import typing

from flask import request
from sqlalchemy.orm import Query
from sqlalchemy.sql.schema import Column


class QueryFiltering:
    """
    Filtering query by provided filter string.

    Filter string example:
    `field1:field1_filter_value,fieldN:fieldN_filter_value`
    """

    def __init__(
        self,
        query: Query,
        allowed_fields: typing.Optional[typing.Iterable[Column]] = None,
        filter_string: str = "",
        fields_mapping: typing.Optional[typing.Mapping] = None,
    ):
        self._query = query
        self._allowed_fields = allowed_fields or []
        self._fields_mapping = fields_mapping or {}
        self._filter_string = filter_string or request.args.get(
            "filter", type=str, default=""
        )
        self._update_query()

    @property
    def query(self):
        return self._query

    @property
    def filter_string(self):
        return self._filter_string

    def _update_query(self):
        filter_params = self._parse_filter_string()
        for key, val in filter_params.items():
            column = self._get_column_by_name(key)
            if column is None:
                continue
            self._query = self._query.filter(column.in_(val))

    def _get_column_by_name(self, name: str):
        for c in self._allowed_fields:
            if c.key == name:
                return c

    def _parse_filter_string(self):
        allowed_params = [f.name for f in self._allowed_fields]
        filter_params = {}
        for param_string in self.filter_string.split(";"):
            try:
                key, value = param_string.split(":")
            except Exception:  # nosec
                continue
            key = key.strip()
            key = self._fields_mapping.get(key) or key
            if key not in allowed_params:
                continue
            filter_params[key] = value.strip().split(",")
        return filter_params