from django.contrib.auth.models import AbstractUser, Group
from django.db import models
from django.conf import settings
from django.dispatch import receiver, Signal
from rest_framework.authtoken.models import Token
from django.db.models.signals import post_save, m2m_changed
from datetime import datetime

import requests
from requests.auth import HTTPBasicAuth

deployment_change = Signal(providing_args=['instance'])


class User(AbstractUser):
    TYPE_CHOICES = (
            ('apiclient', 'API-Client'),
            ('oidcuser', 'OIDC User'),
            ('admin', 'Admin'),
            )
    user_type = models.CharField(
            max_length=20,
            choices=TYPE_CHOICES,
            default='oidcuser',
            )
    sub = models.CharField(max_length=150, blank=True, null=True)
    password = models.CharField(max_length=150, blank=True, null=True)

    # we hide deleted keys here
    # the full list of ssh keys is at self._ssh_keys
    @property
    def ssh_keys(self):
        return self._ssh_keys.filter(deleted=False)


@receiver(post_save, sender=settings.AUTH_USER_MODEL)
def create_auth_token(sender, instance=None, created=False, **kwargs):
    if instance.user_type == 'apiclient' and created:
        Token.objects.create(user=instance)


def construct_user(user_info):
    return User(
            sub=user_info['sub'],
            name=user_info['name'],
            first_name=user_info['given_name'],
            last_name=user_info['family_name'],
            email=user_info['email'],
            username=user_info['email'],
            )


class Site(models.Model):
    client = models.OneToOneField(
            User,
            related_name='site',
            )
    name = models.CharField(max_length=150, unique=True)
    description = models.TextField(max_length=300, blank=True)
    last_fetch = models.DateTimeField(default=datetime.utcfromtimestamp(0))

    def __str__(self):
        return self.name

    def clientapi_get_deployments(self, all=False):
        services = {}

        for service in self.services.all():
            deployments = (
                service.deployments
                .filter(user__user_type='oidcuser')
                # we do not exclude deployments without ssh_keys, as the
                # ssh_keys_to_withdraw still need to be propagated
                # .exclude(ssh_keys=None)
                )
            if not all:
                deployments = deployments.filter(
                        last_change__gt=self.last_fetch)

            # deployments for this site
            services[service.name] = deployments

            for deployment in deployments.all():
                # TODO replace this optimism with an acknowledgement
                deployment.client_got_deployment()

        self.last_fetch = datetime.now()
        self.save()
        return services


@receiver(post_save, sender=Site)
def register_client_at_rabbitmq(sender, instance=None, created=False,
                                **kwargs):
    if not created:
        return

    print('registerring client {}'.format(instance.client.username))

    # %2f: url encoded '/' as this is the vhost we use
    api = 'http://localhost:15672/api'
    username = instance.client.username
    vhost = '%2f'
    exchange = 'deployments'
    # guest only works on the localhost
    auth = HTTPBasicAuth('guest', 'guest')

    # create user
    user_creation_uri = '{}/users/{}/'.format(
            api,
            username
            )
    user_creation_data = {
            'password': str(instance.client.auth_token.key),
            'tags': '',
            }
    r = requests.put(user_creation_uri, json=user_creation_data, auth=auth)
    print('status_code {} {}'.format(r.status_code, r.text))

    # set permissions for the user
    set_permission_uri = '{}/permissions/{}/{}/'.format(
            api,
            vhost,
            username,
            )
    permission = '^(amq\.gen.*|{})'.format(exchange)
    set_permission_data = {
            'configure': permission,
            'write': permission,
            'read': permission,
            }

    set_topic_permission_uri = '{}/topic-permissions/{}/{}/'.format(
            api,
            vhost,
            username,
            )
    r = requests.put(set_permission_uri, json=set_permission_data, auth=auth)
    print('status_code {} {}'.format(r.status_code, r.text))

