from django.conf import settings
from django.contrib import messages
from django.contrib.auth import views as auth_views
from django.contrib.auth import update_session_auth_hash
from django.contrib.auth.forms import PasswordChangeForm
from django.http import Http404
from django.shortcuts import redirect, render
from django.urls import reverse, reverse_lazy
from django.utils.translation import ugettext as _
from django.utils.translation import activate

from wagtail.admin.forms.auth import LoginForm, PasswordResetForm
from wagtail.core import hooks
from wagtail.users.forms import (
    AvatarPreferencesForm, CurrentTimeZoneForm, EmailForm, NotificationPreferencesForm, PreferredLanguageForm)
from wagtail.users.models import UserProfile
from wagtail.utils.loading import get_custom_form


def get_user_login_form():
    form_setting = 'WAGTAILADMIN_USER_LOGIN_FORM'
    if hasattr(settings, form_setting):
        return get_custom_form(form_setting)
    else:
        return LoginForm


# Helper functions to check password management settings to enable/disable views as appropriate.
# These are functions rather than class-level constants so that they can be overridden in tests
# by override_settings

def password_management_enabled():
    return getattr(settings, 'WAGTAIL_PASSWORD_MANAGEMENT_ENABLED', True)


def password_reset_enabled():
    return getattr(settings, 'WAGTAIL_PASSWORD_RESET_ENABLED', password_management_enabled())


# Views

def account(request):
    items = []

    for fn in hooks.get_hooks('register_account_menu_item'):
        item = fn(request)
        if item:
            items.append(item)

    return render(request, 'wagtailadmin/account/account.html', {
        'items': items,
    })


def change_password(request):
    if not password_management_enabled():
        raise Http404

    can_change_password = request.user.has_usable_password()

    if can_change_password:
        if request.method == 'POST':
            form = PasswordChangeForm(request.user, request.POST)

            if form.is_valid():
                form.save()
                update_session_auth_hash(request, form.user)

                messages.success(request, _("Your password has been changed successfully!"))
                return redirect('wagtailadmin_account')
        else:
            form = PasswordChangeForm(request.user)
    else:
        form = None

    return render(request, 'wagtailadmin/account/change_password.html', {
        'form': form,
        'can_change_password': can_change_password,
    })


def change_email(request):
    if request.method == 'POST':
        form = EmailForm(request.POST, instance=request.user)

        if form.is_valid():
            form.save()
            messages.success(request, _("Your email has been changed successfully!"))
            return redirect('wagtailadmin_account')
    else:
        form = EmailForm(instance=request.user)

    return render(request, 'wagtailadmin/account/change_email.html', {
        'form': form,
    })


class PasswordResetEnabledViewMixin:
    """
    Class based view mixin that disables the view if password reset is disabled by one of the following settings:
    - WAGTAIL_PASSWORD_RESET_ENABLED
    - WAGTAIL_PASSWORD_MANAGEMENT_ENABLED
    """
    def dispatch(self, *args, **kwargs):
        if not password_reset_enabled():
            raise Http404

        return super().dispatch(*args, **kwargs)


class PasswordResetView(PasswordResetEnabledViewMixin, auth_views.PasswordResetView):
    template_name = 'wagtailadmin/account/password_reset/form.html'
    email_template_name = 'wagtailadmin/account/password_reset/email.txt'
    subject_template_name = 'wagtailadmin/account/password_reset/email_subject.txt'
    form_class = PasswordResetForm
    success_url = reverse_lazy('wagtailadmin_password_reset_done')


class PasswordResetDoneView(PasswordResetEnabledViewMixin, auth_views.PasswordResetDoneView):
    template_name = 'wagtailadmin/account/password_reset/done.html'


class PasswordResetConfirmView(PasswordResetEnabledViewMixin, auth_views.PasswordResetConfirmView):
    template_name = 'wagtailadmin/account/password_reset/confirm.html'
    success_url = reverse_lazy('wagtailadmin_password_reset_complete')


class PasswordResetCompleteView(PasswordResetEnabledViewMixin, auth_views.PasswordResetCompleteView):
    template_name = 'wagtailadmin/account/password_reset/complete.html'


def notification_preferences(request):
    if request.method == 'POST':
        form = NotificationPreferencesForm(request.POST, instance=UserProfile.get_for_user(request.user))

        if form.is_valid():
            form.save()
            messages.success(request, _("Your preferences have been updated."))
            return redirect('wagtailadmin_account')
    else:
        form = NotificationPreferencesForm(instance=UserProfile.get_for_user(request.user))

