from typing import Optional

import torch
from vllm.distributed.parallel_state import (GroupCoordinator, get_world_group,
                                             init_model_parallel_group)

# vllm-ascend will maintain its own EP GroupCoordinator and ETP GroupCoordinator for
# customize parallel solution
_EP: Optional[GroupCoordinator] = None
_ETP: Optional[GroupCoordinator] = None


def get_ep_group() -> GroupCoordinator:
    assert _EP is not None, ("expert model parallel group is not initialized")
    return _EP


def get_etp_group() -> GroupCoordinator:
    assert _ETP is not None, (
        "expert tensor parallel group is not initialized")
    return _ETP


def init_ascend_model_parallel(
    tensor_model_parallel_size: int = 1,
    pipeline_model_parallel_size: int = 1,
    expert_tensor_parallel_size: int = 1,
    backend: Optional[str] = None,
):
    assert torch.distributed.is_initialized()
    world_size: int = torch.distributed.get_world_size()
    backend = backend or torch.distributed.get_backend(
        get_world_group().device_group)
    num_expert_parallel_groups: int = expert_tensor_parallel_size
    num_expert_tensor_parallel_groups: int = (world_size //
                                              expert_tensor_parallel_size)

    global _EP
    group_ranks = []
    for i in range(num_expert_parallel_groups):
        ranks = list(range(i, world_size, num_expert_parallel_groups))
        group_ranks.append(ranks)

    _EP = init_model_parallel_group(group_ranks,
                                    get_world_group().local_rank,
                                    backend,
                                    group_name="ep")

    group_ranks = []
    global _ETP
    for i in range(num_expert_tensor_parallel_groups):
        ranks = list(
            range(i * expert_tensor_parallel_size,
                  (i + 1) * expert_tensor_parallel_size))
        group_ranks.append(ranks)

    _ETP = init_model_parallel_group(group_ranks,
                                     get_world_group().local_rank,
                                     backend,
                                     group_name="etp")


def destory_ascend_model_parallel():
    global _EP
    if _EP:
        _EP.destroy()
    _EP = None

    global _ETP
    if _ETP:
        _ETP.destroy()
    _ETP = None