import datetime
import json
from django.apps.registry import apps
from django.core.serializers.json import DjangoJSONEncoder
from django.http import HttpResponse
from django.core.urlresolvers import reverse, resolve, NoReverseMatch
from django.contrib import admin
from django.contrib.admin import AdminSite
from django.utils.encoding import smart_text
from django.utils.text import capfirst
import six
from django.contrib import messages
from django.utils.encoding import force_text
from django.utils.functional import Promise


class JsonResponse(HttpResponse):
    """
    An HTTP response class that consumes data to be serialized to JSON.
    :param data: Data to be dumped into json. By default only ``dict`` objects
      are allowed to be passed due to a security flaw before EcmaScript 5. See
      the ``safe`` parameter for more information.
    :param encoder: Should be an json encoder class. Defaults to
      ``django.core.serializers.json.DjangoJSONEncoder``.
    :param safe: Controls if only ``dict`` objects may be serialized. Defaults
      to ``True``.
    """

    def __init__(self, data, encoder=DjangoJSONEncoder, safe=True, **kwargs):
        if safe and not isinstance(data, dict):
            raise TypeError('In order to allow non-dict objects to be '
                'serialized set the safe parameter to False')
        kwargs.setdefault('content_type', 'application/json')
        data = json.dumps(data, cls=encoder)
        super(JsonResponse, self).__init__(content=data, **kwargs)


def get_app_list(context, order=True):
    admin_site = get_admin_site(context.get('current_app', ''))
    request = context['request']

    app_dict = {}
    for model, model_admin in admin_site._registry.items():
        app_label = model._meta.app_label
        has_module_perms = model_admin.has_module_permission(request)

        if has_module_perms:
            perms = model_admin.get_model_perms(request)

            # Check whether user has any perm for this module.
            # If so, add the module to the model_list.
            if True in perms.values():
                info = (app_label, model._meta.model_name)
                model_dict = {
                    'name': capfirst(model._meta.verbose_name_plural),
                    'object_name': model._meta.object_name,
                    'perms': perms,
                }
                if perms.get('change', False):
                    try:
                        model_dict['admin_url'] = reverse('admin:%s_%s_changelist' % info, current_app=admin_site.name)
                    except NoReverseMatch:
                        pass
                if perms.get('add', False):
                    try:
                        model_dict['add_url'] = reverse('admin:%s_%s_add' % info, current_app=admin_site.name)
                    except NoReverseMatch:
                        pass
                if app_label in app_dict:
                    app_dict[app_label]['models'].append(model_dict)
                else:
                    app_dict[app_label] = {
                        'name': apps.get_app_config(app_label).verbose_name,
                        'app_label': app_label,
                        'app_url': reverse(
                            'admin:app_list',
                            kwargs={'app_label': app_label},
                            current_app=admin_site.name,
                        ),
                        'has_module_perms': has_module_perms,
                        'models': [model_dict],
                    }

    # Sort the apps alphabetically.
    app_list = list(six.itervalues(app_dict))

    if order:
        app_list.sort(key=lambda x: x['name'].lower())

        # Sort the models alphabetically within each app.
        for app in app_list:
            app['models'].sort(key=lambda x: x['name'])

    return app_list


def get_admin_site(current_app):
    try:
        resolver_match = resolve(reverse('%s:index' % current_app))
        for func_closure in resolver_match.func.func_closure:
            if isinstance(func_closure.cell_contents, AdminSite):
                return func_closure.cell_contents
    except:
        pass

    return admin.site


def get_admin_site_name(context):
    return get_admin_site(context).name


class LazyDateTimeEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, datetime.datetime) or isinstance(obj, datetime.date):
            return obj.isoformat()
        elif isinstance(obj, Promise):
            return force_text(obj)
        return json.JSONEncoder.default(self, obj)


def get_model_instance_label(instance):
    if getattr(instance, "related_label", None):
        return instance.related_label()
    return smart_text(instance)


class SuccessMessageMixin(object):
    """
    Adds a success message on successful form submission.
    """
    success_message = ''

    def form_valid(self, form):
        response = super(SuccessMessageMixin, self).form_valid(form)
        success_message = self.get_success_message(form.cleaned_data)
        if success_message:
            messages.success(self.request, success_message)
        return response

    def get_success_message(self, cleaned_data):
        return self.success_message % cleaned_data