use core::{cell::UnsafeCell, mem, ptr};

use crate::{
    bindings::bpf_map_type::BPF_MAP_TYPE_STACK,
    btf_maps::AyaBtfMapMarker,
    helpers::{bpf_map_pop_elem, bpf_map_push_elem},
};

#[allow(dead_code)]
pub struct StackDef<T, const M: usize, const F: usize = 0> {
    r#type: *const [i32; BPF_MAP_TYPE_STACK as usize],
    value: *const T,
    max_entries: *const [i32; M],

    // Anonymize the struct.
    _anon: AyaBtfMapMarker,
}

#[repr(transparent)]
pub struct Stack<T, const M: usize, const F: usize = 0>(UnsafeCell<StackDef<T, M, F>>);

impl<T, const M: usize, const F: usize> Stack<T, M, F> {
    pub const fn new() -> Self {
        Self(UnsafeCell::new(StackDef {
            r#type: &[0i32; BPF_MAP_TYPE_STACK as usize],
            value: ptr::null(),
            max_entries: &[0i32; M],
            _anon: AyaBtfMapMarker::new(),
        }))
    }

    pub fn push(&mut self, value: &T, flags: u64) -> Result<(), i64> {
        let ret = unsafe {
            bpf_map_push_elem(
                &mut self.0 as *mut _ as *mut _,
                value as *const _ as *const _,
                flags,
            )
        };
        (ret == 0).then_some(()).ok_or(ret)
    }

    pub fn pop(&mut self) -> Option<T> {
        unsafe {
            let mut value = mem::MaybeUninit::uninit();
            let ret = bpf_map_pop_elem(
                &mut self.0 as *mut _ as *mut _,
                value.as_mut_ptr() as *mut _,
            );
            (ret == 0).then_some(value.assume_init())
        }
    }
}