# django senders need their arguments
# pylint: disable=unused-argument

import json
import logging
import requests
from requests.auth import HTTPBasicAuth
import pika
from django.conf import settings
from django.contrib.auth.models import AbstractUser, Group
from django.core.cache import cache
from django.db import models
from django.db.models.signals import post_save, pre_delete
from django.dispatch import receiver
from rest_framework.authtoken.models import Token
from .auth.v1.models import OIDCConfig

LOGGER = logging.getLogger(__name__)


# singleton for simple configs
# https://steelkiwi.com/blog/practical-application-singleton-design-pattern/
class SingletonModel(models.Model):

    class Meta:
        abstract = True

    def set_cache(self):
        cache.set(self.__class__.__name__, self)

    # pylint: disable=invalid-name, arguments-differ
    def save(self, *args, **kwargs):
        self.pk = 1
        super(SingletonModel, self).save(*args, **kwargs)
        self.set_cache()

    @classmethod
    def load(cls):
        if cache.get(cls.__name__) is None:
            obj, created = cls.objects.get_or_create(pk=1)
            if not created:
                obj.set_cache()
        return cache.get(cls.__name__)


# clients are registerred at rabbitmq, when they are assigned to a site
# (because we only then know what services they provide)
class RabbitMQInstance(SingletonModel):
    host = models.CharField(
        max_length=150,
        default='localhost',
    )
    vhost = models.CharField(
        max_length=150,
        default='%2f',
    )
    exchange = models.CharField(
        max_length=150,
        default='deployments',
    )
    port = models.IntegerField(
        default=15672,
    )
    path = models.CharField(
        max_length=150,
        default='api',
    )
    username = models.CharField(
        max_length=150,
        default='guest',
    )
    password = models.CharField(
        max_length=150,
        default='guest',
    )
    is_active = models.BooleanField(
        default=True,
    )

    def __str__(self):
        return self.host

    def _msg(self, msg):
        return '[RabbitMQ:{}] {}'.format(self.host, msg)

    @property
    def auth(self):
        return HTTPBasicAuth(
            self.username,
            self.password,
        )

    @property
    def _connection_parameters(self):
        return pika.ConnectionParameters(
            host=self.host,
            ssl=True,
        )

    @property
    def connection(self):
        LOGGER.debug(self._msg('opened connection'))
        return pika.BlockingConnection(
            self._connection_parameters,
        )

    @property
    def channel(self):
        rabbitmq_channel = self.connection.channel()
        rabbitmq_channel.exchange_declare(
            exchange=self.exchange,
            durable=True,
            auto_delete=False,
            exchange_type='topic',
        )
        rabbitmq_channel.confirm_delivery()
        LOGGER.debug(self._msg('opened channel'))

        return rabbitmq_channel

    def _get_api_uri(self, path):
        return 'http://{}:{}/{}/{}'.format(
            self.host,
            self.port,
            self.path,
            path,
        )

    def _rest_get(self, api_path):
        req = requests.get(
            self._get_api_uri(api_path),
            auth=self.auth)
        req.raise_for_status()
        return req.json()

    # send a rest call with path and data to the rest interface of
    # the rabbitmq instance
    def _rest_put(self, api_path, data):
        req = requests.put(
            self._get_api_uri(api_path),
            json=data,
            auth=self.auth)
        req.raise_for_status()
        return req

    def _rest_del(self, api_path):
        req = requests.delete(
            self._get_api_uri(api_path),
            auth=self.auth)
        req.raise_for_status()
        return req

    def _set_topic_permissions(self, site):
        username = site.client.username
        path = 'topic-permissions/{}/{}/'.format(
            self.vhost,
            username,
        )

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

            services = services + prefix + service.name

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

        return self._rest_put(path, set_topic_permission_data)

    # set permissions for the user
    def _set_permissions(self, site):
        username = site.client.username
        path = 'permissions/{}/{}/'.format(
            self.vhost,
            username,
        )
        permission = r'^(amq\.gen.*|{})'.format(self.exchange)
        set_permission_data = {
            'configure': permission,
            'write': permission,
            'read': permission,
        }

        return self._rest_put(path, set_permission_data)

    # create user at the rabbitmq instance
    def _create_user(self, site):
        username = site.client.username
        path = 'users/{}/'.format(username)

        user_creation_data = {
            'password': str(site.client.auth_token.key),
            'tags': '',
        }

        return self._rest_put(path, user_creation_data)

    # delete user at the rabbitmq instance
    def _delete_user(self, site):
        username = site.client.username
        path = 'users/{}/'.format(username)

        return self._rest_del(path)

    def _disconnect(self):
        LOGGER.debug(self._msg('closing connection'))
        self.connection.close()

