use anyhow::{bail, Result};
use std::io::Write;

pub struct EbmlWriter<T> {
    inner: T,
    position: usize,
}

impl<T: Write> EbmlWriter<T> {
    pub fn new(inner: T, position: usize) -> Self {
        Self { inner, position }
    }

    pub fn write(&mut self, data: &[u8]) -> Result<()> {
        self.inner.write_all(data)?;
        self.position += data.len();
        Ok(())
    }

    pub fn write_vint(&mut self, i: u64) -> Result<()> {
        if i > (1 << 56) - 1 {
            bail!("vint does not fit");
        }
        let mut len = 1;
        while len <= 8 {
            if i < (1 << ((7 * len) - 1)) {
                break;
            }
            len += 1;
        }
        let mut bytes = i.to_be_bytes();
        bytes[0] |= 1 << (8 - len);
        self.write(&bytes)
    }
}