): Input dimension.
            odim (int): Output dimension.
            dropout_rate (float): Dropout rate.
            pos_enc_class (PositionalEncoding): position encoding class
        """
        super().__init__(pos_enc_class)
        self.out = nn.Sequential(
            Linear(idim, odim),
            LayerNorm(odim, epsilon=1e-12),
            nn.Dropout(dropout_rate),
            nn.ReLU(), )
        self.right_context = 0
        self.subsampling_rate = 1

    def forward(self, x: paddle.Tensor, x_mask: paddle.Tensor, offset: int=0
                ) -> Tuple[paddle.Tensor, paddle.Tensor, paddle.Tensor]:
        """Input x.
        Args:
            x (paddle.Tensor): Input tensor (#batch, time, idim).
            x_mask (paddle.Tensor): Input mask (#batch, 1, time).
            offset (int): position encoding offset.
        Returns:
            paddle.Tensor: linear input tensor (#batch, time', odim),
                where time' = time .
            paddle.Tensor: positional encoding
            paddle.Tensor: linear input mask (#batch, 1, time'),
                where time' = time .
        """
        x = self.out(x)
        x, pos_emb = self.pos_enc(x, offset)
        return x, pos_emb, x_mask


class Conv2dSubsampling(BaseSubsampling):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


class Conv2dSubsampling4(Conv2dSubsampling):
    """Convolutional 2D subsampling (to 1/4 length)."""

    def __init__(self,
                 idim: int,
                 odim: int,
                 dropout_rate: float,
                 pos_enc_class: nn.Layer=PositionalEncoding):
        """Construct an Conv2dSubsampling4 object.

        Args:
            idim (int): Input dimension.
            odim (int): Output dimension.
            dropout_rate (float): Dropout rate.
        """
        super().__init__(pos_enc_class)
        self.conv = nn.Sequential(
            Conv2D(1, odim, 3, 2),
            nn.ReLU(),
            Conv2D(odim, odim, 3, 2),
            nn.ReLU(), )
        self.out = nn.Sequential(
            Linear(odim * (((idim - 1) // 2 - 1) // 2), odim))
        self.subsampling_rate = 4
        # The right context for every conv layer is computed by:
        # (kernel_size - 1) * frame_rate_of_this_layer
        # 6 = (3 - 1) * 1 + (3 - 1) * 2
        self.right_context = 6

    def forward(self, x: paddle.Tensor, x_mask: paddle.Tensor, offset: int=0
                ) -> Tuple[paddle.Tensor, paddle.Tensor, paddle.Tensor]:
        """Subsample x.
        Args:
            x (paddle.Tensor): Input tensor (#batch, time, idim).
            x_mask (paddle.Tensor): Input mask (#batch, 1, time).
            offset (int): position encoding offset.
        Returns:
            paddle.Tensor: Subsampled tensor (#batch, time', odim),
                where time' = time // 4.
            paddle.Tensor: positional encoding
            paddle.Tensor: Subsampled mask (#batch, 1, time'),
                where time' = time // 4.
        """
        x = x.unsqueeze(1)  # (b, c=1, t, f)
        x = self.conv(x)
        b, c, t, f = paddle.shape(x)
        x = self.out(x.transpose([0, 2, 1, 3]).reshape([b, t, c * f]))
        x, pos_emb = self.pos_enc(x, offset)
        return x, pos_emb, x_mask[:, :, :-2:2][:, :, :-2:2]


class Conv2dSubsampling6(Conv2dSubsampling):
    """Convolutional 2D subsampling (to 1/6 length)."""

    def __init__(self,
                 idim: int,
                 odim: int,
                 dropout_rate: float,
                 pos_enc_class: nn.Layer=PositionalEncoding):
        """Construct an Conv2dSubsampling6 object.

