#!/usr/bin/env python

import base64
import hashlib
import hmac
import logging
import random
import string
import sys
import traceback
import zlib

from saml2 import VERSION
from saml2 import saml
from saml2 import samlp
from saml2.time_util import instant


logger = logging.getLogger(__name__)


class SamlException(Exception):
    pass


class RequestVersionTooLow(SamlException):
    pass


class RequestVersionTooHigh(SamlException):
    pass


class UnknownPrincipal(SamlException):
    pass


class UnknownSystemEntity(SamlException):
    pass


class Unsupported(SamlException):
    pass


class UnsupportedBinding(Unsupported):
    pass


class VersionMismatch(Exception):
    pass


class Unknown(Exception):
    pass


class OtherError(Exception):
    pass


class MissingValue(Exception):
    pass


class PolicyError(Exception):
    pass


class BadRequest(Exception):
    pass


class UnravelError(Exception):
    pass


EXCEPTION2STATUS = {
    VersionMismatch: samlp.STATUS_VERSION_MISMATCH,
    UnknownPrincipal: samlp.STATUS_UNKNOWN_PRINCIPAL,
    UnsupportedBinding: samlp.STATUS_UNSUPPORTED_BINDING,
    RequestVersionTooLow: samlp.STATUS_REQUEST_VERSION_TOO_LOW,
    RequestVersionTooHigh: samlp.STATUS_REQUEST_VERSION_TOO_HIGH,
    OtherError: samlp.STATUS_UNKNOWN_PRINCIPAL,
    MissingValue: samlp.STATUS_REQUEST_UNSUPPORTED,
    # Undefined
    Exception: samlp.STATUS_AUTHN_FAILED,
}

GENERIC_DOMAINS = [
    "aero",
    "asia",
    "biz",
    "cat",
    "com",
    "coop",
    "edu",
    "gov",
    "info",
    "int",
    "jobs",
    "mil",
    "mobi",
    "museum",
    "name",
    "net",
    "org",
    "pro",
    "tel",
    "travel",
]


def valid_email(emailaddress, domains=GENERIC_DOMAINS):
    """Checks for a syntactically valid email address."""

    # Email address must be at least 6 characters in total.
    # Assuming noone may have addresses of the type a@com
    if len(emailaddress) < 6:
        return False  # Address too short.

    # Split up email address into parts.
    try:
        localpart, domainname = emailaddress.rsplit("@", 1)
        host, toplevel = domainname.rsplit(".", 1)
    except ValueError:
        return False  # Address does not have enough parts.

    # Check for Country code or Generic Domain.
    if len(toplevel) != 2 and toplevel not in domains:
        return False  # Not a domain name.

    for i in "-_.%+.":
        localpart = localpart.replace(i, "")
    for i in "-_.":
        host = host.replace(i, "")

    if localpart.isalnum() and host.isalnum():
        return True  # Email address is fine.
    else:
        return False  # Email address has funny characters.


def decode_base64_and_inflate(string):
    """base64 decodes and then inflates according to RFC1951

    :param string: a deflated and encoded string
    :return: the string after decoding and inflating
    """

    return zlib.decompress(base64.b64decode(string), -15)


def deflate_and_base64_encode(string_val):
    """
    Deflates and the base64 encodes a string

    :param string_val: The string to deflate and encode
    :return: The deflated and encoded string
    """
    if not isinstance(string_val, bytes):
        string_val = string_val.encode("utf-8")
    return base64.b64encode(zlib.compress(string_val)[2:-4])


def rndstr(size=16, alphabet=""):
    """
    Returns a string of random ascii characters or digits

    :param size: The length of the string
    :return: string
    """
    rng = random.SystemRandom()
    if not alphabet:
        alphabet = string.ascii_letters[0:52] + string.digits
    return type(alphabet)().join(rng.choice(alphabet) for _ in range(size))


def rndbytes(size=16, alphabet=""):
    """
    Returns rndstr always as a binary type
    """
    x = rndstr(size, alphabet)
    if isinstance(x, str):
        return x.encode("utf-8")
    return x


def sid():
    """creates an unique SID for each session.
    160-bits long so it fulfills the SAML2 requirements which states
    128-160 bits

    :return: A random string prefix with 'id-' to make it
        compliant with the NCName specification
    """
    return f"id-{rndstr(17)}"


def parse_attribute_map(filenames):
    """
    Expects a file with each line being composed of the oid for the attribute
    exactly one space, a user friendly name of the attribute and then
    the type specification of the name.

    :param filenames: List of filenames on mapfiles.
    :return: A 2-tuple, one dictionary with the oid as keys and the friendly
        names as values, the other one the other way around.
    """
    forward = {}
    backward = {}
    for filename in filenames:
        with open(filename) as fp:
            for line in fp:
                (name, friendly_name, name_format) = line.strip().split()
                forward[(name, name_format)] = friendly_name
                backward[friendly_name] = (name, name_format)

    return forward, backward


def identity_attribute(form, attribute, forward_map=None):
    if form == "friendly":
        if attribute.friendly_name:
            return attribute.friendly_name
        elif forward_map:
            try:
                return forward_map[(attribute.name, attribute.name_format)]
            except KeyError:
                return attribute.name
    # default is name
    return attribute.name


