"""Base classes for plugin checks"""

# Copyright © 2020  Brett Smith

#

# This program is free software: you can redistribute it and/or modify

# it under the terms of the GNU Affero 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 Affero General Public License for more details.

#

# You should have received a copy of the GNU Affero General Public License

# along with this program.  If not, see <https://www.gnu.org/licenses/>.

from . import errors as errormod

class PostingChecker:

    VALUES_ENUM = {}

    def _meta_get(self, txn, post, key, default=None):

        try:

            return post.meta[key]

        except (KeyError, TypeError):

            return txn.meta.get(key, default)

    def _meta_set(self, post, key, value):

        if post.meta is None:

            post.meta = {}

        post.meta[key] = value

    def _default_value(self, txn, post):

        raise errormod.InvalidMetadataError(txn, post, self.METADATA_KEY)

    def check(self, txn, post):

        errors = []

        source_value = self._meta_get(txn, post, self.METADATA_KEY)

        set_value = source_value

        if source_value is None:

            try:

                set_value = self._default_value(txn, post)

            except errormod._BaseError as error:

                errors.append(error)

        else:

            try:

                set_value = self.VALUES_ENUM[source_value].value

            except KeyError:

                errors.append(errormod.InvalidMetadataError(

                    txn, post, self.METADATA_KEY, source_value,

                ))

        if not errors:

            self._meta_set(post, self.METADATA_KEY, set_value)

        return errors