import argparse
import dgl
import numpy as np
import os
import random
import torch
import torch.optim as optim
from ogb.lsc import DglPCQM4MDataset, PCQM4MEvaluator
from torch.utils.data import DataLoader
from torch.utils.tensorboard import SummaryWriter
from torch.optim.lr_scheduler import StepLR
from tqdm import tqdm

from gnn import GNN

reg_criterion = torch.nn.L1Loss()


def collate_dgl(samples):
    graphs, labels = map(list, zip(*samples))
    batched_graph = dgl.batch(graphs)
    labels = torch.stack(labels)

    return batched_graph, labels


def train(model, device, loader, optimizer):
    model.train()
    loss_accum = 0

    for step, (bg, labels) in enumerate(tqdm(loader, desc="Iteration")):
        bg = bg.to(device)
        x = bg.ndata.pop('feat')
        edge_attr = bg.edata.pop('feat')
        labels = labels.to(device)

        pred = model(bg, x, edge_attr).view(-1,)
        optimizer.zero_grad()
        loss = reg_criterion(pred, labels)
        loss.backward()
        optimizer.step()

        loss_accum += loss.detach().cpu().item()

    return loss_accum / (step + 1)


def eval(model, device, loader, evaluator):
    model.eval()
    y_true = []
    y_pred = []

    for step, (bg, labels) in enumerate(tqdm(loader, desc="Iteration")):
        bg = bg.to(device)
        x = bg.ndata.pop('feat')
        edge_attr = bg.edata.pop('feat')
        labels = labels.to(device)

        with torch.no_grad():
            pred = model(bg, x, edge_attr).view(-1, )

        y_true.append(labels.view(pred.shape).detach().cpu())
        y_pred.append(pred.detach().cpu())

    y_true = torch.cat(y_true, dim=0)
    y_pred = torch.cat(y_pred, dim=0)

    input_dict = {"y_true": y_true, "y_pred": y_pred}

    return evaluator.eval(input_dict)["mae"]


def test(model, device, loader):
    model.eval()
    y_pred = []

    for step, (bg, _) in enumerate(tqdm(loader, desc="Iteration")):
        bg = bg.to(device)
        x = bg.ndata.pop('feat')
        edge_attr = bg.edata.pop('feat')

        with torch.no_grad():
            pred = model(bg, x, edge_attr).view(-1, )

        y_pred.append(pred.detach().cpu())

    y_pred = torch.cat(y_pred, dim=0)

    return y_pred


def main():
    # Training settings
    parser = argparse.ArgumentParser(description='GNN baselines on pcqm4m with DGL')
    parser.add_argument('--seed', type=int, default=42,
                        help='random seed to use (default: 42)')
    parser.add_argument('--device', type=int, default=0,
                        help='which gpu to use if any (default: 0)')
    parser.add_argument('--gnn', type=str, default='gin-virtual',
                        help='GNN to use, which can be from '
                             '[gin, gin-virtual, gcn, gcn-virtual] (default: gin-virtual)')
    parser.add_argument('--graph_pooling', type=str, default='sum',
                        help='graph pooling strategy mean or sum (default: sum)')
    parser.add_argument('--drop_ratio', type=float, default=0,
                        help='dropout ratio (default: 0)')
    parser.add_argument('--num_layers', type=int, default=5,
                        help='number of GNN message passing layers (default: 5)')
    parser.add_argument('--emb_dim', type=int, default=600,
                        help='dimensionality of hidden units in GNNs (default: 600)')
    parser.add_argument('--train_subset', action='store_true',
                        help='use 10% of the training set for training')
    parser.add_argument('--batch_size', type=int, default=256,
                        help='input batch size for training (default: 256)')
    parser.add_argument('--epochs', type=int, default=100,
                        help='number of epochs to train (default: 100)')
    parser.add_argument('--num_workers', type=int, default=4,
                        help='number of workers (default: 4)')
    parser.add_argument('--log_dir', type=str, default="",
                        help='tensorboard log directory. If not specified, '
                             'tensorboard will not be used.')
    parser.add_argument('--checkpoint_dir', type=str, default='',
                        help='directory to save checkpoint')
    parser.add_argument('--save_test_dir', type=str, default='',
                        help='directory to save test submission file')
    args = parser.parse_args()

    print(args)

    np.random.seed(args.seed)
    torch.manual_seed(args.seed)
    random.seed(args.seed)

    if torch.cuda.is_available():
        torch.cuda.manual_seed(args.seed)
        device = torch.device("cuda:" + str(args.device))
    else:
        device = torch.device("cpu")

