use crate::{obj::{reserved::*, prelude::*}, vm::{inst::Inst, Vm}};
use once_cell::sync::Lazy;
use shredder::{GcSafeWrapper, Scan};
use std::fmt::{Debug, Formatter, self};

#[derive(Debug, Scan)]
pub struct Method {
    vtable: Vtable,
    attrs: Attrs,
}

impl Method {
    pub fn new(this: ObjRef, func: ObjRef) -> Self {
        Self {
            vtable: Default::default(),
            attrs: attrs! {
                SELF_MEMBER_NAME.sym => this,
                FUNC_MEMBER_NAME.sym => func,
            }
        }
    }
}

impl_obj!(Method);

pub static CALL_METHOD_WRAPPER_FUN: Lazy<ObjRef<NativeFun>> = Lazy::new(|| {
    NativeFun::new_obj(Box::new(|_vm, _fun, _args| {
        todo!("__call__ function")
    }))
});

//
// struct UserFun
//

pub type UserFunRef = ObjRef<UserFun>;

#[derive(Scan)]
pub struct UserFun {
    vtable: Vtable,
    attrs: Attrs,
    // Safe because Vec<Inst> doesn't need to be scanned
    #[shredder(unsafe_skip)]
    code: Vec<Inst>,
    // Safe because this is just an interner that points to symbols, which aren't GC'd
    #[shredder(unsafe_skip)]
    locals: Names,
}

impl UserFun {
    pub fn code(&self) -> &Vec<Inst> {
        &self.code
    }

    pub fn locals(&self) -> &Names {
        &self.locals
    }
}

impl_obj!(UserFun);

impl Debug for UserFun {
    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
        fmt.debug_struct("UserFun")
            .field("attrs", &self.attrs)
            .field("code", &self.code)
            .field("locals", &self.locals)
            .finish()
    }
}

//
// struct NativeFun
//

pub type NativeFunPtr = Box<dyn Fn(&mut Vm, ObjRef, Vec<ObjRef>) + Send + Sync>;

#[derive(Scan)]
pub struct NativeFun {
    vtable: Vtable,
    attrs: Attrs,
    #[shredder(skip)]
    fun: GcSafeWrapper<NativeFunPtr>,
}

//
// impl NativeFun
//

impl NativeFun {
    pub fn new_obj(fun: NativeFunPtr) -> ObjRef<Self> {
        ObjRef::new(Self {
            // TODO : vtable for NativeFun
            vtable: Default::default(),
            attrs: Default::default(),
            fun: GcSafeWrapper::new(fun),
        })
    }
}

//
// impl Debug for NativeFun
//

impl Debug for NativeFun {
    fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
        fmt.debug_struct("NativeFun")
            .field("fun", &format!("(function at {:x})", &self.fun as *const _ as usize))
            .field("attrs", &self.attrs)
            .finish()
    }
}

impl_obj!(NativeFun);

//
// Native function defs
//

// __access__ is what the "dot" operator calls
// __get_attr__ *should* always bypass the __access__ function and get an attribute directly

pub static GET_ATTR_MEMBER_FUN: Lazy<ObjRef<NativeFun>> = Lazy::new(|| {
    NativeFun::new_obj(Box::new(|_vm, _fun, _args| {
        /*
        let sym_ref = vm.pop();
        let obj_ref = vm.pop();
        obj_ref.access()
        */
        todo!("__get_attr__ function")
    }))
});