"""Utilities to support packages."""

# NOTE: This module must remain compatible with Python 2.3, as it is shared

# by setuptools for distribution with Python 2.3 and up.

import os

import sys

import imp

import os.path

from types import ModuleType

__all__ = [

    'get_importer', 'iter_importers', 'get_loader', 'find_loader',

    'walk_packages', 'iter_modules',

    'ImpImporter', 'ImpLoader', 'read_code', 'extend_path',

]

def read_code(stream):

    # This helper is needed in order for the PEP 302 emulation to

    # correctly handle compiled files

    import marshal

    magic = stream.read(4)

    if magic != imp.get_magic():

        return None

    stream.read(4) # Skip timestamp

    return marshal.load(stream)

def simplegeneric(func):

    """Make a trivial single-dispatch generic function"""

    registry = {}

    def wrapper(*args, **kw):

        ob = args[0]

        try:

            cls = ob.__class__

        except AttributeError:

            cls = type(ob)

        try:

            mro = cls.__mro__

        except AttributeError:

            try:

                class cls(cls, object):

                    pass

                mro = cls.__mro__[1:]

            except TypeError:

                mro = object,   # must be an ExtensionClass or some such  :(

        for t in mro:

            if t in registry:

                return registry[t](*args, **kw)

        else:

            return func(*args, **kw)

    try:

        wrapper.__name__ = func.__name__

    except (TypeError, AttributeError):

        pass    # Python 2.3 doesn't allow functions to be renamed

    def register(typ, func=None):

        if func is None:

            return lambda f: register(typ, f)

        registry[typ] = func

        return func

    wrapper.__dict__ = func.__dict__

    wrapper.__doc__ = func.__doc__

    wrapper.register = register

    return wrapper

def walk_packages(path=None, prefix='', onerror=None):

    """Yields (module_loader, name, ispkg) for all modules recursively

    on path, or, if path is None, all accessible modules.

    'path' should be either None or a list of paths to look for

    modules in.

    'prefix' is a string to output on the front of every module name

    on output.

    Note that this function must import all *packages* (NOT all

    modules!) on the given path, in order to access the __path__

    attribute to find submodules.

    'onerror' is a function which gets called with one argument (the

    name of the package which was being imported) if any exception

    occurs while trying to import a package.  If no onerror function is

    supplied, ImportErrors are caught and ignored, while all other

    exceptions are propagated, terminating the search.

    Examples:

    # list all modules python can access

    walk_packages()

    # list all submodules of ctypes

    walk_packages(ctypes.__path__, ctypes.__name__+'.')

    """

    def seen(p, m={}):

        if p in m:

            return True

        m[p] = True

    for importer, name, ispkg in iter_modules(path, prefix):

        yield importer, name, ispkg

        if ispkg:

            try:

                __import__(name)

            except ImportError:

                if onerror is not None:

                    onerror(name)

            except Exception:

                if onerror is not None:

                    onerror(name)

                else:

                    raise

            else:

                path = getattr(sys.modules[name], '__path__', None) or []

                # don't traverse path items we've seen before

                path = [p for p in path if not seen(p)]

                for item in walk_packages(path, name+'.', onerror):

                    yield item

def iter_modules(path=None, prefix=''):

    """Yields (module_loader, name, ispkg) for all submodules on path,

    or, if path is None, all top-level modules on sys.path.

    'path' should be either None or a list of paths to look for

    modules in.

    'prefix' is a string to output on the front of every module name

    on output.

    """

    if path is None:

        importers = iter_importers()

    else:

        importers = map(get_importer, path)

    yielded = {}

    for i in importers:

        for name, ispkg in iter_importer_modules(i, prefix):

            if name not in yielded:

                yielded[name] = 1

                yield i, name, ispkg

#@simplegeneric

def iter_importer_modules(importer, prefix=''):

    if not hasattr(importer, 'iter_modules'):

        return []

    return importer.iter_modules(prefix)

iter_importer_modules = simplegeneric(iter_importer_modules)

class ImpImporter:

    """PEP 302 Importer that wraps Python's "classic" import algorithm

    ImpImporter(dirname) produces a PEP 302 importer that searches that

    directory.  ImpImporter(None) produces a PEP 302 importer that searches

    the current sys.path, plus any modules that are frozen or built-in.

    Note that ImpImporter does not currently support being used by placement

    on sys.meta_path.

