"""
Provides an emulator/replacement for Python's standard import system.

@@TR: Be warned that Import Hooks are in the deepest, darkest corner of
Python's jungle.  If you need to start hacking with this, be prepared to get
lost for a while. Also note, this module predates the newstyle import hooks in
Python 2.3 http://www.python.org/peps/pep-0302.html.

This is a hacked/documented version of Gordon McMillan's iu.py. I have:

  - made it a little less terse

  - added docstrings and explanatations

  - standardized the variable naming scheme

  - reorganized the code layout to enhance readability
"""

import marshal
import py_compile
import sys
from .compat import PY2, string_type, new_module, get_suffixes, \
    load_module_from_file, RecursionError
if PY2:
    import imp
else:
    import importlib.machinery

_installed = False

# _globalOwnerTypes is defined at the bottom of this file

_os_stat = _os_path_join = _os_getcwd = _os_path_dirname = None

##################################################
# FUNCTIONS


def _os_bootstrap():
    """
    Set up 'os' module replacement functions for use during import bootstrap
    """

    names = sys.builtin_module_names

    join = dirname = None
    if 'posix' in names:
        sep = '/'
        from posix import stat, getcwd
    elif 'nt' in names:
        sep = '\\'
        from nt import stat, getcwd
    elif 'dos' in names:
        sep = '\\'
        from dos import stat, getcwd
    elif 'os2' in names:
        sep = '\\'
        from os2 import stat, getcwd
    elif 'mac' in names:
        from mac import stat, getcwd

        if join is None:
            def join(a, b):
                if a == '':
                    return b
                if ':' not in a:
                    a = ':' + a
                if a[-1:] != ':':
                    a = a + ':'
                return a + b
    else:
        raise ImportError('no os specific module found')

    if join is None:
        def join(a, b, sep=sep):
            if a == '':
                return b
            lastchar = a[-1:]
            if lastchar == '/' or lastchar == sep:
                return a + b
            return a + sep + b

    if dirname is None:
        def dirname(a, sep=sep):
            for i in range(len(a) - 1, -1, -1):
                c = a[i]
                if c == '/' or c == sep:
                    return a[:i]
            return ''

    global _os_stat
    _os_stat = stat

    global _os_path_join
    _os_path_join = join

    global _os_path_dirname
    _os_path_dirname = dirname

    global _os_getcwd
    _os_getcwd = getcwd


_os_bootstrap()


def packageName(s):
    for i in range(len(s) - 1, -1, -1):
        if s[i] == '.':
            break
    else:
        return ''
    return s[:i]


def nameSplit(s):
    rslt = []
    i = j = 0
    for j in range(len(s)):
        if s[j] == '.':
            rslt.append(s[i:j])
            i = j + 1
    if i < len(s):
        rslt.append(s[i:])
    return rslt


def getPathExt(fnm):
    for i in range(len(fnm) - 1, -1, -1):
        if fnm[i] == '.':
            return fnm[i:]
    return ''


def pathIsDir(pathname):
    "Local replacement for os.path.isdir()."
    try:
        s = _os_stat(pathname)
    except OSError:
        return None
    return (s[0] & 0o170000) == 0o040000


def getDescr(fnm):
    ext = getPathExt(fnm)
    for (suffix, mode, typ) in get_suffixes():
        if suffix == ext:
            return (suffix, mode, typ)

##################################################
# CLASSES


class Owner:

