"""Import hook support.

Consistent use of this module will make it possible to change the

different mechanisms involved in loading modules independently.

While the built-in module imp exports interfaces to the built-in

module searching and loading algorithm, and it is possible to replace

the built-in function __import__ in order to change the semantics of

the import statement, until now it has been difficult to combine the

effect of different __import__ hacks, like loading modules from URLs

by rimport.py, or restricted execution by rexec.py.

This module defines three new concepts:

1) A "file system hooks" class provides an interface to a filesystem.

One hooks class is defined (Hooks), which uses the interface provided

by standard modules os and os.path.  It should be used as the base

class for other hooks classes.

2) A "module loader" class provides an interface to search for a

module in a search path and to load it.  It defines a method which

searches for a module in a single directory; by overriding this method

one can redefine the details of the search.  If the directory is None,

built-in and frozen modules are searched instead.

Two module loader class are defined, both implementing the search

strategy used by the built-in __import__ function: ModuleLoader uses

the imp module's find_module interface, while HookableModuleLoader

uses a file system hooks class to interact with the file system.  Both

use the imp module's load_* interfaces to actually load the module.

3) A "module importer" class provides an interface to import a

module, as well as interfaces to reload and unload a module.  It also

provides interfaces to install and uninstall itself instead of the

default __import__ and reload (and unload) functions.

One module importer class is defined (ModuleImporter), which uses a

module loader instance passed in (by default HookableModuleLoader is

instantiated).

The classes defined here should be used as base classes for extended

functionality along those lines.

If a module importer class supports dotted names, its import_module()

must return a different value depending on whether it is called on

behalf of a "from ... import ..." statement or not.  (This is caused

by the way the __import__ hook is used by the Python interpreter.)  It

would also do wise to install a different version of reload().

"""

import __builtin__

import imp

import os

import sys

__all__ = ["BasicModuleLoader","Hooks","ModuleLoader","FancyModuleLoader",

           "BasicModuleImporter","ModuleImporter","install","uninstall"]

VERBOSE = 0

from imp import C_EXTENSION, PY_SOURCE, PY_COMPILED

from imp import C_BUILTIN, PY_FROZEN, PKG_DIRECTORY

BUILTIN_MODULE = C_BUILTIN

FROZEN_MODULE = PY_FROZEN

class _Verbose:

    def __init__(self, verbose = VERBOSE):

        self.verbose = verbose

    def get_verbose(self):

        return self.verbose

    def set_verbose(self, verbose):

        self.verbose = verbose

    # XXX The following is an experimental interface

    def note(self, *args):

        if self.verbose:

            self.message(*args)

    def message(self, format, *args):

        if args:

            print format%args

        else:

            print format

class BasicModuleLoader(_Verbose):

    """Basic module loader.

    This provides the same functionality as built-in import.  It

    doesn't deal with checking sys.modules -- all it provides is

    find_module() and a load_module(), as well as find_module_in_dir()

    which searches just one directory, and can be overridden by a

    derived class to change the module search algorithm when the basic

    dependency on sys.path is unchanged.

    The interface is a little more convenient than imp's:

    find_module(name, [path]) returns None or 'stuff', and

    load_module(name, stuff) loads the module.

    """

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

        if path is None:

            path = [None] + self.default_path()

        for dir in path:

            stuff = self.find_module_in_dir(name, dir)

            if stuff: return stuff

        return None

    def default_path(self):

        return sys.path

    def find_module_in_dir(self, name, dir):

        if dir is None:

            return self.find_builtin_module(name)

        else:

            try:

                return imp.find_module(name, [dir])

            except ImportError:

                return None

    def find_builtin_module(self, name):

        # XXX frozen packages?

        if imp.is_builtin(name):

            return None, '', ('', '', BUILTIN_MODULE)

        if imp.is_frozen(name):

            return None, '', ('', '', FROZEN_MODULE)

        return None

    def load_module(self, name, stuff):

        file, filename, info = stuff

        try:

            return imp.load_module(name, file, filename, info)

        finally:

            if file: file.close()

class Hooks(_Verbose):

    """Hooks into the filesystem and interpreter.

    By deriving a subclass you can redefine your filesystem interface,

    e.g. to merge it with the URL space.

    This base class behaves just like the native filesystem.

