# copyright 2003-2011 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
"""
* the vregistry handles various types of objects interacting
  together. The vregistry handles registration of dynamically loaded
  objects and provides a convenient api to access those objects
  according to a context

* to interact with the vregistry, objects should inherit from the
  AppObject abstract class

* the selection procedure has been generalized by delegating to a
  selector, which is responsible to score the appobject according to the
  current state (req, rset, row, col). At the end of the selection, if
  a appobject class has been found, an instance of this class is
  returned. The selector is instantiated at appobject registration
"""

__docformat__ = "restructuredtext en"

import sys
from os import listdir, stat
from os.path import dirname, join, realpath, isdir, exists
from logging import getLogger
from warnings import warn

from logilab.common.deprecation import deprecated, class_moved
from logilab.common.logging_ext import set_log_methods

from cubicweb import CW_SOFTWARE_ROOT
from cubicweb import RegistryNotFound, ObjectNotFound, NoSelectableObject
from cubicweb.appobject import AppObject, class_regid


def _toload_info(path, extrapath, _toload=None):
    """return a dictionary of <modname>: <modpath> and an ordered list of
    (file, module name) to load
    """
    from logilab.common.modutils import modpath_from_file
    if _toload is None:
        assert isinstance(path, list)
        _toload = {}, []
    for fileordir in path:
        if isdir(fileordir) and exists(join(fileordir, '__init__.py')):
            subfiles = [join(fileordir, fname) for fname in listdir(fileordir)]
            _toload_info(subfiles, extrapath, _toload)
        elif fileordir[-3:] == '.py':
            modpath = modpath_from_file(fileordir, extrapath)
            # omit '__init__' from package's name to avoid loading that module
            # once for each name when it is imported by some other appobject
            # module. This supposes import in modules are done as::
            #
            #   from package import something
            #
            # not::
            #
            #  from package.__init__ import something
            #
            # which seems quite correct.
            if modpath[-1] == '__init__':
                modpath.pop()
            modname = '.'.join(modpath)
            _toload[0][modname] = fileordir
            _toload[1].append((fileordir, modname))
    return _toload


def classid(cls):
    """returns a unique identifier for an appobject class"""
    return '%s.%s' % (cls.__module__, cls.__name__)

def class_registries(cls, registryname):
    if registryname:
        return (registryname,)
    return cls.__registries__


class Registry(dict):

    def __init__(self, config):
        super(Registry, self).__init__()
        self.config = config

    def __getitem__(self, name):
        """return the registry (dictionary of class objects) associated to
        this name
        """
        try:
            return super(Registry, self).__getitem__(name)
        except KeyError:
            raise ObjectNotFound(name), None, sys.exc_info()[-1]

    def initialization_completed(self):
        for appobjects in self.itervalues():
            for appobjectcls in appobjects:
                appobjectcls.__registered__(self)

    def register(self, obj, oid=None, clear=False):
        """base method to add an object in the registry"""
        assert not '__abstract__' in obj.__dict__
        oid = oid or class_regid(obj)
        assert oid
        if clear:
            appobjects = self[oid] =  []
        else:
            appobjects = self.setdefault(oid, [])
        assert not obj in appobjects, \
               'object %s is already registered' % obj
        appobjects.append(obj)

    def register_and_replace(self, obj, replaced):
        # XXXFIXME this is a duplication of unregister()
        # remove register_and_replace in favor of unregister + register
        # or simplify by calling unregister then register here
        if not isinstance(replaced, basestring):
            replaced = classid(replaced)
        # prevent from misspelling
        assert obj is not replaced, 'replacing an object by itself: %s' % obj
        registered_objs = self.get(class_regid(obj), ())
        for index, registered in enumerate(registered_objs):
            if classid(registered) == replaced:
                del registered_objs[index]
                break
        else:
            self.warning('trying to replace an unregistered view %s by %s',
                         replaced, obj)
        self.register(obj)

    def unregister(self, obj):
        clsid = classid(obj)
        oid = class_regid(obj)
        for registered in self.get(oid, ()):
            # use classid() to compare classes because vreg will probably
            # have its own version of the class, loaded through execfile
            if classid(registered) == clsid:
                self[oid].remove(registered)
                break
        else:
            self.warning('can\'t remove %s, no id %s in the registry',
                         clsid, oid)

    def all_objects(self):
        """return a list containing all objects in this registry.
        """
        result = []
        for objs in self.values():
            result += objs
        return result