    # quick-and-dirty catch-all in case the form has been rendered with no
    # fields, as the user has no customisable permissions
    if not form.fields:
        return redirect('wagtailadmin_account')

    return render(request, 'wagtailadmin/account/notification_preferences.html', {
        'form': form,
    })


def language_preferences(request):
    if request.method == 'POST':
        form = PreferredLanguageForm(request.POST, instance=UserProfile.get_for_user(request.user))

        if form.is_valid():
            user_profile = form.save()
            # This will set the language only for this request/thread
            # (so that the 'success' messages is in the right language)
            activate(user_profile.get_preferred_language())
            messages.success(request, _("Your preferences have been updated."))
            return redirect('wagtailadmin_account')
    else:
        form = PreferredLanguageForm(instance=UserProfile.get_for_user(request.user))

    return render(request, 'wagtailadmin/account/language_preferences.html', {
        'form': form,
    })


def current_time_zone(request):
    if request.method == 'POST':
        form = CurrentTimeZoneForm(request.POST, instance=UserProfile.get_for_user(request.user))

        if form.is_valid():
            form.save()
            messages.success(request, _("Your preferences have been updated."))
            return redirect('wagtailadmin_account')
    else:
        form = CurrentTimeZoneForm(instance=UserProfile.get_for_user(request.user))

    return render(request, 'wagtailadmin/account/current_time_zone.html', {
        'form': form,
    })


def change_avatar(request):
    if request.method == 'POST':
        user_profile = UserProfile.get_for_user(request.user)
        form = AvatarPreferencesForm(request.POST, request.FILES, instance=user_profile)
        if form.is_valid():
            form.save()
            messages.success(request, _("Your preferences have been updated successfully!"))
            return redirect('wagtailadmin_account_change_avatar')
    else:
        form = AvatarPreferencesForm(instance=UserProfile.get_for_user(request.user))

    return render(request, 'wagtailadmin/account/change_avatar.html', {'form': form})


class LoginView(auth_views.LoginView):
    template_name = 'wagtailadmin/login.html'

    def get_success_url(self):
        return self.get_redirect_url() or reverse('wagtailadmin_home')

    def get(self, *args, **kwargs):
        # If user is already logged in, redirect them to the dashboard
        if self.request.user.is_authenticated and self.request.user.has_perm('wagtailadmin.access_admin'):
            return redirect(self.get_success_url())

        return super().get(*args, **kwargs)

    def get_form_class(self):
        return get_user_login_form()

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)

        context['show_password_reset'] = password_reset_enabled()

        from django.contrib.auth import get_user_model
        User = get_user_model()
        context['username_field'] = User._meta.get_field(User.USERNAME_FIELD).verbose_name

        return context


class LogoutView(auth_views.LogoutView):
    next_page = 'wagtailadmin_login'

    def dispatch(self, request, *args, **kwargs):
        response = super().dispatch(request, *args, **kwargs)

        messages.success(self.request, _('You have been successfully logged out.'))
        # By default, logging out will generate a fresh sessionid cookie. We want to use the
        # absence of sessionid as an indication that front-end pages are being viewed by a
        # non-logged-in user and are therefore cacheable, so we forcibly delete the cookie here.
        response.delete_cookie(
            settings.SESSION_COOKIE_NAME,
            domain=settings.SESSION_COOKIE_DOMAIN,
            path=settings.SESSION_COOKIE_PATH
        )

        # HACK: pretend that the session hasn't been modified, so that SessionMiddleware
        # won't override the above and write a new cookie.
        self.request.session.modified = False

        return response
