vtse/vtse-server/src/main.rs

use crate::operations::ServerOperation;
use anyhow::{bail, Result};
use bytes::BytesMut;
use log::{debug, error, info};
use operations::{MarketOperation, QueryOperation, UserOperation};
use sqlx::PgPool;
use state::AppState;
use std::env;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::{TcpListener, TcpStream};
use tokio_stream::{wrappers::TcpListenerStream, StreamExt};

mod market;
mod operations;
mod state;
mod user;

#[tokio::main]
async fn main() -> Result<()> {
    dotenv::dotenv().ok();
    // If we can't successfully initialize our crypto library, fail immediately.
    sodiumoxide::init().unwrap();
    simple_logger::SimpleLogger::default().init()?;

    let mut listener_stream = TcpListener::bind(&env::var("BIND_ADDRESS")?)
        .await
        .map(TcpListenerStream::new)?;

    info!("Successfully bound to port.");

    let db_pool = PgPool::connect(&env::var("DATABASE_URL")?).await?;

    info!("Successfully established connection to database.");

    while let Some(Ok(stream)) = listener_stream.next().await {
        // clone simply clones the arc reference, so this is cheap.
        let db_pool = db_pool.clone();
        tokio::task::spawn(async {
            match handle_stream(stream, db_pool).await {
                Ok(_) => (),
                Err(e) => {
                    // stream.write_all(e);
                    error!("{}", e);
                }
            }
        });
    }

    info!("Cleanly shut down. Goodbye!");

    Ok(())
}

async fn handle_stream(mut socket: TcpStream, pool: PgPool) -> Result<()> {
    // only accept data that can fit in 256 bytes
    // the assumption is that a single request should always be within n bytes,
    // otherwise there's a good chance that it's mal{formed,icious}.
    let mut buffer = BytesMut::with_capacity(256);
    let mut state = AppState::new();
    loop {
        let bytes_read = socket.read_buf(&mut buffer).await?;
        if bytes_read == 0 {
            bail!("Failed to read bytes, assuming socket is closed.")
        }
        let data = buffer.split_to(bytes_read); // O(1)
        let parsed = serde_json::from_slice::<ServerOperation>(&data)?;
        debug!("Parsed operation: {:?}", parsed);
        let response = match parsed {
            ServerOperation::Query(op) => match op {
                QueryOperation::StockInfo { stock } => state.stock_info(stock, &pool).await?,
                QueryOperation::User(_) => todo!(),
            },
            ServerOperation::User(op) => match op {
                UserOperation::Login { api_key } => state.login(api_key, &pool).await?,
                UserOperation::Register { username, password } => {
                    state.register(username, password, &pool).await?
                }
                UserOperation::GetKey { username, password } => {
                    state.generate_api_key(username, password, &pool).await?
                }
            },
            ServerOperation::Market(op) => match op {
                MarketOperation::Buy(stock_name) => state.buy(stock_name, &pool)?,
                MarketOperation::Sell(stock_name) => state.sell(stock_name, &pool)?,
            },
        };

        socket
            .write_all(serde_json::to_string(&response).unwrap().as_bytes())
            .await?;
        buffer.unsplit(data); // O(1)
        buffer.clear();
    }
}