    """An Owner does imports from a particular piece of turf That is, there's
    an Owner for each thing on sys.path There are owners for directories and
    .pyz files.  There could be owners for zip files, or even URLs.  A
    shadowpath (a dictionary mapping the names in sys.path to their owners) is
    used so that sys.path (or a package's __path__) is still a bunch of
    strings.
    """

    def __init__(self, path):
        self.path = path

    def __str__(self):
        return self.path

    def getmod(self, nm):
        return None


class DirOwner(Owner):

    def __init__(self, path):
        if path == '':
            path = _os_getcwd()
        if not pathIsDir(path):
            raise ValueError("%s is not a directory" % path)
        Owner.__init__(self, path)

    def getmod(self, nm, getsuffixes=get_suffixes,
               loadco=marshal.loads, newmod=new_module):

        pth = _os_path_join(self.path, nm)

        possibles = [(pth, 0, None)]
        if pathIsDir(pth):
            possibles.insert(0, (_os_path_join(pth, '__init__'), 1, pth))
        py = pyc = None
        for pth, ispkg, pkgpth in possibles:
            for ext, mode, typ in getsuffixes():
                attempt = pth + ext
                try:
                    st = _os_stat(attempt)
                except Exception:
                    pass
                else:
                    if typ == 3:  # imp.C_EXTENSION
                        return load_module_from_file(nm, nm, attempt)
                    elif typ == 1:  # imp.PY_SOURCE
                        py = (attempt, st)
                    else:
                        pyc = (attempt, st)
            if py or pyc:
                break
        if py is None and pyc is None:
            return None
        while True:
            if pyc is None or py and pyc[1][8] < py[1][8]:
                try:
                    with open(py[0], 'r') as py_code_file:
                        py_code = py_code_file.read()
                    co = compile(py_code + '\n', py[0], 'exec')
                    try:
                        py_compile.compile(py[0])
                    except IOError:
                        pass
                    __file__ = py[0]
                    break
                except SyntaxError as e:
                    print("Invalid syntax in %s" % py[0])
                    print(e.args)
                    raise
            elif pyc:
                with open(pyc[0], 'rb') as pyc_file:
                    stuff = pyc_file.read()
                try:
                    co = loadco(stuff[8:])
                    __file__ = pyc[0]
                    break
                except (ValueError, EOFError):
                    pyc = None
            else:
                return None
        mod = newmod(nm)
        mod.__file__ = __file__
        if ispkg:
            mod.__path__ = [pkgpth]
            subimporter = PathImportDirector(mod.__path__)
            mod.__importsub__ = subimporter.getmod
        mod.__co__ = co
        return mod


class ImportDirector(Owner):
    """ImportDirectors live on the metapath There's one for builtins, one for
    frozen modules, and one for sys.path Windows gets one for modules gotten
    from the Registry Mac would have them for PY_RESOURCE modules etc.  A
    generalization of Owner - their concept of 'turf' is broader"""

    pass


class BuiltinImportDirector(ImportDirector):
    """Directs imports of builtin modules"""
    def __init__(self):
        self.path = 'Builtins'

    def getmod(self, nm):
        if nm in sys.builtin_module_names:
            try:
                importfunc = __oldimport__
            except NameError:
                importfunc = __import__
            return importfunc(nm)
        return None


class FrozenImportDirector(ImportDirector):
    """Directs imports of frozen modules"""

    def __init__(self):
        self.path = 'FrozenModules'

    def getmod(self, nm):
        mod = None
        if PY2:
            if imp.is_frozen(nm):
                mod = imp.load_module(nm, None, nm, ('', '', imp.PY_FROZEN))
        else:
            if importlib.machinery.FrozenImporter.find_spec(nm):
                mod = importlib.machinery.FrozenImporter.load_module(nm)
        if mod and hasattr(mod, '__path__'):
            mod.__importsub__ = \
                lambda name, pname=nm, owner=self: \
                owner.getmod(pname + '.' + name)
        return mod


class RegistryImportDirector(ImportDirector):
    """Directs imports of modules stored in the Windows Registry"""

