#################################################################################
# WaterTAP Copyright (c) 2020-2023, The Regents of the University of California,
# through Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory,
# National Renewable Energy Laboratory, and National Energy Technology
# Laboratory (subject to receipt of any required approvals from the U.S. Dept.
# of Energy). All rights reserved.
#
# Please see the files COPYRIGHT.md and LICENSE.md for full copyright and license
# information, respectively. These files are also available online at the URL
# "https://github.com/watertap-org/watertap/"
#################################################################################

from pyomo.common.dependencies import attempt_import
from watertap.tools.parallel.mpi_parallel_manager import MPIParallelManager
from watertap.tools.parallel.concurrent_futures_parallel_manager import (
    ConcurrentFuturesParallelManager,
)
from watertap.tools.parallel.single_process_parallel_manager import (
    SingleProcessParallelManager,
)
from watertap.tools.parallel.multiprocessing_parallel_manager import (
    MultiprocessingParallelManager,
)


MPI, mpi4py_available = attempt_import("mpi4py.MPI", defer_check=False)
ray, ray_avaialble = attempt_import("ray", defer_check=False)
if ray_avaialble:
    from watertap.tools.parallel.ray_io_parallel_manager import (
        RayIoParallelManager,
    )


def create_parallel_manager(parallel_manager_class=None, **kwargs):
    """
    Create and return an instance of a ParallelManager, based on the libraries available in the
    runtime environment.

    Allows an optional python class to be passed in as parallel_manager_class. If so, this class
    is instantiated and returned rather than checking the local environment.
    """
    if parallel_manager_class is not None:
        return parallel_manager_class(**kwargs)

    if has_mpi_peer_processes():
        return MPIParallelManager(MPI)

    number_of_subprocesses = kwargs.get("number_of_subprocesses", 1)
    if should_fan_out(number_of_subprocesses):
        parallel_backend = kwargs.get("parallel_back_end", "ConcurrentFutures")
        if parallel_backend == "ConcurrentFutures":
            return ConcurrentFuturesParallelManager(number_of_subprocesses)
        elif parallel_backend == "MultiProcessing":
            return MultiprocessingParallelManager(number_of_subprocesses)
        elif parallel_backend == "RayIo":
            if ray_avaialble:
                return RayIoParallelManager(number_of_subprocesses)
            else:
                raise ModuleNotFoundError("Ray is not available")

        else:
            raise NotImplementedError(
                f"ParallelManager {parallel_backend} is not yet implemented"
            )

    return SingleProcessParallelManager()


def has_mpi_peer_processes():
    """
    Returns whether the process was run as part of an MPI group with > 1 processes.
    """
    return mpi4py_available and MPI.COMM_WORLD.Get_size() > 1


def should_fan_out(number_of_subprocesses):
    """
    Returns whether the manager should fan out the computation to subprocesses. This
    is mutually exclusive with the process running under MPI.
    """
    return number_of_subprocesses > 1
