import math
import torch
from torch import nn
from torch.nn import Parameter
import torch.onnx.operators
import torch.nn.functional as F
import utils


class Reshape(nn.Module):
    def __init__(self, *args):
        super(Reshape, self).__init__()
        self.shape = args

    def forward(self, x):
        return x.view(self.shape)


class Permute(nn.Module):
    def __init__(self, *args):
        super(Permute, self).__init__()
        self.args = args

    def forward(self, x):
        return x.permute(self.args)


class LinearNorm(torch.nn.Module):
    def __init__(self, in_dim, out_dim, bias=True, w_init_gain='linear'):
        super(LinearNorm, self).__init__()
        self.linear_layer = torch.nn.Linear(in_dim, out_dim, bias=bias)

        torch.nn.init.xavier_uniform_(
            self.linear_layer.weight,
            gain=torch.nn.init.calculate_gain(w_init_gain))

    def forward(self, x):
        return self.linear_layer(x)


class ConvNorm(torch.nn.Module):
    def __init__(self, in_channels, out_channels, kernel_size=1, stride=1,
                 padding=None, dilation=1, bias=True, w_init_gain='linear'):
        super(ConvNorm, self).__init__()
        if padding is None:
            assert (kernel_size % 2 == 1)
            padding = int(dilation * (kernel_size - 1) / 2)

        self.conv = torch.nn.Conv1d(in_channels, out_channels,
                                    kernel_size=kernel_size, stride=stride,
                                    padding=padding, dilation=dilation,
                                    bias=bias)

        torch.nn.init.xavier_uniform_(
            self.conv.weight, gain=torch.nn.init.calculate_gain(w_init_gain))

    def forward(self, signal):
        conv_signal = self.conv(signal)
        return conv_signal


def Embedding(num_embeddings, embedding_dim, padding_idx=None):
    m = nn.Embedding(num_embeddings, embedding_dim, padding_idx=padding_idx)
    nn.init.normal_(m.weight, mean=0, std=embedding_dim ** -0.5)
    if padding_idx is not None:
        nn.init.constant_(m.weight[padding_idx], 0)
    return m


def LayerNorm(normalized_shape, eps=1e-5, elementwise_affine=True, export=False):
    if not export and torch.cuda.is_available():
        try:
            from apex.normalization import FusedLayerNorm
            return FusedLayerNorm(normalized_shape, eps, elementwise_affine)
        except ImportError:
            pass
    return torch.nn.LayerNorm(normalized_shape, eps, elementwise_affine)

def Linear(in_features, out_features, bias=True):
    m = nn.Linear(in_features, out_features, bias)
    nn.init.xavier_uniform_(m.weight)
    if bias:
        nn.init.constant_(m.bias, 0.)
    return m


class SinusoidalPositionalEmbedding(nn.Module):
    """This module produces sinusoidal positional embeddings of any length.

    Padding symbols are ignored.
    """

    def __init__(self, embedding_dim, padding_idx, init_size=1024):
        super().__init__()
        self.embedding_dim = embedding_dim
        self.padding_idx = padding_idx
        self.weights = SinusoidalPositionalEmbedding.get_embedding(
            init_size,
            embedding_dim,
            padding_idx,
        )
        self.register_buffer('_float_tensor', torch.FloatTensor(1))

    @staticmethod
    def get_embedding(num_embeddings, embedding_dim, padding_idx=None):
        """Build sinusoidal embeddings.

        This matches the implementation in tensor2tensor, but differs slightly
        from the description in Section 3.5 of "Attention Is All You Need".
        """
        half_dim = embedding_dim // 2
        emb = math.log(10000) / (half_dim - 1)
        emb = torch.exp(torch.arange(half_dim, dtype=torch.float) * -emb)
        emb = torch.arange(num_embeddings, dtype=torch.float).unsqueeze(1) * emb.unsqueeze(0)
        emb = torch.cat([torch.sin(emb), torch.cos(emb)], dim=1).view(num_embeddings, -1)
        if embedding_dim % 2 == 1:
            # zero pad
            emb = torch.cat([emb, torch.zeros(num_embeddings, 1)], dim=1)
        if padding_idx is not None:
            emb[padding_idx, :] = 0
        return emb

