import pytest
import colossalai
import torch
import torch.multiprocessing as mp
import torch.distributed as dist
from colossalai.testing import rerun_if_address_is_in_use
from colossalai.utils.cuda import get_current_device
from colossalai.utils import free_port
from colossalai.utils.model.colo_init_context import ColoInitContext

from functools import partial
from tests.test_tensor.common_utils import tensor_equal, set_seed, tensor_shard_equal
from tests.components_to_test.registry import non_distributed_component_funcs
from torch.nn.parallel import DistributedDataParallel as DDP
from colossalai.nn.parallel import ZeroDDP
from colossalai.nn.optimizer import HybridAdam
from colossalai.zero import ZeroOptimizer
from colossalai.testing import parameterize
from colossalai.amp import convert_to_apex_amp
from colossalai.gemini.gemini_mgr import GeminiManager
from tests.test_tensor.common_utils import debug_print

from time import time
from colossalai.gemini.chunk import search_chunk_configuration, ChunkManager


def check_param(model: ZeroDDP, torch_model: torch.nn.Module):
    zero_dict = model.state_dict(only_rank_0=False)
    torch_dict = torch_model.state_dict()

    for key, value in torch_dict.items():
        # key is 'module.model.PARAMETER', so we truncate it
        key = key[7:]
        if key == 'model.lm_head.weight':
            continue
        assert key in zero_dict, "{} not in ZeRO dictionary.".format(key)
        temp_zero_value = zero_dict[key].to(device=value.device, dtype=value.dtype)
        # debug_print([0], "max range: ", key, torch.max(torch.abs(value - temp_zero_value)))
        assert torch.allclose(value, temp_zero_value, rtol=1e-3, atol=1e-2), "parameter '{}' has problem.".format(key)


def run_fwd_bwd(model, criterion, optimizer, input_ids, attn_mask):
    optimizer.zero_grad()
    logits = model(input_ids, attn_mask)
    logits = logits.float()
    loss = criterion(logits, input_ids)
    optimizer.backward(loss)
    return logits


@parameterize('placement_policy', ['cuda', 'cpu', 'auto'])
def exam_gpt_fwd_bwd(placement_policy):
    set_seed(42)
    get_components_func = non_distributed_component_funcs.get_callable('gpt2')
    model_builder, train_dataloader, test_dataloader, optimizer_class, criterion = get_components_func()

    with ColoInitContext(device=get_current_device()):
        model = model_builder()

    torch_model = model_builder().cuda()
    for torch_p, p in zip(torch_model.parameters(), model.parameters()):
        torch_p.data.copy_(p.data)

    world_size = torch.distributed.get_world_size()
    config_dict = search_chunk_configuration(model, search_range_mb=1, search_interval_byte=100)
    config_dict[world_size]['chunk_size'] = 5000
    config_dict[world_size]['keep_gathered'] = False
    if placement_policy != 'cuda':
        init_device = torch.device('cpu')
    else:
        init_device = None
    chunk_manager = ChunkManager(config_dict, init_device=init_device)
    gemini_manager = GeminiManager(placement_policy, chunk_manager)
    model = ZeroDDP(model, gemini_manager, pin_memory=True)

    optimizer = HybridAdam(model.parameters(), lr=1e-3)
    zero_optim = ZeroOptimizer(optimizer, model, initial_scale=2)

    amp_config = dict(opt_level='O2', keep_batchnorm_fp32=False, loss_scale=1)
    torch_optim = torch.optim.Adam(torch_model.parameters(), lr=1e-3)
    torch_model, torch_optim = convert_to_apex_amp(torch_model, torch_optim, amp_config)
    torch_model = DDP(torch_model, device_ids=[dist.get_rank()])

    model.eval()
    torch_model.eval()

    set_seed(dist.get_rank() * 3 + 128)
    for i, (input_ids, attn_mask) in enumerate(train_dataloader):
        if i > 2:
            break

        zero_logits = run_fwd_bwd(model, criterion, zero_optim, input_ids, attn_mask)
        torch_logits = run_fwd_bwd(torch_model, criterion, torch_optim, input_ids, attn_mask)
        assert torch.allclose(zero_logits, torch_logits, rtol=1e-3, atol=1e-2)
        # debug_print([0], zero_logits, torch_logits)

        zero_optim.step()
        torch_optim.step()

        check_param(model, torch_model)


def run_dist(rank, world_size, port):
    config = {}
    colossalai.launch(config=config, rank=rank, world_size=world_size, host='localhost', port=port, backend='nccl')
    exam_gpt_fwd_bwd()


@pytest.mark.dist
@pytest.mark.parametrize('world_size', [1, 4])
@rerun_if_address_is_in_use()
def test_gpt(world_size):
    run_func = partial(run_dist, world_size=world_size, port=free_port())
    mp.spawn(run_func, nprocs=world_size)


if __name__ == '__main__':
    test_gpt(1)
