import string
import re
import json

import anunidecode # Don't listen to pylint's lies. This import is required.

from peewee import OperationalError

INVALID_PASSWORD_MESSAGE = 'Invalid password, password must be at least ' + \
                           '8 characters and contain no whitespace.'
VALID_CHARACTERS = string.digits + string.lowercase

MIN_USERNAME_LENGTH = 2
MAX_USERNAME_LENGTH = 255

VALID_LABEL_KEY_REGEX = r'^[a-z0-9](([a-z0-9]|[-.](?![.-]))*[a-z0-9])?$'
VALID_USERNAME_REGEX = r'^([a-z0-9]+(?:[._-][a-z0-9]+)*)$'
VALID_SERVICE_KEY_NAME_REGEX = r'^[\s a-zA-Z0-9\-_:/]*$'

INVALID_USERNAME_CHARACTERS = r'[^a-z0-9_]'


def validate_label_key(label_key):
  if len(label_key) > 255:
    return False

  return bool(re.match(VALID_LABEL_KEY_REGEX, label_key))


def validate_email(email_address):
  if not email_address:
    return False

  return bool(re.match(r'[^@]+@[^@]+\.[^@]+', email_address))


def validate_username(username):
  # Based off the restrictions defined in the Docker Registry API spec
  if not re.match(VALID_USERNAME_REGEX, username):
    return (False, 'Namespace must match expression ' + VALID_USERNAME_REGEX)

  length_match = (len(username) >= MIN_USERNAME_LENGTH and len(username) <= MAX_USERNAME_LENGTH)
  if not length_match:
    return (False, 'Namespace must be between %s and %s characters in length' %
            (MIN_USERNAME_LENGTH, MAX_USERNAME_LENGTH))

  return (True, '')


def validate_password(password):
  # No whitespace and minimum length of 8
  if re.search(r'\s', password):
    return False
  return len(password) > 7


def _gen_filler_chars(num_filler_chars):
  if num_filler_chars == 0:
    yield ''
  else:
    for char in VALID_CHARACTERS:
      for suffix in _gen_filler_chars(num_filler_chars - 1):
        yield char + suffix


def generate_valid_usernames(input_username):
  normalized = input_username.encode('unidecode', 'ignore').strip().lower()
  prefix = re.sub(INVALID_USERNAME_CHARACTERS, '_', normalized)[:MAX_USERNAME_LENGTH]
  prefix = re.sub(r'_{2,}', '_', prefix)

  if prefix.endswith('_'):
    prefix = prefix[0:len(prefix) - 1]

  while prefix.startswith('_'):
    prefix = prefix[1:]

  num_filler_chars = max(0, MIN_USERNAME_LENGTH - len(prefix))

  while num_filler_chars + len(prefix) <= MAX_USERNAME_LENGTH:
    for suffix in _gen_filler_chars(num_filler_chars):
      yield prefix + suffix
    num_filler_chars += 1


def is_json(value):
  if ((value.startswith('{') and value.endswith('}')) or
      (value.startswith('[') and value.endswith(']'))):
    try:
      json.loads(value)
      return True
    except (TypeError, ValueError):
      return False
  return False


def validate_postgres_precondition(driver):
  cursor = driver.execute_sql("SELECT extname FROM pg_extension", ("public",))
  if 'pg_trgm' not in [extname for extname, in cursor.fetchall()]:
    raise OperationalError("""
      "pg_trgm" extension does not exists in the database.
      Please run `CREATE EXTENSION IF NOT EXISTS pg_trgm;` as superuser on this database.
    """)


def validate_service_key_name(name):
  return name is None or bool(re.match(VALID_SERVICE_KEY_NAME_REGEX, name))