    ### automatic dataloading and splitting
    dataset = DglPCQM4MDataset(root='dataset/')

    # split_idx['train'], split_idx['valid'], split_idx['test']
    # separately gives a 1D int64 tensor
    split_idx = dataset.get_idx_split()

    ### automatic evaluator.
    evaluator = PCQM4MEvaluator()

    if args.train_subset:
        subset_ratio = 0.1
        subset_idx = torch.randperm(len(split_idx["train"]))[:int(subset_ratio * len(split_idx["train"]))]
        train_loader = DataLoader(dataset[split_idx["train"][subset_idx]], batch_size=args.batch_size, shuffle=True,
                                  num_workers=args.num_workers, collate_fn=collate_dgl)
    else:
        train_loader = DataLoader(dataset[split_idx["train"]], batch_size=args.batch_size, shuffle=True,
                                  num_workers=args.num_workers, collate_fn=collate_dgl)

    valid_loader = DataLoader(dataset[split_idx["valid"]], batch_size=args.batch_size, shuffle=False,
                              num_workers=args.num_workers, collate_fn=collate_dgl)

    if args.save_test_dir is not '':
        test_loader = DataLoader(dataset[split_idx["test"]], batch_size=args.batch_size, shuffle=False,
                                 num_workers=args.num_workers, collate_fn=collate_dgl)

    if args.checkpoint_dir is not '':
        os.makedirs(args.checkpoint_dir, exist_ok=True)

    shared_params = {
        'num_layers': args.num_layers,
        'emb_dim': args.emb_dim,
        'drop_ratio': args.drop_ratio,
        'graph_pooling': args.graph_pooling
    }

    if args.gnn == 'gin':
        model = GNN(gnn_type='gin', virtual_node=False, **shared_params).to(device)
    elif args.gnn == 'gin-virtual':
        model = GNN(gnn_type='gin', virtual_node=True, **shared_params).to(device)
    elif args.gnn == 'gcn':
        model = GNN(gnn_type='gcn', virtual_node=False, **shared_params).to(device)
    elif args.gnn == 'gcn-virtual':
        model = GNN(gnn_type='gcn', virtual_node=True, **shared_params).to(device)
    else:
        raise ValueError('Invalid GNN type')

    num_params = sum(p.numel() for p in model.parameters())
    print(f'#Params: {num_params}')

    optimizer = optim.Adam(model.parameters(), lr=0.001)

    if args.log_dir is not '':
        writer = SummaryWriter(log_dir=args.log_dir)

    best_valid_mae = 1000

    if args.train_subset:
        scheduler = StepLR(optimizer, step_size=300, gamma=0.25)
        args.epochs = 1000
    else:
        scheduler = StepLR(optimizer, step_size=30, gamma=0.25)

    for epoch in range(1, args.epochs + 1):
        print("=====Epoch {}".format(epoch))
        print('Training...')
        train_mae = train(model, device, train_loader, optimizer)

        print('Evaluating...')
        valid_mae = eval(model, device, valid_loader, evaluator)

        print({'Train': train_mae, 'Validation': valid_mae})

        if args.log_dir is not '':
            writer.add_scalar('valid/mae', valid_mae, epoch)
            writer.add_scalar('train/mae', train_mae, epoch)

        if valid_mae < best_valid_mae:
            best_valid_mae = valid_mae
            if args.checkpoint_dir is not '':
                print('Saving checkpoint...')
                checkpoint = {'epoch': epoch, 'model_state_dict': model.state_dict(),
                              'optimizer_state_dict': optimizer.state_dict(),
                              'scheduler_state_dict': scheduler.state_dict(), 'best_val_mae': best_valid_mae,
                              'num_params': num_params}
                torch.save(checkpoint, os.path.join(args.checkpoint_dir, 'checkpoint.pt'))

            if args.save_test_dir is not '':
                print('Predicting on test data...')
                y_pred = test(model, device, test_loader)
                print('Saving test submission file...')
                evaluator.save_test_submission({'y_pred': y_pred}, args.save_test_dir)

        scheduler.step()

        print(f'Best validation MAE so far: {best_valid_mae}')

    if args.log_dir is not '':
        writer.close()

if __name__ == "__main__":
    main()
