"""JOSE Web Signature."""
import argparse
import base64
import sys

import M2Crypto

from acme.jose import b64
from acme.jose import errors
from acme.jose import json_util
from acme.jose import jwa
from acme.jose import jwk
from acme.jose import util


class MediaType(object):
    """MediaType field encoder/decoder."""

    PREFIX = 'application/'
    """MIME Media Type and Content Type prefix."""

    @classmethod
    def decode(cls, value):
        """Decoder."""
        # 4.1.10
        if '/' not in value:
            if ';' in value:
                raise errors.DeserializationError('Unexpected semi-colon')
            return cls.PREFIX + value
        return value

    @classmethod
    def encode(cls, value):
        """Encoder."""
        # 4.1.10
        if ';' not in value:
            assert value.startswith(cls.PREFIX)
            return value[len(cls.PREFIX):]
        return value


class Header(json_util.JSONObjectWithFields):
    """JOSE Header.

    .. warning:: This class supports **only** Registered Header
        Parameter Names (as defined in section 4.1 of the
        protocol). If you need Public Header Parameter Names (4.2)
        or Private Header Parameter Names (4.3), you must subclass
        and override :meth:`from_json` and :meth:`to_partial_json`
        appropriately.

    .. warning:: This class does not support any extensions through
        the "crit" (Critical) Header Parameter (4.1.11) and as a
        conforming implementation, :meth:`from_json` treats its
        occurence as an error. Please subclass if you seek for
        a diferent behaviour.

    :ivar x5tS256: "x5t#S256"
    :ivar str typ: MIME Media Type, inc. :const:`MediaType.PREFIX`.
    :ivar str cty: Content-Type, inc. :const:`MediaType.PREFIX`.

    """
    alg = json_util.Field(
        'alg', decoder=jwa.JWASignature.from_json, omitempty=True)
    jku = json_util.Field('jku', omitempty=True)
    jwk = json_util.Field('jwk', decoder=jwk.JWK.from_json, omitempty=True)
    kid = json_util.Field('kid', omitempty=True)
    x5u = json_util.Field('x5u', omitempty=True)
    x5c = json_util.Field('x5c', omitempty=True, default=())
    x5t = json_util.Field(
        'x5t', decoder=json_util.decode_b64jose, omitempty=True)
    x5tS256 = json_util.Field(
        'x5t#S256', decoder=json_util.decode_b64jose, omitempty=True)
    typ = json_util.Field('typ', encoder=MediaType.encode,
                          decoder=MediaType.decode, omitempty=True)
    cty = json_util.Field('cty', encoder=MediaType.encode,
                          decoder=MediaType.decode, omitempty=True)
    crit = json_util.Field('crit', omitempty=True, default=())

    def not_omitted(self):
        """Fields that would not be omitted in the JSON object."""
        return dict((name, getattr(self, name))
                    for name, field in self._fields.iteritems()
                    if not field.omit(getattr(self, name)))

    def __add__(self, other):
        if not isinstance(other, type(self)):
            raise TypeError('Header cannot be added to: {0}'.format(
                type(other)))

        not_omitted_self = self.not_omitted()
        not_omitted_other = other.not_omitted()

        if set(not_omitted_self).intersection(not_omitted_other):
            raise TypeError('Addition of overlapping headers not defined')

        not_omitted_self.update(not_omitted_other)
        return type(self)(**not_omitted_self)  # pylint: disable=star-args

    def find_key(self):
        """Find key based on header.

        .. todo:: Supports only "jwk" header parameter lookup.

        :returns: (Public) key found in the header.
        :rtype: :class:`acme.jose.jwk.JWK`

        :raises acme.jose.errors.Error: if key could not be found

        """
        if self.jwk is None:
            raise errors.Error('No key found')
        return self.jwk

    @crit.decoder
    def crit(unused_value):
        # pylint: disable=missing-docstring,no-self-argument,no-self-use
        raise errors.DeserializationError(
            '"crit" is not supported, please subclass')

    # x5c does NOT use JOSE Base64 (4.1.6)

    @x5c.encoder
    def x5c(value):  # pylint: disable=missing-docstring,no-self-argument
        return [base64.b64encode(cert.as_der()) for cert in value]

    @x5c.decoder
    def x5c(value):  # pylint: disable=missing-docstring,no-self-argument
        try:
            return tuple(util.ComparableX509(M2Crypto.X509.load_cert_der_string(
                base64.b64decode(cert))) for cert in value)
        except M2Crypto.X509.X509Error as error:
            raise errors.DeserializationError(error)


class Signature(json_util.JSONObjectWithFields):
    """JWS Signature.

    :ivar combined: Combined Header (protected and unprotected,
        :class:`Header`).
    :ivar unicode protected: JWS protected header (Jose Base-64 decoded).
    :ivar header: JWS Unprotected Header (:class:`Header`).
    :ivar str signature: The signature.

    """
    header_cls = Header

    __slots__ = ('combined',)
    protected = json_util.Field(
        'protected', omitempty=True, default='',
        decoder=json_util.decode_b64jose, encoder=b64.b64encode)  # TODO: utf-8?
    header = json_util.Field(
        'header', omitempty=True, default=header_cls(),
        decoder=header_cls.from_json)
    signature = json_util.Field(
        'signature', decoder=json_util.decode_b64jose,
        encoder=b64.b64encode)

    def __init__(self, **kwargs):
        if 'combined' not in kwargs:
            kwargs = self._with_combined(kwargs)
        super(Signature, self).__init__(**kwargs)
        assert self.combined.alg is not None

    @classmethod
    def _with_combined(cls, kwargs):
        assert 'combined' not in kwargs
        header = kwargs.get('header', cls._fields['header'].default)
        protected = kwargs.get('protected', cls._fields['protected'].default)

        if protected:
            combined = header + cls.header_cls.json_loads(protected)
        else:
            combined = header

        kwargs['combined'] = combined
        return kwargs

    def verify(self, payload, key=None):
        """Verify.

        :param key: Key used for verification.
        :type key: :class:`acme.jose.jwk.JWK`

        """
        key = self.combined.find_key() if key is None else key