"""Funcationality for performing virtualenv installation"""
# Silence this one globally to support the internal function imports for the proxied poetry module.
# See the docstring in 'tox_poetry_installer._poetry' for more context.
# pylint: disable=import-outside-toplevel
import concurrent.futures
import contextlib
import typing
from datetime import datetime
from typing import Collection
from typing import Set

from poetry.core.packages.package import Package as PoetryPackage
from tox.tox_env.api import ToxEnv as ToxVirtualEnv

from tox_poetry_installer import logger
from tox_poetry_installer import utilities

if typing.TYPE_CHECKING:
    from tox_poetry_installer import _poetry


def install(
    poetry: "_poetry.Poetry",
    venv: ToxVirtualEnv,
    packages: Collection[PoetryPackage],
    parallels: int = 0,
):
    """Install a bunch of packages to a virtualenv

    :param poetry: Poetry object the packages were sourced from
    :param venv: Tox virtual environment to install the packages to
    :param packages: List of packages to install to the virtual environment
    :param parallels: Number of parallel processes to use for installing dependency packages, or
                      ``None`` to disable parallelization.
    """
    from tox_poetry_installer import _poetry

    logger.info(f"Installing {len(packages)} packages to environment at {venv.env_dir}")

    pip = _poetry.PipInstaller(
        env=utilities.convert_virtualenv(venv),
        io=_poetry.NullIO(),
        pool=poetry.pool,
    )

    installed: Set[PoetryPackage] = set()

    def logged_install(dependency: PoetryPackage) -> None:
        start = datetime.now()
        logger.debug(f"Installing {dependency}")
        pip.install(dependency)
        end = datetime.now()
        logger.debug(f"Finished installing {dependency} in {end - start}")

    @contextlib.contextmanager
    def _optional_parallelize():
        """A bit of cheat, really

        A context manager that exposes a common interface for the caller that optionally
        enables/disables the usage of the parallel thread pooler depending on the value of
        the ``parallels`` parameter.
        """
        if parallels > 0:
            with concurrent.futures.ThreadPoolExecutor(
                max_workers=parallels
            ) as executor:
                yield executor.submit
        else:
            yield lambda func, arg: func(arg)

    with _optional_parallelize() as executor:
        futures = []
        for dependency in packages:
            if dependency not in installed:
                installed.add(dependency)
                logger.debug(f"Queuing {dependency}")
                future = executor(logged_install, dependency)
                if future is not None:
                    futures.append(future)
            else:
                logger.debug(f"Skipping {dependency}, already installed")
        logger.debug("Waiting for installs to finish...")

        for future in concurrent.futures.as_completed(futures):
            # Don't actually care about the return value, just waiting on the
            # future to ensure any exceptions that were raised in the called
            # function are propagated.
            future.result()