import torch, torch.nn as nn, torch.nn.functional as F


class nconv(nn.Module):
    """
    图卷积操作的实现类
    使用einsum进行矩阵运算，实现图卷积操作
    """
    def forward(self, x, A): return torch.einsum('ncvl,vw->ncwl', (x, A)).contiguous()


class linear(nn.Module):
    """
    线性变换层
    使用1x1卷积实现线性变换
    """
    def __init__(self, c_in, c_out):
        super().__init__()
        self.mlp = nn.Conv2d(c_in, c_out, 1)

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


class gcn(nn.Module):
    """
    图卷积网络层
    实现高阶图卷积操作，支持多阶邻接矩阵
    """
    def __init__(self, c_in, c_out, dropout, support_len=3, order=2):
        super().__init__()
        self.nconv = nconv()
        c_in = (order * support_len + 1) * c_in
        self.mlp, self.dropout, self.order = linear(c_in, c_out), dropout, order

    def forward(self, x, support):
        out = [x]
        for a in support:
            x1 = self.nconv(x, a)
            out.append(x1)
            for _ in range(2, self.order + 1):
                x1 = self.nconv(x1, a)
                out.append(x1)
        return F.dropout(self.mlp(torch.cat(out, dim=1)), self.dropout, training=self.training)


class gwnet(nn.Module):
    """
    Graph WaveNet模型的主类
    结合了图卷积网络和时序卷积网络，用于时空预测任务
    """
    def __init__(self, args):
        super().__init__()
        # 初始化基本参数
        self.dropout, self.blocks, self.layers = args['dropout'], args['blocks'], args['layers']
        self.gcn_bool, self.addaptadj = args['gcn_bool'], args['addaptadj']
        
        # 初始化各种卷积层和模块
        self.filter_convs, self.gate_convs = nn.ModuleList(), nn.ModuleList()
        self.residual_convs, self.skip_convs, self.bn, self.gconv = nn.ModuleList(), nn.ModuleList(), nn.ModuleList(), nn.ModuleList()
        self.start_conv = nn.Conv2d(args['in_dim'], args['residual_channels'], 1)
        self.supports = args.get('supports', None)
        
        # 计算感受野
        receptive_field = 1
        self.supports_len = len(self.supports) if self.supports is not None else 0
        
        # 如果使用自适应邻接矩阵，初始化相关参数
        if self.gcn_bool and self.addaptadj:
            aptinit = args.get('aptinit', None)
            if aptinit is None:
                if self.supports is None: self.supports = []
                self.nodevec1 = nn.Parameter(torch.randn(args['num_nodes'], 10, device=args['device']))
                self.nodevec2 = nn.Parameter(torch.randn(10, args['num_nodes'], device=args['device']))
                self.supports_len += 1
            else:
                if self.supports is None: self.supports = []
                m, p, n = torch.svd(aptinit)
                initemb1 = torch.mm(m[:, :10], torch.diag(p[:10] ** 0.5))
                initemb2 = torch.mm(torch.diag(p[:10] ** 0.5), n[:, :10].t())
                self.nodevec1 = nn.Parameter(initemb1)
                self.nodevec2 = nn.Parameter(initemb2)
                self.supports_len += 1
                
        # 获取模型参数
        ks, res, dil, skip, endc, out_dim = args['kernel_size'], args['residual_channels'], args['dilation_channels'], \
        args['skip_channels'], args['end_channels'], args['out_dim']
        
        # 构建模型层
        for b in range(self.blocks):
            add_scope, new_dil = ks - 1, 1
            for i in range(self.layers):
                # 添加时间卷积层
                self.filter_convs.append(nn.Conv2d(res, dil, (1, ks), dilation=new_dil))
                self.gate_convs.append(nn.Conv2d(res, dil, (1, ks), dilation=new_dil))
                self.residual_convs.append(nn.Conv2d(dil, res, 1))
                self.skip_convs.append(nn.Conv2d(dil, skip, 1))
                self.bn.append(nn.BatchNorm2d(res))
                new_dil *= 2
                receptive_field += add_scope
                add_scope *= 2
                if self.gcn_bool: self.gconv.append(gcn(dil, res, args['dropout'], support_len=self.supports_len))
                
        # 输出层
        self.end_conv_1 = nn.Conv2d(skip, endc, 1)
        self.end_conv_2 = nn.Conv2d(endc, out_dim, 1)
        self.receptive_field = receptive_field

    def forward(self, input):
        """
        前向传播函数
        实现模型的推理过程
        """
        # 数据预处理
        input = input[..., 0:2].transpose(1, 3)
        input = F.pad(input, (1, 0, 0, 0))
        in_len = input.size(3)
        x = F.pad(input, (self.receptive_field - in_len, 0, 0, 0)) if in_len < self.receptive_field else input
        
        # 初始卷积
        x, skip, new_supports = self.start_conv(x), 0, None
        
        # 如果使用自适应邻接矩阵，计算新的邻接矩阵
        if self.gcn_bool and self.addaptadj and self.supports is not None:
            adp = F.softmax(F.relu(torch.mm(self.nodevec1, self.nodevec2)), dim=1)
            new_supports = self.supports + [adp]
            
        # 主网络层的前向传播
        for i in range(self.blocks * self.layers):
            residual = x
            # 时间卷积操作
            f = self.filter_convs[i](residual).tanh()
            g = self.gate_convs[i](residual).sigmoid()
            x = f * g
            s = self.skip_convs[i](x)
            skip = (skip[:, :, :, -s.size(3):] if isinstance(skip, torch.Tensor) else 0) + s
            
            # 图卷积操作
            if self.gcn_bool and self.supports is not None:
                x = self.gconv[i](x, new_supports if self.addaptadj else self.supports)
            else:
                x = self.residual_convs[i](x)
            x = x + residual[:, :, :, -x.size(3):]
            x = self.bn[i](x)
            
        # 输出层处理
        return self.end_conv_2(F.relu(self.end_conv_1(F.relu(skip))))