    def forward(self, input, incremental_state=None, timestep=None, positions=None, **kwargs):
        """Input is expected to be of size [bsz x seqlen]."""
        bsz, seq_len = input.shape[:2]
        max_pos = self.padding_idx + 1 + seq_len
        if self.weights is None or max_pos > self.weights.size(0):
            # recompute/expand embeddings if needed
            self.weights = SinusoidalPositionalEmbedding.get_embedding(
                max_pos,
                self.embedding_dim,
                self.padding_idx,
            )
        self.weights = self.weights.to(self._float_tensor)

        if incremental_state is not None:
            # positions is the same for every token when decoding a single step
            pos = timestep.view(-1)[0] + 1 if timestep is not None else seq_len
            return self.weights[self.padding_idx + pos, :].expand(bsz, 1, -1)

        positions = utils.make_positions(input, self.padding_idx) if positions is None else positions
        return self.weights.index_select(0, positions.view(-1)).view(bsz, seq_len, -1).detach()

    def max_positions(self):
        """Maximum number of supported positions."""
        return int(1e5)  # an arbitrary large number


class ConvTBC(nn.Module):
    def __init__(self, in_channels, out_channels, kernel_size, padding=0):
        super(ConvTBC, self).__init__()
        self.in_channels = in_channels
        self.out_channels = out_channels
        self.kernel_size = kernel_size
        self.padding = padding

        self.weight = torch.nn.Parameter(torch.Tensor(
            self.kernel_size, in_channels, out_channels))
        self.bias = torch.nn.Parameter(torch.Tensor(out_channels))

    def forward(self, input):
        return torch.conv_tbc(input.contiguous(), self.weight, self.bias, self.padding)


class MultiheadAttention(nn.Module):
    def __init__(self, embed_dim, num_heads, kdim=None, vdim=None, dropout=0., bias=True,
                 add_bias_kv=False, add_zero_attn=False, self_attention=False,
                 encoder_decoder_attention=False):
        super().__init__()
        self.embed_dim = embed_dim
        self.kdim = kdim if kdim is not None else embed_dim
        self.vdim = vdim if vdim is not None else embed_dim
        self.qkv_same_dim = self.kdim == embed_dim and self.vdim == embed_dim

        self.num_heads = num_heads
        self.dropout = dropout
        self.head_dim = embed_dim // num_heads
        assert self.head_dim * num_heads == self.embed_dim, "embed_dim must be divisible by num_heads"
        self.scaling = self.head_dim ** -0.5

        self.self_attention = self_attention
        self.encoder_decoder_attention = encoder_decoder_attention

        assert not self.self_attention or self.qkv_same_dim, 'Self-attention requires query, key and ' \
                                                             'value to be of the same size'

        if self.qkv_same_dim:
            self.in_proj_weight = Parameter(torch.Tensor(3 * embed_dim, embed_dim))
        else:
            self.k_proj_weight = Parameter(torch.Tensor(embed_dim, self.kdim))
            self.v_proj_weight = Parameter(torch.Tensor(embed_dim, self.vdim))
            self.q_proj_weight = Parameter(torch.Tensor(embed_dim, embed_dim))

        if bias:
            self.in_proj_bias = Parameter(torch.Tensor(3 * embed_dim))
        else:
            self.register_parameter('in_proj_bias', None)

        self.out_proj = nn.Linear(embed_dim, embed_dim, bias=bias)

        if add_bias_kv:
            self.bias_k = Parameter(torch.Tensor(1, 1, embed_dim))
            self.bias_v = Parameter(torch.Tensor(1, 1, embed_dim))
        else:
            self.bias_k = self.bias_v = None

        self.add_zero_attn = add_zero_attn

        self.reset_parameters()

        self.enable_torch_version = False
        if hasattr(F, "multi_head_attention_forward"):
            self.enable_torch_version = True
        else:
            self.enable_torch_version = False
        self.last_attn_probs = None

    def reset_parameters(self):
        if self.qkv_same_dim:
            nn.init.xavier_uniform_(self.in_proj_weight)
        else:
            nn.init.xavier_uniform_(self.k_proj_weight)
            nn.init.xavier_uniform_(self.v_proj_weight)
            nn.init.xavier_uniform_(self.q_proj_weight)

