from functools import update_wrapper

from django.apps import apps
from django.conf import settings
from django.contrib.admin import ModelAdmin, actions
from django.contrib.auth import REDIRECT_FIELD_NAME
from django.core.exceptions import ImproperlyConfigured, PermissionDenied
from django.core.urlresolvers import NoReverseMatch, reverse
from django.db.models.base import ModelBase
from django.http import Http404, HttpResponseRedirect
from django.template.engine import Engine
from django.template.response import TemplateResponse
from django.utils import six
from django.utils.text import capfirst
from django.utils.translation import ugettext as _, ugettext_lazy
from django.views.decorators.cache import never_cache
from django.views.decorators.csrf import csrf_protect

system_check_errors = []


class AlreadyRegistered(Exception):
    pass


class NotRegistered(Exception):
    pass


class AdminSite(object):
    """
    An AdminSite object encapsulates an instance of the Django admin application, ready
    to be hooked in to your URLconf. Models are registered with the AdminSite using the
    register() method, and the get_urls() method can then be used to access Django view
    functions that present a full admin interface for the collection of registered
    models.
    """

    # Text to put at the end of each page's <title>.
    site_title = ugettext_lazy('Django site admin')

    # Text to put in each page's <h1>.
    site_header = ugettext_lazy('Django administration')

    # Text to put at the top of the admin index page.
    index_title = ugettext_lazy('Site administration')

    # URL for the "View site" link at the top of each admin page.
    site_url = '/'

    _empty_value_display = '-'

    login_form = None
    index_template = None
    app_index_template = None
    login_template = None
    logout_template = None
    password_change_template = None
    password_change_done_template = None

    def __init__(self, name='admin'):
        self._registry = {}  # model_class class -> admin_class instance
        self.name = name
        self._actions = {'delete_selected': actions.delete_selected}
        self._global_actions = self._actions.copy()

    def register(self, model_or_iterable, admin_class=None, **options):
        """
        Registers the given model(s) with the given admin class.

        The model(s) should be Model classes, not instances.

        If an admin class isn't given, it will use ModelAdmin (the default
        admin options). If keyword arguments are given -- e.g., list_display --
        they'll be applied as options to the admin class.

        If a model is already registered, this will raise AlreadyRegistered.

        If a model is abstract, this will raise ImproperlyConfigured.
        """
        if not admin_class:
            admin_class = ModelAdmin

        if isinstance(model_or_iterable, ModelBase):
            model_or_iterable = [model_or_iterable]
        for model in model_or_iterable:
            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__)

            # Ignore the registration if the model has been
            # swapped out.
            if not model._meta.swapped:
                # 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("%sAdmin" % model.__name__, (admin_class,), options)

                # Instantiate the admin class to save in the registry
                admin_obj = admin_class(model, self)
                if admin_class is not ModelAdmin and settings.DEBUG:
                    system_check_errors.extend(admin_obj.check())

                self._registry[model] = admin_obj

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

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

    def is_registered(self, model):
        """
        Check if a model class is registered with this `AdminSite`.
        """
        return model in self._registry

    def add_action(self, action, name=None):
        """
        Register an action to be available globally.
        """
        name = name or action.__name__
        self._actions[name] = action
        self._global_actions[name] = action

    def disable_action(self, name):
        """
        Disable a globally-registered action. Raises KeyError for invalid names.
        """
        del self._actions[name]

    def get_action(self, name):
        """
        Explicitly get a registered global action whether it's enabled or
        not. Raises KeyError for invalid names.
        """
        return self._global_actions[name]

    @property
    def actions(self):
        """
        Get all the enabled actions as an iterable of (name, func).
        """
        return six.iteritems(self._actions)

    @property
    def empty_value_display(self):
        return self._empty_value_display

    @empty_value_display.setter
    def empty_value_display(self, empty_value_display):
        self._empty_value_display = empty_value_display

