import sys
from functools import update_wrapper
from future.utils import iteritems
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.db.models.base import ModelBase
from django.utils import six
from django.views.decorators.cache import never_cache
from django.template.engine import Engine
import inspect

if six.PY2 and sys.getdefaultencoding() == 'ascii':
    import imp
    imp.reload(sys)
    sys.setdefaultencoding("utf-8")


class AlreadyRegistered(Exception):
    pass


class NotRegistered(Exception):
    pass


class MergeAdminMetaclass(type):

    def __new__(cls, name, bases, attrs):
        return type.__new__(cls, str(name), bases, attrs)


class AdminSite(object):

    def __init__(self, name='xadmin'):
        self.name = name
        self.app_name = 'xadmin'

        self._registry = {}  # model_class class -> admin_class class
        self._registry_avs = {}  # admin_view_class class -> admin_class class
        self._registry_settings = {}  # settings name -> admin_class class
        self._registry_views = []
        # url instance contains (path, admin_view class, name)
        self._registry_modelviews = []
        # url instance contains (path, admin_view class, name)
        self._registry_plugins = {}  # view_class class -> plugin_class class

        self._admin_view_cache = {}

        # self.check_dependencies()

        self.model_admins_order = 0

    def copy_registry(self):
        import copy
        return {
            'models': copy.copy(self._registry),
            'avs': copy.copy(self._registry_avs),
            'views': copy.copy(self._registry_views),
            'settings': copy.copy(self._registry_settings),
            'modelviews': copy.copy(self._registry_modelviews),
            'plugins': copy.copy(self._registry_plugins),
        }

    def restore_registry(self, data):
        self._registry = data['models']
        self._registry_avs = data['avs']
        self._registry_views = data['views']
        self._registry_settings = data['settings']
        self._registry_modelviews = data['modelviews']
        self._registry_plugins = data['plugins']

    def register_modelview(self, path, admin_view_class, name):
        from xadmin.views.base import BaseAdminView
        if issubclass(admin_view_class, BaseAdminView):
            self._registry_modelviews.append((path, admin_view_class, name))
        else:
            raise ImproperlyConfigured(u'The registered view class %s isn\'t subclass of %s' %
                                       (admin_view_class.__name__, BaseAdminView.__name__))

    def register_view(self, path, admin_view_class, name):
        self._registry_views.append((path, admin_view_class, name))

    def register_plugin(self, plugin_class, admin_view_class):
        from xadmin.views.base import BaseAdminPlugin
        if issubclass(plugin_class, BaseAdminPlugin):
            self._registry_plugins.setdefault(
                admin_view_class, []).append(plugin_class)
        else:
            raise ImproperlyConfigured(u'The registered plugin class %s isn\'t subclass of %s' %
                                       (plugin_class.__name__, BaseAdminPlugin.__name__))

    def register_settings(self, name, admin_class):
        self._registry_settings[name.lower()] = admin_class

    def register(self, model_or_iterable, admin_class=object, **options):
        from xadmin.views.base import BaseAdminView
        if isinstance(model_or_iterable, ModelBase) or issubclass(model_or_iterable, BaseAdminView):
            model_or_iterable = [model_or_iterable]
        for model in model_or_iterable:
            if isinstance(model, ModelBase):
                if model._meta.abstract:
                    raise ImproperlyConfigured('The model %s is abstract, so it '
                                               'cannot be registered with admin.' % model.__name__)

                if model in self._registry:
                    raise AlreadyRegistered(
                        'The model %s is already registered' % model.__name__)

                # If we got **options then dynamically construct a subclass of
                # admin_class with those **options.
                if options:
                    # For reasons I don't quite understand, without a __module__
                    # the created class appears to "live" in the wrong place,
                    # which causes issues later on.
                    options['__module__'] = __name__

                admin_class = type(str("%s%sAdmin" % (model._meta.app_label, model._meta.model_name)), (admin_class,), options or {})
                admin_class.model = model
                admin_class.order = self.model_admins_order
                self.model_admins_order += 1
                self._registry[model] = admin_class
            else:
                if model in self._registry_avs:
                    raise AlreadyRegistered('The admin_view_class %s is already registered' % model.__name__)
                if options:
                    options['__module__'] = __name__
                    admin_class = type(str(
                        "%sAdmin" % model.__name__), (admin_class,), options)

                # Instantiate the admin class to save in the registry
                self._registry_avs[model] = admin_class

    def unregister(self, model_or_iterable):
        """
        Unregisters the given model(s).