        nn.init.xavier_uniform_(self.out_proj.weight)
        if self.in_proj_bias is not None:
            nn.init.constant_(self.in_proj_bias, 0.)
            nn.init.constant_(self.out_proj.bias, 0.)
        if self.bias_k is not None:
            nn.init.xavier_normal_(self.bias_k)
        if self.bias_v is not None:
            nn.init.xavier_normal_(self.bias_v)

    def forward(
            self,
            query, key, value,
            key_padding_mask=None,
            incremental_state=None,
            need_weights=True,
            static_kv=False,
            attn_mask=None,
            before_softmax=False,
            need_head_weights=False,
            enc_dec_attn_constraint_mask=None,
            reset_attn_weight=None
    ):
        """Input shape: Time x Batch x Channel

        Args:
            key_padding_mask (ByteTensor, optional): mask to exclude
                keys that are pads, of shape `(batch, src_len)`, where
                padding elements are indicated by 1s.
            need_weights (bool, optional): return the attention weights,
                averaged over heads (default: False).
            attn_mask (ByteTensor, optional): typically used to
                implement causal attention, where the mask prevents the
                attention from looking forward in time (default: None).
            before_softmax (bool, optional): return the raw attention
                weights and values before the attention softmax.
            need_head_weights (bool, optional): return the attention
                weights for each head. Implies *need_weights*. Default:
                return the average attention weights over all heads.
        """
        if need_head_weights:
            need_weights = True

        tgt_len, bsz, embed_dim = query.size()
        assert embed_dim == self.embed_dim
        assert list(query.size()) == [tgt_len, bsz, embed_dim]

        if self.enable_torch_version and incremental_state is None and not static_kv and reset_attn_weight is None:
            if self.qkv_same_dim:
                return F.multi_head_attention_forward(query, key, value,
                                                      self.embed_dim, self.num_heads,
                                                      self.in_proj_weight,
                                                      self.in_proj_bias, self.bias_k, self.bias_v,
                                                      self.add_zero_attn, self.dropout,
                                                      self.out_proj.weight, self.out_proj.bias,
                                                      self.training, key_padding_mask, need_weights,
                                                      attn_mask)
            else:
                return F.multi_head_attention_forward(query, key, value,
                                                      self.embed_dim, self.num_heads,
                                                      torch.empty([0]),
                                                      self.in_proj_bias, self.bias_k, self.bias_v,
                                                      self.add_zero_attn, self.dropout,
                                                      self.out_proj.weight, self.out_proj.bias,
                                                      self.training, key_padding_mask, need_weights,
                                                      attn_mask, use_separate_proj_weight=True,
                                                      q_proj_weight=self.q_proj_weight,
                                                      k_proj_weight=self.k_proj_weight,
                                                      v_proj_weight=self.v_proj_weight)

        if incremental_state is not None:
            print('Not implemented error.')
            exit()
        else:
            saved_state = None

        if self.self_attention:
            # self-attention
            q, k, v = self.in_proj_qkv(query)
        elif self.encoder_decoder_attention:
            # encoder-decoder attention
            q = self.in_proj_q(query)
            if key is None:
                assert value is None
                k = v = None
            else:
                k = self.in_proj_k(key)
                v = self.in_proj_v(key)

        else:
            q = self.in_proj_q(query)
            k = self.in_proj_k(key)
            v = self.in_proj_v(value)
        q *= self.scaling

        if self.bias_k is not None:
            assert self.bias_v is not None
            k = torch.cat([k, self.bias_k.repeat(1, bsz, 1)])
            v = torch.cat([v, self.bias_v.repeat(1, bsz, 1)])
            if attn_mask is not None:
                attn_mask = torch.cat([attn_mask, attn_mask.new_zeros(attn_mask.size(0), 1)], dim=1)
            if key_padding_mask is not None:
                key_padding_mask = torch.cat(
                    [key_padding_mask, key_padding_mask.new_zeros(key_padding_mask.size(0), 1)], dim=1)

        q = q.contiguous().view(tgt_len, bsz * self.num_heads, self.head_dim).transpose(0, 1)
        if k is not None:
            k = k.contiguous().view(-1, bsz * self.num_heads, self.head_dim).transpose(0, 1)
        if v is not None:
            v = v.contiguous().view(-1, bsz * self.num_heads, self.head_dim).transpose(0, 1)

        if saved_state is not None:
            print('Not implemented error.')
            exit()

        src_len = k.size(1)

