#!/usr/bin/env python
# -*- encoding: utf-8 -*-

import os
from pathlib import Path

import pytest
import torch
import torch.distributed as dist
from torchvision import datasets, transforms

import colossalai
from colossalai.context import Config, ParallelMode
from colossalai.core import global_context as gpc
from colossalai.testing import rerun_if_address_is_in_use, spawn
from colossalai.utils import get_dataloader

CONFIG = Config(
    dict(
        train_data=dict(
            dataset=dict(
                type='CIFAR10',
                root=Path(os.environ['DATA']),
                train=True,
                download=True,
            ),
            dataloader=dict(num_workers=2, batch_size=2, shuffle=True),
        ),
        parallel=dict(
            pipeline=dict(size=1),
            tensor=dict(size=1, mode=None),
        ),
        seed=1024,
    ))


def run_data_sampler(rank, world_size, port):
    dist_args = dict(config=CONFIG, rank=rank, world_size=world_size, backend='gloo', port=port, host='localhost')
    colossalai.launch(**dist_args)

    # build dataset
    transform_pipeline = [transforms.ToTensor(), transforms.RandomCrop(size=32, padding=4)]
    transform_pipeline = transforms.Compose(transform_pipeline)
    dataset = datasets.CIFAR10(root=Path(os.environ['DATA']), train=True, download=True, transform=transform_pipeline)

    # build dataloader
    dataloader = get_dataloader(dataset, batch_size=8, add_sampler=False)

    data_iter = iter(dataloader)
    img, label = data_iter.next()
    img = img[0]

    if gpc.get_local_rank(ParallelMode.DATA) != 0:
        img_to_compare = img.clone()
    else:
        img_to_compare = img
    dist.broadcast(img_to_compare, src=0, group=gpc.get_group(ParallelMode.DATA))

    if gpc.get_local_rank(ParallelMode.DATA) != 0:
        # this is without sampler
        # this should be false if data parallel sampler to given to the dataloader
        assert torch.equal(img,
                           img_to_compare), 'Same image was distributed across ranks and expected it to be the same'
    torch.cuda.empty_cache()


@pytest.mark.cpu
@rerun_if_address_is_in_use()
def test_data_sampler():
    spawn(run_data_sampler, 4)


if __name__ == '__main__':
    test_data_sampler()
