import datetime
from hashlib import sha1
import logging

from pymongo import MongoClient
from pymongo.mongo_replica_set_client import MongoReplicaSetClient
import pymongo.uri_parser
import pymongo.errors
from saml2.saml import NAMEID_FORMAT_PERSISTENT

from saml2.eptid import Eptid
from saml2.mdstore import InMemoryMetaData
from saml2.mdstore import metadata_modules
from saml2.mdstore import load_metadata_modules
from saml2.s_utils import PolicyError

from saml2.ident import code_binary
from saml2.ident import IdentDB
from saml2.ident import Unknown
from saml2.mdie import to_dict
from saml2.mdie import from_dict

import six


__author__ = 'rolandh'

logger = logging.getLogger(__name__)

ONTS = load_metadata_modules()
MMODS = metadata_modules()

class CorruptDatabase(Exception):
    pass


def context_match(cfilter, cntx):
    # TODO
    return True


class SessionStorageMDB(object):
    """ Session information is stored in a MongoDB database"""

    def __init__(self, database="", collection="assertion", **kwargs):
        db = _mdb_get_database(database, **kwargs)
        self.assertion = db[collection]

    def store_assertion(self, assertion, to_sign):
        name_id = assertion.subject.name_id
        nkey = sha1(code_binary(name_id)).hexdigest()

        doc = {
            "name_id_key": nkey,
            "assertion_id": assertion.id,
            "assertion": to_dict(assertion, MMODS, True),
            "to_sign": to_sign
        }

        _ = self.assertion.insert(doc)

    def get_assertion(self, cid):
        res = []
        for item in self.assertion.find({"assertion_id": cid}):
            res.append({"assertion": from_dict(item["assertion"], ONTS, True),
                        "to_sign": item["to_sign"]})
        if len(res) == 1:
            return res[0]
        elif res is []:
            return None
        else:
            raise SystemError("More then one assertion with the same ID")

    def get_assertions_by_subject(self, name_id=None, session_index=None,
                                  requested_context=None):
        """

        :param name_id: One of name_id or key can be used to get the authn
            statement
        :param session_index: If match against a session index should be done
        :param requested_context: Authn statements should match a specific
            authn context
        :return:
        """
        result = []
        key = sha1(code_binary(name_id)).hexdigest()
        for item in self.assertion.find({"name_id_key": key}):
            assertion = from_dict(item["assertion"], ONTS, True)
            if session_index or requested_context:
                for statement in assertion.authn_statement:
                    if session_index:
                        if statement.session_index == session_index:
                            result.append(assertion)
                            break
                    if requested_context:
                        if context_match(requested_context,
                                         statement.authn_context):
                            result.append(assertion)
                            break
            else:
                result.append(assertion)
        return result

    def remove_authn_statements(self, name_id):
        logger.debug("remove authn about: %s", name_id)
        key = sha1(code_binary(name_id)).hexdigest()
        for item in self.assertion.find({"name_id_key": key}):
            self.assertion.remove(item["_id"])

    def get_authn_statements(self, name_id, session_index=None,
                             requested_context=None):
        """

        :param name_id:
        :param session_index:
        :param requested_context:
        :return:
        """
        return [k.authn_statement for k in self.get_assertions_by_subject(
            name_id, session_index, requested_context)]


class IdentMDB(IdentDB):
    def __init__(self, database="", collection="ident", domain="",
                 name_qualifier=""):
        IdentDB.__init__(self, None, domain, name_qualifier)
        self.mdb = MDB(database=database, collection=collection)
        self.mdb.primary_key = "user_id"

    def in_store(self, _id):
        if [x for x in self.mdb.get(ident_id=_id)]:
            return True
        else:
            return False

    def create_id(self, nformat, name_qualifier="", sp_name_qualifier=""):
        _id = self._create_id(nformat, name_qualifier, sp_name_qualifier)
        while self.in_store(_id):
            _id = self._create_id(nformat, name_qualifier, sp_name_qualifier)
        return _id

    def store(self, ident, name_id):
        self.mdb.store(ident, name_id=to_dict(name_id, MMODS, True))

