Frames and Wire

use bytes::{Bytes, BytesMut};
use zer0_proto_mp::{decode_varint, encode_varint, ChannelId, Frame, MessageType};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Frame::encode serializes a typed frame to its on-wire bytes. The first
    // byte carries the MessageType; channel id and payload follow as varints.
    let frame = Frame::new(
        ChannelId(7),
        MessageType::Data,
        Bytes::from_static(b"frames are typed"),
    );
    let wire = frame.encode();

    // The decoder is incremental: feed bytes into a BytesMut and call
    // decode() until it returns Ok(Some(frame)).
    let mut buffer = BytesMut::from(&wire[..]);
    let parsed = Frame::decode(&mut buffer)?.expect("complete frame");

    // varint helpers are exported for callers building their own framing.
    let mut len_buf = BytesMut::new();
    encode_varint(parsed.payload.len() as u64, &mut len_buf);
    let (decoded_len, _consumed) = decode_varint(&len_buf)?;

    println!(
        "wire_bytes={} encoded_size={} parsed_channel={} payload_len_varint={}",
        wire.len(),
        frame.encoded_size(),
        parsed.channel.0,
        decoded_len,
    );
    Ok(())
}