    # PUBLIC API

    def register_site(self, site):
        self._create_user(site)
        self._set_permissions(site)
        self._set_topic_permissions(site)
        LOGGER.info(self._msg('registered {}'.format(site.client)))

    def update_site(self, site):
        self._set_topic_permissions(site)
        LOGGER.info(self._msg('updated permissions for {}'.format(site.client)))

    def deregister_site(self, site):
        # TODO implement
        LOGGER.info(self._msg('deregistered {}'.format(site.client)))

    def is_client_connected(self, site):
        connections = self._rest_get("connections/")
        clients_for_site = [c
                            for c in connections
                            if c['user'] == site.client.username]
        return len(clients_for_site) > 0

    def online_clients(self, service):
        return [site
                for site in service.site.all()
                if self.is_client_connected(site)]

    def publish_by_service(self, service, msg):
        # FIXME publish can fail -> catch error
        return self.channel.basic_publish(
            exchange=self.exchange,
            routing_key=service.routing_key,
            body=msg,
            properties=pika.BasicProperties(
                delivery_mode=1,
            ),
        )


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,
    )
    # the real state of the user
    # (self.is_active is the supposed state of the user)
    _is_active = models.BooleanField(
        default=True,
        editable=False,
    )
    # the idp which authenticated the user
    idp = models.ForeignKey(
        OIDCConfig,
        related_name='users',
        on_delete=models.CASCADE,
    )

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

    @property
    def is_active_at_clients(self):
        return self._is_active

    def __str__(self):
        if self.user_type == 'admin':
            return 'ADMIN {}'.format(self.username)
        elif self.user_type == 'oidcuser':
            if not self.is_active:
                return 'DEACTIVATED USER {}'.format(self.username)
            return 'USER {}'.format(self.username)
        elif self.user_type == 'apiclient':
            return 'APICLIENT {}@{}'.format(self.username, self.site)
        else:
            raise Exception()

    def _msg(self, msg):
        return '[{}] {}'.format(self, msg)

    # oidcuser: withdraw and delete all credentials and delete the user
    def remove(self):
        if self.user_type == 'oidcuser':
            self.deactivate()
            LOGGER.info(self._msg('Deleting'))

            # TODO: deleting the user brings problems:
            # the deletion cascades down to DeploymentTask and DeploymentTaskItem
            # but these need to be conserved so all clients withdrawals can be tracked
            self.delete()

    def activate(self):
        if self._is_active:
            LOGGER.error(self._msg('already activated'))
            return

        if self.user_type == 'oidcuser':
            self.is_active = True
            self._is_active = True
            self.save()

            for dep in self.deployments.all():
                dep.activate()

            LOGGER.info(self._msg('activated'))

    # oidcuser: withdraw all credentials
    def deactivate(self):
        if not self._is_active:
            LOGGER.error(self._msg('already deactivated'))
            return

        if self.user_type == 'oidcuser':
            self.is_active = False
            self._is_active = False
            self.save()

            for dep in self.deployments.all():
                dep.deactivate()

            LOGGER.info(self._msg('deactivated'))


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)

    def __str__(self):
        return self.name

    # tasks which are still to be executed on this site
    @property
    def tasks(self):
        return [item.task
                for item
                in self.task_items.all()]


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

    @property
    def routing_key(self):
        return 'service.{}'.format(self.name)

    def __str__(self):
        return self.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,
    )

    def _msg(self, msg):
        return '[SSHPublicKey:{}] {}'.format(self, msg)

    # 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.tasks.exists() and not self.deployments.exists()):
            LOGGER.info(self._msg('Direct deletion of key'))
            self.delete()
            return

        LOGGER.info(self._msg('Deletion of key started'))
        self.deleted = True
        self.save()

        # delete implies withdrawing the key from all clients
        for deployment in self.deployments.all():
            deployment.withdraw_key(self)

    # when a key is withdrawn by a client we try to finally delete it
    def try_final_deletion(self):
        if (self.deleted and not self.tasks.exists()):
            LOGGER.info(self._msg(
                'All clients have withdrawn this key. Final deletion'))
            self.delete()
            return

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


# Deployment describes the credential state per user as it is supposed to be
#
# (exception: if is_active=False the ssh_keys contain the keys to be deployed
# if the deployment is reactivated)
#
# DeploymentTask is what is sent to the clients via rabbitmq
# The DeploymentTaskItem track the acknowledgements from the clients
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,
    )
    ssh_keys = models.ManyToManyField(
        SSHPublicKey,
        related_name='deployments',
        blank=True,
    )
    ssh_keys_to_withdraw = models.ManyToManyField(
        SSHPublicKey,
        related_name='withdrawn_deployments',
        blank=True,
    )
    is_active = models.BooleanField(
        default=True,
    )

    @property
    def withdrawals(self):
        return self.tasks.filter(action='withdraw')

    @property
    def deploys(self):
        return self.tasks.filter(action='deploy')

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

    def _msg(self, msg):
        return '[Deployment:{}] {}'.format(self, msg)

    # deploy credentials which were deployed prior to deactivation
    def activate(self):
        if self.is_active:
            LOGGER.error(self._msg('already active'))
            return

        LOGGER.debug(self._msg(str(self.ssh_keys.all())))
        for key in self.ssh_keys.all():
            self._deploy_key(key)

        self.is_active = True
        self.save()
        LOGGER.info(self._msg('activated'))

