"""
Study python3's ``tempfile`` library.
"""
from __future__ import print_function
import os
import tempfile
import unittest


class TestTempFile(unittest.TestCase):
    """
    Test of some futures of the ``tempfile`` standard library module.
    """

    def test_buggy_future_with_wrong_mode_value(self):
        """
        When you give some wrong value to the ``mode`` argument
        (i.e. ``mode='wr'``) the next error is occurred:

            ValueError: must have exactly one of create/read/write/append mode

        Which is a blunder of the particular developer, you need be more
        careful, but "temporary" file are created on the disk anyway, and now
        it becomes not so temporary as expected.
        Because of error, program is interrupted, empty file remains on the
        disk.
        Temp file will not be deleted automatically, how it happens whilst
        normally finish the program without running the ``close()`` method,
        or when it will be stopped because of any exception.

        Furthermore, it is occur only with python 3.x versions.

        :Note: tested on Python 3.4.3 (default, Oct 14 2015, 20:28:29)
        """
        containing_dir = os.path.dirname(os.path.abspath(__file__))
        dir_content_before_fail = os.listdir(containing_dir)
        with self.assertRaises(ValueError):
            tempfile.NamedTemporaryFile(prefix='eggs_spam_foo_',
                                        suffix='.pig',
                                        mode='wr',
                                        dir=containing_dir)

        dir_content_after_fail = os.listdir(containing_dir)
        dir_content_diff = list(
            set(dir_content_after_fail) - set(dir_content_before_fail)
        )
        smug_git = dir_content_diff.pop()
        self.addCleanup(os.remove, smug_git)
        self.assertNotEqual(dir_content_before_fail, dir_content_after_fail)
        print("Gotcha, smug git! I've knew about you! You shall not pass!"
              "\n({} was deleted automatically.)".format(smug_git))


if __name__ == '__main__':
    unittest.main()