use std::io;
use std::os::fd::RawFd;

use crate::SandboxError;

const FIRST_FD_AFTER_STDIO: libc::c_uint = 3;

pub fn keep_out_of_sandbox(kept_fds: &[RawFd]) -> Result<(), SandboxError> {
    mark_all_after_stdio_cloexec().map_err(SandboxError::InheritedFdsCloexec)?;

    for &fd in kept_fds {
        clear_cloexec(fd).map_err(|e| SandboxError::KeepFd(fd, e))?;
    }
    Ok(())
}

fn mark_all_after_stdio_cloexec() -> io::Result<()> {
    let result = unsafe {
        libc::syscall(
            libc::SYS_close_range,
            FIRST_FD_AFTER_STDIO,
            libc::c_uint::MAX,
            libc::CLOSE_RANGE_CLOEXEC,
        )
    };
    if result < 0 {
        return Err(io::Error::last_os_error());
    }
    Ok(())
}

pub fn clear_cloexec(fd: RawFd) -> io::Result<()> {
    let flags = unsafe { libc::fcntl(fd, libc::F_GETFD) };
    if flags < 0 {
        return Err(io::Error::last_os_error());
    }
    if unsafe { libc::fcntl(fd, libc::F_SETFD, flags & !libc::FD_CLOEXEC) } < 0 {
        return Err(io::Error::last_os_error());
    }
    Ok(())
}