"""Utilities to support packages."""

from collections import namedtuple
from functools import singledispatch as simplegeneric
import importlib
import importlib.util
import importlib.machinery
import os
import os.path
import sys
from types import ModuleType
import warnings

__all__ = [
 'get_importer', 'iter_importers', 'get_loader', 'find_loader',
 'walk_packages', 'iter_modules', 'get_data',
 'ImpImporter', 'ImpLoader', 'read_code', 'extend_path',
 'ModuleInfo',
]


ModuleInfo = namedtuple('ModuleInfo', 'module_finder name ispkg')
ModuleInfo.__doc__ = 'A namedtuple with minimal info about a module.'


def _get_spec(finder, name):
 """Return the finder-specific module spec."""
 # Works with legacy finders.
 try:
 find_spec = finder.find_spec
 except AttributeError:
 loader = finder.find_module(name)
 if loader is None:
 return None
 return importlib.util.spec_from_loader(name, loader)
 else:
 return find_spec(name)


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 != importlib.util.MAGIC_NUMBER:
 return None

 stream.read(12) # Skip rest of the header
 return marshal.load(stream)


def walk_packages(path=None, prefix='', onerror=None):
 """Yields ModuleInfo 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 info in iter_modules(path, prefix):
 yield info

 if info.ispkg:
 try:
 __import__(info.name)
 except ImportError:
 if onerror is not None:
 onerror(info.name)
 except Exception:
 if onerror is not None:
 onerror(info.name)
 else:
 raise
 else:
 path = getattr(sys.modules[info.name], '__path__', None) or []

 # don't traverse path items we've seen before
 path = [p for p in path if not seen(p)]

 yield from walk_packages(path, info.name+'.', onerror)


def iter_modules(path=None, prefix=''):
 """Yields ModuleInfo 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()
 elif isinstance(path, str):
 raise ValueError("path must be None or list of paths to look for "
 "modules in")
 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 ModuleInfo(i, name, ispkg)


@simplegeneric
def iter_importer_modules(importer, prefix=''):
 if not hasattr(importer, 'iter_modules'):
 return []
 return importer.iter_modules(prefix)


# Implement a file walker for the normal importlib path hook
def _iter_file_finder_modules(importer, prefix=''):
 if importer.path is None or not os.path.isdir(importer.path):
 return

 yielded = {}
 import inspect
 try:
 filenames = os.listdir(importer.path)
 except OSError:
 # ignore unreadable directories like import does
 filenames = []
 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(importer.path, fn)
 ispkg = False

 if not modname and os.path.isdir(path) and '.' not in fn:
 modname = fn
 try:
 dircontents = os.listdir(path)
 except OSError:
 # ignore unreadable directories like import does
 dircontents = []
 for fn in dircontents:
 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

iter_importer_modules.register(
 importlib.machinery.FileFinder, _iter_file_finder_modules)


def _import_imp():
 global imp
 with warnings.catch_warnings():
 warnings.simplefilter('ignore', DeprecationWarning)
 imp = importlib.import_module('imp')

class ImpImporter:
 """PEP 302 Finder that wraps Python's "classic" import algorithm

 ImpImporter(dirname) produces a PEP 302 finder that searches that
 directory. ImpImporter(None) produces a PEP 302 finder 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):
 global imp
 warnings.warn("This emulation is deprecated, use 'importlib' instead",
 DeprecationWarning)
 _import_imp()
 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
 try:
 filenames = os.listdir(self.path)
 except OSError:
 # ignore unreadable directories like import does
 filenames = []
 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
 try:
 dircontents = os.listdir(path)
 except OSError:
 # ignore unreadable directories like import does
 dircontents = []
 for fn in dircontents:
 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):
 warnings.warn("This emulation is deprecated, use 'importlib' instead",
 DeprecationWarning)
 _import_imp()
 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):
 with open(pathname, "rb") as file:
 return file.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, 'r')
 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]):
 with open(self.filename[:-1], 'r') as f:
 self.source = f.read()
 elif mod_type==imp.PKG_DIRECTORY:
 self.source = self._get_delegate().get_source()
 return self.source

 def _get_delegate(self):
 finder = ImpImporter(self.filename)
 spec = _get_spec(finder, '__init__')
 return spec.loader

 def get_filename(self, fullname=None):
 fullname = self._fix_name(fullname)
 mod_type = self.etc[2]
 if mod_type==imp.PKG_DIRECTORY:
 return self._get_delegate().get_filename()
 elif mod_type 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 = sorted(zipimport._zip_directory_cache[importer.archive])
 _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 prefix + 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 finder for the given path item

 The returned finder is cached in sys.path_importer_cache
 if it was newly created by a path hook.

 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)
 sys.path_importer_cache.setdefault(path_item, importer)
 break
 except ImportError:
 pass
 else:
 importer = None
 return importer


def iter_importers(fullname=""):
 """Yield finders for the given module name

 If fullname contains a '.', the finders will be for the package
 containing fullname, otherwise they will be all registered top level
 finders (i.e. those on both sys.meta_path and sys.path_hooks).

