#![feature(backtrace)]
extern crate hptp;
extern crate tokio;
#[macro_use]
extern crate thiserror;

use hptp::logger::Logger;
use hptp::msg::{DownMsg, UpMsg};
use hptp::peer::{self, Peer, UpPeer};
use std::net::SocketAddr;
use tokio::io::AsyncRead;
// use tokio::net::UdpSocket;

#[derive(Error, Debug)]
enum Error {
    #[error("io error: {source}")]
    Io {
        #[from]
        source: tokio::io::Error,
        backtrace: std::backtrace::Backtrace,
    },
    #[error("invalid command-line arguments")]
    InvalidArgs,
}

fn main() {
    match entry() {
        Err(Error::InvalidArgs) => print_usage(),
        Err(e) => {
            use std::error::Error;
            println!("Error: {:?}", e);
            for bt in e.backtrace() {
                println!("{}", bt);
            }
        }
        Ok(()) => (),
    }
}

fn print_usage() {
    print!("Usage:\n./3700send <host-ip>:<host-port>\n")
}

fn entry() -> Result<(), Error> {
    let mut rt = tokio::runtime::Runtime::new().unwrap();
    let mut log = Logger::new();
    rt.block_on(start(&mut log))
}

async fn start(log: &mut Logger) -> Result<(), Error> {
    let targ_addr = parse_args(std::env::args())?;
    let sock = tokio::net::UdpSocket::bind((std::net::Ipv4Addr::LOCALHOST, 0)).await?;
    log.debug_msg(format!("bound on {}", sock.local_addr()?))
        .await;
    let mut out = tokio::io::stdin();
    let mut peer = Peer::new(sock);
    peer.set_known_target(targ_addr);
    upload(log, &mut peer, &mut out).await
}

fn parse_args(mut args: impl Iterator<Item = String>) -> Result<SocketAddr, Error> {
    args.nth(1)
        .ok_or(Error::InvalidArgs)?
        .parse()
        .map_err(|_| Error::InvalidArgs)
}

async fn read_segment<IN>(inp: &mut IN) -> Result<Option<Vec<u8>>, Error>
where
    IN: AsyncRead + Unpin,
{
    use tokio::io::AsyncReadExt;
    let mut buf = [0u8; hptp::seg::MAX_SEG_SIZE];
    let len = inp.read(&mut buf).await?;
    Ok(if len > 0 {
        Some(buf[..len].into())
    } else {
        None
    })
}

async fn send(peer: &mut UpPeer, m: UpMsg) -> Result<(), Error> {
    match peer.send(m).await {
        Ok(()) => Ok(()),
        Err(peer::SendError::Io { source }) => Err(source.into()),
        Err(peer::SendError::NoTarget) => panic!("tried to send w/ no target!"),
    }
}

async fn upload<IN>(log: &mut Logger, peer: &mut UpPeer, inp: &mut IN) -> Result<(), Error>
where
    IN: AsyncRead + Unpin,
{
    let mut pos = 0;
    let mut next_ack_len: Option<usize> = None;
    loop {
        if let Some(ack_len) = next_ack_len {
            match peer.recv().await {
                Ok(DownMsg::Ack { .. }) => {
                    log.recv_ack(pos).await;
                    pos += ack_len;
                    next_ack_len = None;
                }

                Err(peer::RecvError::InvalidMessage { .. }) => log.recv_corrupt().await,
                Err(peer::RecvError::Io { source }) => return Err(source.into()),
            }
        } else {
            match read_segment(inp).await? {
                Some(data) => {
                    next_ack_len = Some(data.len());
                    log.send_data(pos, data.len()).await;
                    send(peer, UpMsg::Data { payload: data }).await?;
                }
                None => break,
            }
        }
    }
    log.completed().await;
    Ok(())
}