//! S4 class support.
//!
//! It is not possible to create an S4 class from R's C-API, and thus it is
//! not possible to do so in Rust. But an S4 class can be instantiated.
//!
//! Thus, the S4 class definition must be evaluated prior to using [`S4::new`].
//! Conveniently, to inline the defintion of an S4 class with R, one can
//! use [`S4::set_class`].
//!
//! Ideally, in an R-package setting, there will be no calls to `set_class`,
//! and the definition of an S4-class will be present in the `/R` folder.
//!
//! ```r
//! person_class <- setClass(
//!   "person",
//!   slots = c(name = "character", age = "integer")
//! )
//!
//! person_class(name = "Lubo", age = 74L)
//! #> An object of class "person"
//! #> Slot "name":
//! #> [1] "Lubo"
//! #>
//! #> Slot "age":
//! #> [1] 74
//! ```
//! Now, `person` can be instantiated from Rust.
//!

use super::*;

#[derive(PartialEq, Clone)]
pub struct S4 {
    pub(crate) robj: Robj,
}

impl S4 {
    /// Create a S4 class.
    ///
    /// Equivalent to R's `setClass`.
    ///
    /// Example:
    ///
    /// ```
    /// use extendr_api::prelude::*;
    ///
    /// test! {
    ///     let class = S4::set_class("fred", pairlist!(x="numeric"), r!(()))?;
    /// }
    /// ```
    pub fn set_class(name: &str, representation: Pairlist, contains: Robj) -> Result<S4> {
        use crate as extendr_api;
        let res = R!(r#"setClass({{name}}, {{representation}}, {{contains}})"#)?;
        res.try_into()
    }

    /// Create a S4 object.
    ///
    /// Example:
    /// ```
    /// use extendr_api::prelude::*;
    ///
    /// test! {
    ///     S4::set_class("fred", pairlist!(x="numeric"), r!(()))?;
    ///     let mut robj : S4 = R!(r#"new("fred")"#)?.try_into()?;
    /// }
    /// ```
    pub fn new(name: &str) -> Result<S4> {
        use crate as extendr_api;
        let res = R!(r#"new({{name}})"#)?;
        res.try_into()
    }

    /// Get a named slot from a S4 object.
    ///
    /// Example:
    /// ```
    /// use extendr_api::prelude::*;
    ///
    /// test! {
    ///     S4::set_class("fred", pairlist!(xyz="numeric"), r!(()))?;
    ///     let robj : S4 = R!(r#"new("fred")"#)?.try_into()?;
    ///     assert_eq!(robj.get_slot("xyz").unwrap().len(), 0);
    /// }
    /// ```
    pub fn get_slot<'a, N>(&self, name: N) -> Option<Robj>
    where
        Self: 'a,
        Robj: From<N> + 'a,
    {
        let name = Robj::from(name);
        unsafe {
            if R_has_slot(self.get(), name.get()) != 0 {
                Some(Robj::from_sexp(R_do_slot(self.get(), name.get())))
            } else {
                None
            }
        }
    }

    /// Set a named slot in a S4 object.
    ///
    /// Example:
    /// ```
    /// use extendr_api::prelude::*;
    ///
    /// test! {
    ///     S4::set_class("fred", pairlist!(xyz="numeric"), r!(()))?;
    ///     let mut robj : S4 = R!(r#"new("fred")"#)?.try_into()?;
    ///     let xyz = sym!(xyz);
    ///     assert_eq!(robj.get_slot(xyz.clone()).unwrap().len(), 0);
    ///     robj.set_slot(xyz.clone(), r!([0.0, 1.0]));
    ///     assert_eq!(robj.get_slot(xyz), Some(r!([0.0, 1.0])));
    /// }
    /// ```
    pub fn set_slot<N, V>(&mut self, name: N, value: V) -> Result<S4>
    where
        N: Into<Robj>,
        V: Into<Robj>,
    {
        let name = name.into();
        let value = value.into();
        single_threaded(|| unsafe {
            catch_r_error(|| R_do_slot_assign(self.get(), name.get(), value.get()))
                .map(|_| self.clone())
        })
    }

    /// Check if a named slot exists.
    ///
    /// Example:
    /// ```
    /// use extendr_api::prelude::*;
    ///
    /// test! {
    ///     S4::set_class("fred", pairlist!(xyz="numeric"), r!(()))?;
    ///     let robj : S4 = R!(r#"new("fred")"#)?.try_into()?;
    ///     assert_eq!(robj.has_slot("xyz"), true);
    /// }
    /// ```
    pub fn has_slot<'a, N>(&self, name: N) -> bool
    where
        Self: 'a,
        Robj: From<N> + 'a,
    {
        let name = Robj::from(name);
        unsafe { R_has_slot(self.get(), name.get()) != 0 }
    }
}

// TODO: Think about these functions in the future.
//
// Currently, S4 support is not a top priority, but we hope that what we have
// covered the basics for now.
//
// extern "C" {
//     pub fn R_S4_extends(klass: SEXP, useTable: SEXP) -> SEXP;
// }
// extern "C" {
//     pub fn R_getClassDef(what: *const ::std::os::raw::c_char) -> SEXP;
// }
// extern "C" {
//     pub fn R_getClassDef_R(what: SEXP) -> SEXP;
// }
// extern "C" {
//     pub fn R_has_methods_attached() -> Rboolean;
// }
// extern "C" {
//     pub fn R_isVirtualClass(class_def: SEXP, env: SEXP) -> Rboolean;
// }
// extern "C" {
//     pub fn R_extends(class1: SEXP, class2: SEXP, env: SEXP) -> Rboolean;
// }
// extern "C" {
//     pub fn R_check_class_and_super(
//         x: SEXP,
//         valid: *mut *const ::std::os::raw::c_char,
//         rho: SEXP,
//     ) -> ::std::os::raw::c_int;
// }
// extern "C" {
//     pub fn R_check_class_etc(
//         x: SEXP,
//         valid: *mut *const ::std::os::raw::c_char,
//     ) -> ::std::os::raw::c_int;
// }

impl std::fmt::Debug for S4 {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("S4").finish()
    }
}