//! Miscellaneous utility functions/macros/types.

use serde::{Deserialize, Serialize};

#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]

#[serde(into = "Vec<T>")]

#[serde(try_from = "Vec<T>")]

/// A list that contains at least one item.

///

/// We mainly use this for ensuring the user configures at least one item during config

/// deserialization, but may be useful for enforcing at least one item in the type system.

pub(crate) struct NonEmptyList<T: Clone>(T, Vec<T>);

impl<T: Clone> NonEmptyList<T> {

    /// Get the items in the list.

    ///

    /// Is guaranteed to have at least one item.

}

impl<T: Clone> From<NonEmptyList<T>> for Vec<T> {

}

impl<T: Clone> TryFrom<Vec<T>> for NonEmptyList<T> {

    type Error = EmptyListError;

}

#[derive(Debug, thiserror::Error)]

/// An error indicating that the list was empty, so cannot be converted to a [`NonEmptyList`].

#[error("The list is empty")]

pub(crate) struct EmptyListError;

#[cfg(test)]

mod test {

    #![allow(clippy::unwrap_used)]

    use super::*;

    #[test]

    fn non_empty_list() {

        let v = vec![1, 2, 3];

        let l: NonEmptyList<_> = v.clone().try_into().unwrap();

        assert_eq!(v, Vec::from(l));

        assert!(NonEmptyList::<u32>::try_from(Vec::new()).is_err());

    }

}