        If a model isn't already registered, this will raise NotRegistered.
        """
        from xadmin.views.base import BaseAdminView
        if isinstance(model_or_iterable, (ModelBase, BaseAdminView)):
            model_or_iterable = [model_or_iterable]
        for model in model_or_iterable:
            if isinstance(model, ModelBase):
                if model not in self._registry:
                    raise NotRegistered(
                        'The model %s is not registered' % model.__name__)
                del self._registry[model]
            else:
                if model not in self._registry_avs:
                    raise NotRegistered('The admin_view_class %s is not registered' % model.__name__)
                del self._registry_avs[model]

    def set_loginview(self, login_view):
        self.login_view = login_view

    def has_permission(self, request):
        """
        Returns True if the given HttpRequest has permission to view
        *at least one* page in the admin site.
        """
        return request.user.is_active and request.user.is_staff

    def check_dependencies(self):
        """
        Check that all things needed to run the admin have been correctly installed.

        The default implementation checks that LogEntry, ContentType and the
        auth context processor are installed.
        """
        from django.contrib.contenttypes.models import ContentType

        if not ContentType._meta.installed:
            raise ImproperlyConfigured("Put 'django.contrib.contenttypes' in "
                                       "your INSTALLED_APPS setting in order to use the admin application.")

        default_template_engine = Engine.get_default()
        if not ('django.contrib.auth.context_processors.auth' in default_template_engine.context_processors or
                'django.core.context_processors.auth' in default_template_engine.context_processors):
            raise ImproperlyConfigured("Put 'django.contrib.auth.context_processors.auth' "
                                       "in your TEMPLATE_CONTEXT_PROCESSORS setting in order to use the admin application.")

    def admin_view(self, view, cacheable=False):
        """
        Decorator to create an admin view attached to this ``AdminSite``. This
        wraps the view and provides permission checking by calling
        ``self.has_permission``.

        You'll want to use this from within ``AdminSite.get_urls()``:

            class MyAdminSite(AdminSite):

                def get_urls(self):
                    from django.conf.urls import url

                    urls = super(MyAdminSite, self).get_urls()
                    urls += [
                        url(r'^my_view/$', self.admin_view(some_view))
                    ]
                    return urls

        By default, admin_views are marked non-cacheable using the
        ``never_cache`` decorator. If the view can be safely cached, set
        cacheable=True.
        """
        def inner(request, *args, **kwargs):
            if not self.has_permission(request) and getattr(view, 'need_site_permission', True):
                return self.create_admin_view(self.login_view)(request, *args, **kwargs)
            return view(request, *args, **kwargs)
        if not cacheable:
            inner = never_cache(inner)
        return update_wrapper(inner, view)

    def _get_merge_attrs(self, option_class, plugin_class):
        return dict([(name, getattr(option_class, name)) for name in dir(option_class)
                     if name[0] != '_' and not callable(getattr(option_class, name)) and hasattr(plugin_class, name)])

    def _get_settings_class(self, admin_view_class):
        name = admin_view_class.__name__.lower()

        if name in self._registry_settings:
            return self._registry_settings[name]
        elif name.endswith('admin') and name[0:-5] in self._registry_settings:
            return self._registry_settings[name[0:-5]]
        elif name.endswith('adminview') and name[0:-9] in self._registry_settings:
            return self._registry_settings[name[0:-9]]

        return None

    def _create_plugin(self, option_classes):
        def merge_class(plugin_class):
            if option_classes:
                attrs = {}
                bases = [plugin_class]
                for oc in option_classes:
                    attrs.update(self._get_merge_attrs(oc, plugin_class))
                    meta_class = getattr(oc, plugin_class.__name__, getattr(oc, plugin_class.__name__.replace('Plugin', ''), None))
                    if meta_class:
                        bases.insert(0, meta_class)
                if attrs:
                    plugin_class = MergeAdminMetaclass(
                        '%s%s' % (''.join([oc.__name__ for oc in option_classes]), plugin_class.__name__),
                        tuple(bases), attrs)
            return plugin_class
        return merge_class