 If the named module is in a package, that package is imported as a side
 effect of invoking this function.

 If no module name is specified, all top level finders are produced.
 """
 if fullname.startswith('.'):
 msg = "Relative module name {!r} not supported".format(fullname)
 raise ImportError(msg)
 if '.' in fullname:
 # Get the containing package's __path__
 pkg_name = fullname.rpartition(".")[0]
 pkg = importlib.import_module(pkg_name)
 path = getattr(pkg, '__path__', None)
 if path is None:
 return
 else:
 yield from sys.meta_path
 path = sys.path
 for item in path:
 yield get_importer(item)


def get_loader(module_or_name):
 """Get a "loader" object for module_or_name

 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__.
 """
 if module_or_name in sys.modules:
 module_or_name = sys.modules[module_or_name]
 if module_or_name is None:
 return None
 if isinstance(module_or_name, ModuleType):
 module = module_or_name
 loader = getattr(module, '__loader__', None)
 if loader is not None:
 return loader
 if getattr(module, '__spec__', None) is None:
 return None
 fullname = module.__name__
 else:
 fullname = module_or_name
 return find_loader(fullname)


def find_loader(fullname):
 """Find a "loader" object for fullname

 This is a backwards compatibility wrapper around
 importlib.util.find_spec that converts most failures to ImportError
 and only returns the loader rather than the full spec
 """
 if fullname.startswith('.'):
 msg = "Relative module name {!r} not supported".format(fullname)
 raise ImportError(msg)
 try:
 spec = importlib.util.find_spec(fullname)
 except (ImportError, AttributeError, TypeError, ValueError) as ex:
 # This hack fixes an impedance mismatch between pkgutil and
 # importlib, where the latter raises other errors for cases where
 # pkgutil previously raised ImportError
 msg = "Error while finding loader for {!r} ({}: {})"
 raise ImportError(msg.format(fullname, type(ex), ex)) from ex
 return spec.loader if spec is not None else 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

 sname_pkg = name + ".pkg"

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

 parent_package, _, final_name = name.rpartition('.')
 if parent_package:
 try:
 search_path = sys.modules[parent_package].__path__
 except (KeyError, AttributeError):
 # We can't do anything: find_loader() returns None when
 # passed a dotted name.
 return path
 else:
 search_path = sys.path

 for dir in search_path:
 if not isinstance(dir, str):
 continue

 finder = get_importer(dir)
 if finder is not None:
 portions = []
 if hasattr(finder, 'find_spec'):
 spec = finder.find_spec(final_name)
 if spec is not None:
 portions = spec.submodule_search_locations or []
 # Is this finder PEP 420 compliant?
 elif hasattr(finder, 'find_loader'):
 _, portions = finder.find_loader(final_name)

 for portion in portions:
 # XXX This may still add duplicate entries to path on
 # case-insensitive filesystems
 if portion not in path:
 path.append(portion)

 # XXX Is this the right thing for subpackages like zope.app?
 # It looks for a file named "zope.app.pkg"
 pkgfile = os.path.join(dir, sname_pkg)
 if os.path.isfile(pkgfile):
 try:
 f = open(pkgfile)
 except OSError as msg:
 sys.stderr.write("Can't open %s: %s\n" %
 (pkgfile, msg))
 else:
 with f:
 for line in f:
 line = line.rstrip('\n')
 if not line or line.startswith('#'):
 continue
 path.append(line) # Don't check for existence!

 return path


def get_data(package, resource):
 """Get a resource from a package.

 This is a wrapper round the PEP 302 loader get_data API. The package
 argument should be the name of a package, in standard module format
 (foo.bar). The resource argument should be in the form of a relative
 filename, using '/' as the path separator. The parent directory name '..'
 is not allowed, and nor is a rooted name (starting with a '/').

 The function returns a binary string, which is the contents of the
 specified resource.

 For packages located in the filesystem, which have already been imported,
 this is the rough equivalent of

 d = os.path.dirname(sys.modules[package].__file__)
 data = open(os.path.join(d, resource), 'rb').read()

 If the package cannot be located or loaded, or it uses a PEP 302 loader
 which does not support get_data(), then None is returned.
 """

 spec = importlib.util.find_spec(package)
 if spec is None:
 return None
 loader = spec.loader
 if loader is None or not hasattr(loader, 'get_data'):
 return None
 # XXX needs test
 mod = (sys.modules.get(package) or
 importlib._bootstrap._load(spec))
 if mod is None or not hasattr(mod, '__file__'):
 return None

 # Modify the resource name to be compatible with the loader.get_data
 # signature - an os.path format "filename" starting with the dirname of
 # the package's __file__
 parts = resource.split('/')
 parts.insert(0, os.path.dirname(mod.__file__))
 resource_name = os.path.join(*parts)
 return loader.get_data(resource_name)