import math

import torch
import torch.nn as nn
import torch.nn.functional as F
from torch_geometric.nn import GCNConv, GATConv
from torch_geometric.nn.conv import MessagePassing
from torch_geometric.nn.inits import glorot
from torch_geometric.utils import softmax


class HGTConv(MessagePassing):
    def __init__(self, in_dim, out_dim, num_types, num_relations, n_heads, dropout=0.2, use_norm=True, use_RTE=True,
                 **kwargs):
        super(HGTConv, self).__init__(node_dim=0, aggr='add', **kwargs)

        self.in_dim = in_dim
        self.out_dim = out_dim
        self.num_types = num_types
        self.num_relations = num_relations
        self.total_rel = num_types * num_relations * num_types
        self.n_heads = n_heads
        self.d_k = out_dim // n_heads
        self.sqrt_dk = math.sqrt(self.d_k)
        self.use_norm = use_norm
        self.use_RTE = use_RTE
        self.att = None

        self.k_linears = nn.ModuleList()
        self.q_linears = nn.ModuleList()
        self.v_linears = nn.ModuleList()
        self.a_linears = nn.ModuleList()
        self.norms = nn.ModuleList()

        for t in range(num_types):
            self.k_linears.append(nn.Linear(in_dim, out_dim))
            self.q_linears.append(nn.Linear(in_dim, out_dim))
            self.v_linears.append(nn.Linear(in_dim, out_dim))
            self.a_linears.append(nn.Linear(out_dim, out_dim))
            if use_norm:
                self.norms.append(nn.LayerNorm(out_dim))
        '''
            TODO: make relation_pri smaller, as not all <st, rt, tt> pair exist in meta relation list.
        '''
        self.relation_pri = nn.Parameter(torch.ones(num_relations, self.n_heads))
        self.relation_att = nn.Parameter(torch.Tensor(num_relations, n_heads, self.d_k, self.d_k))
        self.relation_msg = nn.Parameter(torch.Tensor(num_relations, n_heads, self.d_k, self.d_k))
        self.skip = nn.Parameter(torch.ones(num_types))
        self.drop = nn.Dropout(dropout)

        if self.use_RTE:
            self.emb = RelTemporalEncoding(in_dim)

        glorot(self.relation_att)
        glorot(self.relation_msg)

    def forward(self, node_inp, node_type, edge_index, edge_type, edge_time):
        return self.propagate(edge_index, node_inp=node_inp, node_type=node_type, \
                              edge_type=edge_type, edge_time=edge_time)

    def message(self, edge_index_i, node_inp_i, node_inp_j, node_type_i, node_type_j, edge_type, edge_time):
        '''
            j: source, i: target; <j, i>
        '''
        data_size = edge_index_i.size(0)
        '''
            Create Attention and Message tensor beforehand.
        '''
        res_att = torch.zeros(data_size, self.n_heads).to(node_inp_i.device)
        res_msg = torch.zeros(data_size, self.n_heads, self.d_k).to(node_inp_i.device)

        for source_type in range(self.num_types):
            sb = (node_type_j == int(source_type))
            k_linear = self.k_linears[source_type]
            v_linear = self.v_linears[source_type]
            for target_type in range(self.num_types):
                tb = (node_type_i == int(target_type)) & sb
                q_linear = self.q_linears[target_type]
                for relation_type in range(self.num_relations):
                    '''
                        idx is all the edges with meta relation <source_type, relation_type, target_type>
                    '''
                    idx = (edge_type == int(relation_type)) & tb
                    if idx.sum() == 0:
                        continue
                    '''
                        Get the corresponding input node representations by idx.
                        Add tempotal encoding to source representation (j)
                    '''
                    target_node_vec = node_inp_i[idx]
                    source_node_vec = node_inp_j[idx]
                    if self.use_RTE:
                        source_node_vec = self.emb(source_node_vec, edge_time[idx])
                    '''
                        Step 1: Heterogeneous Mutual Attention
                    '''
                    q_mat = q_linear(target_node_vec).view(-1, self.n_heads, self.d_k)
                    k_mat = k_linear(source_node_vec).view(-1, self.n_heads, self.d_k)
                    k_mat = torch.bmm(k_mat.transpose(1, 0), self.relation_att[relation_type]).transpose(1, 0)
                    res_att[idx] = (q_mat * k_mat).sum(dim=-1) * self.relation_pri[relation_type] / self.sqrt_dk
                    '''
                        Step 2: Heterogeneous Message Passing
                    '''
                    v_mat = v_linear(source_node_vec).view(-1, self.n_heads, self.d_k)
                    res_msg[idx] = torch.bmm(v_mat.transpose(1, 0), self.relation_msg[relation_type]).transpose(1, 0)
        '''
            Softmax based on target node's id (edge_index_i). Store attention value in self.att for later visualization.
        '''
        self.att = softmax(res_att, edge_index_i)
        res = res_msg * self.att.view(-1, self.n_heads, 1)
        del res_att, res_msg
        return res.view(-1, self.out_dim)

