import math
import torch
from torch import nn


class AddNorm(nn.Module):
    """残差连接后进行层归一化"""

    def __init__(self, normalized, dropout):
        super(AddNorm, self).__init__()
        self.dropout = nn.Dropout(dropout)
        self.ln = nn.LayerNorm(normalized)

    def forward(self, x, y):
        return  self.ln(x + self.dropout(y)) 


class PositionWiseFFN(nn.Module):
    """基于位置的前馈⽹络"""

    def __init__(self, ffn_input, ffn_hiddens,mlp_bias=True):
        super(PositionWiseFFN, self).__init__()
        self.ffn = nn.Sequential(
            nn.Linear(ffn_input, ffn_hiddens, bias=mlp_bias),
            nn.ReLU(),
            nn.Linear(ffn_hiddens, ffn_input, bias=mlp_bias),
        )

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

from torch.autograd import Variable
class PositionalEncoding1(nn.Module):
    "Implement the PE function."
    def __init__(self, d_model, dropout, max_len=5000):
        super(PositionalEncoding1, self).__init__()
        self.dropout = nn.Dropout(p=dropout)
        
        # Compute the positional encodings once in log space.
        pe = torch.zeros(max_len, d_model)
        position = torch.arange(0, max_len).unsqueeze(1)
        div_term = torch.exp(torch.arange(0, d_model, 2) *
                             -(math.log(10000.0) / d_model))
        pe[:, 0::2] = torch.sin(position * div_term)
        pe[:, 1::2] = torch.cos(position * div_term)
        pe = pe.unsqueeze(0)
        self.register_buffer('pe', pe)
        
    def forward(self, x):
        x = x + Variable(self.pe[:, :x.size(1)], 
                         requires_grad=False)
        return self.dropout(x)
    
class PositionalEncoding(nn.Module):
    """位置编码"""

    def __init__(self, num_hiddens, dropout, max_len=1000):
        super(PositionalEncoding, self).__init__()
        self.dropout = nn.Dropout(dropout)
        # 创建⼀个⾜够⻓的P
        self.P = torch.zeros((1, max_len, num_hiddens))
        X = torch.arange(max_len, dtype=torch.float32).reshape(-1, 1) / torch.pow(10000, torch.arange(0, num_hiddens, 2,
                                                                                                      dtype=torch.float32) / num_hiddens)
        self.P[:, :, 0::2] = torch.sin(X)
        self.P[:, :, 1::2] = torch.cos(X)

    def forward(self, X):
        X = X + self.P[:, :X.shape[1], :].to(X.device)
        return self.dropout(X)


class AttentionEncode(nn.Module):

    def __init__(self, dropout, embedding_size, num_heads,seq_len: int=40,ffn=False):
        super(AttentionEncode, self).__init__()
        self.dropout = dropout
        self.embedding_size = embedding_size
        self.num_heads = num_heads
        self.seq_len = seq_len
        self.is_ffn = ffn
        
        self.att = nn.MultiheadAttention(embed_dim=self.embedding_size,
                                         num_heads=num_heads,
                                         dropout=0.6
                                         )
    
        self.addNorm = AddNorm(normalized=[self.seq_len, self.embedding_size], dropout=self.dropout)

        self.FFN = PositionWiseFFN(ffn_input=self.embedding_size, ffn_hiddens=self.embedding_size*2)

    def forward(self, x):
        bs,_,_ = x.size()
        MHAtt, _ = self.att(x, x, x)
        MHAtt_encode = self.addNorm(x, MHAtt)

        if self.is_ffn:
            ffn_in = MHAtt_encode # bs,seq_len,feat_dims
            ffn_out = self.FFN(ffn_in)
            MHAtt_encode = self.addNorm(ffn_in,ffn_out)

        return MHAtt_encode


class FAN_encode(nn.Module):