    def __init__(self):
        self.path = "WindowsRegistry"
        self.map = {}
        try:
            import win32api
            # import win32con
        except ImportError:
            pass
        else:
            HKEY_CURRENT_USER = -2147483647
            HKEY_LOCAL_MACHINE = -2147483646
            KEY_ALL_ACCESS = 983103
            subkey = r"Software\Python\PythonCore\%s\Modules" % sys.winver
            for root in (HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE):
                try:
                    hkey = win32api.RegOpenKeyEx(root, subkey,
                                                 0, KEY_ALL_ACCESS)
                except Exception:
                    pass
                else:
                    numsubkeys, numvalues, lastmodified = \
                        win32api.RegQueryInfoKey(hkey)
                    for i in range(numsubkeys):
                        subkeyname = win32api.RegEnumKey(hkey, i)
                        hskey = win32api.RegOpenKeyEx(hkey, subkeyname,
                                                      0, KEY_ALL_ACCESS)
                        val = win32api.RegQueryValueEx(hskey, '')
                        desc = getDescr(val[0])
                        self.map[subkeyname] = (val[0], desc)
                        hskey.Close()
                    hkey.Close()
                    break

    def getmod(self, nm):
        stuff = self.map.get(nm)
        if stuff:
            fnm = stuff[0]
            return load_module_from_file(nm, nm, fnm)
        return None


class PathImportDirector(ImportDirector):
    """Directs imports of modules stored on the filesystem."""

    def __init__(self, pathlist=None, importers=None, ownertypes=None):
        if pathlist is None:
            self.path = sys.path
        else:
            self.path = pathlist
        if ownertypes is None:
            self._ownertypes = _globalOwnerTypes
        else:
            self._ownertypes = ownertypes
        if importers:
            self._shadowPath = importers
        else:
            self._shadowPath = {}
        self._inMakeOwner = False
        self._building = {}

    def getmod(self, nm):
        mod = None
        for thing in self.path:
            if isinstance(thing, string_type):
                owner = self._shadowPath.get(thing, -1)
                if owner == -1:
                    owner = self._shadowPath[thing] = self._makeOwner(thing)
                if owner:
                    mod = owner.getmod(nm)
            else:
                mod = thing.getmod(nm)
            if mod:
                break
        return mod

    def _makeOwner(self, path):
        if self._building.get(path):
            return None
        self._building[path] = 1
        owner = None
        for klass in self._ownertypes:
            try:
                # this may cause an import, which may cause recursion
                # hence the protection
                owner = klass(path)
            except Exception:
                pass
            else:
                break
        del self._building[path]
        return owner

# =================ImportManager============================#
# The one-and-only ImportManager
# ie, the builtin import


UNTRIED = -1


class ImportManager:
    # really the equivalent of builtin import
    def __init__(self):
        self.metapath = [
            BuiltinImportDirector(),
            FrozenImportDirector(),
            RegistryImportDirector(),
            PathImportDirector()
        ]
        self.threaded = 0
        self.rlock = None
        self.locker = None
        self.setThreaded()

    def setThreaded(self):
        thread = sys.modules.get('thread', None)
        if thread and not self.threaded:
            self.threaded = 1
            self.rlock = thread.allocate_lock()
            self._get_ident = thread.get_ident

    def install(self):
        try:
            import builtins as builtin
        except ImportError:  # PY2
            import __builtin__ as builtin
        builtin.__import__ = self.importHook
        builtin.reload = self.reloadHook