    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 admin and contenttypes apps are
        installed, as well as the auth context processor.
        """
        if not apps.is_installed('django.contrib.admin'):
            raise ImproperlyConfigured(
                "Put 'django.contrib.admin' in your INSTALLED_APPS "
                "setting in order to use the admin application.")
        if not apps.is_installed('django.contrib.contenttypes'):
            raise ImproperlyConfigured(
                "Put 'django.contrib.contenttypes' in your INSTALLED_APPS "
                "setting in order to use the admin application.")
        try:
            default_template_engine = Engine.get_default()
        except Exception:
            # Skip this non-critical check:
            # 1. if the user has a non-trivial TEMPLATES setting and Django
            #    can't find a default template engine
            # 2. if anything goes wrong while loading template engines, in
            #    order to avoid raising an exception from a confusing location
            # Catching ImproperlyConfigured suffices for 1. but 2. requires
            # catching all exceptions.
            pass
        else:
            if ('django.contrib.auth.context_processors.auth'
                    not in default_template_engine.context_processors):
                raise ImproperlyConfigured(
                    "Enable 'django.contrib.auth.context_processors.auth' "
                    "in your TEMPLATES 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):
                if request.path == reverse('admin:logout', current_app=self.name):
                    index_path = reverse('admin:index', current_app=self.name)
                    return HttpResponseRedirect(index_path)
                # Inner import to prevent django.contrib.admin (app) from
                # importing django.contrib.auth.models.User (unrelated model).
                from django.contrib.auth.views import redirect_to_login
                return redirect_to_login(
                    request.get_full_path(),
                    reverse('admin:login', current_app=self.name)
                )
            return view(request, *args, **kwargs)
        if not cacheable:
            inner = never_cache(inner)
        # We add csrf_protect here so this function can be used as a utility
        # function for any view, without having to repeat 'csrf_protect'.
        if not getattr(view, 'csrf_exempt', False):
            inner = csrf_protect(inner)
        return update_wrapper(inner, view)

    def get_urls(self):
        from django.conf.urls import url, include
        # Since this module gets imported in the application's root package,
        # it cannot import models from other applications at the module level,
        # and django.contrib.contenttypes.views imports ContentType.
        from django.contrib.contenttypes import views as contenttype_views

        if settings.DEBUG:
            self.check_dependencies()

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

        # Admin-site-wide views.
        urlpatterns = [
            url(r'^$', wrap(self.index), name='index'),
            url(r'^login/$', self.login, name='login'),
            url(r'^logout/$', wrap(self.logout), name='logout'),
            url(r'^password_change/$', wrap(self.password_change, cacheable=True), name='password_change'),
            url(r'^password_change/done/$', wrap(self.password_change_done, cacheable=True),
                name='password_change_done'),
            url(r'^jsi18n/$', wrap(self.i18n_javascript, cacheable=True), name='jsi18n'),
            url(r'^r/(?P<content_type_id>\d+)/(?P<object_id>.+)/$', wrap(contenttype_views.shortcut),
                name='view_on_site'),
        ]

        # Add in each model's views, and create a list of valid URLS for the
        # app_index
        valid_app_labels = []
        for model, model_admin in self._registry.items():
            urlpatterns += [
                url(r'^%s/%s/' % (model._meta.app_label, model._meta.model_name), include(model_admin.urls)),
            ]
            if model._meta.app_label not in valid_app_labels:
                valid_app_labels.append(model._meta.app_label)

        # If there were ModelAdmins registered, we should have a list of app
        # labels for which we need to allow access to the app_index view,
        if valid_app_labels:
            regex = r'^(?P<app_label>' + '|'.join(valid_app_labels) + ')/$'
            urlpatterns += [
                url(regex, wrap(self.app_index), name='app_list'),
            ]
        return urlpatterns

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

    def each_context(self, request):
        """
        Returns a dictionary of variables to put in the template context for
        *every* page in the admin site.
        """
        return {
            'site_title': self.site_title,
            'site_header': self.site_header,
            'site_url': self.site_url,
            'has_permission': self.has_permission(request),
            'available_apps': self.get_app_list(request),
        }

    def password_change(self, request, extra_context=None):
        """
        Handles the "change password" task -- both form display and validation.
        """
        from django.contrib.admin.forms import AdminPasswordChangeForm
        from django.contrib.auth.views import password_change
        url = reverse('admin:password_change_done', current_app=self.name)
        defaults = {
            'password_change_form': AdminPasswordChangeForm,
            'post_change_redirect': url,
            'extra_context': dict(self.each_context(request), **(extra_context or {})),
        }
        if self.password_change_template is not None:
            defaults['template_name'] = self.password_change_template
        request.current_app = self.name
        return password_change(request, **defaults)

    def password_change_done(self, request, extra_context=None):
        """
        Displays the "success" page after a password change.
        """
        from django.contrib.auth.views import password_change_done
        defaults = {
            'extra_context': dict(self.each_context(request), **(extra_context or {})),
        }
        if self.password_change_done_template is not None:
            defaults['template_name'] = self.password_change_done_template
        request.current_app = self.name