"""meta_entity - Validate entity metadata"""
# 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/>.

# Type stubs aren't available for regex.
# Fortunately, we're using it in a way that's API-compatible with the re
# module. We mitigate the lack of type stubs by providing type declarations
# for returned objects. This way, the only thing that isn't type checked are
# the calls to regex functions.
import regex  # type:ignore[import]

from . import core
from .. import data
from .. import errors as errormod
from ..beancount_types import (
    Transaction,
)

from typing import (
    Pattern,
)

class MetaEntity(core.TransactionHook):
    METADATA_KEY = 'entity'
    HOOK_GROUPS = frozenset(['posting', 'metadata', METADATA_KEY])

    # alnum is the set of characters we always accept in entity metadata:
    # letters and digits, minus the Latin 1 supplement (i.e., Roman letters
    # with diacritics: áÁàÀâÂåÅäÄãà çÇ ðÐ ñÑ øØ ß etc.)
    # See the tests for specific cases.
    alnum = r'\p{Letter}\p{Digit}--\p{Block=Latin_1_Supplement}'
    # A regexp that would be reasonably stricter would be:
    #   f'^[{alnum}][.{alnum}]*(?:-[.{alnum}])*$'
    # However, current producers fail that regexp in a few different ways.
    # See the tests for specific cases.
    ENTITY_RE: Pattern[str] = regex.compile(f'^[{alnum}][-.{alnum}]*$', regex.VERSION1)
    del alnum

    def run(self, txn: Transaction) -> errormod.Iter:
        if data.is_opening_balance_txn(txn):
            return
        txn_entity = txn.meta.get(self.METADATA_KEY, txn.payee)
        if txn_entity is None:
            txn_entity_ok = None
        elif isinstance(txn_entity, str):
            txn_entity_ok = bool(self.ENTITY_RE.match(txn_entity))
        else:
            txn_entity_ok = False
        if txn_entity_ok is False:
            yield errormod.InvalidMetadataError(txn, self.METADATA_KEY, txn_entity)
        for post in data.Posting.from_txn(txn):
            if not post.account.is_under(
                    'Assets:Receivable',
                    'Expenses',
                    'Income',
                    'Liabilities:Payable',
            ):
                continue
            entity = post.meta.get(self.METADATA_KEY)
            if entity is None:
                yield errormod.InvalidMetadataError(txn, self.METADATA_KEY, entity, post)
            elif entity is txn_entity:
                pass
            elif not self.ENTITY_RE.match(entity):
                yield errormod.InvalidMetadataError(txn, self.METADATA_KEY, entity, post)