import datetime
from uuid import uuid4

import pytz
from lxml import etree
from lxml.builder import ElementMaker

from zeep import ns
from zeep.wsdl.utils import get_or_create_header

NSMAP = {
    'wsse': ns.WSSE,
    'wsu': ns.WSU,
}
WSSE = ElementMaker(namespace=NSMAP['wsse'], nsmap={'wsse': ns.WSSE})
WSU = ElementMaker(namespace=NSMAP['wsu'], nsmap={'wsu': ns.WSU})
ID_ATTR = etree.QName(NSMAP['wsu'], 'Id')


def get_security_header(doc):
    """Return the security header. If the header doesn't exist it will be
    created.

    """
    header = get_or_create_header(doc)
    security = header.find('wsse:Security', namespaces=NSMAP)
    if security is None:
        security = WSSE.Security()
        header.append(security)
    return security


def get_timestamp(timestamp=None):
    timestamp = timestamp or datetime.datetime.utcnow()
    timestamp = timestamp.replace(tzinfo=pytz.utc, microsecond=0)
    return timestamp.isoformat()


def get_unique_id():
    return 'id-{0}'.format(uuid4())


def ensure_id(node):
    """Ensure given node has a wsu:Id attribute; add unique one if not.

    Return found/created attribute value.

    """
    assert node is not None
    id_val = node.get(ID_ATTR)
    if not id_val:
        id_val = get_unique_id()
        node.set(ID_ATTR, id_val)
    return id_val