import re

from calendar import timegm
from datetime import datetime, timedelta
from peewee import JOIN_LEFT_OUTER

from Crypto.PublicKey import RSA
from jwkest.jwk import RSAKey

from data.database import db_for_update, User, ServiceKey, ServiceKeyApproval
from data.model import (ServiceKeyDoesNotExist, ServiceKeyAlreadyApproved, ServiceNameInvalid,
                        db_transaction, config)
from data.model.notification import create_notification, delete_all_notifications_by_path_prefix
from util.security.fingerprint import canonical_kid


_SERVICE_NAME_REGEX = re.compile(r'^[a-z0-9_]+$')

def _expired_keys_clause(service):
  return ((ServiceKey.service == service) &
          (ServiceKey.expiration_date <= datetime.utcnow()))

def _stale_expired_keys_service_clause(service):
  return ((ServiceKey.service == service) & _stale_expired_keys_clause())

def _stale_expired_keys_clause():
  expired_ttl = timedelta(seconds=config.app_config['EXPIRED_SERVICE_KEY_TTL_SEC'])
  return (ServiceKey.expiration_date <= (datetime.utcnow() - expired_ttl))

def _stale_unapproved_keys_clause(service):
  unapproved_ttl = timedelta(seconds=config.app_config['UNAPPROVED_SERVICE_KEY_TTL_SEC'])
  return ((ServiceKey.service == service) &
          (ServiceKey.approval >> None) &
          (ServiceKey.created_date <= (datetime.utcnow() - unapproved_ttl)))


def _gc_expired(service):
  ServiceKey.delete().where(_stale_expired_keys_service_clause(service) |
                            _stale_unapproved_keys_clause(service)).execute()


def _verify_service_name(service_name):
  if not _SERVICE_NAME_REGEX.match(service_name):
    raise ServiceNameInvalid


def _notify_superusers(key):
  notification_metadata = {
    'name': key.name,
    'kid': key.kid,
    'service': key.service,
    'jwk': key.jwk,
    'metadata': key.metadata,
    'created_date': timegm(key.created_date.utctimetuple()),
  }

  if key.expiration_date is not None:
    notification_metadata['expiration_date'] = timegm(key.expiration_date.utctimetuple())

  superusers = User.select().where(User.username << config.app_config['SUPER_USERS'])
  for superuser in superusers:
    create_notification('service_key_submitted', superuser, metadata=notification_metadata,
                        lookup_path='/service_key_approval/{0}/{1}'.format(key.kid, superuser.id))


def create_service_key(name, kid, service, jwk, metadata, expiration_date, rotation_duration=None):
  _verify_service_name(service)
  _gc_expired(service)

  key = ServiceKey.create(name=name, kid=kid, service=service, jwk=jwk, metadata=metadata,
                          expiration_date=expiration_date, rotation_duration=rotation_duration)

  _notify_superusers(key)
  return key


def generate_service_key(service, expiration_date, kid=None, name='', metadata=None,
                         rotation_duration=None):
  private_key = RSA.generate(2048)
  jwk = RSAKey(key=private_key.publickey()).serialize()
  if kid is None:
    kid = canonical_kid(jwk)

  key = create_service_key(name, kid, service, jwk, metadata or {}, expiration_date,
                           rotation_duration=rotation_duration)
  return (private_key, key)


def replace_service_key(old_kid, kid, jwk, metadata, expiration_date):
  try:
    with db_transaction():
      key = db_for_update(ServiceKey.select().where(ServiceKey.kid == old_kid)).get()
      key.metadata.update(metadata)

      ServiceKey.create(name=key.name, kid=kid, service=key.service, jwk=jwk,
                        metadata=key.metadata, expiration_date=expiration_date,
                        rotation_duration=key.rotation_duration, approval=key.approval)
      key.delete_instance()
  except ServiceKey.DoesNotExist:
    raise ServiceKeyDoesNotExist

  _notify_superusers(key)
  delete_all_notifications_by_path_prefix('/service_key_approval/{0}'.format(old_kid))
  _gc_expired(key.service)


def update_service_key(kid, name=None, metadata=None):
  try:
    with db_transaction():
      key = db_for_update(ServiceKey.select().where(ServiceKey.kid == kid)).get()
      if name is not None:
        key.name = name

      if metadata is not None:
        key.metadata.update(metadata)

      key.save()
  except ServiceKey.DoesNotExist:
    raise ServiceKeyDoesNotExist


def delete_service_key(kid):
  try:
    key = ServiceKey.get(kid=kid)
    ServiceKey.delete().where(ServiceKey.kid == kid).execute()
  except ServiceKey.DoesNotExist:
    raise ServiceKeyDoesNotExist

  delete_all_notifications_by_path_prefix('/service_key_approval/{0}'.format(kid))
  _gc_expired(key.service)
  return key


def set_key_expiration(kid, expiration_date):
  try:
    service_key = get_service_key(kid)
  except ServiceKey.DoesNotExist:
    raise ServiceKeyDoesNotExist

  service_key.expiration_date = expiration_date
  service_key.save()


def approve_service_key(kid, approver, approval_type, notes=''):
  try:
    with db_transaction():
      key = db_for_update(ServiceKey.select().where(ServiceKey.kid == kid)).get()
      if key.approval is not None:
        raise ServiceKeyAlreadyApproved

      approval = ServiceKeyApproval.create(approver=approver, approval_type=approval_type,
                                           notes=notes)
      key.approval = approval
      key.save()
  except ServiceKey.DoesNotExist:
    raise ServiceKeyDoesNotExist

  delete_all_notifications_by_path_prefix('/service_key_approval/{0}'.format(kid))
  return key


def _list_service_keys_query(kid=None, service=None, approved_only=False):
  query = ServiceKey.select().join(ServiceKeyApproval, JOIN_LEFT_OUTER)

  if approved_only:
    query = query.where(~(ServiceKey.approval >> None))

  if service is not None:
    query = query.where(ServiceKey.service == service)
    query = query.where(~(_expired_keys_clause(service)) |
                        ~(_stale_unapproved_keys_clause(service)))

  if kid is not None:
    query = query.where(ServiceKey.kid == kid)

  query = query.where(~(_stale_expired_keys_clause()) | (ServiceKey.expiration_date >> None))
  return query


def list_all_keys():
  return list(_list_service_keys_query())


def list_service_keys(service):
  return list(_list_service_keys_query(service=service, approved_only=True))


def get_service_key(kid, service=None):
  try:
    return _list_service_keys_query(kid=kid, service=service).get()
  except ServiceKey.DoesNotExist:
    raise ServiceKeyDoesNotExist