    def find_nameid(self, userid, nformat=None, sp_name_qualifier=None,
                    name_qualifier=None, sp_provided_id=None, **kwargs):
        # reset passed for compatibility kwargs for next usage
        kwargs = {}
        if nformat:
            kwargs["name_format"] = nformat
        if sp_name_qualifier:
            kwargs["sp_name_qualifier"] = sp_name_qualifier
        if name_qualifier:
            kwargs["name_qualifier"] = name_qualifier
        if sp_provided_id:
            kwargs["sp_provided_id"] = sp_provided_id

        res = []
        for item in self.mdb.get(userid, **kwargs):
            res.append(from_dict(item["name_id"], ONTS, True))
        return res

    def find_local_id(self, name_id):
        cnid = to_dict(name_id, MMODS, True)
        for item in self.mdb.get(name_id=cnid):
            return item[self.mdb.primary_key]
        return None

    def match_local_id(self, userid, sp_name_qualifier, name_qualifier):
        """
        Match a local persistent identifier.

        Look for an existing persistent NameID matching userid,
        sp_name_qualifier and name_qualifier.
        """
        filter = {
            "name_id.sp_name_qualifier": sp_name_qualifier,
            "name_id.name_qualifier": name_qualifier,
            "name_id.format": NAMEID_FORMAT_PERSISTENT,
        }
        res = self.mdb.get(value=userid, **filter)
        if not res:
            return None
        return from_dict(res[0]["name_id"], ONTS, True)

    def remove_remote(self, name_id):
        cnid = to_dict(name_id, MMODS, True)
        self.mdb.remove(name_id=cnid)

    def handle_name_id_mapping_request(self, name_id, name_id_policy):
        _id = self.find_local_id(name_id)
        if not _id:
            raise Unknown("Unknown entity")

        if name_id_policy.allow_create == "false":
            raise PolicyError("Not allowed to create new identifier")

        # else create and return a new one
        return self.construct_nameid(_id, name_id_policy=name_id_policy)


class MDB(object):
    primary_key = "mdb"

    def __init__(self, database, collection, **kwargs):
        _db = _mdb_get_database(database, **kwargs)
        self.db = _db[collection]

    def store(self, value, **kwargs):
        if value:
            doc = {self.primary_key: value}
        else:
            doc = {}
        doc.update(kwargs)
        # Add timestamp to all documents to allow external garbage collecting
        if "created_at" not in doc:
            doc["created_at"] = datetime.datetime.utcnow()
        _ = self.db.insert(doc)

    def get(self, value=None, **kwargs):
        if value is not None:
            doc = {self.primary_key: value}
            doc.update(kwargs)
            return [item for item in self.db.find(doc)]
        elif kwargs:
            return [item for item in self.db.find(kwargs)]

    def remove(self, key=None, **kwargs):
        if key is None:
            if kwargs:
                for item in self.db.find(kwargs):
                    self.db.remove(item["_id"])
        else:
            doc = {self.primary_key: key}
            doc.update(kwargs)
            for item in self.db.find(doc):
                self.db.remove(item["_id"])

    def keys(self):
        for item in self.db.find():
            yield item[self.primary_key]

    def items(self):
        for item in self.db.find():
            _key = item[self.primary_key]
            del item[self.primary_key]
            del item["_id"]
            yield _key, item

    def __contains__(self, key):
        doc = {self.primary_key: key}
        res = [item for item in self.db.find(doc)]
        if not res:
            return False
        else:
            return True

    def reset(self):
        self.db.drop()


def _mdb_get_database(uri, **kwargs):
    """
    Helper-function to connect to MongoDB and return a database object.

    The `uri' argument should be either a full MongoDB connection URI string,
    or just a database name in which case a connection to the default mongo
    instance at mongodb://localhost:27017 will be made.

    Performs explicit authentication if a username is provided in a connection
    string URI, since PyMongo does not always seem to do that as promised.

