import dgl
import numpy as np
import torch as th
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
import dgl.multiprocessing as mp
import dgl.function as fn
import dgl.nn.pytorch as dglnn
import time
import argparse
from dgl.data import RedditDataset
from torch.nn.parallel import DistributedDataParallel
import tqdm

from model import SAGE, compute_acc_unsupervised as compute_acc
from negative_sampler import NegativeSampler

class CrossEntropyLoss(nn.Module):
    def forward(self, block_outputs, pos_graph, neg_graph):
        with pos_graph.local_scope():
            pos_graph.ndata['h'] = block_outputs
            pos_graph.apply_edges(fn.u_dot_v('h', 'h', 'score'))
            pos_score = pos_graph.edata['score']
        with neg_graph.local_scope():
            neg_graph.ndata['h'] = block_outputs
            neg_graph.apply_edges(fn.u_dot_v('h', 'h', 'score'))
            neg_score = neg_graph.edata['score']

        score = th.cat([pos_score, neg_score])
        label = th.cat([th.ones_like(pos_score), th.zeros_like(neg_score)]).long()
        loss = F.binary_cross_entropy_with_logits(score, label.float())
        return loss

def evaluate(model, g, nfeat, labels, train_nids, val_nids, test_nids, device):
    """
    Evaluate the model on the validation set specified by ``val_mask``.
    g : The entire graph.
    inputs : The features of all the nodes.
    labels : The labels of all the nodes.
    val_mask : A 0-1 mask indicating which nodes do we actually compute the accuracy for.
    device : The GPU device to evaluate on.
    """
    model.eval()
    with th.no_grad():
        # single gpu
        if isinstance(model, SAGE):
            pred = model.inference(g, nfeat, device, args.batch_size, args.num_workers)
        # multi gpu
        else:
            pred = model.module.inference(g, nfeat, device, args.batch_size, args.num_workers)
    model.train()
    return compute_acc(pred, labels, train_nids, val_nids, test_nids)

#### Entry point
def run(proc_id, n_gpus, args, devices, data):
    # Unpack data
    device = devices[proc_id]
    if n_gpus > 1:
        dist_init_method = 'tcp://{master_ip}:{master_port}'.format(
            master_ip='127.0.0.1', master_port='12345')
        world_size = n_gpus
        th.distributed.init_process_group(backend="nccl",
                                          init_method=dist_init_method,
                                          world_size=world_size,
                                          rank=proc_id)
    train_mask, val_mask, test_mask, n_classes, g = data
    nfeat = g.ndata.pop('feat')
    labels = g.ndata.pop('label')
    in_feats = nfeat.shape[1]

    train_nid = th.LongTensor(np.nonzero(train_mask)).squeeze()
    val_nid = th.LongTensor(np.nonzero(val_mask)).squeeze()
    test_nid = th.LongTensor(np.nonzero(test_mask)).squeeze()

    # Create PyTorch DataLoader for constructing blocks
    n_edges = g.num_edges()
    train_seeds = th.arange(n_edges)

    # Create sampler
    sampler = dgl.dataloading.MultiLayerNeighborSampler(
        [int(fanout) for fanout in args.fan_out.split(',')])
    dataloader = dgl.dataloading.EdgeDataLoader(
        g, train_seeds, sampler, exclude='reverse_id',
        # For each edge with ID e in Reddit dataset, the reverse edge is e ± |E|/2.
        reverse_eids=th.cat([
            th.arange(n_edges // 2, n_edges),
            th.arange(0, n_edges // 2)]).to(train_seeds),
        negative_sampler=NegativeSampler(g, args.num_negs, args.neg_share),
        device=device,
        use_ddp=n_gpus > 1,
        batch_size=args.batch_size,
        shuffle=True,
        drop_last=False,
        num_workers=args.num_workers)

    # Define model and optimizer
    model = SAGE(in_feats, args.num_hidden, args.num_hidden, args.num_layers, F.relu, args.dropout)
    model = model.to(device)
    if n_gpus > 1:
        model = DistributedDataParallel(model, device_ids=[device], output_device=device)
    loss_fcn = CrossEntropyLoss()
    optimizer = optim.Adam(model.parameters(), lr=args.lr)

    # Training loop
    avg = 0
    iter_pos = []
    iter_neg = []
    iter_d = []
    iter_t = []
    best_eval_acc = 0
    best_test_acc = 0
    for epoch in range(args.num_epochs):
        if n_gpus > 1:
            dataloader.set_epoch(epoch)
        tic = time.time()