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


def error_status_factory(info):
    if not isinstance(info, Exception):
        (status_code_status_code_value, status_message_text) = info
    else:
        try:
            exc_val = EXCEPTION2STATUS[info.__class__]
        except KeyError:
            exc_val = samlp.STATUS_AUTHN_FAILED

        try:
            exc_context = info.args[0]
            err_ctx = {"status_message_text": exc_context} if isinstance(exc_context, str) else exc_context
        except IndexError:
            err_ctx = {"status_message_text": str(info)}

        status_message_text = err_ctx.get("status_message_text")
        status_code_status_code_value = err_ctx.get("status_code_status_code_value", exc_val)

    status_msg = samlp.StatusMessage(text=status_message_text) if status_message_text else None

    status = samlp.Status(
        status_message=status_msg,
        status_code=samlp.StatusCode(
            value=samlp.STATUS_RESPONDER,
            status_code=samlp.StatusCode(value=status_code_status_code_value),
        ),
    )
    return status


def success_status_factory():
    return samlp.Status(status_code=samlp.StatusCode(value=samlp.STATUS_SUCCESS))


def status_message_factory(message, code, fro=samlp.STATUS_RESPONDER):
    return samlp.Status(
        status_message=samlp.StatusMessage(text=message),
        status_code=samlp.StatusCode(value=fro, status_code=samlp.StatusCode(value=code)),
    )


def assertion_factory(**kwargs):
    assertion = saml.Assertion(version=VERSION, id=sid(), issue_instant=instant())
    for key, val in kwargs.items():
        setattr(assertion, key, val)
    return assertion


def _attrval(val, typ=""):
    if isinstance(val, list) or isinstance(val, set):
        attrval = [saml.AttributeValue(text=v) for v in val]
    elif val is None:
        attrval = None
    else:
        attrval = [saml.AttributeValue(text=val)]

    if typ:
        for ava in attrval:
            ava.set_type(typ)

    return attrval


# --- attribute profiles -----

# xmlns:xs="http://www.w3.org/2001/XMLSchema"
# xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"


def do_ava(val, typ=""):
    if isinstance(val, str):
        ava = saml.AttributeValue()
        ava.set_text(val)
        attrval = [ava]
    elif isinstance(val, list):
        attrval = [do_ava(v)[0] for v in val]
    elif val or val is False:
        ava = saml.AttributeValue()
        ava.set_text(val)
        attrval = [ava]
    elif val is None:
        attrval = None
    else:
        raise OtherError(f"strange value type on: {val}")

    if typ:
        for ava in attrval:
            ava.set_type(typ)

    return attrval


def do_attribute(val, typ, key):
    attr = saml.Attribute()
    attrval = do_ava(val, typ)
    if attrval:
        attr.attribute_value = attrval

    if isinstance(key, str):
        attr.name = key
    elif isinstance(key, tuple):  # 3-tuple or 2-tuple
        try:
            (name, nformat, friendly) = key
        except ValueError:
            (name, nformat) = key
            friendly = ""
        if name:
            attr.name = name
        if format:
            attr.name_format = nformat
        if friendly:
            attr.friendly_name = friendly
    return attr


def do_attributes(identity):
    attrs = []
    if not identity:
        return attrs
    for key, spec in identity.items():
        try:
            val, typ = spec
        except ValueError:
            val = spec
            typ = ""
        except TypeError:
            val = ""
            typ = ""

        attr = do_attribute(val, typ, key)
        attrs.append(attr)
    return attrs


def do_attribute_statement(identity):
    """
    :param identity: A dictionary with fiendly names as keys
    :return:
    """
    return saml.AttributeStatement(attribute=do_attributes(identity))


def factory(klass, **kwargs):
    instance = klass()
    for key, val in kwargs.items():
        if isinstance(val, dict):
            cls = instance.child_class(key)
            val = factory(cls, **val)
        setattr(instance, key, val)
    return instance


def signature(secret, parts):
    """Generates a signature. All strings are assumed to be utf-8"""
    if not isinstance(secret, bytes):
        secret = secret.encode("utf-8")
    newparts = []
    for part in parts:
        if not isinstance(part, bytes):
            part = part.encode("utf-8")
        newparts.append(part)
    parts = newparts
    csum = hmac.new(secret, digestmod=hashlib.sha1)

    for part in parts:
        csum.update(part)

    return csum.hexdigest()


def verify_signature(secret, parts):
    """Checks that the signature is correct"""
    if signature(secret, parts[:-1]) == parts[-1]:
        return True
    else:
        return False


def exception_trace(exc):
    message = traceback.format_exception(*sys.exc_info())

    try:
        _exc = f"Exception: {exc}"
    except UnicodeEncodeError:
        _exc = f"Exception: {exc.message.encode('utf-8', 'replace')}"

    return {"message": _exc, "content": "".join(message)}


def rec_factory(cls, **kwargs):
    _inst = cls()
    for key, val in kwargs.items():
        if key in ["text", "lang"]:
            setattr(_inst, key, val)
        elif key in _inst.c_attributes:
            try:
                val = str(val)
            except Exception:
                continue
            else:
                setattr(_inst, _inst.c_attributes[key][0], val)
        elif key in _inst.c_child_order:
            for tag, _cls in _inst.c_children.values():
                if tag == key:
                    if isinstance(_cls, list):
                        _cls = _cls[0]
                        claim = []
                        if isinstance(val, list):
                            for v in val:
                                claim.append(rec_factory(_cls, **v))
                        else:
                            claim.append(rec_factory(_cls, **val))
                    else:
                        claim = rec_factory(_cls, **val)
                    setattr(_inst, key, claim)
                    break

    return _inst