    def get_plugins(self, admin_view_class, *option_classes):
        from xadmin.views import BaseAdminView
        plugins = []
        opts = [oc for oc in option_classes if oc]
        for klass in admin_view_class.mro():
            if klass == BaseAdminView or issubclass(klass, BaseAdminView):
                merge_opts = []
                reg_class = self._registry_avs.get(klass)
                if reg_class:
                    merge_opts.append(reg_class)
                settings_class = self._get_settings_class(klass)
                if settings_class:
                    merge_opts.append(settings_class)
                merge_opts.extend(opts)
                ps = self._registry_plugins.get(klass, [])
                plugins.extend(map(self._create_plugin(
                    merge_opts), ps) if merge_opts else ps)
        return plugins

    def get_view_class(self, view_class, option_class=None, **opts):
        merges = [option_class] if option_class else []
        for klass in view_class.mro():
            reg_class = self._registry_avs.get(klass)
            if reg_class:
                merges.append(reg_class)
            settings_class = self._get_settings_class(klass)
            if settings_class:
                merges.append(settings_class)
            merges.append(klass)
        new_class_name = ''.join([c.__name__ for c in merges])

        if new_class_name not in self._admin_view_cache:
            plugins = self.get_plugins(view_class, option_class)
            self._admin_view_cache[new_class_name] = MergeAdminMetaclass(
                new_class_name, tuple(merges),
                dict({'plugin_classes': plugins, 'admin_site': self}, **opts))

        return self._admin_view_cache[new_class_name]

    def create_admin_view(self, admin_view_class):
        return self.get_view_class(admin_view_class).as_view()

    def create_model_admin_view(self, admin_view_class, model, option_class):
        return self.get_view_class(admin_view_class, option_class).as_view()

    def get_urls(self):
        from django.conf.urls import url, include
        from xadmin.views.base import BaseAdminView

        if settings.DEBUG:
            self.check_dependencies()

        def wrap(view, cacheable=False):
            def wrapper(*args, **kwargs):
                return self.admin_view(view, cacheable)(*args, **kwargs)
            return update_wrapper(wrapper, view)

        # Admin-site-wide views.
        urlpatterns = [
            url(r'^jsi18n/$', wrap(self.i18n_javascript, cacheable=True), name='jsi18n')
        ]

        # Registed admin views
        # inspect[isclass]: Only checks if the object is a class. With it lets you create an custom view that
        # inherits from multiple views and have more of a metaclass.
        urlpatterns += [
            url(
                path,
                wrap(self.create_admin_view(clz_or_func))
                if inspect.isclass(clz_or_func) and issubclass(clz_or_func, BaseAdminView)
                else include(clz_or_func(self)),
                name=name
            )
            for path, clz_or_func, name in self._registry_views
        ]

        # Add in each model's views.
        for model, admin_class in iteritems(self._registry):
            view_urls = [
                url(
                    path,
                    wrap(self.create_model_admin_view(clz, model, admin_class)),
                    name=name % (model._meta.app_label, model._meta.model_name)
                )
                for path, clz, name in self._registry_modelviews
            ]
            urlpatterns += [
                url(r'^%s/%s/' % (model._meta.app_label, model._meta.model_name), include(view_urls))
            ]
        return urlpatterns

    @property
    def urls(self):
        return self.get_urls(), self.name, self.app_name

    def i18n_javascript(self, request):
        """
        Displays the i18n JavaScript that the Django admin requires.

        This takes into account the USE_I18N setting. If it's set to False, the
        generated JavaScript will be leaner and faster.
        """
        if settings.USE_I18N:
            from django.views.i18n import javascript_catalog
        else:
            from django.views.i18n import null_javascript_catalog as javascript_catalog
        return javascript_catalog(request, packages=['django.conf', 'xadmin'])

# This global object represents the default admin site, for the common case.
# You can instantiate AdminSite in your own code to create a custom admin site.
site = AdminSite()


def register(models, **kwargs):

    def _model_admin_wrapper(admin_class):
        site.register(models, admin_class)
    return _model_admin_wrapper
