"""Custom marshmallow fields."""

import datetime
import re

from marshmallow import fields


class UnifiedDate(fields.Field):
    """Field that serializes unified date string."""

    date_pattern = re.compile(r"^\d{4}-\d{2}-\d{2}$")
    date_format = "%Y-%m-%dT%H:%M:%SZ"

    def _serialize(self, value, attr, obj, **kwargs):
        if value is None:
            return None

        if isinstance(value, (datetime.datetime, datetime.date)):
            return value.strftime(self.date_format)

        elif self.date_pattern.match(value):
            return datetime.datetime.strptime(value, "%Y-%m-%d").strftime(
                self.date_format
            )

        return value