rdest 0.1.0

rdest is simple BitTorrent client, currently supporting BEP3 specification.
Documentation 
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// Copyright 2020 Mateusz Janda.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use crate::constants::MAX_FRAME_SIZE;
use crate::frame::Frame;
use crate::serializer::Serializer;
use crate::Error;
use bytes::{Buf, BytesMut};
use std::io::Cursor;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::TcpStream;

pub struct Connection {
    pub addr: String,
    socket: Option<TcpStream>,
    buffer: BytesMut,
}

impl Connection {
    pub fn new(addr: String) -> Connection {
        Connection {
            addr,
            socket: None,
            buffer: BytesMut::with_capacity(MAX_FRAME_SIZE),
        }
    }

    pub fn with_socket(&mut self, socket: TcpStream) -> &mut Self {
        self.socket = Some(socket);
        self
    }

    pub async fn send_frame(&mut self, frame: &Frame) -> Result<(), Box<dyn std::error::Error>> {
        match frame {
            Frame::Handshake(msg) => self.send_msg(msg).await?,
            Frame::KeepAlive(msg) => self.send_msg(msg).await?,
            Frame::Choke(msg) => self.send_msg(msg).await?,
            Frame::Unchoke(msg) => self.send_msg(msg).await?,
            Frame::Interested(msg) => self.send_msg(msg).await?,
            Frame::NotInterested(msg) => self.send_msg(msg).await?,
            Frame::Have(msg) => self.send_msg(msg).await?,
            Frame::Bitfield(msg) => self.send_msg(msg).await?,
            Frame::Request(msg) => self.send_msg(msg).await?,
            Frame::Piece(msg) => self.send_msg(msg).await?,
            Frame::Cancel(msg) => self.send_msg(msg).await?,
        }

        Ok(())
    }

    pub async fn send_msg<T: Serializer>(
        &mut self,
        msg: &T,
    ) -> Result<(), Box<dyn std::error::Error>> {
        if let Some(socket) = self.socket.as_mut() {
            socket.write_all(msg.data().as_slice()).await?;
        }

        Ok(())
    }

    pub async fn recv_frame(&mut self) -> Result<Option<Frame>, Error> {
        loop {
            if let Some(frame) = self.parse_frame()? {
                return Ok(Some(frame));
            }

            match self.socket.as_mut() {
                Some(socket) => {
                    let n = match socket.read_buf(&mut self.buffer).await {
                        Err(_) => return Err(Error::CantReadFromSocket),
                        Ok(n) => n,
                    };

                    if n == 0 {
                        return match self.buffer.is_empty() {
                            // Connection closed by peer
                            true => Ok(None),
                            false => Err(Error::ConnectionReset),
                        };
                    }
                }
                None => return Err(Error::SocketNotAvailable),
            }
        }
    }

    fn parse_frame(&mut self) -> Result<Option<Frame>, Error> {
        let mut crs = Cursor::new(&self.buffer[..]);

        // Check whether a full frame is available
        match Frame::parse(&mut crs) {
            // Discard the frame from the buffer
            Ok(frame) => {
                let len = crs.position() as usize;
                self.buffer.advance(len);

                Ok(Some(frame))
            }
            // Discard the frame for unknown message from the buffer
            Err(Error::UnknownId(_)) => {
                let len = crs.position() as usize;
                self.buffer.advance(len);

                Ok(None)
            }
            // Not enough data has been buffered
            Err(Error::Incomplete(_)) => Ok(None),
            Err(e) => Err(e.into()),
        }
    }
}