import logging

from dateutil import parser
from datetime import datetime, timedelta
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.serialization import load_pem_public_key

import jwt

logger = logging.getLogger(__name__)

TRIAL_GRACE_PERIOD = timedelta(7, 0)    # 1 week
MONTHLY_GRACE_PERIOD = timedelta(30, 0) # 1 month
YEARLY_GRACE_PERIOD = timedelta(90, 0)  # 3 months

LICENSE_PRODUCT_NAME = "quay-enterprise"

class LicenseError(Exception):
  """ Exception raised if the license could not be read, decoded or has expired. """
  pass


class LicenseDecodeError(LicenseError):
  """ Exception raised if the license could not be decoded. """
  pass


class LicenseValidationError(LicenseError):
  """ Exception raised if the license could not be validated. """
  pass


def _get_date(decoded, field):
  """ Retrieves the encoded date found at the given field under the decoded license block. """
  date_str = decoded.get(field)
  if date_str:
    return parser.parse(date_str).replace(tzinfo=None)

  return datetime.now() - timedelta(days=2)


class License(object):
  """ License represents a fully decoded and validated (but potentially expired) license. """
  def __init__(self, decoded):
    self.decoded = decoded

  def validate(self, config):
    """ Validates the license and all its entitlements against the given config. """
    # Check that the license has not expired.
    if self.is_expired:
      raise LicenseValidationError('License has expired')

    # Check the maximum number of replication regions.
    max_regions = min(self.decoded.get('entitlements', {}).get('software.quay.regions', 1), 1)
    config_regions = len(config.get('DISTRIBUTED_STORAGE_CONFIG', []))
    if max_regions != -1 and config_regions > max_regions:
      msg = '{} regions configured, but license file allows up to {}'.format(config_regions,
                                                                             max_regions)
      raise LicenseValidationError(msg)

  @property
  def is_expired(self):
    return self._get_expired(datetime.now())

  def _get_expired(self, compare_date):
    # Check if the license overall has expired.
    expiration_date = _get_date(self.decoded, 'expirationDate')
    if expiration_date <= compare_date:
      logger.debug('License expired on %s', expiration_date)
      return True

    # Check for any QE subscriptions.
    for sub in self.decoded.get('subscriptions', []):
      if sub.get('productName') != LICENSE_PRODUCT_NAME:
        continue

      # Check for a trial-only license.
      if sub.get('trialOnly', False):
        trial_end_date = _get_date(sub, 'trialEnd')
        logger.debug('Trial-only license expires on %s', trial_end_date)
        return trial_end_date <= (compare_date - TRIAL_GRACE_PERIOD)

      # Check for a normal license that is in trial.
      service_end_date = _get_date(sub, 'serviceEnd')
      if sub.get('inTrial', False):
        # If the subscription is in a trial, but not a trial only
        # subscription, give 7 days after trial end to update license
        # to one which has been paid (they've put in a credit card and it
        # might auto convert, so we could assume it will auto-renew)
        logger.debug('In-trial license expires on %s', service_end_date)
        return service_end_date <= (compare_date - TRIAL_GRACE_PERIOD)

      # Otherwise, check the service expiration.
      duration_period = sub.get('durationPeriod', 'monthly')

      # If the subscription is monthly, give 3 months grace period
      if duration_period == "monthly":
        logger.debug('Monthly license expires on %s', service_end_date)
        return service_end_date <= (compare_date - MONTHLY_GRACE_PERIOD)

      if duration_period == "years":
        logger.debug('Yearly license expires on %s', service_end_date)
        return service_end_date <= (compare_date - YEARLY_GRACE_PERIOD)

    return True


LICENSE_FILENAME = 'license'

_PROD_LICENSE_PUBLIC_KEY_DATA = """
-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAuCkRnkuqox3A0djgRnHR
e3U3jHrcbd5iUqdbfO/8E2TMbiByIy3NzUyJrMIzrTjdxTVIZF/ueaHLEtgaofUA
1X73OZlsaGyNVDFA2eGZRgyNrmfLFoxnN2KB+gEJ88nPkHZXY+4ncZBjVMKfHQEv
busC7xpnF7Diy2GxZKDZRnvjL4ZNrocdoeE0GuroWwebtck5Ea7LqzRxCJ5T3UWt
EozttOBQAqCmKxSDdtdw+CsK/uTfl6Yh9xCZUrCeh5taSOHOvU0ne/p3gM+AsjU4
ScjObTKaSUOGen6aYFF5Bd6V/ucxHmcmJlycwNZOKGFpbhLU173/oBJ+okvDbJpN
qwIDAQAB
-----END PUBLIC KEY-----
"""

def decode_license(license_contents, public_key_contents=None):
  """ Decodes the specified license contents, returning the decoded license. """
  public_key_data = public_key_contents or _PROD_LICENSE_PUBLIC_KEY_DATA
  license_public_key = load_pem_public_key(public_key_data, backend=default_backend())
  try:
    decoded = jwt.decode(license_contents, key=license_public_key)
  except jwt.exceptions.DecodeError as de:
    logger.exception('Could not decode license file')
    raise LicenseDecodeError('Could not decode license found: %s' % de.message)

  return License(decoded)