    # withdraw all credentials
    def deactivate(self):
        if not self.is_active:
            LOGGER.error(self._msg('already deactivated'))
            return

        self.is_active = False
        self.save()

        for key in self.ssh_keys.all():
            self._withdraw_key(key)

        LOGGER.info(self._msg('deactivated'))

    # only deploy the key
    def _deploy_key(self, key):
        # delete outstanding tasks which are made obsolete by this task
        for withdrawal in self.withdrawals.filter(key=key):
            LOGGER.debug(withdrawal._msg('now obsolete'))
            withdrawal.delete()

        # generate task
        task = DeploymentTask(
            action='deploy',
            deployment=self,
            key=key,
        )
        task.save()
        LOGGER.debug(task._msg('generated'))

        # generate task items
        for site in self.service.site.all():
            deploy = DeploymentTaskItem(
                task=task,
                site=site,
            )
            deploy.save()
            LOGGER.debug(deploy._msg('generated'))

        # publish the task
        task.publish()

    def _withdraw_key(self, key):
        # delete outstanding tasks which are made obsolete by this task
        for deploy in self.deploys.filter(key=key):
            LOGGER.debug(deploy._msg("now obsolete"))
            deploy.delete()

        # generate task
        task = DeploymentTask(
            action='withdraw',
            deployment=self,
            key=key,
        )
        task.save()
        LOGGER.debug(task._msg('generated'))

        # generate task items
        for site in self.service.site.all():
            withdrawal = DeploymentTaskItem(
                task=task,
                site=site,
            )
            withdrawal.save()
            LOGGER.debug(withdrawal._msg('generated'))

        # publish the task
        task.publish()

    # deploy key and track changes in the key lists
    def deploy_key(self, key):
        if not self.is_active:
            LOGGER.error(self._msg('cannot deploy while deactivated'))
            raise Exception('deployment deactivated')

        self.ssh_keys.add(key)

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

        self._deploy_key(key)

    # withdraw key and track changes in the key lists
    def withdraw_key(self, key):
        if not self.is_active:
            LOGGER.error(self._msg('cannot withdraw while deactivated'))
            raise Exception('deployment deactivated')

        self.ssh_keys.remove(key)

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

        self._withdraw_key(key)


class DeploymentTask(models.Model):
    ACTION_CHOICES = (
        ('deploy', 'deploy'),
        ('withdraw', 'withdraw'),
    )
    action = models.CharField(
        max_length=10,
        choices=ACTION_CHOICES,
    )
    key = models.ForeignKey(
        SSHPublicKey,
        related_name='tasks',
        on_delete=models.CASCADE,
    )
    deployment = models.ForeignKey(
        Deployment,
        related_name='tasks',
        on_delete=models.CASCADE,
    )

    @property
    def user(self):
        return self.deployment.user

    @property
    def service(self):
        return self.deployment.service

    def __str__(self):
        return "{}:{}:{} - {}".format(
            self.deployment.service,
            self.deployment.user,
            self.key,
            self.action,
        )

    def _msg(self, msg):
        return '[DeploymentTask:{}] {}'.format(self, msg)

    def publish(self):
        # FIXME mitigating circular dependencies here
        from .clientapi.serializers import DeploymentTaskSerializer
        msg = json.dumps(DeploymentTaskSerializer(self).data)

        # FIXME select the rabbitmq instance more meaningful
        RabbitMQInstance.load().publish_by_service(
            self.service,
            msg,
        )

    # the client acked the receipt and execution of the task for his site
    def item_finished(self, site):
        item = self.task_items.get(site=site)
        LOGGER.debug(item._msg('done'))
        item.delete()

        if not self.task_items.exists():
            self.finished()

    # maintenance after all task items are done
    def finished(self):
        LOGGER.info(self._msg('done'))
        self.delete()

        # check if this was the final withdraw in a key deletion
        if self.action == 'withdraw':
            self.key.try_final_deletion()


class DeploymentTaskItem(models.Model):
    task = models.ForeignKey(
        DeploymentTask,
        related_name='task_items',
        on_delete=models.CASCADE,
    )
    site = models.ForeignKey(
        Site,
        related_name='task_items',
        on_delete=models.CASCADE,
    )

    def __str__(self):
        return "{}@{}".format(
            self.task,
            self.site,
        )

    def _msg(self, msg):
        return '[DeploymentTaskItem:{}] {}'.format(self, msg)


#
# RECEIVERS
#

@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)


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

    RabbitMQInstance().register_site(instance)


@receiver(pre_delete, sender=Site)
def deregister_at_rabbitmq(sender, instance=None, **kwargs):
    RabbitMQInstance().deregister_site(instance)


@receiver(post_save, sender=User)
def deactivate_user(sender, instance=None, created=False, **kwargs):
    if created:
        return

    if not instance.is_active and instance.is_active_at_clients:
        instance.deactivate()


@receiver(post_save, sender=User)
def activate_user(sender, instance=None, created=False, **kwargs):
    if created:
        return

    if instance.is_active and not instance.is_active_at_clients:
        instance.activate()