use tokio::{fs::File, io::BufReader};
use crate::{aggregation::TradeTradeTimestamp, instrument::InstrumentSpec};
pub trait DataBackend<IS: InstrumentSpec> {
fn new(key: Option<&str>) -> Self;
fn file_name_postpend() -> &'static str;
fn stream_in(
&mut self,
buf_reader: BufReader<File>,
) -> impl Future<Output = impl ExactSizeIterator<Item = TradeTradeTimestamp<IS>>> + Send;
}