        # This is part of a workaround to get around fork/join parallelism
        # not supporting Optional types.
        if key_padding_mask is not None and key_padding_mask.shape == torch.Size([]):
            key_padding_mask = None

        if key_padding_mask is not None:
            assert key_padding_mask.size(0) == bsz
            assert key_padding_mask.size(1) == src_len

        if self.add_zero_attn:
            src_len += 1
            k = torch.cat([k, k.new_zeros((k.size(0), 1) + k.size()[2:])], dim=1)
            v = torch.cat([v, v.new_zeros((v.size(0), 1) + v.size()[2:])], dim=1)
            if attn_mask is not None:
                attn_mask = torch.cat([attn_mask, attn_mask.new_zeros(attn_mask.size(0), 1)], dim=1)
            if key_padding_mask is not None:
                key_padding_mask = torch.cat(
                    [key_padding_mask, torch.zeros(key_padding_mask.size(0), 1).type_as(key_padding_mask)], dim=1)

        attn_weights = torch.bmm(q, k.transpose(1, 2))
        attn_weights = self.apply_sparse_mask(attn_weights, tgt_len, src_len, bsz)

        assert list(attn_weights.size()) == [bsz * self.num_heads, tgt_len, src_len]

        if attn_mask is not None:
            if len(attn_mask.shape) == 2:
                attn_mask = attn_mask.unsqueeze(0)
            elif len(attn_mask.shape) == 3:
                attn_mask = attn_mask[:, None].repeat([1, self.num_heads, 1, 1]).reshape(
                    bsz * self.num_heads, tgt_len, src_len)
            attn_weights = attn_weights + attn_mask

        if enc_dec_attn_constraint_mask is not None:  # bs x head x L_kv
            attn_weights = attn_weights.view(bsz, self.num_heads, tgt_len, src_len)
            attn_weights = attn_weights.masked_fill(
                enc_dec_attn_constraint_mask.unsqueeze(2).bool(),
                -1e9,
            )
            attn_weights = attn_weights.view(bsz * self.num_heads, tgt_len, src_len)

        if key_padding_mask is not None:
            # don't attend to padding symbols
            attn_weights = attn_weights.view(bsz, self.num_heads, tgt_len, src_len)
            attn_weights = attn_weights.masked_fill(
                key_padding_mask.unsqueeze(1).unsqueeze(2),
                -1e9,
            )
            attn_weights = attn_weights.view(bsz * self.num_heads, tgt_len, src_len)

        attn_logits = attn_weights.view(bsz, self.num_heads, tgt_len, src_len)

        if before_softmax:
            return attn_weights, v

        attn_weights_float = utils.softmax(attn_weights, dim=-1)
        attn_weights = attn_weights_float.type_as(attn_weights)
        attn_probs = F.dropout(attn_weights_float.type_as(attn_weights), p=self.dropout, training=self.training)

        if reset_attn_weight is not None:
            if reset_attn_weight:
                self.last_attn_probs = attn_probs.detach()
            else:
                assert self.last_attn_probs is not None
                attn_probs = self.last_attn_probs
        attn = torch.bmm(attn_probs, v)
        assert list(attn.size()) == [bsz * self.num_heads, tgt_len, self.head_dim]
        attn = attn.transpose(0, 1).contiguous().view(tgt_len, bsz, embed_dim)
        attn = self.out_proj(attn)

        if need_weights:
            attn_weights = attn_weights_float.view(bsz, self.num_heads, tgt_len, src_len).transpose(1, 0)
            if not need_head_weights:
                # average attention weights over heads
                attn_weights = attn_weights.mean(dim=0)
        else:
            attn_weights = None

        return attn, (attn_weights, attn_logits)

    def in_proj_qkv(self, query):
        return self._in_proj(query).chunk(3, dim=-1)

    def in_proj_q(self, query):
        if self.qkv_same_dim:
            return self._in_proj(query, end=self.embed_dim)
        else:
            bias = self.in_proj_bias
            if bias is not None:
                bias = bias[:self.embed_dim]
            return F.linear(query, self.q_proj_weight, bias)