    """

    # imp interface

    def get_suffixes(self): return imp.get_suffixes()

    def new_module(self, name): return imp.new_module(name)

    def is_builtin(self, name): return imp.is_builtin(name)

    def init_builtin(self, name): return imp.init_builtin(name)

    def is_frozen(self, name): return imp.is_frozen(name)

    def init_frozen(self, name): return imp.init_frozen(name)

    def get_frozen_object(self, name): return imp.get_frozen_object(name)

    def load_source(self, name, filename, file=None):

        return imp.load_source(name, filename, file)

    def load_compiled(self, name, filename, file=None):

        return imp.load_compiled(name, filename, file)

    def load_dynamic(self, name, filename, file=None):

        return imp.load_dynamic(name, filename, file)

    def load_package(self, name, filename, file=None):

        return imp.load_module(name, file, filename, ("", "", PKG_DIRECTORY))

    def add_module(self, name):

        d = self.modules_dict()

        if name in d: return d[name]

        d[name] = m = self.new_module(name)

        return m

    # sys interface

    def modules_dict(self): return sys.modules

    def default_path(self): return sys.path

    def path_split(self, x): return os.path.split(x)

    def path_join(self, x, y): return os.path.join(x, y)

    def path_isabs(self, x): return os.path.isabs(x)

    # etc.

    def path_exists(self, x): return os.path.exists(x)

    def path_isdir(self, x): return os.path.isdir(x)

    def path_isfile(self, x): return os.path.isfile(x)

    def path_islink(self, x): return os.path.islink(x)

    # etc.

    def openfile(self, *x): return open(*x)

    openfile_error = IOError

    def listdir(self, x): return os.listdir(x)

    listdir_error = os.error

    # etc.

class ModuleLoader(BasicModuleLoader):

    """Default module loader; uses file system hooks.

    By defining suitable hooks, you might be able to load modules from

    other sources than the file system, e.g. from compressed or

    encrypted files, tar files or (if you're brave!) URLs.

    """

    def __init__(self, hooks = None, verbose = VERBOSE):

        BasicModuleLoader.__init__(self, verbose)

        self.hooks = hooks or Hooks(verbose)

    def default_path(self):

        return self.hooks.default_path()

    def modules_dict(self):

        return self.hooks.modules_dict()

    def get_hooks(self):

        return self.hooks

    def set_hooks(self, hooks):

        self.hooks = hooks

    def find_builtin_module(self, name):

        # XXX frozen packages?

        if self.hooks.is_builtin(name):

            return None, '', ('', '', BUILTIN_MODULE)

        if self.hooks.is_frozen(name):

            return None, '', ('', '', FROZEN_MODULE)

        return None

    def find_module_in_dir(self, name, dir, allow_packages=1):

        if dir is None:

            return self.find_builtin_module(name)

        if allow_packages:

            fullname = self.hooks.path_join(dir, name)

            if self.hooks.path_isdir(fullname):

                stuff = self.find_module_in_dir("__init__", fullname, 0)

                if stuff:

                    file = stuff[0]

                    if file: file.close()

                    return None, fullname, ('', '', PKG_DIRECTORY)

        for info in self.hooks.get_suffixes():

            suff, mode, type = info

            fullname = self.hooks.path_join(dir, name+suff)

            try:

                fp = self.hooks.openfile(fullname, mode)

                return fp, fullname, info

            except self.hooks.openfile_error:

                pass

        return None

    def load_module(self, name, stuff):

        file, filename, info = stuff

        (suff, mode, type) = info

        try:

            if type == BUILTIN_MODULE:

                return self.hooks.init_builtin(name)

            if type == FROZEN_MODULE:

                return self.hooks.init_frozen(name)

            if type == C_EXTENSION:

                m = self.hooks.load_dynamic(name, filename, file)

            elif type == PY_SOURCE:

                m = self.hooks.load_source(name, filename, file)

            elif type == PY_COMPILED:

                m = self.hooks.load_compiled(name, filename, file)

            elif type == PKG_DIRECTORY:

                m = self.hooks.load_package(name, filename, file)

            else:

                raise ImportError, "Unrecognized module type (%r) for %s" % \

                      (type, name)

        finally:

            if file: file.close()

        m.__file__ = filename

        return m

class FancyModuleLoader(ModuleLoader):

    """Fancy module loader -- parses and execs the code itself."""

    def load_module(self, name, stuff):

        file, filename, (suff, mode, type) = stuff

        realfilename = filename

        path = None

        if type == PKG_DIRECTORY:

            initstuff = self.find_module_in_dir("__init__", filename, 0)

            if not initstuff:

                raise ImportError, "No __init__ module in package %s" % name

            initfile, initfilename, initinfo = initstuff

            initsuff, initmode, inittype = initinfo

            if inittype not in (PY_COMPILED, PY_SOURCE):

                if initfile: initfile.close()

                raise ImportError, \

                    "Bad type (%r) for __init__ module in package %s" % (

                    inittype, name)

            path = [filename]

            file = initfile

            realfilename = initfilename

            type = inittype

        if type == FROZEN_MODULE:

            code = self.hooks.get_frozen_object(name)

        elif type == PY_COMPILED:

            import marshal

            file.seek(8)

            code = marshal.load(file)

        elif type == PY_SOURCE:

            data = file.read()

            code = compile(data, realfilename, 'exec')

        else:

            return ModuleLoader.load_module(self, name, stuff)

        m = self.hooks.add_module(name)

        if path:

            m.__path__ = path

        m.__file__ = filename

        try:

            exec code in m.__dict__

        except:

            d = self.hooks.modules_dict()

            if name in d:

                del d[name]

            raise

        return m

class BasicModuleImporter(_Verbose):

    """Basic module importer; uses module loader.

