use std::convert::Infallible;

use pyo3::{types::PyNone, Borrowed, FromPyObject, IntoPyObject, PyAny, PyErr, Python};

#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct IsNone;

impl<'a, 'py> FromPyObject<'a, 'py> for IsNone {
    type Error = PyErr;

    fn extract(ob: Borrowed<'a, 'py, PyAny>) -> Result<Self, Self::Error> {
        ob.cast::<PyNone>()?;
        Ok(IsNone)
    }
}

impl<'py> IntoPyObject<'py> for IsNone {
    type Target = PyNone;

    type Output = Borrowed<'py, 'py, Self::Target>;

    type Error = Infallible;

    fn into_pyobject(self, py: Python<'py>) -> Result<Self::Output, Self::Error> {
        Ok(PyNone::get(py))
    }
}