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//! [![pipeline status](https://gitlab.com/mexus/clone-fields/badges/master/pipeline.svg)](https://gitlab.com/mexus/clone-fields/commits/master)
//! [![crates.io](https://img.shields.io/crates/v/clone-fields.svg)](https://crates.io/crates/clone-fields)
//! [![docs.rs](https://docs.rs/clone-fields/badge.svg)](https://docs.rs/clone-fields)
//!
//! [[Release docs]](https://docs.rs/clone-fields/)
//!
//! [[Master docs]](https://mexus.gitlab.io/clone-fields/clone_fields/)
//!
//! Fields-wise types cloning. Nothing more, nothing less.
//!
//! ```
//! use clone_fields::CloneFields;
//!
//! // PartialEq and Debug traits are only required for `assert` macros in the example.
//! #[derive(PartialEq, Debug, CloneFields)]
//! #[clone_fields(External)]
//! struct Original<'a, T: Clone> {
//!     field1: &'a i64,
//!     field2: T,
//!     nested: OriginalNested,
//! }
//!
//! #[derive(PartialEq, Debug, CloneFields)]
//! #[clone_fields(ExternalNested, ExternalNested2)]
//! struct OriginalNested {
//!     value: i32,
//! }
//!
//! // S2 might be a *foreign* type, i.e. declared in a different crate.
//! struct External<'a, T: Clone> {
//!     field1: &'a i64,
//!     field2: T,
//!     nested: ExternalNested,
//! }
//!
//! struct ExternalNested {
//!     value: i32,
//! }
//!
//! // This struct only exists for the sake of using `clone_fields` attribute with more than one
//! // type :)
//! struct ExternalNested2 {
//!     value: i32,
//! }
//!
//! fn main() {
//!     let obj: Original<_> = Original {
//!         field1: &0,
//!         field2: String::from("lol"),
//!         nested: OriginalNested { value: 15 }
//!     };
//!     let cloned: External<_> = obj.clone_into();
//!     assert_eq!(obj.field1, cloned.field1);
//!     assert_eq!(obj.field2, cloned.field2);
//!     assert_eq!(obj.nested.value, cloned.nested.value);
//!     let cloned2: Original<_> = CloneFields::clone_from(&cloned);
//!     assert_eq!(cloned.field1, cloned2.field1);
//!     assert_eq!(cloned.field2, cloned2.field2);
//!     assert_eq!(obj, cloned2);
//! }
//! ```

#![deny(missing_docs)]

extern crate clone_fields_derive;

pub use clone_fields_derive::*;

/// A trait to clone a type into another type field-by-field.
///
/// It is automatically implemented for any clonable type, i.e. `CloneFields<T> for T` where
/// `T: Clone`.
///
/// Refer to [clone-fields-derive](https://docs.rs/clone-fields-derive) docs for info on how to
/// automatically derive this trait. Yes, you typically don't need to do it manually.
pub trait CloneFields<Target> {
    /// Clones `self` into another type by cloning its fields.
    fn clone_into(&self) -> Target;

    /// Constructs `Self` from another type by cloning its fields.
    fn clone_from(other: &Target) -> Self;
}

impl<T> CloneFields<T> for T
where
    T: Clone,
{
    fn clone_into(&self) -> T {
        self.clone()
    }

    fn clone_from(other: &T) -> Self {
        other.clone()
    }
}

#[cfg(test)]
mod test {
    use super::*;

    #[derive(Debug, PartialEq, CloneFields)]
    #[clone_fields(S2)]
    struct S1<'a, T: Clone> {
        field1: &'a i64,
        field2: T,
        field3: Inner1,
    }

    #[derive(Debug)]
    struct S2<'a, T: Clone> {
        field1: &'a i64,
        field2: T,
        field3: Inner2,
    }

    impl<'a, T> PartialEq<S2<'a, T>> for S1<'a, T>
    where
        T: PartialEq + Clone,
    {
        fn eq(&self, other: &S2<'a, T>) -> bool {
            self.field1 == other.field1
                && self.field2 == other.field2
                && self.field3 == other.field3
        }
    }

    #[derive(Debug, PartialEq, CloneFields)]
    #[clone_fields(Inner2)]
    struct Inner1 {
        x: i32,
    }

    #[derive(Debug, PartialEq)]
    struct Inner2 {
        x: i32,
    }

    impl PartialEq<Inner2> for Inner1 {
        fn eq(&self, other: &Inner2) -> bool {
            self.x == other.x
        }
    }

    #[test]
    fn check() {
        let original = S1 {
            field1: &10,
            field2: "lol".to_string(),
            field3: Inner1 { x: 15 },
        };
        let cloned: S2<String> = original.clone_into();
        assert_eq!(original, cloned);
        let double_cloned = S1::clone_from(&cloned);
        assert_eq!(original, double_cloned)
    }
}