        # Loop over the dataloader to sample the computation dependency graph as a list of
        # blocks.

        tic_step = time.time()
        for step, (input_nodes, pos_graph, neg_graph, blocks) in enumerate(dataloader):
            batch_inputs = nfeat[input_nodes].to(device)
            d_step = time.time()

            pos_graph = pos_graph.to(device)
            neg_graph = neg_graph.to(device)
            blocks = [block.int().to(device) for block in blocks]
            # Compute loss and prediction
            batch_pred = model(blocks, batch_inputs)
            loss = loss_fcn(batch_pred, pos_graph, neg_graph)
            optimizer.zero_grad()
            loss.backward()
            optimizer.step()

            t = time.time()
            pos_edges = pos_graph.num_edges()
            neg_edges = neg_graph.num_edges()
            iter_pos.append(pos_edges / (t - tic_step))
            iter_neg.append(neg_edges / (t - tic_step))
            iter_d.append(d_step - tic_step)
            iter_t.append(t - d_step)
            if step % args.log_every == 0:
                gpu_mem_alloc = th.cuda.max_memory_allocated() / 1000000 if th.cuda.is_available() else 0
                print('[{}]Epoch {:05d} | Step {:05d} | Loss {:.4f} | Speed (samples/sec) {:.4f}|{:.4f} | Load {:.4f}| train {:.4f} | GPU {:.1f} MB'.format(
                    proc_id, epoch, step, loss.item(), np.mean(iter_pos[3:]), np.mean(iter_neg[3:]), np.mean(iter_d[3:]), np.mean(iter_t[3:]), gpu_mem_alloc))
            tic_step = time.time()

            if step % args.eval_every == 0 and proc_id == 0:
                eval_acc, test_acc = evaluate(model, g, nfeat, labels, train_nid, val_nid, test_nid, device)
                print('Eval Acc {:.4f} Test Acc {:.4f}'.format(eval_acc, test_acc))
                if eval_acc > best_eval_acc:
                    best_eval_acc = eval_acc
                    best_test_acc = test_acc
                print('Best Eval Acc {:.4f} Test Acc {:.4f}'.format(best_eval_acc, best_test_acc))
        toc = time.time()
        if proc_id == 0:
            print('Epoch Time(s): {:.4f}'.format(toc - tic))
        if epoch >= 5:
            avg += toc - tic
        if n_gpus > 1:
            th.distributed.barrier()

    if proc_id == 0:
        print('Avg epoch time: {}'.format(avg / (epoch - 4)))

def main(args, devices):
    # load reddit data
    data = RedditDataset(self_loop=False)
    n_classes = data.num_classes
    g = data[0]
    train_mask = g.ndata['train_mask']
    val_mask = g.ndata['val_mask']
    test_mask = g.ndata['test_mask']

    # Create csr/coo/csc formats before launching training processes with multi-gpu.
    # This avoids creating certain formats in each sub-process, which saves memory and CPU.
    g.create_formats_()
    # Pack data
    data = train_mask, val_mask, test_mask, n_classes, g

    n_gpus = len(devices)
    if devices[0] == -1:
        run(0, 0, args, ['cpu'], data)
    elif n_gpus == 1:
        run(0, n_gpus, args, devices, data)
    else:
        procs = []
        for proc_id in range(n_gpus):
            p = mp.Process(target=run, args=(proc_id, n_gpus, args, devices, data))
            p.start()
            procs.append(p)
        for p in procs:
            p.join()


if __name__ == '__main__':
    argparser = argparse.ArgumentParser("multi-gpu training")
    argparser.add_argument("--gpu", type=str, default='0',
                           help="GPU, can be a list of gpus for multi-gpu training,"
                                " e.g., 0,1,2,3; -1 for CPU")
    argparser.add_argument('--num-epochs', type=int, default=20)
    argparser.add_argument('--num-hidden', type=int, default=16)
    argparser.add_argument('--num-layers', type=int, default=2)
    argparser.add_argument('--num-negs', type=int, default=1)
    argparser.add_argument('--neg-share', default=False, action='store_true',
                           help="sharing neg nodes for positive nodes")
    argparser.add_argument('--fan-out', type=str, default='10,25')
    argparser.add_argument('--batch-size', type=int, default=10000)
    argparser.add_argument('--log-every', type=int, default=20)
    argparser.add_argument('--eval-every', type=int, default=1000)
    argparser.add_argument('--lr', type=float, default=0.003)
    argparser.add_argument('--dropout', type=float, default=0.5)
    argparser.add_argument('--num-workers', type=int, default=0,
                           help="Number of sampling processes. Use 0 for no extra process.")
    args = argparser.parse_args()

    devices = list(map(int, args.gpu.split(',')))

    main(args, devices)
