import logging
import os
import tempfile

import psutil

from app import build_logs, storage, authentication, instance_keys
from health.models_pre_oci import pre_oci_model as model

logger = logging.getLogger(__name__)

def _check_gunicorn(endpoint):
  def fn(app):
    """ Returns the status of the gunicorn workers. """
    # Compute the URL for checking the endpoint. We append a port if and only if the
    # hostname contains one.
    client = app.config['HTTPCLIENT']
    hostname_parts = app.config['SERVER_HOSTNAME'].split(':')
    port = ''
    if hostname_parts[0] == 'localhost':
      if len(hostname_parts) == 2:
        port = ':' + hostname_parts[1]

    scheme = app.config['PREFERRED_URL_SCHEME']
    if app.config.get('EXTERNAL_TLS_TERMINATION', False):
      scheme = 'http'

    registry_url = '%s://localhost%s/%s' % (scheme, port, endpoint)
    try:
      status_code = client.get(registry_url, verify=False, timeout=2).status_code
      okay = status_code == 200
      message = 'Got non-200 response for worker: %s' % status_code if not okay else None
      return (okay, message)
    except Exception as ex:
      logger.exception('Exception when checking worker health: %s', registry_url)
      return (False, 'Exception when checking worker health: %s' % registry_url)

  return fn


def _check_database(app):
  """ Returns the status of the database, as accessed from this instance. """
  return model.check_health(app.config)


def _check_redis(app):
  """ Returns the status of Redis, as accessed from this instance. """
  return build_logs.check_health()


def _check_storage(app):
  """ Returns the status of storage, as accessed from this instance. """
  try:
    storage.validate(storage.preferred_locations, app.config['HTTPCLIENT'])
    return (True, None)
  except Exception as ex:
    logger.exception('Storage check failed with exception %s', ex)
    return (False, 'Storage check failed with exception %s' % ex.message)


def _check_auth(app):
  """ Returns the status of the auth engine, as accessed from this instance. """
  return authentication.ping()


def _check_service_key(app):
  """ Returns the status of the service key for this instance. If the key has disappeared or
      has expired, then will return False.
  """
  if not app.config.get('SETUP_COMPLETE', False):
    return (True, 'Stack not fully setup; skipping check')

  try:
    kid = instance_keys.local_key_id
  except IOError as ex:
    # Key has not been created yet.
    return (True, 'Stack not fully setup; skipping check')

  try:
    key_is_valid = bool(instance_keys.get_service_key_public_key(kid))
    message = 'Could not find valid instance service key %s' % kid if not key_is_valid else None
    return (key_is_valid, message)
  except Exception as ex:
    logger.exception('Got exception when trying to retrieve the instance key')

    # NOTE: We return *True* here if there was an exception when retrieving the key, as it means
    # the database is down, which will be handled by the database health check.
    return (True, 'Failed to get instance key due to a database issue; skipping check')



def _disk_within_threshold(path, threshold):
  usage = psutil.disk_usage(path)
  return (1.0 - (usage.percent / 100.0)) >= threshold


def _check_disk_space(for_warning):
  def _check_disk_space(app):
    """ Returns the status of the disk space for this instance. If the available disk space is below
        a certain threshold, then will return False.
    """
    if not app.config.get('SETUP_COMPLETE', False):
      return (True, 'Stack not fully setup; skipping check')

    config_key = ('DISKSPACE_HEALTH_WARNING_THRESHOLD'
                  if for_warning else 'DISKSPACE_HEALTH_THRESHOLD')
    default_threshold = 0.1 if for_warning else 0.01

    # Check the directory in which we're running.
    currentfile = os.path.abspath(__file__)
    if not _disk_within_threshold(currentfile, app.config.get(config_key, default_threshold)):
      stats = psutil.disk_usage(currentfile)
      logger.debug('Disk space on main volume: %s', stats)
      return (False, 'Disk space has gone below threshold on main volume: %s' % stats.percent)

    # Check the temp directory as well.
    tempdir = tempfile.gettempdir()
    if tempdir is not None:
      if not _disk_within_threshold(tempdir, app.config.get(config_key, default_threshold)):
        stats = psutil.disk_usage(tempdir)
        logger.debug('Disk space on temp volume: %s', stats)
        return (False, 'Disk space has gone below threshold on temp volume: %s' % stats.percent)

    return (True, '')

  return _check_disk_space


_INSTANCE_SERVICES = {
  'registry_gunicorn': _check_gunicorn('v1/_internal_ping'),
  'web_gunicorn': _check_gunicorn('_internal_ping'),
  'verbs_gunicorn': _check_gunicorn('c1/_internal_ping'),
  'service_key': _check_service_key,
  'disk_space': _check_disk_space(for_warning=False),
}

_GLOBAL_SERVICES = {
  'database': _check_database,
  'redis': _check_redis,
  'storage': _check_storage,
  'auth': _check_auth,
}

_WARNING_SERVICES = {
  'disk_space_warning': _check_disk_space(for_warning=True),
}

def check_all_services(app, skip, for_instance=False):
  """ Returns a dictionary containing the status of all the services defined. """
  if for_instance:
    services = dict(_INSTANCE_SERVICES)
    services.update(_GLOBAL_SERVICES)
  else:
    services = _GLOBAL_SERVICES

  return _check_services(app, skip, services)

def check_warning_services(app, skip):
  """ Returns a dictionary containing the status of all the warning services defined. """
  return _check_services(app, skip, _WARNING_SERVICES)

def _check_services(app, skip, services):
  status = {}
  for name in services:
    if name in skip:
      continue

    status[name] = services[name](app)

  return status