    def __init__(self, dropout, shape):
        super(FAN_encode, self).__init__()
        self.dropout = dropout
        self.addNorm = AddNorm(normalized=[1, shape], dropout=self.dropout)
        self.FFN = PositionWiseFFN(ffn_input=shape, ffn_hiddens=(2*shape))
        self.ln = nn.LayerNorm(shape)

    def forward(self, x):
        #x = self.ln(x)
        ffn_out = self.FFN(x)
        encode_output = self.addNorm(x, ffn_out)

        return encode_output

class ffn_norm(nn.Module):
    # 可接受二维输入和一维输入
    def __init__(self,input_dims:int,hidden_dims:int,dropout:float,bias:bool=True):
        super(ffn_norm,self).__init__()

        self.inps_dims = input_dims
        self.hidden_dims = hidden_dims
        self.dropout = nn.Dropout(dropout)
        self.ffn_bias = bias
        self.ffn = nn.Sequential(
            nn.Linear(self.inps_dims, self.hidden_dims, bias=self.ffn_bias),
            nn.LeakyReLU(),
            nn.Linear(self.hidden_dims, self.inps_dims, bias=self.ffn_bias),
        )

        self.ln = nn.LayerNorm(self.inps_dims)
    
    def forward(self,x):
        # x:[B,S,H] OR [B,shape],shape:S*H
        ffn_out = self.ffn(x)
        norm_out = self.ln(x + self.dropout(ffn_out))

        return norm_out


def sequence_mask(X, valid_len, value=0.):
    """在序列中屏蔽不相关的项"""
    valid_len = valid_len.float()
    MaxLen = X.size(1)
    mask = torch.arange(MaxLen, dtype=torch.float32, device=X.device)[None, :] < valid_len[:, None].to(X.device)
    X[~mask] = value
    return X


def masked_softmax(X, valid_lens):
    """通过在最后⼀个轴上掩蔽元素来执⾏softmax操作"""
    # X:3D张量，valid_lens:1D或2D张量
    if valid_lens is None:
        return nn.functional.softmax(X, dim=-1)
    else:
        shape = X.shape
    if valid_lens.dim() == 1:
        valid_lens = torch.repeat_interleave(valid_lens, shape[1])
    else:
        valid_lens = valid_lens.reshape(-1)  # 最后⼀轴上被掩蔽的元素使⽤⼀个⾮常⼤的负值替换，从⽽其softmax输出为0
    X = sequence_mask(X.reshape(-1, shape[-1]), valid_lens, value=-1e6)
    return nn.functional.softmax(X.reshape(shape), dim=-1)


# class AdditiveAttention(nn.Module):
#     """加性注意⼒"""
#
#     def __init__(self, key_size, query_size, num_hiddens, dropout):
#         super(AdditiveAttention, self).__init__()
#         self.W_k = nn.Linear(key_size, num_hiddens, bias=False)
#         self.W_q = nn.Linear(query_size, num_hiddens, bias=False)
#         self.w_v = nn.Linear(num_hiddens, 1, bias=False)
#         self.dropout = nn.Dropout(dropout)
#
#     def forward(self, queries, keys, values, valid_lens):
#         queries, keys = self.W_q(queries), self.W_k(keys)
#         # 在维度扩展后，
#         # queries的形状：(batch_size，查询的个数，1，num_hidden)
#         # key的形状：(batch_size，1，“键－值”对的个数，num_hiddens)
#         # 使⽤⼴播⽅式进⾏求和
#         features = queries.unsqueeze(2) + keys.unsqueeze(1)
#         features = torch.tanh(features)
#         # self.w_v仅有⼀个输出，因此从形状中移除最后那个维度。
#         # scores的形状：(batch_size，查询的个数，“键-值”对的个数)
#         scores = self.w_v(features).squeeze(-1)
#         attention_weights = masked_softmax(scores, valid_lens)
#         # values的形状：(batch_size，“键－值”对的个数，值的维度)
#         return torch.bmm(self.dropout(attention_weights), values)


