# This file is part of Radicale Server - Calendar Server
# Copyright © 2012-2017 Guillaume Ayoub
# Copyright © 2017-2019 Unrud <unrud@outlook.com>
#
# This library 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 library 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 Radicale.  If not, see <http://www.gnu.org/licenses/>.

"""
Rights backend based on a regex-based file whose name is specified in the
config (section "rights", key "file").

The login is matched against the "user" key, and the collection path
is matched against the "collection" key. In the "collection" regex you can use
`{user}` and get groups from the "user" regex with `{0}`, `{1}`, etc.
In consequence of the parameter subsitution you have to write `{{` and `}}`
if you want to use regular curly braces in the "user" and "collection" regexes.

For example, for the "user" key, ".+" means "authenticated user" and ".*"
means "anybody" (including anonymous users).

Section names are only used for naming the rule.

Leading or ending slashes are trimmed from collection's path.

"""

import configparser
import re

from radicale import pathutils, rights
from radicale.log import logger


class Rights(rights.BaseRights):
    def __init__(self, configuration):
        super().__init__(configuration)
        self._filename = configuration.get("rights", "file")

    def authorization(self, user, path):
        user = user or ""
        sane_path = pathutils.strip_path(path)
        # Prevent "regex injection"
        escaped_user = re.escape(user)
        rights_config = configparser.ConfigParser()
        try:
            if not rights_config.read(self._filename):
                raise RuntimeError("No such file: %r" %
                                   self._filename)
        except Exception as e:
            raise RuntimeError("Failed to load rights file %r: %s" %
                               (self._filename, e)) from e
        for section in rights_config.sections():
            try:
                user_pattern = rights_config.get(section, "user")
                collection_pattern = rights_config.get(section, "collection")
                # Use empty format() for harmonized handling of curly braces
                user_match = re.fullmatch(user_pattern.format(), user)
                collection_match = user_match and re.fullmatch(
                    collection_pattern.format(
                        *map(re.escape, user_match.groups()),
                        user=escaped_user), sane_path)
            except Exception as e:
                raise RuntimeError("Error in section %r of rights file %r: "
                                   "%s" % (section, self._filename, e)) from e
            if user_match and collection_match:
                logger.debug("Rule %r:%r matches %r:%r from section %r",
                             user, sane_path, user_pattern,
                             collection_pattern, section)
                return rights_config.get(section, "permissions")
            logger.debug("Rule %r:%r doesn't match %r:%r from section %r",
                         user, sane_path, user_pattern, collection_pattern,
                         section)
        logger.info("Rights: %r:%r doesn't match any section", user, sane_path)
        return ""