"""Test lazymod.py"""

import sys
import unittest

from xmodule.capa.safe_exec.lazymod import LazyModule


class ModuleIsolation:  # pylint: disable=too-few-public-methods
    """
    Manage changes to sys.modules so that we can roll back imported modules.

    Create this object, it will snapshot the currently imported modules. When
    you call `clean_up()`, it will delete any module imported since its creation.
    """

    def __init__(self):
        # Save all the names of all the imported modules.
        self.mods = set(sys.modules)

    def clean_up(self):
        """Remove any modules imported after initialization to restore state."""

        # Get a list of modules that didn't exist when we were created
        new_mods = [m for m in sys.modules if m not in self.mods]
        # and delete them all so another import will run code for real again.
        for m in new_mods:
            del sys.modules[m]


class TestLazyMod(unittest.TestCase):
    """Unit tests for verifying lazy module importing with LazyModule."""

    def setUp(self):
        super().setUp()
        # Each test will remove modules that it imported.
        self.addCleanup(ModuleIsolation().clean_up)

    def test_simple(self):
        """Test lazy import of a standard module and verify functionality."""
        # Import some stdlib module that has not been imported before
        module_name = "colorsys"
        if module_name in sys.modules:
            # May have been imported during test discovery, remove it again
            del sys.modules[module_name]
        assert module_name not in sys.modules
        colorsys = LazyModule(module_name)
        hsv = colorsys.rgb_to_hsv(0.3, 0.4, 0.2)
        assert hsv[0] == 0.25

    def test_dotted(self):
        """Test lazy import of a dotted submodule and verify functionality."""
        # wsgiref is a module with submodules that is not already imported.
        # Any similar module would do. This test demonstrates that the module
        # is not already imported
        module_name = "wsgiref.util"
        if module_name in sys.modules:
            # May have been imported during test discovery, remove it again
            del sys.modules[module_name]
        assert module_name not in sys.modules
        wsgiref_util = LazyModule(module_name)
        assert wsgiref_util.guess_scheme({}) == "http"