import json
from app import db


class ContainerColumn(db.TypeDecorator):
    impl = db.String

    def __init__(self, container_type, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.container_type = container_type

    def process_bind_param(self, value, dialect):
        if isinstance(value, self.container_type):
            return json.dumps(value)
        elif isinstance(value, str) and isinstance(json.loads(value), self.container_type):
            return value
        else:
            return TypeError()

    def process_result_value(self, value, dialect):
        return json.loads(value)