    # dynamic selection methods ################################################

    def object_by_id(self, oid, *args, **kwargs):
        """return object with the `oid` identifier. Only one object is expected
        to be found.

        raise :exc:`ObjectNotFound` if not object with id <oid> in <registry>

        raise :exc:`AssertionError` if there is more than one object there
        """
        objects = self[oid]
        assert len(objects) == 1, objects
        return objects[0](*args, **kwargs)

    def select(self, __oid, *args, **kwargs):
        """return the most specific object among those with the given oid
        according to the given context.

        raise :exc:`ObjectNotFound` if not object with id <oid> in <registry>

        raise :exc:`NoSelectableObject` if not object apply
        """
        obj =  self._select_best(self[__oid], *args, **kwargs)
        if obj is None:
            raise NoSelectableObject(args, kwargs, self[__oid] )
        return obj

    def select_or_none(self, __oid, *args, **kwargs):
        """return the most specific object among those with the given oid
        according to the given context, or None if no object applies.
        """
        try:
            return self.select(__oid, *args, **kwargs)
        except (NoSelectableObject, ObjectNotFound):
            return None

    def possible_objects(self, *args, **kwargs):
        """return an iterator on possible objects in this registry for the given
        context
        """
        for appobjects in self.itervalues():
            obj = self._select_best(appobjects,  *args, **kwargs)
            if obj is None:
                continue
            yield obj

    def _select_best(self, appobjects, *args, **kwargs):
        """return an instance of the most specific object according
        to parameters

        return None if not object apply (don't raise `NoSelectableObject` since
        it's costly when searching appobjects using `possible_objects`
        (e.g. searching for hooks).
        """
        score, winners = 0, None
        for appobject in appobjects:
            appobjectscore = appobject.__select__(appobject, *args, **kwargs)
            if appobjectscore > score:
                score, winners = appobjectscore, [appobject]
            elif appobjectscore > 0 and appobjectscore == score:
                winners.append(appobject)
        if winners is None:
            return None
        if len(winners) > 1:
            # log in production environement / test, error while debugging
            msg = 'select ambiguity: %s\n(args: %s, kwargs: %s)'
            if self.config.debugmode or self.config.mode == 'test':
                # raise bare exception in debug mode
                raise Exception(msg % (winners, args, kwargs.keys()))
            self.error(msg, winners, args, kwargs.keys())
        # return the result of calling the appobject
        return winners[0](*args, **kwargs)

    # these are overridden by set_log_methods below
    # only defining here to prevent pylint from complaining
    info = warning = error = critical = exception = debug = lambda msg,*a,**kw: None


class VRegistry(dict):
    """class responsible to register, propose and select the various
    elements used to build the web interface. Currently, we have templates,
    views, actions and components.
    """

    def __init__(self, config):
        super(VRegistry, self).__init__()
        self.config = config
        # need to clean sys.path this to avoid import confusion pb (i.e.  having
        # the same module loaded as 'cubicweb.web.views' subpackage and as
        # views' or 'web.views' subpackage. This is mainly for testing purpose,
        # we should'nt need this in production environment
        for webdir in (join(dirname(realpath(__file__)), 'web'),
                       join(dirname(__file__), 'web')):
            if webdir in sys.path:
                sys.path.remove(webdir)
        if CW_SOFTWARE_ROOT in sys.path:
            sys.path.remove(CW_SOFTWARE_ROOT)

    def reset(self):
        # don't use self.clear, we want to keep existing subdictionaries
        for subdict in self.itervalues():
            subdict.clear()
        self._lastmodifs = {}

    def __getitem__(self, name):
        """return the registry (dictionary of class objects) associated to
        this name
        """
        try:
            return super(VRegistry, self).__getitem__(name)
        except KeyError:
            raise RegistryNotFound(name), None, sys.exc_info()[-1]