    """

    def __init__(self, path=None):

        self.path = path

    def find_module(self, fullname, path=None):

        # Note: we ignore 'path' argument since it is only used via meta_path

        subname = fullname.split(".")[-1]

        if subname != fullname and self.path is None:

            return None

        if self.path is None:

            path = None

        else:

            path = [os.path.realpath(self.path)]

        try:

            file, filename, etc = imp.find_module(subname, path)

        except ImportError:

            return None

        return ImpLoader(fullname, file, filename, etc)

    def iter_modules(self, prefix=''):

        if self.path is None or not os.path.isdir(self.path):

            return

        yielded = {}

        import inspect

        filenames = os.listdir(self.path)

        filenames.sort()  # handle packages before same-named modules

        for fn in filenames:

            modname = inspect.getmodulename(fn)

            if modname=='__init__' or modname in yielded:

                continue

            path = os.path.join(self.path, fn)

            ispkg = False

            if not modname and os.path.isdir(path) and '.' not in fn:

                modname = fn

                for fn in os.listdir(path):

                    subname = inspect.getmodulename(fn)

                    if subname=='__init__':

                        ispkg = True

                        break

                else:

                    continue    # not a package

            if modname and '.' not in modname:

                yielded[modname] = 1

                yield prefix + modname, ispkg

class ImpLoader:

    """PEP 302 Loader that wraps Python's "classic" import algorithm

    """

    code = source = None

    def __init__(self, fullname, file, filename, etc):

        self.file = file

        self.filename = filename

        self.fullname = fullname

        self.etc = etc

    def load_module(self, fullname):

        self._reopen()

        try:

            mod = imp.load_module(fullname, self.file, self.filename, self.etc)

        finally:

            if self.file:

                self.file.close()

        # Note: we don't set __loader__ because we want the module to look

        # normal; i.e. this is just a wrapper for standard import machinery

        return mod

    def get_data(self, pathname):

        return open(pathname, "rb").read()

    def _reopen(self):

        if self.file and self.file.closed:

            mod_type = self.etc[2]

            if mod_type==imp.PY_SOURCE:

                self.file = open(self.filename, 'rU')

            elif mod_type in (imp.PY_COMPILED, imp.C_EXTENSION):

                self.file = open(self.filename, 'rb')

    def _fix_name(self, fullname):

        if fullname is None:

            fullname = self.fullname

        elif fullname != self.fullname:

            raise ImportError("Loader for module %s cannot handle "

                              "module %s" % (self.fullname, fullname))

        return fullname

    def is_package(self, fullname):

        fullname = self._fix_name(fullname)

        return self.etc[2]==imp.PKG_DIRECTORY

    def get_code(self, fullname=None):

        fullname = self._fix_name(fullname)

        if self.code is None:

            mod_type = self.etc[2]

            if mod_type==imp.PY_SOURCE:

                source = self.get_source(fullname)

                self.code = compile(source, self.filename, 'exec')

            elif mod_type==imp.PY_COMPILED:

                self._reopen()

                try:

                    self.code = read_code(self.file)

                finally:

                    self.file.close()

            elif mod_type==imp.PKG_DIRECTORY:

                self.code = self._get_delegate().get_code()

        return self.code

    def get_source(self, fullname=None):

        fullname = self._fix_name(fullname)

        if self.source is None:

            mod_type = self.etc[2]

            if mod_type==imp.PY_SOURCE:

                self._reopen()

                try:

                    self.source = self.file.read()

                finally:

                    self.file.close()

            elif mod_type==imp.PY_COMPILED:

                if os.path.exists(self.filename[:-1]):

                    f = open(self.filename[:-1], 'rU')

                    self.source = f.read()

                    f.close()

            elif mod_type==imp.PKG_DIRECTORY:

                self.source = self._get_delegate().get_source()

        return self.source

    def _get_delegate(self):

        return ImpImporter(self.filename).find_module('__init__')

    def get_filename(self, fullname=None):

        fullname = self._fix_name(fullname)

        mod_type = self.etc[2]

        if self.etc[2]==imp.PKG_DIRECTORY:

            return self._get_delegate().get_filename()

        elif self.etc[2] in (imp.PY_SOURCE, imp.PY_COMPILED, imp.C_EXTENSION):

            return self.filename

        return None

try:

    import zipimport

    from zipimport import zipimporter

    def iter_zipimport_modules(importer, prefix=''):

        dirlist = zipimport._zip_directory_cache[importer.archive].keys()

        dirlist.sort()

        _prefix = importer.prefix

        plen = len(_prefix)

        yielded = {}

        import inspect

        for fn in dirlist:

            if not fn.startswith(_prefix):

                continue

            fn = fn[plen:].split(os.sep)

            if len(fn)==2 and fn[1].startswith('__init__.py'):

                if fn[0] not in yielded:

                    yielded[fn[0]] = 1

                    yield fn[0], True

            if len(fn)!=1:

                continue

            modname = inspect.getmodulename(fn[0])

            if modname=='__init__':

                continue

            if modname and '.' not in modname and modname not in yielded:

                yielded[modname] = 1

                yield prefix + modname, False

    iter_importer_modules.register(zipimporter, iter_zipimport_modules)

except ImportError:

    pass

def get_importer(path_item):

    """Retrieve a PEP 302 importer for the given path item

    The returned importer is cached in sys.path_importer_cache

    if it was newly created by a path hook.

    If there is no importer, a wrapper around the basic import

    machinery is returned. This wrapper is never inserted into

    the importer cache (None is inserted instead).

    The cache (or part of it) can be cleared manually if a

    rescan of sys.path_hooks is necessary.

