use core::fmt;

pub struct FmtWrapper<'a> {
    buf: &'a mut [u8],
    offset: usize,
}

impl<'a> FmtWrapper<'a> {
    pub fn new(buf: &'a mut [u8]) -> Self {
        FmtWrapper {
            buf: buf,
            offset: 0,
        }
    }

    pub fn contents(&self) -> &[u8] {
        &self.buf[..self.offset]
    }
}

impl<'a> fmt::Write for FmtWrapper<'a> {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        let bytes = s.as_bytes();
        let remainder = &mut self.buf[self.offset..];
        let remainder = &mut remainder[..bytes.len()];
        remainder.copy_from_slice(bytes);
        self.offset += bytes.len();
        Ok(())
    }
}