    def update(self, aggr_out, node_inp, node_type):
        '''
            Step 3: Target-specific Aggregation
            x = W[node_type] * gelu(Agg(x)) + x
        '''
        aggr_out = F.gelu(aggr_out)
        res = torch.zeros(aggr_out.size(0), self.out_dim).to(node_inp.device)
        for target_type in range(self.num_types):
            idx = (node_type == int(target_type))
            if idx.sum() == 0:
                continue
            trans_out = self.drop(self.a_linears[target_type](aggr_out[idx]))
            '''
                Add skip connection with learnable weight self.skip[t_id]
            '''
            alpha = torch.sigmoid(self.skip[target_type])
            if self.use_norm:
                res[idx] = self.norms[target_type](trans_out * alpha + node_inp[idx] * (1 - alpha))
            else:
                res[idx] = trans_out * alpha + node_inp[idx] * (1 - alpha)
        return res

    def __repr__(self):
        return '{}(in_dim={}, out_dim={}, num_types={}, num_types={})'.format(
            self.__class__.__name__, self.in_dim, self.out_dim,
            self.num_types, self.num_relations)


class DenseHGTConv(MessagePassing):
    def __init__(self, in_dim, out_dim, num_types, num_relations, n_heads, dropout=0.2, use_norm=True, use_RTE=True,
                 **kwargs):
        super(DenseHGTConv, self).__init__(node_dim=0, aggr='add', **kwargs)

        self.in_dim = in_dim
        self.out_dim = out_dim
        self.num_types = num_types
        self.num_relations = num_relations
        self.total_rel = num_types * num_relations * num_types
        self.n_heads = n_heads
        self.d_k = out_dim // n_heads
        self.sqrt_dk = math.sqrt(self.d_k)
        self.use_norm = use_norm
        self.use_RTE = use_RTE
        self.att = None

        self.k_linears = nn.ModuleList()
        self.q_linears = nn.ModuleList()
        self.v_linears = nn.ModuleList()
        self.a_linears = nn.ModuleList()
        self.norms = nn.ModuleList()

        for t in range(num_types):
            self.k_linears.append(nn.Linear(in_dim, out_dim))
            self.q_linears.append(nn.Linear(in_dim, out_dim))
            self.v_linears.append(nn.Linear(in_dim, out_dim))
            self.a_linears.append(nn.Linear(out_dim, out_dim))
            if use_norm:
                self.norms.append(nn.LayerNorm(out_dim))
        '''
            TODO: make relation_pri smaller, as not all <st, rt, tt> pair exist in meta relation list.
        '''
        self.relation_pri = nn.Parameter(torch.ones(num_relations, self.n_heads))
        self.relation_att = nn.Parameter(torch.Tensor(num_relations, n_heads, self.d_k, self.d_k))
        self.relation_msg = nn.Parameter(torch.Tensor(num_relations, n_heads, self.d_k, self.d_k))
        self.drop = nn.Dropout(dropout)

        if self.use_RTE:
            self.emb = RelTemporalEncoding(in_dim)

        glorot(self.relation_att)
        glorot(self.relation_msg)

        self.mid_linear = nn.Linear(out_dim, out_dim * 2)
        self.out_linear = nn.Linear(out_dim * 2, out_dim)
        self.out_norm = nn.LayerNorm(out_dim)

    def forward(self, node_inp, node_type, edge_index, edge_type, edge_time):
        return self.propagate(edge_index, node_inp=node_inp, node_type=node_type, \
                              edge_type=edge_type, edge_time=edge_time)

    def message(self, edge_index_i, node_inp_i, node_inp_j, node_type_i, node_type_j, edge_type, edge_time):
        '''
            j: source, i: target; <j, i>
        '''
        data_size = edge_index_i.size(0)
        '''
            Create Attention and Message tensor beforehand.
        '''
        res_att = torch.zeros(data_size, self.n_heads).to(node_inp_i.device)
        res_msg = torch.zeros(data_size, self.n_heads, self.d_k).to(node_inp_i.device)

