echo.go

package main

import (
	"fmt"
	"io"
	"log"

	"github.com/libp2p/go-libp2p/core/host"
	"github.com/libp2p/go-libp2p/core/network"

	"github.com/gogo/protobuf/proto"
	"github.com/google/uuid"
	pb "github.com/libp2p/go-libp2p/examples/multipro/pb"
)

// pattern: /protocol-name/request-or-response-message/version
const echoRequest = "/echo/echoreq/0.0.1"
const echoResponse = "/echo/echoresp/0.0.1"

type EchoProtocol struct {
	node     *Node                      // local host
	requests map[string]*pb.EchoRequest // used to access request data from response handlers
	done     chan bool                  // only for demo purposes to hold main from terminating
}

func NewEchoProtocol(node *Node, done chan bool) *EchoProtocol {
	e := EchoProtocol{node: node, requests: make(map[string]*pb.EchoRequest), done: done}
	node.SetStreamHandler(echoRequest, e.onEchoRequest)
	node.SetStreamHandler(echoResponse, e.onEchoResponse)

	// design note: to implement fire-and-forget style messages you may just skip specifying a response callback.
	// a fire-and-forget message will just include a request and not specify a response object

	return &e
}

// remote peer requests handler
func (e *EchoProtocol) onEchoRequest(s network.Stream) {

	// get request data
	data := &pb.EchoRequest{}
	buf, err := io.ReadAll(s)
	if err != nil {
		s.Reset()
		log.Println(err)
		return
	}
	s.Close()

	// unmarshal it
	err = proto.Unmarshal(buf, data)
	if err != nil {
		log.Println(err)
		return
	}

	log.Printf("%s: Received echo request from %s. Message: %s", s.Conn().LocalPeer(), s.Conn().RemotePeer(), data.Message)

	valid := e.node.authenticateMessage(data, data.MessageData)

	if !valid {
		log.Println("Failed to authenticate message")
		return
	}

	log.Printf("%s: Sending echo response to %s. Message id: %s...", s.Conn().LocalPeer(), s.Conn().RemotePeer(), data.MessageData.Id)

	// send response to the request using the message string he provided

	resp := &pb.EchoResponse{
		MessageData: e.node.NewMessageData(data.MessageData.Id, false),
		Message:     data.Message}

	// sign the data
	signature, err := e.node.signProtoMessage(resp)
	if err != nil {
		log.Println("failed to sign response")
		return
	}

	// add the signature to the message
	resp.MessageData.Sign = signature

	ok := e.node.sendProtoMessage(s.Conn().RemotePeer(), echoResponse, resp)

	if ok {
		log.Printf("%s: Echo response to %s sent.", s.Conn().LocalPeer().String(), s.Conn().RemotePeer().String())
	}
	e.done <- true
}

// remote echo response handler
func (e *EchoProtocol) onEchoResponse(s network.Stream) {

	data := &pb.EchoResponse{}
	buf, err := io.ReadAll(s)
	if err != nil {
		s.Reset()
		log.Println(err)
		return
	}
	s.Close()

	// unmarshal it
	err = proto.Unmarshal(buf, data)
	if err != nil {
		log.Println(err)
		return
	}

	// authenticate message content
	valid := e.node.authenticateMessage(data, data.MessageData)

	if !valid {
		log.Println("Failed to authenticate message")
		return
	}

	// locate request data and remove it if found
	req, ok := e.requests[data.MessageData.Id]
	if ok {
		// remove request from map as we have processed it here
		delete(e.requests, data.MessageData.Id)
	} else {
		log.Println("Failed to locate request data boject for response")
		return
	}

	if req.Message != data.Message {
		log.Fatalln("Expected echo to respond with request message")
	}

	log.Printf("%s: Received echo response from %s. Message id:%s. Message: %s.", s.Conn().LocalPeer(), s.Conn().RemotePeer(), data.MessageData.Id, data.Message)
	e.done <- true
}

func (e *EchoProtocol) Echo(host host.Host) bool {
	log.Printf("%s: Sending echo to: %s....", e.node.ID(), host.ID())

	// create message data
	req := &pb.EchoRequest{
		MessageData: e.node.NewMessageData(uuid.New().String(), false),
		Message:     fmt.Sprintf("Echo from %s", e.node.ID())}

	signature, err := e.node.signProtoMessage(req)
	if err != nil {
		log.Println("failed to sign message")
		return false
	}

	// add the signature to the message
	req.MessageData.Sign = signature

	ok := e.node.sendProtoMessage(host.ID(), echoRequest, req)

	if !ok {
		return false
	}

	// store request so response handler has access to it
	e.requests[req.MessageData.Id] = req
	log.Printf("%s: Echo to: %s was sent. Message Id: %s, Message: %s", e.node.ID(), host.ID(), req.MessageData.Id, req.Message)
	return true
}