use std::ffi::{CStr, CString};
use std::borrow::Cow;
use std::os::raw;

use crate::Error;

/// Checks for last byte and avoids allocating if it is zero.
///
/// Non-last null bytes still result in an error.
pub(crate) fn cstr_cow_from_bytes<'a>(slice: &'a [u8]) -> Result<Cow<'a, CStr>, Error> {
    static ZERO: raw::c_char = 0;
    Ok(match slice.last() {
        // Slice out of 0 elements
        None => unsafe { Cow::Borrowed(CStr::from_ptr(&ZERO)) },
        // Slice with trailing 0
        Some(&0) => Cow::Borrowed(CStr::from_bytes_with_nul(slice)
            .map_err(|source| Error::CreateCStringWithTrailing { source })?),
        // Slice with no trailing 0
        Some(_) => Cow::Owned(CString::new(slice)
            .map_err(|source| Error::CreateCString { source })?),
    })
}

#[inline]
pub(crate) fn ensure_compatible_types<T, E>() -> Result<(), Error> {
    if ::std::mem::size_of::<T>() != ::std::mem::size_of::<E>() {
        Err(Error::IncompatibleSize)
    } else {
        Ok(())
    }
}