//! Modules that help with serializing and deserializing struct fields via the
//! `#[serde(with ="path")]` attribute.
use serde::{Deserialize, Deserializer, Serialize, Serializer};

/// A helper for serializing and deserializing fields which are "smart pointers", types like
/// [std::sync::Arc], [std::rc::Rc], and [Box].
pub mod smart_ptr {
    use super::*;
    use std::{ops::Deref, rc::Rc, sync::Arc};

    /// Trait for general smart pointers.
    pub trait SmartPtr: Deref {
        /// Creates a new pointer which points to the given target.
        fn new(inner: Self::Target) -> Self;
    }

    macro_rules! impl_smart_ptr {
        ($ptr:ident) => {
            impl<T> SmartPtr for $ptr<T> {
                fn new(inner: Self::Target) -> Self {
                    $ptr::new(inner)
                }
            }
        };
    }

    impl_smart_ptr!(Arc);
    impl_smart_ptr!(Box);
    impl_smart_ptr!(Rc);

    pub fn serialize<P, T, S>(field: &P, ser: S) -> Result<S::Ok, S::Error>
    where
        P: SmartPtr<Target = T>,
        T: ?Sized + Serialize,
        S: Serializer,
    {
        field.deref().serialize(ser)
    }

    pub fn deserialize<'de, P, T, D>(de: D) -> Result<P, D::Error>
    where
        P: SmartPtr<Target = T>,
        T: ?Sized + Deserialize<'de>,
        D: Deserializer<'de>,
    {
        Ok(P::new(T::deserialize(de)?))
    }
}

#[cfg(test)]
mod smart_ptr_tests {
    use crate::{from_vec, to_vec};
    use paste::paste;
    use serde::{Deserialize, Serialize};
    use std::{rc::Rc, sync::Arc};

    use super::smart_ptr::{self, SmartPtr};

    #[derive(Debug, PartialEq, Eq, Serialize, Deserialize)]
    struct Test<P: SmartPtr<Target = String>> {
        #[serde(with = "smart_ptr")]
        field: P,
    }

    impl<P: SmartPtr<Target = String>> Test<P> {
        fn new(expected: &str) -> Self {
            Test {
                field: P::new(expected.to_string()),
            }
        }
    }

    macro_rules! check_ptr {
        ($ptr:ty) => {
            paste! {
                #[test]
                fn [<"check_" $ptr:lower>]() {
                    let expected = Test::new("expected");

                    let actual: Test<$ptr<String>> = from_vec(&to_vec(&expected).unwrap()).unwrap();

                    assert_eq!(expected, actual);
                }
            }
        };
    }

    check_ptr!(Arc);
    check_ptr!(Box);
    check_ptr!(Rc);
}