    This provides basic import facilities but no package imports.

    """

    def __init__(self, loader = None, verbose = VERBOSE):

        _Verbose.__init__(self, verbose)

        self.loader = loader or ModuleLoader(None, verbose)

        self.modules = self.loader.modules_dict()

    def get_loader(self):

        return self.loader

    def set_loader(self, loader):

        self.loader = loader

    def get_hooks(self):

        return self.loader.get_hooks()

    def set_hooks(self, hooks):

        return self.loader.set_hooks(hooks)

    def import_module(self, name, globals={}, locals={}, fromlist=[]):

        name = str(name)

        if name in self.modules:

            return self.modules[name] # Fast path

        stuff = self.loader.find_module(name)

        if not stuff:

            raise ImportError, "No module named %s" % name

        return self.loader.load_module(name, stuff)

    def reload(self, module, path = None):

        name = str(module.__name__)

        stuff = self.loader.find_module(name, path)

        if not stuff:

            raise ImportError, "Module %s not found for reload" % name

        return self.loader.load_module(name, stuff)

    def unload(self, module):

        del self.modules[str(module.__name__)]

        # XXX Should this try to clear the module's namespace?

    def install(self):

        self.save_import_module = __builtin__.__import__

        self.save_reload = __builtin__.reload

        if not hasattr(__builtin__, 'unload'):

            __builtin__.unload = None

        self.save_unload = __builtin__.unload

        __builtin__.__import__ = self.import_module

        __builtin__.reload = self.reload

        __builtin__.unload = self.unload

    def uninstall(self):

        __builtin__.__import__ = self.save_import_module

        __builtin__.reload = self.save_reload

        __builtin__.unload = self.save_unload

        if not __builtin__.unload:

            del __builtin__.unload

class ModuleImporter(BasicModuleImporter):

    """A module importer that supports packages."""

    def import_module(self, name, globals=None, locals=None, fromlist=None):

        parent = self.determine_parent(globals)

        q, tail = self.find_head_package(parent, str(name))

        m = self.load_tail(q, tail)

        if not fromlist:

            return q

        if hasattr(m, "__path__"):

            self.ensure_fromlist(m, fromlist)

        return m

    def determine_parent(self, globals):

        if not globals or not "__name__" in globals:

            return None

        pname = globals['__name__']

        if "__path__" in globals:

            parent = self.modules[pname]

            assert globals is parent.__dict__

            return parent

        if '.' in pname:

            i = pname.rfind('.')

            pname = pname[:i]

            parent = self.modules[pname]

            assert parent.__name__ == pname

            return parent

        return None

    def find_head_package(self, parent, name):

        if '.' in name:

            i = name.find('.')

            head = name[:i]

            tail = name[i+1:]

        else:

            head = name

            tail = ""

        if parent:

            qname = "%s.%s" % (parent.__name__, head)

        else:

            qname = head

        q = self.import_it(head, qname, parent)

        if q: return q, tail

        if parent:

            qname = head

            parent = None

            q = self.import_it(head, qname, parent)

            if q: return q, tail

        raise ImportError, "No module named " + qname

    def load_tail(self, q, tail):

        m = q

        while tail:

            i = tail.find('.')

            if i < 0: i = len(tail)

            head, tail = tail[:i], tail[i+1:]

            mname = "%s.%s" % (m.__name__, head)

            m = self.import_it(head, mname, m)

            if not m:

                raise ImportError, "No module named " + mname

        return m

    def ensure_fromlist(self, m, fromlist, recursive=0):

        for sub in fromlist:

            if sub == "*":

                if not recursive:

                    try:

                        all = m.__all__

                    except AttributeError:

                        pass

                    else:

                        self.ensure_fromlist(m, all, 1)

                continue

            if sub != "*" and not hasattr(m, sub):

                subname = "%s.%s" % (m.__name__, sub)

                submod = self.import_it(sub, subname, m)

                if not submod:

                    raise ImportError, "No module named " + subname

    def import_it(self, partname, fqname, parent, force_load=0):

        if not partname:

            raise ValueError, "Empty module name"

        if not force_load:

            try:

                return self.modules[fqname]

            except KeyError:

                pass

        try:

            path = parent and parent.__path__

        except AttributeError:

            return None

        partname = str(partname)

        stuff = self.loader.find_module(partname, path)

        if not stuff:

            return None

        fqname = str(fqname)

        m = self.loader.load_module(fqname, stuff)

        if parent:

            setattr(parent, partname, m)

        return m

    def reload(self, module):

        name = str(module.__name__)

        if '.' not in name:

            return self.import_it(name, name, None, force_load=1)

        i = name.rfind('.')

        pname = name[:i]

        parent = self.modules[pname]

        return self.import_it(name[i+1:], name, parent, force_load=1)

default_importer = None

current_importer = None

def install(importer = None):

    global current_importer

    current_importer = importer or default_importer or ModuleImporter()

    current_importer.install()

def uninstall():

    global current_importer

    current_importer.uninstall()