use crate::obj::prelude::*;
use shredder::{GcSafe, Scan, Scanner};

/// A stack call frame.
#[derive(Debug, Clone)]
pub enum FrameKind {
    Native(NativeFunRef, Vec<ObjRef>),
    User {
        last_pc: usize,
        stack_base: usize,
        fun: UserFunRef,
    },
}

unsafe impl Scan for FrameKind {
    fn scan(&self, scanner: &mut Scanner<'_>) {
        match self {
            FrameKind::User { fun, .. } => scanner.scan(fun),
            _ => { /* no-op */ }
        }
    }
}

unsafe impl GcSafe for FrameKind {}

#[derive(Scan, Debug, Clone)]
pub struct Frame {
    locals: Names,
    kind: FrameKind,
}

impl Frame {
    pub fn new(locals: Names, kind: FrameKind) -> Self {
        Self { locals, kind, }
    }

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

    pub fn locals_mut(&mut self) -> &mut Names {
        &mut self.locals
    }
    
    pub fn kind(&self) -> &FrameKind {
        &self.kind
    }
}