# Copyright (C) 2017 Jan Jancar
#
# This file is a part of the Mailman PGP plugin.
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
# more details.
#
# You should have received a copy of the GNU General Public License along with
# this program.  If not, see <http://www.gnu.org/licenses/>.

""""""

from glob import glob
from os import makedirs
from os.path import join

from mailman.config import config as mailman_config
from mailman.utilities.string import expand
from pgpy import PGPKeyring
from pgpy.constants import PubKeyAlgorithm, EllipticCurveOID
from public import public

from mailman_pgp.config import config

KEYDIR_CONFIG_PATHS = ['list_keydir', 'user_keydir', 'archive_keydir']
KEYPAIR_CONFIG_VARIABLES = ['autogenerate', 'primary_key', 'sub_key']

KEYPAIR_TYPE_MAP = {
    'RSA': PubKeyAlgorithm.RSAEncryptOrSign,
    'DSA': PubKeyAlgorithm.DSA,
    'ECDSA': PubKeyAlgorithm.ECDSA,
    'ECDH': PubKeyAlgorithm.ECDH
}
ECC_OID_MAP = {
    'nistp256': EllipticCurveOID.NIST_P256,
    'nistp384': EllipticCurveOID.NIST_P384,
    'nistp521': EllipticCurveOID.NIST_P521,
    'brainpoolP256r1': EllipticCurveOID.Brainpool_P256,
    'brainpoolP384r1': EllipticCurveOID.Brainpool_P384,
    'brainpoolP512r1': EllipticCurveOID.Brainpool_P512,
    'secp256k1': EllipticCurveOID.SECP256K1
}


@public
class PGP:
    def __init__(self):
        self._load_config()
        self._validate_config()

    def _load_config(self):
        """
        Load [keypairs] and [keydirs] config sections. Expand paths in them.
        """
        # Get all the [keypairs] config variables.
        self._keypair_config = dict(
                (k, config.get('keypairs', k)) for k in
                KEYPAIR_CONFIG_VARIABLES)

        # Get and expand all [keydirs] config paths against Mailman's paths.
        self.keydir_config = dict(
                (k,
                 expand(config.get('keydirs', k), None, mailman_config.paths))
                for k in KEYDIR_CONFIG_PATHS)

    def _parse_key_directive(self, value):
        key_type, key_length = value.split(':')
        key_type = key_type.upper()
        key_length = key_length.lower()

        if key_type not in KEYPAIR_TYPE_MAP:
            raise ValueError('Invalid key type: {}.'.format(key_type))

        out_type = KEYPAIR_TYPE_MAP[key_type]
        if key_type in ('ECDSA', 'ECDH'):
            if key_length not in ECC_OID_MAP:
                raise ValueError('Invalid key length: {}.'.format(key_length))
            out_length = ECC_OID_MAP[key_length]
        else:
            out_length = int(key_length)
        return (out_type, out_length)

    def _validate_config(self):
        """
        Validate [keypairs] and [keydirs] config sections. And create
        keydirs if necessary.
        """
        # Validate keypair config.
        self.primary_key_args = self._parse_key_directive(
                self._keypair_config['primary_key'])
        if not self.primary_key_args[0].can_sign:
            raise ValueError(
                    'Invalid primary key type: {}.'.format(
                            self.primary_key_args[0]))

        self.sub_key_args = self._parse_key_directive(
                self._keypair_config['sub_key'])
        if not self.sub_key_args[0].can_encrypt:
            raise ValueError(
                    'Invalid sub key type: {}.'.format(self.sub_key_args[0]))

        # Make sure the keydir paths are directories and exist.
        for keydir in self.keydir_config.values():
            # TODO set a strict mode here
            makedirs(keydir, exist_ok=True)

    def _keyring(self, keydir):
        directory = self.keydir_config[keydir]
        return PGPKeyring(*glob(join(directory, '*.asc')))

    @property
    def list_keyring(self):
        return self._keyring('list_keydir')

    @property
    def user_keyring(self):
        return self._keyring('user_keydir')

    @property
    def archive_keyring(self):
        return self._keyring('archive_keydir')