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"""Module containing the OneToOne related column."""

from pygasus.engine.generic.columns.base import BaseColumn

class OneToOneColumn(BaseColumn):

    """Column to contain a reference to a model."""

    def __init__(self, table, from_model, to_model, from_field, to_field, primary):
        super().__init__(from_field, table)
        model_name = to_model._alt_name or to_model.__name__.lower()
        self.name = f"{model_name}_{primary.name}"
        self.from_model = from_model
        self.to_model = to_model
        self.from_field = from_field
        self.to_field = to_field
        self.primary = primary
        to_field.column = self

    def retrieve_additional_columns(self, fields):
        """Return additional columns for this column type."""
        try:
            model = fields[self.from_field.name]
        except KeyError:
            return {}

        return {
                self: getattr(model, self.primary.name, None),
        }
