package main import ( "context" "encoding/json" "github.com/libp2p/go-libp2p/core/peer" pubsub "github.com/libp2p/go-libp2p-pubsub" ) // ChatRoomBufSize is the number of incoming messages to buffer for each topic. const ChatRoomBufSize = 128 // ChatRoom represents a subscription to a single PubSub topic. Messages // can be published to the topic with ChatRoom.Publish, and received // messages are pushed to the Messages channel. type ChatRoom struct { // Messages is a channel of messages received from other peers in the chat room Messages chan *ChatMessage ctx context.Context ps *pubsub.PubSub topic *pubsub.Topic sub *pubsub.Subscription roomName string self peer.ID nick string } // ChatMessage gets converted to/from JSON and sent in the body of pubsub messages. type ChatMessage struct { Message string SenderID string SenderNick string } // JoinChatRoom tries to subscribe to the PubSub topic for the room name, returning // a ChatRoom on success. func JoinChatRoom(ctx context.Context, ps *pubsub.PubSub, selfID peer.ID, nickname string, roomName string) (*ChatRoom, error) { // join the pubsub topic topic, err := ps.Join(topicName(roomName)) if err != nil { return nil, err } // and subscribe to it sub, err := topic.Subscribe() if err != nil { return nil, err } cr := &ChatRoom{ ctx: ctx, ps: ps, topic: topic, sub: sub, self: selfID, nick: nickname, roomName: roomName, Messages: make(chan *ChatMessage, ChatRoomBufSize), } // start reading messages from the subscription in a loop go cr.readLoop() return cr, nil } // Publish sends a message to the pubsub topic. func (cr *ChatRoom) Publish(message string) error { m := ChatMessage{ Message: message, SenderID: cr.self.Pretty(), SenderNick: cr.nick, } msgBytes, err := json.Marshal(m) if err != nil { return err } return cr.topic.Publish(cr.ctx, msgBytes) } func (cr *ChatRoom) ListPeers() []peer.ID { return cr.ps.ListPeers(topicName(cr.roomName)) } // readLoop pulls messages from the pubsub topic and pushes them onto the Messages channel. func (cr *ChatRoom) readLoop() { for { msg, err := cr.sub.Next(cr.ctx) if err != nil { close(cr.Messages) return } // only forward messages delivered by others if msg.ReceivedFrom == cr.self { continue } cm := new(ChatMessage) err = json.Unmarshal(msg.Data, cm) if err != nil { continue } // send valid messages onto the Messages channel cr.Messages <- cm } } func topicName(roomName string) string { return "chat-room:" + roomName }