    def in_proj_k(self, key):
        if self.qkv_same_dim:
            return self._in_proj(key, start=self.embed_dim, end=2 * self.embed_dim)
        else:
            weight = self.k_proj_weight
            bias = self.in_proj_bias
            if bias is not None:
                bias = bias[self.embed_dim:2 * self.embed_dim]
            return F.linear(key, weight, bias)

    def in_proj_v(self, value):
        if self.qkv_same_dim:
            return self._in_proj(value, start=2 * self.embed_dim)
        else:
            weight = self.v_proj_weight
            bias = self.in_proj_bias
            if bias is not None:
                bias = bias[2 * self.embed_dim:]
            return F.linear(value, weight, bias)

    def _in_proj(self, input, start=0, end=None):
        weight = self.in_proj_weight
        bias = self.in_proj_bias
        weight = weight[start:end, :]
        if bias is not None:
            bias = bias[start:end]
        return F.linear(input, weight, bias)


    def apply_sparse_mask(self, attn_weights, tgt_len, src_len, bsz):
        return attn_weights


class Swish(torch.autograd.Function):
    @staticmethod
    def forward(ctx, i):
        result = i * torch.sigmoid(i)
        ctx.save_for_backward(i)
        return result

    @staticmethod
    def backward(ctx, grad_output):
        i = ctx.saved_variables[0]
        sigmoid_i = torch.sigmoid(i)
        return grad_output * (sigmoid_i * (1 + i * (1 - sigmoid_i)))


class CustomSwish(nn.Module):
    def forward(self, input_tensor):
        return Swish.apply(input_tensor)


class TransformerFFNLayer(nn.Module):
    def __init__(self, hidden_size, filter_size, padding="SAME", kernel_size=1, dropout=0., act='gelu'):
        super().__init__()
        self.kernel_size = kernel_size
        self.dropout = dropout
        self.act = act
        if padding == 'SAME':
            self.ffn_1 = nn.Conv1d(hidden_size, filter_size, kernel_size, padding=kernel_size // 2)
        elif padding == 'LEFT':
            self.ffn_1 = nn.Sequential(
                nn.ConstantPad1d((kernel_size - 1, 0), 0.0),
                nn.Conv1d(hidden_size, filter_size, kernel_size)
            )
        self.ffn_2 = Linear(filter_size, hidden_size)
        if self.act == 'swish':
            self.swish_fn = CustomSwish()

    def forward(self, x, incremental_state=None):
        # x: T x B x C
        if incremental_state is not None:
            assert incremental_state is None, 'Nar-generation does not allow this.'
            exit(1)

        x = self.ffn_1(x.permute(1, 2, 0)).permute(2, 0, 1)
        x = x * self.kernel_size ** -0.5

        if incremental_state is not None:
            x = x[-1:]
        if self.act == 'gelu':
            x = F.gelu(x)
        if self.act == 'relu':
            x = F.relu(x)
        if self.act == 'swish':
            x = self.swish_fn(x)
        x = F.dropout(x, self.dropout, training=self.training)
        x = self.ffn_2(x)
        return x


class BatchNorm1dTBC(nn.Module):
    def __init__(self, c):
        super(BatchNorm1dTBC, self).__init__()
        self.bn = nn.BatchNorm1d(c)

    def forward(self, x):
        """

        :param x: [T, B, C]
        :return: [T, B, C]
        """
        x = x.permute(1, 2, 0)  # [B, C, T]
        x = self.bn(x)  # [B, C, T]
        x = x.permute(2, 0, 1)  # [T, B, C]
        return x


class EncSALayer(nn.Module):
    def __init__(self, c, num_heads, dropout, attention_dropout=0.1,
                 relu_dropout=0.1, kernel_size=9, padding='SAME', norm='ln', act='gelu'):
        super().__init__()
        self.c = c
        self.dropout = dropout
        self.num_heads = num_heads
        if num_heads > 0:
            if norm == 'ln':
                self.layer_norm1 = LayerNorm(c)
            elif norm == 'bn':
                self.layer_norm1 = BatchNorm1dTBC(c)
            self.self_attn = MultiheadAttention(
                self.c, num_heads, self_attention=True, dropout=attention_dropout, bias=False,
            )
        if norm == 'ln':
            self.layer_norm2 = LayerNorm(c)
        elif norm == 'bn':
            self.layer_norm2 = BatchNorm1dTBC(c)
        self.ffn = TransformerFFNLayer(
            c, 4 * c, kernel_size=kernel_size, dropout=relu_dropout, padding=padding, act=act)

