import logging
import os
from collections import defaultdict
from typing import TYPE_CHECKING, Any, Dict, List

import ray
import ray._private.ray_constants as ray_constants
from ray._private.accelerators.nvidia_gpu import CUDA_VISIBLE_DEVICES_ENV_VAR
from ray._private.ray_constants import env_bool
from ray.train import BackendConfig
from ray.train.constants import ENABLE_SHARE_CUDA_VISIBLE_DEVICES_ENV
from ray.train.v2._internal.execution.callback import WorkerGroupCallback
from ray.train.v2._internal.execution.worker_group import ActorMetadata
from ray.train.v2.api.config import ScalingConfig

if TYPE_CHECKING:
    from ray.train.v2._internal.execution.worker_group.worker import Worker

logger = logging.getLogger(__name__)


class AcceleratorSetupCallback(WorkerGroupCallback):
    """Perform accelerator setup for workers.

    For example, this callback can be used to share CUDA_VISIBLE_DEVICES
    among workers on the same node.
    """

    def __init__(self, backend_config: BackendConfig, scaling_config: ScalingConfig):
        self._backend = backend_config.backend_cls()
        self._scaling_config = scaling_config

    def before_init_train_context(
        self, workers: List["Worker"]
    ) -> Dict[str, List[Any]]:
        self._maybe_share_cuda_visible_devices(workers)
        # TODO: Add support for sharing other accelerator resources.

        return {}

    def _maybe_share_cuda_visible_devices(self, workers: List["Worker"]):
        """Set CUDA visible devices environment variables on workers."""
        share_cuda_visible_devices_enabled = env_bool(
            ENABLE_SHARE_CUDA_VISIBLE_DEVICES_ENV,
            self._backend.share_cuda_visible_devices,
        )

        if (
            self._scaling_config._resources_per_worker_not_none.get("GPU", 0) > 0
            and share_cuda_visible_devices_enabled
        ):
            _share_cuda_visible_devices(workers)


def _share_cuda_visible_devices(workers: List["Worker"]):
    """Sets CUDA_VISIBLE_DEVICES on all workers.
    For each worker, CUDA_VISIBLE_DEVICES will be set to the GPU IDs
    visible to all workers on that worker's node.
    This allows GPU workers on the same node to communicate with one
    another.

    Example:
        Setup:
        - Node1:
            - Worker1: {0, 1}
            - Worker2: {2, 3}
        - Node2:
            - Worker3: {0, 1}
        CUDA_VISIBLE_DEVICES:
        - Worker1: "0,1,2,3"
        - Worker2: "0,1,2,3"
        - Worker3: "0,1"

    Args:
        workers: List of worker objects.
    """
    _share_accelerator_ids(workers, ray_constants.GPU, CUDA_VISIBLE_DEVICES_ENV_VAR)


def _share_accelerator_ids(
    workers: List["Worker"], accelerator_name: str, env_var: str
):
    """Sets the given env_var on all workers.
    For each worker, the cores/devices are visible to all the
    workers on that worker's node. This allows workers on the
    same node to communicate with one another.

    Example:
        Setup:
        - Node1:
            - Worker1: {0, 1}
            - Worker2: {2, 3}
        - Node2:
            - Worker3: {0, 1}
        NEURON_RT_VISIBLE_CORES/TPU_VISIBLE_CHIPS/...:
        - Worker1: "0,1,2,3"
        - Worker2: "0,1,2,3"
        - Worker3: "0,1"

    Args:
        workers: List of worker objects.
        accelerator_name: The name of the accelerator.
        env_var: The name of the environment variable to set.
    """
    worker_metadatas = [worker.metadata for worker in workers]
    visible_accelerator_ids_per_worker = _get_visible_accelerator_ids_per_worker(
        worker_metadatas=worker_metadatas, accelerator_name=accelerator_name
    )

    def set_accelerator_ids(accelerator_ids):
        os.environ[env_var] = accelerator_ids

    futures = []
    for rank, visible_accelerator_ids in enumerate(visible_accelerator_ids_per_worker):
        futures.append(
            workers[rank].execute_async(
                set_accelerator_ids, accelerator_ids=visible_accelerator_ids
            )
        )
    ray.get(futures)


def _get_visible_accelerator_ids_per_worker(
    worker_metadatas: List[ActorMetadata], accelerator_name: str
) -> List[str]:
    """Returns a list of comma-separated accelerator IDs visible to each worker.

    All workers on a node should have the same set of visible accelerators,
    which is the union of accelerator ids of the workers.

    Args:
        worker_metadatas: The actor metadata for each worker.
        accelerator_name: The name of the accelerator resource to inspect.

    Returns:
        A list of comma-separated accelerator ID strings. This list is the
        same length as the number of workers.
    """
    for metadata in worker_metadatas:
        if accelerator_name not in metadata.accelerator_ids:
            raise ValueError(
                f"Accelerator '{accelerator_name}' is not available on all workers. "
                f"Got these available accelerators instead: {metadata.accelerator_ids}"
            )

    node_id_to_accelerator_ids = defaultdict(set)

    for metadata in worker_metadatas:
        node_id_to_accelerator_ids[metadata.node_id].update(
            metadata.accelerator_ids[accelerator_name]
        )

    visible_accelerator_ids_per_worker = []
    for worker_id in range(len(worker_metadatas)):
        node_id = worker_metadatas[worker_id].node_id
        accelerator_ids = sorted(node_id_to_accelerator_ids[node_id])
        all_resource_ids = ",".join([str(id) for id in accelerator_ids])
        visible_accelerator_ids_per_worker.append(all_resource_ids)

    return visible_accelerator_ids_per_worker