    def importHook(self, name, globals=None, locals=None,
                   fromlist=None, level=-1):
        '''
        NOTE: Currently importHook will accept the keyword-argument "level"
        but it will *NOT* use it. Details about the "level" keyword
        argument can be found here:
        https://docs.python.org/2/library/functions.html#__import__
        '''
        # first see if we could be importing a relative name
        _sys_modules_get = sys.modules.get
        contexts = [None]
        if globals:
            importernm = globals.get('__name__', '')
            if importernm:
                if hasattr(_sys_modules_get(importernm), '__path__'):
                    contexts.insert(0, importernm)
                else:
                    pkgnm = packageName(importernm)
                    if pkgnm:
                        contexts.insert(0, pkgnm)
        # so contexts is [pkgnm, None] or just [None]
        # now break the name being imported up so we get:
        # a.b.c -> [a, b, c]
        nmparts = nameSplit(name)
        _self_doimport = self.doimport
        threaded = self.threaded
        for context in contexts:
            ctx = context
            for i in range(len(nmparts)):
                nm = nmparts[i]
                if ctx:
                    fqname = ctx + '.' + nm
                else:
                    fqname = nm
                if threaded:
                    self._acquire()
                mod = _sys_modules_get(fqname, UNTRIED)
                if mod is UNTRIED:
                    mod = _self_doimport(nm, ctx, fqname)
                if threaded:
                    self._release()
                if mod:
                    ctx = fqname
                else:
                    break
            else:
                # no break, point i beyond end
                i = i + 1
            if i:
                break

        if i < len(nmparts):
            if ctx and hasattr(sys.modules[ctx], nmparts[i]):
                return sys.modules[nmparts[0]]
            del sys.modules[fqname]
            raise ImportError("No module named %s" % fqname)
        if fromlist is None:
            if context:
                return sys.modules[context + '.' + nmparts[0]]
            return sys.modules[nmparts[0]]
        bottommod = sys.modules[ctx]
        if hasattr(bottommod, '__path__'):
            fromlist = list(fromlist)
            i = 0
            while i < len(fromlist):
                nm = fromlist[i]
                if nm == '*':
                    fromlist[i:i+1] = list(getattr(bottommod, '__all__', []))  # noqa: E226,E501 missing whitespace around operator
                    if i >= len(fromlist):
                        break
                    nm = fromlist[i]
                i = i + 1
                if not hasattr(bottommod, nm):
                    if self.threaded:
                        self._acquire()
                    mod = self.doimport(nm, ctx, ctx + '.' + nm)
                    if self.threaded:
                        self._release()
                    if not mod:
                        raise ImportError("%s not found in %s" % (nm, ctx))
        return bottommod

    def doimport(self, nm, parentnm, fqname):
        # Not that nm is NEVER a dotted name at this point
        if parentnm:
            parent = sys.modules[parentnm]
            if hasattr(parent, '__path__'):
                importfunc = getattr(parent, '__importsub__', None)
                if not importfunc:
                    subimporter = PathImportDirector(parent.__path__)
                    importfunc = parent.__importsub__ = subimporter.getmod
                mod = importfunc(nm)
                if mod:
                    setattr(parent, nm, mod)
            else:
                return None
        else:
            # now we're dealing with an absolute import
            for director in self.metapath:
                try:
                    mod = director.getmod(nm)
                except RecursionError:
                    mod = __oldimport__(nm)  # noqa: F821 undefined name
                if mod:
                    break
        if mod:
            mod.__name__ = fqname
            sys.modules[fqname] = mod
            if hasattr(mod, '__co__'):
                co = mod.__co__
                del mod.__co__
                exec(co, mod.__dict__)
            if fqname == 'thread' and not self.threaded:
                self.setThreaded()
        else:
            sys.modules[fqname] = None
        return mod

    def reloadHook(self, mod):
        fqnm = mod.__name__
        nm = nameSplit(fqnm)[-1]
        parentnm = packageName(fqnm)
        newmod = self.doimport(nm, parentnm, fqnm)
        mod.__dict__.update(newmod.__dict__)
#        return newmod

    def _acquire(self):
        if self.rlock.locked():
            if self.locker == self._get_ident():
                self.lockcount = self.lockcount + 1
                return
        self.rlock.acquire()
        self.locker = self._get_ident()
        self.lockcount = 0

    def _release(self):
        if self.lockcount:
            self.lockcount = self.lockcount - 1
        else:
            self.rlock.release()


##################################################
# MORE CONSTANTS & GLOBALS

_globalOwnerTypes = [
    DirOwner,
    Owner,
]