class AdditiveAttention(nn.Module):
    """注意⼒机制"""

    def __init__(self, input_size, value_size, num_hiddens, dropout):
        super(AdditiveAttention, self).__init__()
        self.W_k = nn.Linear(input_size, num_hiddens, bias=False)
        self.W_q = nn.Linear(input_size, num_hiddens, bias=False)
        self.w_v = nn.Linear(input_size, num_hiddens, bias=False)
        self.w_o = nn.Linear(50, value_size, bias=False)
        self.dropout = nn.Dropout(dropout)

    def forward(self, queries, keys, values, valid_lens=None):
        queries, keys = self.W_q(queries), self.W_k(keys)
        d = queries.shape[-1]
        # 在维度扩展后，
        # queries的形状：(batch_size，查询的个数，1，num_hidden)
        # key的形状：(batch_size，1，“键－值”对的个数，num_hiddens)
        # 使⽤⼴播⽅式进⾏求和
        # features = queries + keys
        # features = torch.tanh(features)
        # self.w_v仅有⼀个输出，因此从形状中移除最后那个维度。
        # scores的形状：(batch_size，查询的个数，“键-值”对的个数)

        scores = torch.bmm(queries, keys.transpose(1, 2)) / math.sqrt(d)
        scores = self.w_o(scores).permute(0, 2, 1)
        attention_weights = masked_softmax(scores, valid_lens)

        # attention_weights = nn.Softmax(dim=1)(scores)
        values = self.w_v(values)
        # values = torch.transpose(values, 1, 2)
        # values的形状：(batch_size，“键－值”对的个数，值的维度)
        return torch.bmm(self.dropout(attention_weights), values), attention_weights


class MultiHeadAttention(nn.Module):
    """多头注意力"""

    def __init__(self, key_size, query_size, value_size, num_hiddens,
                 num_heads, dropout, bias=False):
        super(MultiHeadAttention, self).__init__()
        self.num_heads = num_heads
        self.attention = DotProductAttention(dropout)
        self.W_q = nn.Linear(query_size, num_hiddens, bias=bias)
        self.W_k = nn.Linear(key_size, num_hiddens, bias=bias)
        self.W_v = nn.Linear(value_size, num_hiddens, bias=bias)
        self.W_o = nn.Linear(num_hiddens, num_hiddens, bias=bias)

    def forward(self, queries, keys, values, valid_lens=None):
        # queries，keys，values的形状:
        # (batch_size，查询或者“键－值”对的个数，num_hiddens)
        # valid_lens　的形状:
        # (batch_size，)或(batch_size，查询的个数)
        # 经过变换后，输出的queries，keys，values　的形状:
        # (batch_size*num_heads，查询或者“键－值”对的个数，
        # num_hiddens/num_heads)
        queries = transpose_qkv(self.W_q(queries), self.num_heads)
        keys = transpose_qkv(self.W_k(keys), self.num_heads)
        values = transpose_qkv(self.W_v(values), self.num_heads)

        if valid_lens is not None:
            # 在轴0，将第一项（标量或者矢量）复制num_heads次，
            # 然后如此复制第二项，然后诸如此类。
            valid_lens = torch.repeat_interleave(valid_lens, repeats=self.num_heads, dim=0)

        # output的形状:(batch_size*num_heads，查询的个数，num_hiddens/num_heads)
        output = self.attention(queries, keys, values, valid_lens)

        # output_concat的形状:(batch_size，查询的个数，num_hiddens)
        output_concat = transpose_output(output, self.num_heads)
        return self.W_o(output_concat)


def transpose_qkv(X, num_heads):
    """为了多注意力头的并行计算而变换形状"""
    # 输入X的形状:(batch_size，查询或者“键－值”对的个数，num_hiddens)
    # 输出X的形状:(batch_size，查询或者“键－值”对的个数，num_heads，
    # num_hiddens/num_heads)
    X = X.reshape(X.shape[0], X.shape[1], num_heads, -1)