    # methods for explicit (un)registration ###################################

    # default class, when no specific class set
    REGISTRY_FACTORY = {None: Registry}

    def registry_class(self, regid):
        try:
            return self.REGISTRY_FACTORY[regid]
        except KeyError:
            return self.REGISTRY_FACTORY[None]

    def setdefault(self, regid):
        try:
            return self[regid]
        except KeyError:
            self[regid] = self.registry_class(regid)(self.config)
            return self[regid]

#     def clear(self, key):
#         regname, oid = key.split('.')
#         self[regname].pop(oid, None)

    def register_all(self, objects, modname, butclasses=()):
        """register all `objects` given. Objects which are not from the module
        `modname` or which are in `butclasses` won't be registered.

        Typical usage is:

        .. sourcecode:: python

            vreg.register_all(globals().values(), __name__, (ClassIWantToRegisterExplicitly,))

        So you get partially automatic registration, keeping manual registration
        for some object (to use
        :meth:`~cubicweb.cwvreg.CubicWebRegistry.register_and_replace` for
        instance)
        """
        for obj in objects:
            try:
                if obj.__module__ != modname or obj in butclasses:
                    continue
                oid = class_regid(obj)
            except AttributeError:
                continue
            if oid and not '__abstract__' in obj.__dict__:
                self.register(obj, oid=oid)

    def register(self, obj, registryname=None, oid=None, clear=False):
        """register `obj` application object into `registryname` or
        `obj.__registry__` if not specified, with identifier `oid` or
        `obj.__regid__` if not specified.

        If `clear` is true, all objects with the same identifier will be
        previously unregistered.
        """
        assert not '__abstract__' in obj.__dict__
        try:
            vname = obj.__name__
        except AttributeError:
            # XXX may occurs?
            vname = obj.__class__.__name__
        for registryname in class_registries(obj, registryname):
            registry = self.setdefault(registryname)
            registry.register(obj, oid=oid, clear=clear)
            self.debug('register %s in %s[\'%s\']',
                       vname, registryname, oid or class_regid(obj))
        self._loadedmods.setdefault(obj.__module__, {})[classid(obj)] = obj

    def unregister(self, obj, registryname=None):
        """unregister `obj` application object from the registry `registryname` or
        `obj.__registry__` if not specified.
        """
        for registryname in class_registries(obj, registryname):
            self[registryname].unregister(obj)

    def register_and_replace(self, obj, replaced, registryname=None):
        """register `obj` application object into `registryname` or
        `obj.__registry__` if not specified. If found, the `replaced` object
        will be unregistered first (else a warning will be issued as it's
        generally unexpected).
        """
        for registryname in class_registries(obj, registryname):
            self[registryname].register_and_replace(obj, replaced)

    # initialization methods ###################################################

    def init_registration(self, path, extrapath=None):
        self.reset()
        # compute list of all modules that have to be loaded
        self._toloadmods, filemods = _toload_info(path, extrapath)
        # XXX is _loadedmods still necessary ? It seems like it's useful
        #     to avoid loading same module twice, especially with the
        #     _load_ancestors_then_object logic but this needs to be checked
        self._loadedmods = {}
        return filemods

    def register_objects(self, path, extrapath=None):
        # load views from each directory in the instance's path
        filemods = self.init_registration(path, extrapath)
        for filepath, modname in filemods:
            self.load_file(filepath, modname)
        self.initialization_completed()

    def initialization_completed(self):
        for regname, reg in self.iteritems():
            reg.initialization_completed()

