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

logger = get_logger(__name__)


# clients are registerred at rabbitmq, when they are assigned to a site
# (because we only then know what services they provide)
class RabbitMQInstance(models.Model):
    host = models.CharField(
        max_length=150,
        default='localhost',
    )
    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 api(self):
        return 'http://{}:{}/{}'.format(
            self.host,
            self.port,
            self.path,
        )

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

    @property
    def vhost(self):
        return '%2f'

    # singletons
    rabbitmq_connection = None
    rabbitmq_channel = None

    @property
    def connection(self):
        if self.rabbitmq_connection is None:
            rabbitmqconnection_properties = pika.ConnectionParameters(
                host=self.host,
                ssl=True,
            )
            self.rabbitmq_connection = pika.BlockingConnection(
                rabbitmqconnection_properties
            )
            logger.debug(self.msg('opened connection'))

        return self.rabbitmq_connection

    @property
    def channel(self):
        if self.rabbitmq_channel is None:
            self.rabbitmq_channel = self.connection.channel()
            self.rabbitmq_channel.exchange_declare(
                exchange=self.exchange,
                durable=True,
                exchange_type='topic')
            self.rabbitmq_channel.confirm_delivery()
            logger.debug(self.msg('opened channel'))

        return self.rabbitmq_channel

    def get_uri(self, path):
        return '{}/{}'.format(self.api, path)

    def rest_get(self, api_path):
        r = requests.get(
            self.get_uri(api_path),
            auth=self.auth)
        r.raise_for_status()
        return r.json()

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

    def rest_del(self, api_path):
        r = requests.delete(
            self.get_uri(api_path),
            auth=self.auth)
        r.raise_for_status()
        return r

    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 = ''
        omitBar = True
        for service in site.services.all():
            prefix = '|'
            if omitBar:
                prefix = ''
                omitBar = False

            services = services + prefix + service.name

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

    # 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):
        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 disconnect(self):
        logger.debug(self.msg('closing connection'))
        self.connection.close()

    def service_routing_key(self, service):
        return 'service.' + service.name

    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):
        return self.channel.basic_publish(
            exchange=self.exchange,
            routing_key=self.service_routing_key(service),
            body=msg,
            properties=pika.BasicProperties(
                delivery_mode=1,
            ),
        )


def rabbitmq_instance():
    return RabbitMQInstance.objects.get(is_active=True)


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,
    )

    # 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)

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

    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)

    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):
        from .clientapi.serializers import DeploymentTaskSerializer
        msg = json.dumps(DeploymentTaskSerializer(self).data)

        rabbitmq_instance().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:
        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:
        instance.activate()