        for source_type in range(self.num_types):
            sb = (node_type_j == int(source_type))
            k_linear = self.k_linears[source_type]
            v_linear = self.v_linears[source_type]
            for target_type in range(self.num_types):
                tb = (node_type_i == int(target_type)) & sb
                q_linear = self.q_linears[target_type]
                for relation_type in range(self.num_relations):
                    '''
                        idx is all the edges with meta relation <source_type, relation_type, target_type>
                    '''
                    idx = (edge_type == int(relation_type)) & tb
                    if idx.sum() == 0:
                        continue
                    '''
                        Get the corresponding input node representations by idx.
                        Add tempotal encoding to source representation (j)
                    '''
                    target_node_vec = node_inp_i[idx]
                    source_node_vec = node_inp_j[idx]
                    if self.use_RTE:
                        source_node_vec = self.emb(source_node_vec, edge_time[idx])
                    '''
                        Step 1: Heterogeneous Mutual Attention
                    '''
                    q_mat = q_linear(target_node_vec).view(-1, self.n_heads, self.d_k)
                    k_mat = k_linear(source_node_vec).view(-1, self.n_heads, self.d_k)
                    k_mat = torch.bmm(k_mat.transpose(1, 0), self.relation_att[relation_type]).transpose(1, 0)
                    res_att[idx] = (q_mat * k_mat).sum(dim=-1) * self.relation_pri[relation_type] / self.sqrt_dk
                    '''
                        Step 2: Heterogeneous Message Passing
                    '''
                    v_mat = v_linear(source_node_vec).view(-1, self.n_heads, self.d_k)
                    res_msg[idx] = torch.bmm(v_mat.transpose(1, 0), self.relation_msg[relation_type]).transpose(1, 0)
        '''
            Softmax based on target node's id (edge_index_i). Store attention value in self.att for later visualization.
        '''
        self.att = softmax(res_att, edge_index_i)
        res = res_msg * self.att.view(-1, self.n_heads, 1)
        del res_att, res_msg
        return res.view(-1, self.out_dim)

    def update(self, aggr_out, node_inp, node_type):
        '''
            Step 3: Target-specific Aggregation
            x = W[node_type] * Agg(x) + x
        '''
        res = torch.zeros(aggr_out.size(0), self.out_dim).to(node_inp.device)
        for target_type in range(self.num_types):
            idx = (node_type == int(target_type))
            if idx.sum() == 0:
                continue
            trans_out = self.drop(self.a_linears[target_type](aggr_out[idx])) + node_inp[idx]
            '''
                Add skip connection with learnable weight self.skip[t_id]
            '''
            if self.use_norm:
                trans_out = self.norms[target_type](trans_out)

            '''
                Step 4: Shared Dense Layer
                x = Out_L(gelu(Mid_L(x))) + x
            '''

            trans_out = self.drop(self.out_linear(F.gelu(self.mid_linear(trans_out)))) + trans_out
            res[idx] = self.out_norm(trans_out)
        return res

    def __repr__(self):
        return '{}(in_dim={}, out_dim={}, num_types={}, num_types={})'.format(
            self.__class__.__name__, self.in_dim, self.out_dim,
            self.num_types, self.num_relations)


class RelTemporalEncoding(nn.Module):
    '''
        Implement the Temporal Encoding (Sinusoid) function.
    '''

    def __init__(self, n_hid, max_len=240, dropout=0.2):
        super(RelTemporalEncoding, self).__init__()
        position = torch.arange(0., max_len).unsqueeze(1)
        div_term = torch.exp(torch.arange(0, n_hid, 2) *
                             -(math.log(10000.0) / n_hid))
        emb = nn.Embedding(max_len, n_hid)
        emb.weight.data[:, 0::2] = torch.sin(position * div_term) / math.sqrt(n_hid)
        emb.weight.data[:, 1::2] = torch.cos(position * div_term) / math.sqrt(n_hid)
        emb.requires_grad = False
        self.emb = emb
        self.lin = nn.Linear(n_hid, n_hid)

    def forward(self, x, t):
        return x + self.lin(self.emb(t))


class GeneralConv(nn.Module):
    def __init__(self, conv_name, in_hid, out_hid, num_types, num_relations, n_heads, dropout, use_norm=True,
                 use_RTE=True):
        super(GeneralConv, self).__init__()
        self.conv_name = conv_name
        if self.conv_name == 'hgt':
            self.base_conv = HGTConv(in_hid, out_hid, num_types, num_relations, n_heads, dropout, use_norm, use_RTE)
        elif self.conv_name == 'dense_hgt':
            self.base_conv = DenseHGTConv(in_hid, out_hid, num_types, num_relations, n_heads, dropout, use_norm,
                                          use_RTE)
        elif self.conv_name == 'gcn':
            self.base_conv = GCNConv(in_hid, out_hid)
        elif self.conv_name == 'gat':
            self.base_conv = GATConv(in_hid, out_hid // n_heads, heads=n_heads)

    def forward(self, meta_xs, node_type, edge_index, edge_type, edge_time):
        if self.conv_name == 'hgt':
            return self.base_conv(meta_xs, node_type, edge_index, edge_type, edge_time)
        elif self.conv_name == 'gcn':
            return self.base_conv(meta_xs, edge_index)
        elif self.conv_name == 'gat':
            return self.base_conv(meta_xs, edge_index)
        elif self.conv_name == 'dense_hgt':
            return self.base_conv(meta_xs, node_type, edge_index, edge_type, edge_time)

torch.nn.Linear torch.sigmoid torch.nn.Dropout torch.nn.LayerNorm torch.cos torch.zeros torch.nn.ModuleList torch.sin torch.arange torch.nn.functional.gelu torch.ones torch.Tensor torch.nn.Embedding