Gossip Glomers Challenge #3b: Multi-Node Broadcast

3b.go

package main

import (
	"encoding/json"
	maelstrom "github.com/jepsen-io/maelstrom/demo/go"
	"log"
	"sync"
)

func main() {
	n := maelstrom.NewNode()

	var mu sync.Mutex
	messageStore := make(map[any]struct{})

	var topology map[string]interface{}

	n.Handle("broadcast", func(msg maelstrom.Message) error {
		var body map[string]any
		if err := json.Unmarshal(msg.Body, &body); err != nil {
			return err
		}

		mu.Lock()
		defer mu.Unlock()
		if _, ok := messageStore[body["message"]]; ok {
			return nil
		}

		messageStore[body["message"]] = struct{}{}


		for node, neighbours := range topology {
			if node == n.ID() {
				for _, v := range neighbours.([]interface{}) {
					n.Send(v.(string), body)
				}
			}
		}

		body = map[string]any{}
		body["type"] = "broadcast_ok"

		return n.Reply(msg, body)
	})

	n.Handle("read", func(msg maelstrom.Message) error {
		var body map[string]any
		if err := json.Unmarshal(msg.Body, &body); err != nil {
			return err
		}

		body = map[string]any{}
		body["type"] = "read_ok"

		var keys []any
		mu.Lock()
		for k := range messageStore {
			keys = append(keys, k)
		}
		mu.Unlock()

		body["messages"] = keys

		return n.Reply(msg, body)
	})

	n.Handle("topology", func(msg maelstrom.Message) error {
		var body map[string]any
		if err := json.Unmarshal(msg.Body, &body); err != nil {
			return err
		}

		topology = body["topology"].(map[string]interface{})

		body = map[string]any{}
		body["type"] = "topology_ok"

		return n.Reply(msg, body)
	})

	if err := n.Run(); err != nil {
		log.Fatal(err)
	}
}