from rest_framework import status
from rest_framework.decorators import api_view, permission_classes
from rest_framework.response import Response

from django.contrib import auth
from django.contrib.auth.password_validation import validate_password
from django.core.exceptions import ValidationError
from django.utils.translation import ugettext as _
from django.views.decorators.csrf import csrf_protect

from misago.conf import settings
from misago.core.mail import mail_user
from misago.users.bans import get_user_ban
from misago.users.forms.auth import AuthenticationForm, ResendActivationForm, ResetPasswordForm
from misago.users.serializers import AnonymousUserSerializer, AuthenticatedUserSerializer
from misago.users.tokens import (
    is_password_change_token_valid, make_activation_token, make_password_change_token)

from .rest_permissions import UnbannedAnonOnly, UnbannedOnly


UserModel = auth.get_user_model()


def gateway(request):
    if request.method == 'POST':
        return login(request)
    else:
        return session_user(request)


@api_view(['POST'])
@permission_classes((UnbannedAnonOnly, ))
@csrf_protect
def login(request):
    """
    POST /auth/ with CSRF, username and password
    will attempt to authenticate new user
    """
    form = AuthenticationForm(request, data=request.data)
    if form.is_valid():
        auth.login(request, form.user_cache)
        return Response(
            AuthenticatedUserSerializer(form.user_cache).data,
        )
    else:
        return Response(
            form.get_errors_dict(),
            status=status.HTTP_400_BAD_REQUEST,
        )


@api_view()
def session_user(request):
    """GET /auth/ will return current auth user, either User or AnonymousUser"""
    if request.user.is_authenticated:
        UserSerializer = AuthenticatedUserSerializer
    else:
        UserSerializer = AnonymousUserSerializer

    return Response(UserSerializer(request.user).data)


@api_view(['GET'])
def get_criteria(request):
    """GET /auth/criteria/ will return password and username criteria for accounts"""
    criteria = {
        'username': {
            'min_length': settings.username_length_min,
            'max_length': settings.username_length_max,
        },
        'password': [],
    }

    for validator in settings.AUTH_PASSWORD_VALIDATORS:
        validator_dict = {'name': validator['NAME'].split('.')[-1]}

        validator_dict.update(validator.get('OPTIONS', {}))

        criteria['password'].append(validator_dict)

    return Response(criteria)


@api_view(['POST'])
@permission_classes((UnbannedAnonOnly, ))
@csrf_protect
def send_activation(request):
    """
    POST /auth/send-activation/ with CSRF token and email
    will mail account activation link to requester
    """
    form = ResendActivationForm(request.data)
    if form.is_valid():
        requesting_user = form.user_cache

        mail_subject = _("Activate %(user)s account on %(forum_name)s forums") % {
            'user': requesting_user.username,
            'forum_name': settings.forum_name,
        }

        mail_user(
            request,
            requesting_user,
            mail_subject,
            'misago/emails/activation/by_user',
            {
                'activation_token': make_activation_token(requesting_user),
            },
        )

        return Response({
            'username': form.user_cache.username,
            'email': form.user_cache.email,
        })
    else:
        return Response(
            form.get_errors_dict(),
            status=status.HTTP_400_BAD_REQUEST,
        )


@api_view(['POST'])
@permission_classes((UnbannedOnly, ))
@csrf_protect
def send_password_form(request):
    """
    POST /auth/send-password-form/ with CSRF token and email
    will mail change password form link to requester
    """
    form = ResetPasswordForm(request.data)
    if form.is_valid():
        requesting_user = form.user_cache

        mail_subject = _("Change %(user)s password on %(forum_name)s forums") % {
            'user': requesting_user.username,
            'forum_name': settings.forum_name,
        }

        confirmation_token = make_password_change_token(requesting_user)

        mail_user(
            request,
            requesting_user,
            mail_subject,
            'misago/emails/change_password_form_link',
            {
                'confirmation_token': confirmation_token,
            },
        )

        return Response({
            'username': form.user_cache.username,
            'email': form.user_cache.email,
        })
    else:
        return Response(
            form.get_errors_dict(),
            status=status.HTTP_400_BAD_REQUEST,
        )


class PasswordChangeFailed(Exception):
    pass


@api_view(['POST'])
@permission_classes((UnbannedOnly, ))
@csrf_protect
def change_forgotten_password(request, pk, token):
    """
    POST /auth/change-password/user/token/ with CSRF and new password
    will change forgotten password
    """
    invalid_message = _("Form link is invalid. Please try again.")
    expired_message = _("Your link has expired. Please request new one.")

    try:
        try:
            user = UserModel.objects.get(pk=pk, is_active=True)
        except UserModel.DoesNotExist:
            raise PasswordChangeFailed(invalid_message)

        if request.user.is_authenticated and request.user.id != user.id:
            raise PasswordChangeFailed(invalid_message)
        if not is_password_change_token_valid(user, token):
            raise PasswordChangeFailed(invalid_message)

        if user.requires_activation:
            raise PasswordChangeFailed(expired_message)
        if get_user_ban(user):
            raise PasswordChangeFailed(expired_message)
    except PasswordChangeFailed as e:
        return Response(
            {
                'detail': e.args[0],
            },
            status=status.HTTP_400_BAD_REQUEST,
        )

    try:
        new_password = request.data.get('password', '')
        validate_password(new_password, user=user)
        user.set_password(new_password)
        user.save()
    except ValidationError as e:
        return Response(
            {
                'detail': e.messages[0],
            },
            status=status.HTTP_400_BAD_REQUEST,
        )

    return Response({'username': user.username})