import logging
import datetime
import importlib
from functools import wraps
from xml.etree import ElementTree as ET
import requests
import requests.exceptions
import dateutil.parser

from django.core.urlresolvers import reverse
from django.template.loader import render_to_string
from django.utils.timezone import make_aware, now, make_naive, is_aware
from django.conf import settings
import lasso

from . import app_settings


def create_metadata(request):
    entity_id = reverse('mellon_metadata')
    cache = getattr(settings, '_MELLON_METADATA_CACHE', {})
    if not entity_id in cache:
        login_url = reverse('mellon_login')
        logout_url = reverse('mellon_logout')
        public_keys = []
        for public_key in app_settings.PUBLIC_KEYS:
            if public_key.startswith('/'):
                # clean PEM file
                public_key = ''.join(file(public_key).read().splitlines()[1:-1])
            public_keys.append(public_key)
        name_id_formats = app_settings.NAME_ID_FORMATS
        cache[entity_id] = render_to_string('mellon/metadata.xml', {
            'entity_id': request.build_absolute_uri(entity_id),
            'login_url': request.build_absolute_uri(login_url),
            'logout_url': request.build_absolute_uri(logout_url),
            'public_keys': public_keys,
            'name_id_formats': name_id_formats,
            'default_assertion_consumer_binding': app_settings.DEFAULT_ASSERTION_CONSUMER_BINDING,
        })
        settings._MELLON_METADATA_CACHE = cache
    return settings._MELLON_METADATA_CACHE[entity_id]

SERVERS = {}


def create_server(request):
    logger = logging.getLogger(__name__)
    root = request.build_absolute_uri('/')
    if root not in SERVERS:
        idps = get_idps()
        metadata = create_metadata(request)
        if app_settings.PRIVATE_KEY:
            private_key = app_settings.PRIVATE_KEY
            private_key_password = app_settings.PRIVATE_KEY_PASSWORD
        elif app_settings.PRIVATE_KEYS:
            private_key = app_settings.PRIVATE_KEYS
            private_key_password = None
            if isinstance(private_key, (tuple, list)):
                private_key_password = private_key[1]
                private_key = private_key[0]
        else:  # no signature
            private_key = None
            private_key_password = None
        server = lasso.Server.newFromBuffers(metadata,
                private_key_content=private_key,
                private_key_password=private_key_password)
        server.setEncryptionPrivateKeyWithPassword(private_key, private_key_password)
        for key in app_settings.PRIVATE_KEYS:
            password = None
            if isinstance(key, (tuple, list)):
                password = key[1]
                key = key[0]
            server.setEncryptionPrivateKeyWithPassword(key, password)
        for i, idp in enumerate(idps):
            if 'METADATA_URL' in idp and 'METADATA' not in idp:
                verify_ssl_certificate = get_setting(
                    idp, 'VERIFY_SSL_CERTIFICATE')
                try:
                    response = requests.get(idp['METADATA_URL'],
                                        verify=verify_ssl_certificate)
                    response.raise_for_status()
                except requests.exceptions.RequestException, e:
                    logger.error(u'retrieval of metadata URL %r failed with error %s for %d-th idp',
                                 idp['METADATA_URL'], e, i)
                    continue
                metadata = response.content
            elif 'METADATA' in idp:
                if idp['METADATA'].startswith('/'):
                    metadata = file(idp['METADATA']).read()
            else:
                logger.error(u'missing METADATA or METADATA_URL in %d-th idp', i)
                continue
            try:
                server.addProviderFromBuffer(lasso.PROVIDER_ROLE_IDP, metadata)
            except lasso.Error, e:
                logger.error(u'bad metadata in %d-th idp', i)
                logger.debug(u'lasso error: %s', e)
                continue
            idp['ENTITY_ID'] = ET.fromstring(metadata).attrib['entityID']
            idp['METADATA'] = metadata
        SERVERS[root] = server
    return SERVERS[root]


def create_login(request):
    server = create_server(request)
    login = lasso.Login(server)
    if not app_settings.PRIVATE_KEY and not app_settings.PRIVATE_KEYS:
        login.setSignatureHint(lasso.PROFILE_SIGNATURE_HINT_FORBID)
    return login


def get_idp(entity_id):
    for adapter in get_adapters():
        if hasattr(adapter, 'get_idp'):
            idp = adapter.get_idp(entity_id)
            if idp:
                return idp
    return {}


def get_idps():
    for adapter in get_adapters():
        if hasattr(adapter, 'get_idps'):
            for idp in adapter.get_idps():
                yield idp


def flatten_datetime(d):
    d = d.copy()
    for key, value in d.iteritems():
        if isinstance(value, datetime.datetime):
            d[key] = value.isoformat() + 'Z'
    return d


def iso8601_to_datetime(date_string):
    '''Convert a string formatted as an ISO8601 date into a time_t
       value.

       This function ignores the sub-second resolution'''
    dt = dateutil.parser.parse(date_string)
    if is_aware(dt):
        if not settings.USE_TZ:
            dt = make_naive(dt)
    else:
        if settings.USE_TZ:
            dt = make_aware(dt)
    return dt


def get_seconds_expiry(datetime_expiry):
    return (datetime_expiry - now()).total_seconds()


def to_list(func):
    @wraps(func)
    def f(*args, **kwargs):
        return list(func(*args, **kwargs))
    return f


def import_object(path):
    module, name = path.rsplit('.', 1)
    module = importlib.import_module(module)
    return getattr(module, name)


@to_list
def get_adapters(idp={}):
    idp = idp or {}
    adapters = tuple(idp.get('ADAPTER', ())) + tuple(app_settings.ADAPTER)
    for adapter in adapters:
        yield import_object(adapter)()


def get_values(saml_attributes, name):
    values = saml_attributes.get(name)
    if values is None:
        return ()
    if not isinstance(values, (list, tuple)):
        return (values,)
    return values


def get_setting(idp, name, default=None):
    '''Get a parameter from an IdP specific configuration or from the main
       settings.
    '''
    return idp.get(name) or getattr(app_settings, name, default)


def create_logout(request):
    logger = logging.getLogger(__name__)
    server = create_server(request)
    mellon_session = request.session.get('mellon_session', {})
    entity_id = mellon_session.get('issuer')
    session_index = mellon_session.get('session_index')
    name_id_format = mellon_session.get('name_id_format')
    name_id_content = mellon_session.get('name_id_content')
    name_id_name_qualifier = mellon_session.get('name_id_name_qualifier')
    name_id_sp_name_qualifier = mellon_session.get('name_id_sp_name_qualifier')
    session_dump = render_to_string('mellon/session_dump.xml', {
        'entity_id': entity_id,
        'session_index': session_index,
        'name_id_format': name_id_format,
        'name_id_content': name_id_content,
        'name_id_name_qualifier': name_id_name_qualifier,
        'name_id_sp_name_qualifier': name_id_sp_name_qualifier,
    })
    logger.debug('session_dump %s', session_dump)
    logout = lasso.Logout(server)
    if not app_settings.PRIVATE_KEY:
        logout.setSignatureHint(lasso.PROFILE_SIGNATURE_HINT_FORBID)
    logout.setSessionFromDump(session_dump)
    return logout


def is_nonnull(s):
    return not '\x00' in s