use core::{
    ffi::c_void,
    mem::{self, MaybeUninit},
};

use aya_bpf_bindings::helpers::{bpf_l4_csum_replace, bpf_skb_load_bytes, bpf_skb_store_bytes};
use aya_bpf_cty::c_long;

use crate::{bindings::__sk_buff, BpfContext};

pub struct SkSkbContext {
    skb: *mut __sk_buff,
}

impl SkSkbContext {
    pub fn new(skb: *mut __sk_buff) -> SkSkbContext {
        SkSkbContext { skb }
    }

    #[inline]
    pub fn load<T>(&self, offset: usize) -> Result<T, c_long> {
        unsafe {
            let mut data = MaybeUninit::<T>::uninit();
            let ret = bpf_skb_load_bytes(
                self.skb as *const _,
                offset as u32,
                &mut data as *mut _ as *mut _,
                mem::size_of::<T>() as u32,
            );
            if ret < 0 {
                return Err(ret);
            }

            Ok(data.assume_init())
        }
    }

    #[inline]
    pub fn store<T>(&self, offset: usize, v: &T) -> Result<(), c_long> {
        unsafe {
            let ret = bpf_skb_store_bytes(
                self.skb as *mut _,
                offset as u32,
                v as *const _ as *const _,
                mem::size_of::<T>() as u32,
                0,
            );
            if ret < 0 {
                return Err(ret);
            }
        }

        Ok(())
    }

    #[inline]
    pub fn l4_csum_replace(
        &self,
        offset: usize,
        from: u64,
        to: u64,
        flags: u64,
    ) -> Result<(), c_long> {
        unsafe {
            let ret = bpf_l4_csum_replace(self.skb as *mut _, offset as u32, from, to, flags);
            if ret < 0 {
                return Err(ret);
            }
        }

        Ok(())
    }
}

impl BpfContext for SkSkbContext {
    fn as_ptr(&self) -> *mut c_void {
        self.skb as *mut _
    }
}