#!/usr/bin/env python
# coding: utf-8
import math

from ogb.lsc import MAG240MDataset, MAG240MEvaluator
import dgl
import torch
import tqdm
import numpy as np
import dgl.nn as dglnn
import torch.nn as nn
import torch.nn.functional as F
import argparse
import dgl.multiprocessing as mp
import sys
from torch.nn.parallel import DistributedDataParallel
from collections import OrderedDict


class RGAT(nn.Module):
    def __init__(self, in_channels, out_channels, hidden_channels, num_etypes, num_layers, num_heads, dropout,
                 pred_ntype):
        super().__init__()
        self.convs = nn.ModuleList()
        self.norms = nn.ModuleList()
        self.skips = nn.ModuleList()

        self.convs.append(nn.ModuleList([
            dglnn.GATConv(in_channels, hidden_channels // num_heads, num_heads, allow_zero_in_degree=True)
            for _ in range(num_etypes)
        ]))
        self.norms.append(nn.BatchNorm1d(hidden_channels))
        self.skips.append(nn.Linear(in_channels, hidden_channels))
        for _ in range(num_layers - 1):
            self.convs.append(nn.ModuleList([
                dglnn.GATConv(hidden_channels, hidden_channels // num_heads, num_heads, allow_zero_in_degree=True)
                for _ in range(num_etypes)
            ]))
            self.norms.append(nn.BatchNorm1d(hidden_channels))
            self.skips.append(nn.Linear(hidden_channels, hidden_channels))

        self.mlp = nn.Sequential(
            nn.Linear(hidden_channels, hidden_channels),
            nn.BatchNorm1d(hidden_channels),
            nn.ReLU(),
            nn.Dropout(dropout),
            nn.Linear(hidden_channels, out_channels)
        )
        self.dropout = nn.Dropout(dropout)

        self.hidden_channels = hidden_channels
        self.pred_ntype = pred_ntype
        self.num_etypes = num_etypes

    def forward(self, mfgs, x):
        for i in range(len(mfgs)):
            mfg = mfgs[i]
            x_dst = x[:mfg.num_dst_nodes()]
            n_src = mfg.num_src_nodes()
            n_dst = mfg.num_dst_nodes()
            mfg = dgl.block_to_graph(mfg)
            x_skip = self.skips[i](x_dst)
            for j in range(self.num_etypes):
                subg = mfg.edge_subgraph(mfg.edata['etype'] == j, relabel_nodes=False)
                x_skip += self.convs[i][j](subg, (x, x_dst)).view(-1, self.hidden_channels)
            x = self.norms[i](x_skip)
            x = F.elu(x)
            x = self.dropout(x)
        return self.mlp(x)


class ExternalNodeCollator(dgl.dataloading.NodeCollator):
    def __init__(self, g, idx, sampler, offset, feats, label):
        super().__init__(g, idx, sampler)
        self.offset = offset
        self.feats = feats
        self.label = label

    def collate(self, items):
        input_nodes, output_nodes, mfgs = super().collate(items)
        # Copy input features
        mfgs[0].srcdata['x'] = torch.FloatTensor(self.feats[input_nodes])
        mfgs[-1].dstdata['y'] = torch.LongTensor(self.label[output_nodes - self.offset])
        return input_nodes, output_nodes, mfgs


def train(proc_id, n_gpus, args, dataset, g, feats, paper_offset):
    dev_id = devices[proc_id]
    if n_gpus > 1:
        dist_init_method = 'tcp://{master_ip}:{master_port}'.format(
            master_ip='127.0.0.1', master_port='12346')
        world_size = n_gpus
        torch.distributed.init_process_group(backend='nccl',
                                             init_method=dist_init_method,
                                             world_size=world_size,
                                             rank=proc_id)

    torch.cuda.set_device(dev_id)

    print('Loading masks and labels')
    train_idx = torch.LongTensor(dataset.get_idx_split('train')) + paper_offset
    valid_idx = torch.LongTensor(dataset.get_idx_split('valid')) + paper_offset
    label = dataset.paper_label

