# Copyright 2018 New Vector Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from synapse.util import glob_to_regex

from ._base import Config, ConfigError


class RoomDirectoryConfig(Config):
    section = "roomdirectory"

    def read_config(self, config, **kwargs):
        self.enable_room_list_search = config.get("enable_room_list_search", True)

        alias_creation_rules = config.get("alias_creation_rules")

        if alias_creation_rules is not None:
            self._alias_creation_rules = [
                _RoomDirectoryRule("alias_creation_rules", rule)
                for rule in alias_creation_rules
            ]
        else:
            self._alias_creation_rules = [
                _RoomDirectoryRule("alias_creation_rules", {"action": "allow"})
            ]

        room_list_publication_rules = config.get("room_list_publication_rules")

        if room_list_publication_rules is not None:
            self._room_list_publication_rules = [
                _RoomDirectoryRule("room_list_publication_rules", rule)
                for rule in room_list_publication_rules
            ]
        else:
            self._room_list_publication_rules = [
                _RoomDirectoryRule("room_list_publication_rules", {"action": "allow"})
            ]

    def generate_config_section(self, config_dir_path, server_name, **kwargs):
        return """
        # Uncomment to disable searching the public room list. When disabled
        # blocks searching local and remote room lists for local and remote
        # users by always returning an empty list for all queries.
        #
        #enable_room_list_search: false

        # The `alias_creation` option controls who's allowed to create aliases
        # on this server.
        #
        # The format of this option is a list of rules that contain globs that
        # match against user_id, room_id and the new alias (fully qualified with
        # server name). The action in the first rule that matches is taken,
        # which can currently either be "allow" or "deny".
        #
        # Missing user_id/room_id/alias fields default to "*".
        #
        # If no rules match the request is denied. An empty list means no one
        # can create aliases.
        #
        # Options for the rules include:
        #
        #   user_id: Matches against the creator of the alias
        #   alias: Matches against the alias being created
        #   room_id: Matches against the room ID the alias is being pointed at
        #   action: Whether to "allow" or "deny" the request if the rule matches
        #
        # The default is:
        #
        #alias_creation_rules:
        #  - user_id: "*"
        #    alias: "*"
        #    room_id: "*"
        #    action: allow

        # The `room_list_publication_rules` option controls who can publish and
        # which rooms can be published in the public room list.
        #
        # The format of this option is the same as that for
        # `alias_creation_rules`.
        #
        # If the room has one or more aliases associated with it, only one of
        # the aliases needs to match the alias rule. If there are no aliases
        # then only rules with `alias: *` match.
        #
        # If no rules match the request is denied. An empty list means no one
        # can publish rooms.
        #
        # Options for the rules include:
        #
        #   user_id: Matches against the creator of the alias
        #   room_id: Matches against the room ID being published
        #   alias: Matches against any current local or canonical aliases
        #            associated with the room
        #   action: Whether to "allow" or "deny" the request if the rule matches
        #
        # The default is:
        #
        #room_list_publication_rules:
        #  - user_id: "*"
        #    alias: "*"
        #    room_id: "*"
        #    action: allow
        """

    def is_alias_creation_allowed(self, user_id, room_id, alias):
        """Checks if the given user is allowed to create the given alias

        Args:
            user_id (str)
            room_id (str)
            alias (str)

        Returns:
            boolean: True if user is allowed to create the alias
        """
        for rule in self._alias_creation_rules:
            if rule.matches(user_id, room_id, [alias]):
                return rule.action == "allow"

        return False

    def is_publishing_room_allowed(self, user_id, room_id, aliases):
        """Checks if the given user is allowed to publish the room

        Args:
            user_id (str)
            room_id (str)
            aliases (list[str]): any local aliases associated with the room

        Returns:
            boolean: True if user can publish room
        """
        for rule in self._room_list_publication_rules:
            if rule.matches(user_id, room_id, aliases):
                return rule.action == "allow"

        return False


class _RoomDirectoryRule:
    """Helper class to test whether a room directory action is allowed, like
    creating an alias or publishing a room.
    """

    def __init__(self, option_name, rule):
        """
        Args:
            option_name (str): Name of the config option this rule belongs to
            rule (dict): The rule as specified in the config
        """

        action = rule["action"]
        user_id = rule.get("user_id", "*")
        room_id = rule.get("room_id", "*")
        alias = rule.get("alias", "*")

        if action in ("allow", "deny"):
            self.action = action
        else:
            raise ConfigError(
                "%s rules can only have action of 'allow' or 'deny'" % (option_name,)
            )

        self._alias_matches_all = alias == "*"

        try:
            self._user_id_regex = glob_to_regex(user_id)
            self._alias_regex = glob_to_regex(alias)
            self._room_id_regex = glob_to_regex(room_id)
        except Exception as e:
            raise ConfigError("Failed to parse glob into regex") from e

    def matches(self, user_id, room_id, aliases):
        """Tests if this rule matches the given user_id, room_id and aliases.

        Args:
            user_id (str)
            room_id (str)
            aliases (list[str]): The associated aliases to the room. Will be a
                single element for testing alias creation, and can be empty for
                testing room publishing.

        Returns:
            boolean
        """

        # Note: The regexes are anchored at both ends
        if not self._user_id_regex.match(user_id):
            return False

        if not self._room_id_regex.match(room_id):
            return False

        # We only have alias checks left, so we can short circuit if the alias
        # rule matches everything.
        if self._alias_matches_all:
            return True

        # If we are not given any aliases then this rule only matches if the
        # alias glob matches all aliases, which we checked above.
        if not aliases:
            return False

        # Otherwise, we just need one alias to match
        for alias in aliases:
            if self._alias_regex.match(alias):
                return True

        return False