    # set permissions for the correct topics
    # we construct a regex to match the services of the site
    services = ''
    omitBar = True
    for service in instance.services.all():
        prefix = '|'
        if omitBar:
            prefix = ''
            omitBar = False

        services = services + prefix + service.name

    set_topic_permission_data = {
            'exchange': exchange,
            'write': '^$',
            'read': '^service\.({})$'.format(services),
            }

    r = requests.put(
            set_topic_permission_uri,
            json=set_topic_permission_data, auth=auth)
    print('status_code {} {}'.format(r.status_code, r.text))


class Service(models.Model):
    name = models.CharField(max_length=150, unique=True)
    description = models.TextField(max_length=300, blank=True)
    site = models.ForeignKey(
            Site,
            related_name='services')
    groups = models.ManyToManyField(
            Group,
            related_name='services',
            blank=True)

    def __str__(self):
        return self.name + '@' + self.site.name


class SSHPublicKey(models.Model):
    name = models.CharField(max_length=150, unique=True)
    key = models.TextField(max_length=1000)
    # hidden field at the user
    user = models.ForeignKey(
            User,
            related_name='_ssh_keys')

    # has the user triggered the deletion of this key
    deleted = models.BooleanField(
            default=False,
            editable=False,
            )

    # does not directly delete the key if the key is deployed or withdrawn
    # somewhere
    # the receiver 'delete_withdrawn_ssh_key' does the actual deletion
    def delete_key(self):
        if (not self.deployments.exists()
                and not self.withdrawn_deployments.exists()):
            self.delete()
            return

        self.deleted = True
        self.save()

        for deployment in self.deployments.all():
            deployment.withdraw_key(self)

    def __str__(self):
        if self.deleted:
            return "DELETED: {}".format(self.name)
        return self.name


# finally delete the key if all the deployments are withdrawn
# and the withdrawal was seen by all clients
@receiver(m2m_changed, sender=SSHPublicKey)
def delete_withdrawn_ssh_key(
        sender, instance=None, created=False, **kwargs):

    if (instance.deleted
            and not instance.deployments.exists()
            and not instance.withdrawn_deployments.exists()):
        instance.delete()


class Deployment(models.Model):
    user = models.ForeignKey(
            User,
            related_name='deployments',
            on_delete=models.CASCADE,
            )
    service = models.ForeignKey(
            Service,
            related_name='deployments',
            on_delete=models.CASCADE,
            )
    # SET_NULL: we allow credentials to be deleted after deployment
    ssh_keys = models.ManyToManyField(
            SSHPublicKey,
            related_name='deployments',
            blank=True,
            )

    # these ssh keys are to be withdrawn by the clients
    ssh_keys_to_withdraw = models.ManyToManyField(
            SSHPublicKey,
            related_name='withdrawn_deployments',
            blank=True,
            )

    last_change = models.DateTimeField(
            auto_now=True
            )

    def deploy_key(self, key):
        # key state: -> (2.5)
        self.ssh_keys.add(key)

        if key in self.ssh_keys_to_withdraw.all():
            self.ssh_keys_to_withdraw.remove(key)
        self.save()
        self.send_change()

    def withdraw_key(self, key):
        # key state: -> (4)
        self.ssh_keys.remove(key)

        # keys which are to be withdrawn by the clients
        self.ssh_keys_to_withdraw.add(key)
        self.save()
        self.send_change()

    def client_got_deployment(self):
        # the client has withdrawn the keys so we can empty the list
        self.ssh_keys_to_withdraw.clear()
        # TODO: does the deletion of the ssh_keys actually occur?
        self.save()

    def send_change(self):
        deployment_change.send(sender=self.__class__, instance=self)

    def __str__(self):
        return '{}@{}'.format(self.user, self.service)


@receiver(post_save, sender=Deployment)
def publish_deployment_creation(
        sender, instance=None, created=False, **kwargs):
    instance.send_change()