    print('Initializing dataloader...')
    sampler = dgl.dataloading.MultiLayerNeighborSampler([15, 25])

    train_collator = ExternalNodeCollator(g, train_idx, sampler, paper_offset, feats, label)
    valid_collator = ExternalNodeCollator(g, valid_idx, sampler, paper_offset, feats, label)
    # Necessary according to https://yangkky.github.io/2019/07/08/distributed-pytorch-tutorial.html
    train_sampler = torch.utils.data.distributed.DistributedSampler(
        train_collator.dataset, num_replicas=world_size, rank=proc_id, shuffle=True, drop_last=False)
    valid_sampler = torch.utils.data.distributed.DistributedSampler(
        valid_collator.dataset, num_replicas=world_size, rank=proc_id, shuffle=True, drop_last=False)

    train_dataloader = torch.utils.data.DataLoader(
        train_collator.dataset,
        batch_size=1024,
        collate_fn=train_collator.collate,
        num_workers=4,
        sampler=train_sampler
    )

    valid_dataloader = torch.utils.data.DataLoader(
        valid_collator.dataset,
        batch_size=1024,
        collate_fn=valid_collator.collate,
        num_workers=2,
        sampler=valid_sampler
    )

    print('Initializing model...')
    model = RGAT(dataset.num_paper_features, dataset.num_classes, 1024, 5, 2, 4, 0.5, 'paper').to(dev_id)

    # convert BN to SyncBatchNorm. see https://pytorch.org/docs/stable/generated/torch.nn.SyncBatchNorm.html
    model = nn.SyncBatchNorm.convert_sync_batchnorm(model)

    model = DistributedDataParallel(model, device_ids=[dev_id], output_device=dev_id)
    opt = torch.optim.Adam(model.parameters(), lr=0.001)
    sched = torch.optim.lr_scheduler.StepLR(opt, step_size=25, gamma=0.25)

    best_acc = 0

    for i in range(args.epochs):
        # make shuffling work properly across multiple epochs.
        # see https://pytorch.org/docs/stable/data.html#torch.utils.data.distributed.DistributedSampler
        train_sampler.set_epoch(i)
        model.train()
        with tqdm.tqdm(train_dataloader) as tq:
            for i, (input_nodes, output_nodes, mfgs) in enumerate(tq):
                mfgs = [g.to(dev_id) for g in mfgs]
                x = mfgs[0].srcdata['x']
                y = mfgs[-1].dstdata['y']
                y_hat = model(mfgs, x)
                loss = F.cross_entropy(y_hat, y)
                opt.zero_grad()
                loss.backward()
                opt.step()
                acc = (y_hat.argmax(1) == y).float().mean()
                tq.set_postfix({'loss': '%.4f' % loss.item(), 'acc': '%.4f' % acc.item()}, refresh=False)

        # eval in each process
        model.eval()
        correct = torch.LongTensor([0]).to(dev_id)
        total = torch.LongTensor([0]).to(dev_id)
        for i, (input_nodes, output_nodes, mfgs) in enumerate(tqdm.tqdm(valid_dataloader)):
            with torch.no_grad():
                mfgs = [g.to(dev_id) for g in mfgs]
                x = mfgs[0].srcdata['x']
                y = mfgs[-1].dstdata['y']
                y_hat = model(mfgs, x)
                correct += (y_hat.argmax(1) == y).sum().item()
                total += y_hat.shape[0]

        # `reduce` data into process 0
        torch.distributed.reduce(correct, dst=0, op=torch.distributed.ReduceOp.SUM)
        torch.distributed.reduce(total, dst=0, op=torch.distributed.ReduceOp.SUM)
        acc = (correct / total).item()

        sched.step()

