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

from ..compat import StringIO


@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 = StringIO()
    new_stderr = sys.stderr = 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