import contextlib
import io
import os
import shutil
import site
import sys
import tempfile

from filelock import FileLock


@contextlib.contextmanager
def tempdir(cd=lambda dir: None, **kwargs):
    temp_dir = tempfile.mkdtemp(**kwargs)
    orig_dir = os.getcwd()
    try:
        cd(temp_dir)
        yield temp_dir
    finally:
        cd(orig_dir)
        shutil.rmtree(temp_dir)


@contextlib.contextmanager
def environment(**replacements):
    """
    In a context, patch the environment with replacements. Pass None values
    to clear the values.
    """
    saved = dict((key, os.environ[key]) for key in replacements if key in os.environ)

    # remove values that are null
    remove = (key for (key, value) in replacements.items() if value is None)
    for key in list(remove):
        os.environ.pop(key, None)
        replacements.pop(key)

    os.environ.update(replacements)

    try:
        yield saved
    finally:
        for key in replacements:
            os.environ.pop(key, None)
        os.environ.update(saved)


@contextlib.contextmanager
def quiet():
    """
    Redirect stdout/stderr to StringIO objects to prevent console output from
    distutils commands.
    """

    old_stdout = sys.stdout
    old_stderr = sys.stderr
    new_stdout = sys.stdout = io.StringIO()
    new_stderr = sys.stderr = io.StringIO()
    try:
        yield new_stdout, new_stderr
    finally:
        new_stdout.seek(0)
        new_stderr.seek(0)
        sys.stdout = old_stdout
        sys.stderr = old_stderr


@contextlib.contextmanager
def save_user_site_setting():
    saved = site.ENABLE_USER_SITE
    try:
        yield saved
    finally:
        site.ENABLE_USER_SITE = saved


@contextlib.contextmanager
def suppress_exceptions(*excs):
    try:
        yield
    except excs:
        pass


def multiproc(request):
    """
    Return True if running under xdist and multiple
    workers are used.
    """
    try:
        worker_id = request.getfixturevalue('worker_id')
    except Exception:
        return False
    return worker_id != 'master'


@contextlib.contextmanager
def session_locked_tmp_dir(request, tmp_path_factory, name):
    """Uses a file lock to guarantee only one worker can access a temp dir"""
    # get the temp directory shared by all workers
    base = tmp_path_factory.getbasetemp()
    shared_dir = base.parent if multiproc(request) else base

    locked_dir = shared_dir / name
    with FileLock(locked_dir.with_suffix(".lock")):
        # ^-- prevent multiple workers to access the directory at once
        locked_dir.mkdir(exist_ok=True, parents=True)
        yield locked_dir


@contextlib.contextmanager
def save_paths():
    """Make sure ``sys.path``, ``sys.meta_path`` and ``sys.path_hooks`` are preserved"""
    prev = sys.path[:], sys.meta_path[:], sys.path_hooks[:]

    try:
        yield
    finally:
        sys.path, sys.meta_path, sys.path_hooks = prev


@contextlib.contextmanager
def save_sys_modules():
    """Make sure initial ``sys.modules`` is preserved"""
    prev_modules = sys.modules

    try:
        sys.modules = sys.modules.copy()
        yield
    finally:
        sys.modules = prev_modules