use fehler::throws;
use libc::{sockaddr_ctl, AF_SYSTEM, AF_SYS_CONTROL};
use std::io::Error;
use std::mem::size_of;
use std::os::unix::io::AsRawFd;

/// Trait to connect to kernel extensions on Apple platforms
///
/// Pulled from XNU source: https://github.com/apple/darwin-xnu/blob/main/bsd/sys/kern_control.h
pub trait SysControlSocket {
    #[throws]
    fn resolve(&self, name: &str, index: u32) -> socket2::SockAddr;
}

impl SysControlSocket for socket2::Socket {
    #[throws]
    fn resolve(&self, name: &str, index: u32) -> socket2::SockAddr {
        let mut info = sys::ctl_info {
            ctl_id: 0,
            ctl_name: [0; 96],
        };
        info.ctl_name[..name.len()].copy_from_slice(name.as_bytes());

        unsafe { sys::resolve_ctl_info(self.as_raw_fd(), &mut info as *mut sys::ctl_info)? };

        let (_, addr) = unsafe {
            socket2::SockAddr::init(|addr_storage, len| {
                *len = size_of::<sockaddr_ctl>() as u32;

                let mut addr: &mut sockaddr_ctl = &mut *addr_storage.cast();
                addr.sc_len = *len as u8;
                addr.sc_family = AF_SYSTEM as u8;
                addr.ss_sysaddr = AF_SYS_CONTROL as u16;
                addr.sc_id = info.ctl_id;
                addr.sc_unit = index;
                Ok(())
            })
        }?;

        addr
    }
}

mod sys {
    use nix::ioctl_readwrite;

    const MAX_KCTL_NAME: usize = 96;

    #[repr(C)]
    pub struct ctl_info {
        pub ctl_id: u32,
        pub ctl_name: [u8; MAX_KCTL_NAME],
    }

    ioctl_readwrite!(resolve_ctl_info, b'N', 3, ctl_info);
}