use std::{
    ffi::{CStr, OsStr},
    os::unix::ffi::OsStrExt as _,
};

pub trait SliceExt {
    fn split_once_ch(&self, ch: u8) -> Option<(&[u8], &[u8])>;
}

impl SliceExt for [u8] {
    fn split_once_ch(&self, ch: u8) -> Option<(&[u8], &[u8])> {
        let (idx, _) = self.iter().enumerate().find(|(_, b)| **b == ch)?;
        // SAFETY: idx is IN-OF-BOUNDS index of the slice
        unsafe { Some((self.get_unchecked(0..idx), self.get_unchecked((idx + 1)..))) }
    }
}

pub trait CStrExt {
    fn to_os_str(&self) -> &OsStr;
    fn split_ch(&self, ch: u8) -> Option<(&[u8], &CStr)>;
}

impl CStrExt for CStr {
    fn to_os_str(&self) -> &OsStr {
        OsStr::from_bytes(self.to_bytes())
    }

    fn split_ch(&self, ch: u8) -> Option<(&[u8], &CStr)> {
        let self_slice = self.to_bytes_with_nul();

        self_slice.split_once_ch(ch).map(|(k, v)| {
            // # SAFETY split originated in a slice with final null byte, hence second split will be
            // null terminated
            (k, unsafe { Self::from_bytes_with_nul_unchecked(v) })
        })
    }
}

pub trait StrExt {
    fn as_os_str(&self) -> &OsStr;
}

impl StrExt for str {
    fn as_os_str(&self) -> &OsStr {
        OsStr::from_bytes(self.as_bytes())
    }
}