    """

    try:

        importer = sys.path_importer_cache[path_item]

    except KeyError:

        for path_hook in sys.path_hooks:

            try:

                importer = path_hook(path_item)

                break

            except ImportError:

                pass

        else:

            importer = None

        sys.path_importer_cache.setdefault(path_item, importer)

    if importer is None:

        try:

            importer = ImpImporter(path_item)

        except ImportError:

            importer = None

    return importer

def iter_importers(fullname=""):

    """Yield PEP 302 importers for the given module name

    If fullname contains a '.', the importers will be for the package

    containing fullname, otherwise they will be importers for sys.meta_path,

    sys.path, and Python's "classic" import machinery, in that order.  If

    the named module is in a package, that package is imported as a side

    effect of invoking this function.

    Non PEP 302 mechanisms (e.g. the Windows registry) used by the

    standard import machinery to find files in alternative locations

    are partially supported, but are searched AFTER sys.path. Normally,

    these locations are searched BEFORE sys.path, preventing sys.path

    entries from shadowing them.

    For this to cause a visible difference in behaviour, there must

    be a module or package name that is accessible via both sys.path

    and one of the non PEP 302 file system mechanisms. In this case,

    the emulation will find the former version, while the builtin

    import mechanism will find the latter.

    Items of the following types can be affected by this discrepancy:

        imp.C_EXTENSION, imp.PY_SOURCE, imp.PY_COMPILED, imp.PKG_DIRECTORY

    """

    if fullname.startswith('.'):

        raise ImportError("Relative module names not supported")

    if '.' in fullname:

        # Get the containing package's __path__

        pkg = '.'.join(fullname.split('.')[:-1])

        if pkg not in sys.modules:

            __import__(pkg)

        path = getattr(sys.modules[pkg], '__path__', None) or []

    else:

        for importer in sys.meta_path:

            yield importer

        path = sys.path

    for item in path:

        yield get_importer(item)

    if '.' not in fullname:

        yield ImpImporter()

def get_loader(module_or_name):

    """Get a PEP 302 "loader" object for module_or_name

    If the module or package is accessible via the normal import

    mechanism, a wrapper around the relevant part of that machinery

    is returned.  Returns None if the module cannot be found or imported.

    If the named module is not already imported, its containing package

    (if any) is imported, in order to establish the package __path__.

    This function uses iter_importers(), and is thus subject to the same

    limitations regarding platform-specific special import locations such

    as the Windows registry.

    """

    if module_or_name in sys.modules:

        module_or_name = sys.modules[module_or_name]

    if isinstance(module_or_name, ModuleType):

        module = module_or_name

        loader = getattr(module, '__loader__', None)

        if loader is not None:

            return loader

        fullname = module.__name__

    else:

        fullname = module_or_name

    return find_loader(fullname)

def find_loader(fullname):

    """Find a PEP 302 "loader" object for fullname

    If fullname contains dots, path must be the containing package's __path__.

    Returns None if the module cannot be found or imported. This function uses

    iter_importers(), and is thus subject to the same limitations regarding

    platform-specific special import locations such as the Windows registry.

    """

    for importer in iter_importers(fullname):

        loader = importer.find_module(fullname)

        if loader is not None:

            return loader

    return None

def extend_path(path, name):

    """Extend a package's path.

    Intended use is to place the following code in a package's __init__.py:

        from pkgutil import extend_path

        __path__ = extend_path(__path__, __name__)

    This will add to the package's __path__ all subdirectories of

    directories on sys.path named after the package.  This is useful

    if one wants to distribute different parts of a single logical

    package as multiple directories.

    It also looks for *.pkg files beginning where * matches the name

    argument.  This feature is similar to *.pth files (see site.py),

    except that it doesn't special-case lines starting with 'import'.

    A *.pkg file is trusted at face value: apart from checking for

    duplicates, all entries found in a *.pkg file are added to the

    path, regardless of whether they are exist the filesystem.  (This

    is a feature.)

    If the input path is not a list (as is the case for frozen

    packages) it is returned unchanged.  The input path is not

    modified; an extended copy is returned.  Items are only appended

    to the copy at the end.

    It is assumed that sys.path is a sequence.  Items of sys.path that

    are not (unicode or 8-bit) strings referring to existing

    directories are ignored.  Unicode items of sys.path that cause

    errors when used as filenames may cause this function to raise an

    exception (in line with os.path.isdir() behavior).

    """

    if not isinstance(path, list):

        # This could happen e.g. when this is called from inside a

        # frozen package.  Return the path unchanged in that case.

        return path

    pname = os.path.join(*name.split('.')) # Reconstitute as relative path

    # Just in case os.extsep != '.'

    sname = os.extsep.join(name.split('.'))

    sname_pkg = sname + os.extsep + "pkg"

    init_py = "__init__" + os.extsep + "py"

    path = path[:] # Start with a copy of the existing path

    for dir in sys.path:

        if not isinstance(dir, basestring) or not os.path.isdir(dir):

            continue

        subdir = os.path.join(dir, pname)

        # XXX This may still add duplicate entries to path on

        # case-insensitive filesystems

        initfile = os.path.join(subdir, init_py)

        if subdir not in path and os.path.isfile(initfile):

            path.append(subdir)