        Args:
            idim (int): Input dimension.
            odim (int): Output dimension.
            dropout_rate (float): Dropout rate.
            pos_enc (PositionalEncoding): Custom position encoding layer.
        """
        super().__init__(pos_enc_class)
        self.conv = nn.Sequential(
            Conv2D(1, odim, 3, 2),
            nn.ReLU(),
            Conv2D(odim, odim, 5, 3),
            nn.ReLU(), )
        # O = (I - F + Pstart + Pend) // S + 1
        # when Padding == 0, O = (I - F - S) // S
        self.linear = Linear(odim * (((idim - 1) // 2 - 2) // 3), odim)
        # The right context for every conv layer is computed by:
        # (kernel_size - 1) * frame_rate_of_this_layer
        # 10 = (3 - 1) * 1 + (5 - 1) * 2
        self.subsampling_rate = 6
        self.right_context = 10

    def forward(self, x: paddle.Tensor, x_mask: paddle.Tensor, offset: int=0
                ) -> Tuple[paddle.Tensor, paddle.Tensor, paddle.Tensor]:
        """Subsample x.
        Args:
            x (paddle.Tensor): Input tensor (#batch, time, idim).
            x_mask (paddle.Tensor): Input mask (#batch, 1, time).
            offset (int): position encoding offset.
        Returns:
            paddle.Tensor: Subsampled tensor (#batch, time', odim),
                where time' = time // 6.
            paddle.Tensor: positional encoding
            paddle.Tensor: Subsampled mask (#batch, 1, time'),
                where time' = time // 6.
        """
        x = x.unsqueeze(1)  # (b, c, t, f)
        x = self.conv(x)
        b, c, t, f = paddle.shape(x)
        x = self.linear(x.transpose([0, 2, 1, 3]).reshape([b, t, c * f]))
        x, pos_emb = self.pos_enc(x, offset)
        return x, pos_emb, x_mask[:, :, :-2:2][:, :, :-4:3]


class Conv2dSubsampling8(Conv2dSubsampling):
    """Convolutional 2D subsampling (to 1/8 length)."""

    def __init__(self,
                 idim: int,
                 odim: int,
                 dropout_rate: float,
                 pos_enc_class: nn.Layer=PositionalEncoding):
        """Construct an Conv2dSubsampling8 object.

        Args:
            idim (int): Input dimension.
            odim (int): Output dimension.
            dropout_rate (float): Dropout rate.
        """
        super().__init__(pos_enc_class)
        self.conv = nn.Sequential(
            Conv2D(1, odim, 3, 2),
            nn.ReLU(),
            Conv2D(odim, odim, 3, 2),
            nn.ReLU(),
            Conv2D(odim, odim, 3, 2),
            nn.ReLU(), )
        self.linear = Linear(odim * ((((idim - 1) // 2 - 1) // 2 - 1) // 2),
                             odim)
        self.subsampling_rate = 8
        # The right context for every conv layer is computed by:
        # (kernel_size - 1) * frame_rate_of_this_layer
        # 14 = (3 - 1) * 1 + (3 - 1) * 2 + (3 - 1) * 4
        self.right_context = 14

    def forward(self, x: paddle.Tensor, x_mask: paddle.Tensor, offset: int=0
                ) -> Tuple[paddle.Tensor, paddle.Tensor, paddle.Tensor]:
        """Subsample x.
        Args:
            x (paddle.Tensor): Input tensor (#batch, time, idim).
            x_mask (paddle.Tensor): Input mask (#batch, 1, time).
            offset (int): position encoding offset.
        Returns:
            paddle.Tensor: Subsampled tensor (#batch, time', odim),
                where time' = time // 8.
            paddle.Tensor: positional encoding
            paddle.Tensor: Subsampled mask (#batch, 1, time'),
                where time' = time // 8.
        """
        x = x.unsqueeze(1)  # (b, c, t, f)
        x = self.conv(x)
        x = self.linear(x.transpose([0, 2, 1, 3]).reshape([b, t, c * f]))
        x, pos_emb = self.pos_enc(x, offset)
        return x, pos_emb, x_mask[:, :, :-2:2][:, :, :-2:2][:, :, :-2:2]