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

import json
import time
import logging
import pika
from requests.auth import HTTPBasicAuth
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
from django.dispatch import receiver
from django_mysql.models import JSONField
from .auth.v1.models import OIDCConfig

LOGGER = logging.getLogger(__name__)
RECONNECT_TIMEOUT = 5
RECONNECT_RETRIES = 3


# 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,
    )
    username = models.CharField(
        max_length=150,
        default='guest',
    )
    password = models.CharField(
        max_length=150,
        default='guest',
    )

    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,
        )

    # PUBLIC API

    def publish_by_service(self, service, msg):
        # FIXME dirty
        tries = 0
        while tries < RECONNECT_RETRIES:
            try:
                # open connection
                connection = pika.BlockingConnection(
                    self._connection_parameters,
                )

                # open channel
                channel = connection.channel()
                channel.exchange_declare(
                    exchange=self.exchange,
                    durable=True,
                    auto_delete=False,
                    exchange_type='topic',
                )
                channel.confirm_delivery()

                channel.basic_publish(
                    exchange=self.exchange,
                    routing_key=service.routing_key,
                    body=msg,
                    properties=pika.BasicProperties(
                        delivery_mode=1,
                    ),
                )
                channel.close()
                connection.close()
                return
            except:
                time.sleep(RECONNECT_TIMEOUT)

            tries += 1


def user_info_default():
    return {}


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,
        editable=False,
    )
    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,
        blank=True,
        null=True,
        editable=False,
    )
    userinfo = JSONField(
        default=user_info_default,
        null=True,
        blank=True,
        editable=False,
    )

    # 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':
            try:
                return 'APICLIENT {}@{}'.format(self.username, self.site)
            except:
                return 'APICLIENT {}'.format(self.username)

        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()

            # FIXME: 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
            LOGGER.info(self.msg('Deleting'))
            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'))


    @classmethod
    def construct_from_user_info(cls, user_info, idp):
        LOGGER.debug('User: constructing from %s', user_info)
        return cls(
            sub=user_info.get('sub', ''),
            first_name=user_info.get('given_name', ''),
            last_name=user_info.get('family_name', ''),
            email=user_info.get('email', ''),
            username=user_info.get('email', ''),
            idp=idp,
            userinfo=user_info,
        )


class Site(models.Model):
    client = models.OneToOneField(
        User,
        related_name='site',
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
    )
    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,
    )
    key = models.TextField(
        max_length=1000
    )
    # hidden field at the user
    # TODO checks: if the user is null
    user = models.ForeignKey(
        User,
        related_name='_ssh_keys',
        on_delete=models.SET_NULL,
        null=True,
    )

    # 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,
            self.id,
        )

    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)

        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,
            self.id,
        )

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


#
# RECEIVERS
#

@receiver(post_save, sender=User)
def upgrade_password(sender, instance=None, created=False, **kwargs):
    if created and instance is not None and instance.user_type == 'apiclient':
        instance.set_password(instance.password)
        instance.save()

@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()