    def forward(self, x, encoder_padding_mask=None, **kwargs):
        layer_norm_training = kwargs.get('layer_norm_training', None)
        if layer_norm_training is not None:
            self.layer_norm1.training = layer_norm_training
            self.layer_norm2.training = layer_norm_training
        if self.num_heads > 0:
            residual = x
            x = self.layer_norm1(x)
            x, _, = self.self_attn(
                query=x,
                key=x,
                value=x,
                key_padding_mask=encoder_padding_mask
            )
            x = F.dropout(x, self.dropout, training=self.training)
            x = residual + x
            x = x * (1 - encoder_padding_mask.float()).transpose(0, 1)[..., None]

        residual = x
        x = self.layer_norm2(x)
        x = self.ffn(x)
        x = F.dropout(x, self.dropout, training=self.training)
        x = residual + x
        x = x * (1 - encoder_padding_mask.float()).transpose(0, 1)[..., None]
        return x


class DecSALayer(nn.Module):
    def __init__(self, c, num_heads, dropout, attention_dropout=0.1, relu_dropout=0.1, kernel_size=9, act='gelu'):
        super().__init__()
        self.c = c
        self.dropout = dropout
        self.layer_norm1 = LayerNorm(c)
        self.self_attn = MultiheadAttention(
            c, num_heads, self_attention=True, dropout=attention_dropout, bias=False
        )
        self.layer_norm2 = LayerNorm(c)
        self.encoder_attn = MultiheadAttention(
            c, num_heads, encoder_decoder_attention=True, dropout=attention_dropout, bias=False,
        )
        self.layer_norm3 = LayerNorm(c)
        self.ffn = TransformerFFNLayer(
            c, 4 * c, padding='LEFT', kernel_size=kernel_size, dropout=relu_dropout, act=act)

    def forward(
            self,
            x,
            encoder_out=None,
            encoder_padding_mask=None,
            incremental_state=None,
            self_attn_mask=None,
            self_attn_padding_mask=None,
            attn_out=None,
            reset_attn_weight=None,
            **kwargs,
    ):
        layer_norm_training = kwargs.get('layer_norm_training', None)
        if layer_norm_training is not None:
            self.layer_norm1.training = layer_norm_training
            self.layer_norm2.training = layer_norm_training
            self.layer_norm3.training = layer_norm_training
        residual = x
        x = self.layer_norm1(x)
        x, _ = self.self_attn(
            query=x,
            key=x,
            value=x,
            key_padding_mask=self_attn_padding_mask,
            incremental_state=incremental_state,
            attn_mask=self_attn_mask
        )
        x = F.dropout(x, self.dropout, training=self.training)
        x = residual + x

        residual = x
        x = self.layer_norm2(x)
        if encoder_out is not None:
            x, attn = self.encoder_attn(
                query=x,
                key=encoder_out,
                value=encoder_out,
                key_padding_mask=encoder_padding_mask,
                incremental_state=incremental_state,
                static_kv=True,
                enc_dec_attn_constraint_mask=None, #utils.get_incremental_state(self, incremental_state, 'enc_dec_attn_constraint_mask'),
                reset_attn_weight=reset_attn_weight
            )
            attn_logits = attn[1]
        else:
            assert attn_out is not None
            x = self.encoder_attn.in_proj_v(attn_out.transpose(0, 1))
            attn_logits = None
        x = F.dropout(x, self.dropout, training=self.training)
        x = residual + x

        residual = x
        x = self.layer_norm3(x)
        x = self.ffn(x, incremental_state=incremental_state)
        x = F.dropout(x, self.dropout, training=self.training)
        x = residual + x
        # if len(attn_logits.size()) > 3:
        #    indices = attn_logits.softmax(-1).max(-1).values.sum(-1).argmax(-1)
        #    attn_logits = attn_logits.gather(1,
        #        indices[:, None, None, None].repeat(1, 1, attn_logits.size(-2), attn_logits.size(-1))).squeeze(1)
        return x, attn_logits
