import os.path as osp

import torch
import torch.nn.functional as F

import torch_geometric.transforms as T
from torch_geometric.datasets import Planetoid
from torch_geometric.nn import GATConv

dataset = 'Cora'
path = osp.join(osp.dirname(osp.realpath(__file__)), '..', '..', 'data',
                dataset)
dataset = Planetoid(path, dataset, transform=T.NormalizeFeatures())


class GAT(torch.nn.Module):
    def __init__(self):
        super().__init__()
        self.conv1 = GATConv(dataset.num_features, 8, heads=8, dropout=0.6)

        self.conv2 = GATConv(64, dataset.num_classes, heads=1, concat=True,
                             dropout=0.6)

    def forward(self, x, edge_index):
        x = F.dropout(x, p=0.6, training=self.training)
        x = F.elu(self.conv1(x, edge_index))
        x = F.dropout(x, p=0.6, training=self.training)
        x = self.conv2(x, edge_index)
        return F.log_softmax(x, dim=1)


device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
model, data = GAT().to(device), dataset[0].to(device)
model = torch.jit.script(model)
optimizer = torch.optim.Adam(model.parameters(), lr=0.005, weight_decay=5e-4)


def train():
    model.train()
    optimizer.zero_grad()
    out = model(data.x, data.edge_index)
    loss = F.nll_loss(out[data.train_mask], data.y[data.train_mask])
    loss.backward()
    optimizer.step()
    return loss.item()


@torch.no_grad()
def test():
    model.eval()
    out, accs = model(data.x, data.edge_index), []
    for _, mask in data('train_mask', 'val_mask', 'test_mask'):
        pred = out[mask].argmax(1)
        acc = pred.eq(data.y[mask]).sum().item() / mask.sum().item()
        accs.append(acc)
    return accs


for epoch in range(1, 201):
    loss = train()
    train_acc, val_acc, test_acc = test()
    print(f'Epoch: {epoch:03d}, Loss: {loss:.4f}, '
          f'Train: {train_acc:.4f}, Val: {val_acc:.4f}, Test: {test_acc:.4f}')