    def _mdate(self, filepath):
        try:
            return stat(filepath)[-2]
        except OSError:
            # this typically happens on emacs backup files (.#foo.py)
            self.warning('Unable to load %s. It is likely to be a backup file',
                         filepath)
            return None

    def is_reload_needed(self, path):
        """return True if something module changed and the registry should be
        reloaded
        """
        lastmodifs = self._lastmodifs
        for fileordir in path:
            if isdir(fileordir) and exists(join(fileordir, '__init__.py')):
                if self.is_reload_needed([join(fileordir, fname)
                                          for fname in listdir(fileordir)]):
                    return True
            elif fileordir[-3:] == '.py':
                mdate = self._mdate(fileordir)
                if mdate is None:
                    continue # backup file, see _mdate implementation
                elif "flymake" in fileordir:
                    # flymake + pylint in use, don't consider these they will corrupt the registry
                    continue
                if fileordir not in lastmodifs or lastmodifs[fileordir] < mdate:
                    self.info('File %s changed since last visit', fileordir)
                    return True
        return False

    def load_file(self, filepath, modname):
        """load app objects from a python file"""
        from logilab.common.modutils import load_module_from_name
        if modname in self._loadedmods:
            return
        self._loadedmods[modname] = {}
        mdate = self._mdate(filepath)
        if mdate is None:
            return # backup file, see _mdate implementation
        elif "flymake" in filepath:
            # flymake + pylint in use, don't consider these they will corrupt the registry
            return
        # set update time before module loading, else we get some reloading
        # weirdness in case of syntax error or other error while importing the
        # module
        self._lastmodifs[filepath] = mdate
        # load the module
        module = load_module_from_name(modname)
        self.load_module(module)

    def load_module(self, module):
        self.info('loading %s from %s', module.__name__, module.__file__)
        if hasattr(module, 'registration_callback'):
            module.registration_callback(self)
        else:
            for objname, obj in vars(module).items():
                if objname.startswith('_'):
                    continue
                self._load_ancestors_then_object(module.__name__, obj)

    def _load_ancestors_then_object(self, modname, appobjectcls):
        """handle automatic appobject class registration:

        - first ensure parent classes are already registered

        - class with __abstract__ == True in their local dictionnary or
          with a name starting with an underscore are not registered

        - appobject class needs to have __registry__ and __regid__ attributes
          set to a non empty string to be registered.
        """
        # imported classes
        objmodname = getattr(appobjectcls, '__module__', None)
        if objmodname != modname:
            if objmodname in self._toloadmods:
                self.load_file(self._toloadmods[objmodname], objmodname)
            return
        # skip non registerable object
        try:
            if not issubclass(appobjectcls, AppObject):
                return
        except TypeError:
            return
        clsid = classid(appobjectcls)
        if clsid in self._loadedmods[modname]:
            return
        self._loadedmods[modname][clsid] = appobjectcls
        for parent in appobjectcls.__bases__:
            self._load_ancestors_then_object(modname, parent)
        if (appobjectcls.__dict__.get('__abstract__')
            or appobjectcls.__name__[0] == '_'
            or not appobjectcls.__registries__
            or not class_regid(appobjectcls)):
            return
        try:
            self.register(appobjectcls)
        except Exception, ex:
            if self.config.mode in ('test', 'dev'):
                raise
            self.exception('appobject %s registration failed: %s',
                           appobjectcls, ex)
    # these are overridden by set_log_methods below
    # only defining here to prevent pylint from complaining
    info = warning = error = critical = exception = debug = lambda msg,*a,**kw: None


# init logging
set_log_methods(VRegistry, getLogger('cubicweb.vreg'))
set_log_methods(Registry, getLogger('cubicweb.registry'))


# XXX bw compat functions #####################################################

from cubicweb.appobject import objectify_selector, AndSelector, OrSelector, Selector

Selector = class_moved(Selector)