        # process 0 print accuracy and save model
        if proc_id == 0:
            print('Validation accuracy:', acc)

            if best_acc < acc:
                best_acc = acc
                print('Updating best model...')
                torch.save(model.state_dict(), args.model_path)


def test(args, dataset, g, feats, paper_offset):
    print('Loading masks and labels...')
    valid_idx = torch.LongTensor(dataset.get_idx_split('valid')) + paper_offset
    test_idx = torch.LongTensor(dataset.get_idx_split('test')) + paper_offset
    label = dataset.paper_label

    print('Initializing data loader...')
    sampler = dgl.dataloading.MultiLayerNeighborSampler([160, 160])
    valid_collator = ExternalNodeCollator(g, valid_idx, sampler, paper_offset, feats, label)
    valid_dataloader = torch.utils.data.DataLoader(
        valid_collator.dataset,
        batch_size=16,
        shuffle=False,
        drop_last=False,
        collate_fn=valid_collator.collate,
        num_workers=2
    )
    test_collator = ExternalNodeCollator(g, test_idx, sampler, paper_offset, feats, label)
    test_dataloader = torch.utils.data.DataLoader(
        test_collator.dataset,
        batch_size=16,
        shuffle=False,
        drop_last=False,
        collate_fn=test_collator.collate,
        num_workers=4
    )

    print('Loading model...')
    model = RGAT(dataset.num_paper_features, dataset.num_classes, 1024, 5, 2, 4, 0.5, 'paper').cuda()

    # load ddp's model parameters, we need to remove the name of 'module.'
    state_dict = torch.load(args.model_path)
    new_state_dict = OrderedDict()
    for k, v in state_dict.items():
        name = k[7:]
        new_state_dict[name] = v
    model.load_state_dict(new_state_dict)

    model.eval()
    correct = total = 0
    for i, (input_nodes, output_nodes, mfgs) in enumerate(tqdm.tqdm(valid_dataloader)):
        with torch.no_grad():
            mfgs = [g.to('cuda') for g in mfgs]
            x = mfgs[0].srcdata['x']
            y = mfgs[-1].dstdata['y']
            y_hat = model(mfgs, x)
            correct += (y_hat.argmax(1) == y).sum().item()
            total += y_hat.shape[0]
    acc = correct / total
    print('Validation accuracy:', acc)
    evaluator = MAG240MEvaluator()
    y_preds = []
    for i, (input_nodes, output_nodes, mfgs) in enumerate(tqdm.tqdm(test_dataloader)):
        with torch.no_grad():
            mfgs = [g.to('cuda') for g in mfgs]
            x = mfgs[0].srcdata['x']
            y = mfgs[-1].dstdata['y']
            y_hat = model(mfgs, x)
            y_preds.append(y_hat.argmax(1).cpu())
    evaluator.save_test_submission({'y_pred': torch.cat(y_preds)}, args.submission_path)


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('--rootdir', type=str, default='.', help='Directory to download the OGB dataset.')
    parser.add_argument('--graph-path', type=str, default='./graph.dgl', help='Path to the graph.')
    parser.add_argument('--full-feature-path', type=str, default='./full.npy',
                        help='Path to the features of all nodes.')
    parser.add_argument('--epochs', type=int, default=100, help='Number of epochs.')
    parser.add_argument('--model-path', type=str, default='./model_ddp.pt', help='Path to store the best model.')
    parser.add_argument('--submission-path', type=str, default='./results_ddp', help='Submission directory.')
    parser.add_argument('--gpus', type=str, default='0,1,2')
    args = parser.parse_args()

    devices = list(map(int, args.gpus.split(',')))
    n_gpus = len(devices)

    if n_gpus <= 1:
        print("make sure the number of gpus greater than 1!")
        sys.exit()

    dataset = MAG240MDataset(root=args.rootdir)

    print('Loading graph')
    (g,), _ = dgl.load_graphs(args.graph_path)
    g = g.formats(['csc'])

    print('Loading features')
    paper_offset = dataset.num_authors + dataset.num_institutions
    num_nodes = paper_offset + dataset.num_papers
    num_features = dataset.num_paper_features
    feats = np.memmap(args.full_feature_path, mode='r', dtype='float16', shape=(num_nodes, num_features))

    procs = []
    for proc_id in range(n_gpus):
        p = mp.Process(target=train, args=(proc_id, n_gpus, args, dataset, g, feats, paper_offset))
        p.start()
        procs.append(p)

    for p in procs:
        p.join()

    test(args, dataset, g, feats, paper_offset)