    # 输出X的形状:(batch_size，num_heads，查询或者“键－值”对的个数,
    # num_hiddens/num_heads)
    X = X.permute(0, 2, 1, 3)

    # 最终输出的形状:(batch_size*num_heads,查询或者“键－值”对的个数,
    # num_hiddens/num_heads)
    return X.reshape(-1, X.shape[2], X.shape[3])


def transpose_output(X, num_heads):
    """逆转transpose_qkv函数的操作"""
    X = X.reshape(-1, num_heads, X.shape[1], X.shape[2])
    X = X.permute(0, 2, 1, 3)
    return X.reshape(X.shape[0], X.shape[1], -1)


class DotProductAttention(nn.Module):
    """缩放点积注意力"""

    def __init__(self, dropout):
        super(DotProductAttention, self).__init__()
        self.dropout = nn.Dropout(dropout)

    # queries的形状：(batch_size，查询的个数，d)
    # keys的形状：(batch_size，“键－值”对的个数，d)
    # values的形状：(batch_size，“键－值”对的个数，值的维度)
    # valid_lens的形状:(batch_size，)或者(batch_size，查询的个数)
    def forward(self, queries, keys, values, valid_lens=None):
        d = queries.shape[-1]
        # 设置transpose_b=True为了交换keys的最后两个维度
        scores = torch.bmm(queries, keys.transpose(1, 2)) / math.sqrt(d)
        attention_weights = masked_softmax(scores, valid_lens)
        return torch.bmm(self.dropout(attention_weights), values)


class MASK_AttentionEncode(nn.Module):

    def __init__(self, dropout, embedding_size, num_heads):
        super(MASK_AttentionEncode, self).__init__()
        self.dropout = dropout
        self.embedding_size = embedding_size
        self.num_heads = num_heads

        self.at1 = MultiHeadAttention(key_size=self.embedding_size,
                                      query_size=self.embedding_size,
                                      value_size=self.embedding_size,
                                      num_hiddens=self.embedding_size,
                                      num_heads=self.num_heads,
                                      dropout=self.dropout)
        self.addNorm = AddNorm(normalized=[50, self.embedding_size], dropout=self.dropout)

        self.FFN = PositionWiseFFN(ffn_num_input=64, ffn_num_hiddens=192, ffn_num_outputs=64)

    def forward(self, x, y=None):
        # Multi, _ = self.at1(x, x, x)
        Multi = self.at1(x, x, x, y)
        Multi_encode = self.addNorm(x, Multi)

        # encode_output = self.addNorm(Multi_encode, self.FFN(Multi_encode))

        return Multi_encode


class transformer_encode(nn.Module):

    def __init__(self, dropout, embedding, num_heads):
        super(transformer_encode, self).__init__()
        self.dropout = dropout
        self.embedding_size = embedding
        self.num_heads = num_heads
        self.attention = nn.MultiheadAttention(embed_dim=192,
                                               num_heads=8,
                                               dropout=0.6
                                               )
        self.at1 = MultiHeadAttention(key_size=self.embedding_size,
                                      query_size=self.embedding_size,
                                      value_size=self.embedding_size,
                                      num_hiddens=self.embedding_size,
                                      num_heads=self.num_heads,
                                      dropout=self.dropout)

        self.addNorm = AddNorm(normalized=[50, self.embedding_size], dropout=self.dropout)

        self.ffn = PositionWiseFFN(ffn_num_input=self.embedding_size, ffn_num_hiddens=2*self.embedding_size,
                                   ffn_num_outputs=self.embedding_size)

    def forward(self, x, valid=None):
        # Multi, _ = self.attention(x, x, x)
        Multi = self.at1(x, x, x, valid)
        Multi_encode = self.addNorm(x, Multi)

        encode_output = self.addNorm(Multi_encode, self.ffn(Multi_encode))

        return encode_output