    :params database: name as string or (uri, name)
    :returns: pymongo database object
    """
    if not "tz_aware" in kwargs:
        # default, but not forced
        kwargs["tz_aware"] = True

    connection_factory = MongoClient
    _parsed_uri = {}

    try:
        _parsed_uri = pymongo.uri_parser.parse_uri(uri)
    except pymongo.errors.InvalidURI:
        # assume URI to be just the database name
        db_name = uri
        _conn = MongoClient()
        pass
    else:
        if "replicaset" in _parsed_uri["options"]:
            connection_factory = MongoReplicaSetClient
        db_name = _parsed_uri.get("database", "pysaml2")
        _conn = connection_factory(uri, **kwargs)

    _db = _conn[db_name]

    if "username" in _parsed_uri:
        _db.authenticate(
            _parsed_uri.get("username", None),
            _parsed_uri.get("password", None)
        )

    return _db


#------------------------------------------------------------------------------
class EptidMDB(Eptid):
    def __init__(self, secret, database="", collection="eptid"):
        Eptid.__init__(self, secret)
        self.mdb = MDB(database, collection)
        self.mdb.primary_key = "eptid_key"

    def __getitem__(self, key):
        res = self.mdb.get(key)
        if not res:
            raise KeyError(key)
        elif len(res) == 1:
            return res[0]["eptid"]
        else:
            raise CorruptDatabase("Found more than one EPTID document")

    def __setitem__(self, key, value):
        _ = self.mdb.store(key, **{"eptid": value})


#------------------------------------------------------------------------------

def protect(dic):
    res = {}
    for key, val in dic.items():
        key = key.replace(".", "__")
        if isinstance(val, six.string_types):
            pass
        elif isinstance(val, dict):
            val = protect(val)
        elif isinstance(val, list):
            li = []
            for va in val:
                if isinstance(va, six.string_types):
                    pass
                elif isinstance(va, dict):
                    va = protect(va)
                    # I don't think lists of lists will appear am I wrong ?
                li.append(va)
            val = li
        res[key] = val
    return res


def unprotect(dic):
    res = {}
    for key, val in dic.items():
        if key == "__class__":
            pass
        else:
            key = key.replace("__", ".")
        if isinstance(val, six.string_types):
            pass
        elif isinstance(val, dict):
            val = unprotect(val)
        elif isinstance(val, list):
            li = []
            for va in val:
                if isinstance(va, six.string_types):
                    pass
                elif isinstance(val, dict):
                    va = unprotect(va)
                li.append(va)
            val = li
        res[key] = val
    return res


def export_mdstore_to_mongo_db(mds, database, collection, sub_collection=""):
    mdb = MDB(database, collection, sub_collection=sub_collection)
    mdb.reset()
    mdb.primary_key = "entity_id"
    for key, desc in mds.items():
        kwargs = {
            "entity_description": protect(desc),
        }
        mdb.store(key, **kwargs)


class MetadataMDB(InMemoryMetaData):
    def __init__(self, attrc, database="", collection=""):
        super(MetadataMDB, self).__init__(attrc)
        self.mdb = MDB(database, collection)
        self.mdb.primary_key = "entity_id"

    def _ext_service(self, entity_id, typ, service, binding):
        try:
            srvs = self[entity_id][typ]
        except KeyError:
            return None

        if not srvs:
            return srvs

        res = []
        for srv in srvs:
            if "extensions" in srv:
                for elem in srv["extensions"]["extension_elements"]:
                    if elem["__class__"] == service:
                        if elem["binding"] == binding:
                            res.append(elem)

        return res

    def load(self):
        pass

    def items(self):
        for key, item in self.mdb.items():
            yield key, unprotect(item["entity_description"])

    def keys(self):
        return self.mdb.keys()

    def values(self):
        for key, item in self.mdb.items():
            yield unprotect(item["entity_description"])

    def __contains__(self, item):
        return item in self.mdb

    def __getitem__(self, item):
        res = self.mdb.get(item)
        if not res:
            raise KeyError(item)
        elif len(res) == 1:
            return unprotect(res[0]["entity_description"])
        else:
            raise CorruptDatabase("More then one document with key %s" % item)

    def bindings(self, entity_id, typ, service):
        pass