# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Facilities for helping test code which interacts with Python's module system
to load code.
"""

from __future__ import division, absolute_import

import sys

from twisted.python.filepath import FilePath


class TwistedModulesMixin:
"""
A mixin for C{twisted.trial.unittest.SynchronousTestCase} providing useful
methods for manipulating Python's module system.
"""

def replaceSysPath(self, sysPath):
"""
Replace sys.path, for the duration of the test, with the given value.
"""
originalSysPath = sys.path[:]
def cleanUpSysPath():
sys.path[:] = originalSysPath
self.addCleanup(cleanUpSysPath)
sys.path[:] = sysPath


def replaceSysModules(self, sysModules):
"""
Replace sys.modules, for the duration of the test, with the given value.
"""
originalSysModules = sys.modules.copy()
def cleanUpSysModules():
sys.modules.clear()
sys.modules.update(originalSysModules)
self.addCleanup(cleanUpSysModules)
sys.modules.clear()
sys.modules.update(sysModules)


def pathEntryWithOnePackage(self, pkgname=b"test_package"):
"""
Generate a L{FilePath} with one package, named C{pkgname}, on it, and
return the L{FilePath} of the path entry.
"""
# Remove utf-8 encode and bytes for path segments when Filepath
# supports Unicode paths on Python 3 (#2366, #4736, #5203).
entry = FilePath(self.mktemp().encode("utf-8"))
pkg = entry.child(b"test_package")
pkg.makedirs()
pkg.child(b"__init__.py").setContent(b"")
return entry