import datetime
import json

from app import app
from util.security.crypto import encrypt_string, decrypt_string

# TTL (in seconds) for page tokens.
_PAGE_TOKEN_TTL = datetime.timedelta(days=2).total_seconds()

def decrypt_page_token(token_string):
  if token_string is None:
    return None

  unencrypted = decrypt_string(token_string, app.config['PAGE_TOKEN_KEY'], ttl=_PAGE_TOKEN_TTL)
  if unencrypted is None:
    return None

  try:
    return json.loads(unencrypted)
  except ValueError:
    return None


def encrypt_page_token(page_token):
  return encrypt_string(json.dumps(page_token), app.config['PAGE_TOKEN_KEY'])