create the default cache direcotry, and initalize it.. also,

currently always reread the cache directory, but this needs to be
fixed..

casimport/__init__.py

@@ -22,20 +22,35 @@
 # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 # SUCH DAMAGE.
 
+import contextlib
 import glob
 import hashlib
+import importlib
 import os.path
+import pathlib
+import shutil
 import sys
+import tempfile
 
 from importlib.abc import MetaPathFinder, Loader
 from importlib.machinery import ModuleSpec
 
+@contextlib.contextmanager
+def tempset(obj, key, value):
+	try:
+		oldvalue = obj[key]
+		obj[key] = value
+		yield
+	finally:
+		obj[key] = oldvalue
+
 class FileDirCAS(object):
 	def __init__(self, path):
-		self._path = path
+		self._path = pathlib.Path(path)
 		self._hashes = {}
 
-		for i in glob.glob(os.path.join(path, '*.py')):
+	def refresh_dir(self):
+		for i in glob.glob(os.path.join(self._path, '*.py')):
 			_, hash = self.read_hash_file(i)
 			self._hashes[hash] = i
 
@@ -50,6 +65,8 @@ class FileDirCAS(object):
 		return False
 
 	def exec_module(self, hash, module):
+		self.refresh_dir()
+
 		parts = hash.split('_', 2)
 		fname = self._hashes[parts[2]]
 
@@ -93,6 +110,8 @@ class CASFinder(MetaPathFinder, Loader):
 			for l in self._loaders:
 				ispkg = l.is_package(parts[1])
 				break
+			else:
+				return None
 
 			ms = ModuleSpec(fullname, self, is_package=True, loader_state=(parts[1], l))
 
@@ -109,25 +128,56 @@ class CASFinder(MetaPathFinder, Loader):
 			hash, load = module.__spec__.loader_state
 			load.exec_module(hash, module)
 
+def defaultinit(casf):
+	cachedir = pathlib.Path.home() / '.casimport_cache'
+	cachedir.mkdir(exist_ok=True)
+
+	casf.register(FileDirCAS(cachedir))
+
 # The global version
 _casfinder = CASFinder()
+defaultinit(_casfinder)
 
 import unittest
 
 class Test(unittest.TestCase):
 	def setUp(self):
+		# clear out the default casfinder if there is one
 		self.old_meta_path = sys.meta_path
 		sys.meta_path = [ x for x in sys.meta_path if not isinstance(x, CASFinder) ]
 
+		# setup temporary directory
+		d = pathlib.Path(os.path.realpath(tempfile.mkdtemp()))
+		self.basetempdir = d
+		self.tempdir = d / 'subdir'
+		self.tempdir.mkdir()
+
+		self.fixtures = pathlib.Path(__file__).parent.parent / 'fixtures'
+
 	def tearDown(self):
+		# restore environment
 		sys.meta_path = self.old_meta_path
 
+		importlib.invalidate_caches()
+
+		# clean up sys.modules
+		[ sys.modules.pop(x) for x in list(sys.modules.keys()) if
+		    x == 'cas' or x.startswith('cas.') ]
+
+		shutil.rmtree(self.basetempdir)
+		self.tempdir = None
+
+	def test_filedircas_limit_refresh(self):
+		# XXX - only refresh when the dir has changed, and each
+		# file has changed
+		pass
+
 	def test_casimport(self):
 		# That a CASFinder
 		f = CASFinder()
 
 		# when registering the fixtures directory
-		f.register(FileDirCAS(os.path.join(os.path.dirname(__file__), '..', 'fixtures')))
+		f.register(FileDirCAS(self.fixtures))
 
 		# can import the function
 		from cas.v1_f_330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3 import hello
@@ -145,6 +195,31 @@ class Test(unittest.TestCase):
 		# and when disconnected as second time, nothing happens
 		f.disconnect()
 
+	def test_defaultinit(self):
+		temphome = self.tempdir / 'home'
+		temphome.mkdir()
+		cachedir = temphome / '.casimport_cache'
+
+		with tempset(os.environ, 'HOME', str(temphome)):
+			with CASFinder() as f:
+				# Setup the defaults
+				defaultinit(f)
+
+				# that the cache got created
+				self.assertTrue(cachedir.is_dir())
+
+				# and that when hello.py is copied to the cache
+				shutil.copy(self.fixtures / 'hello.py', cachedir)
+
+				# it can be imported
+				from cas.v1_f_330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3 import hello
+
+			with CASFinder() as f:
+				defaultinit(f)
+
+				# and that a new CASFinder can still find it
+				from cas.v1_f_330884aa2febb5e19fb7194ec6a69ed11dd3d77122f1a5175ee93e73cf0161c3 import hello
+
 	def test_multiplecas(self):
 		# that once we have one
 		with CASFinder() as f: