server.go

/*
Copyright 2024 Robert Andrei STEFAN

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"encoding/json"
	"errors"
	"log/slog"

	maelstrom "github.com/jepsen-io/maelstrom/demo/go"

	"github.com/rstefan1/bimodal-multicast/pkg/bmmc"
)

const (
	typeBodyKey    = "type"
	messageBodyKey = "message"
)

var errCannotCast = errors.New("cannot cast")

func createAndRunServer(b *bmmc.BMMC, n *maelstrom.Node, logger *slog.Logger) { //nolint: funlen, gocyclo, cyclop
	n.Handle(bmmc.GossipRoute, func(msg maelstrom.Message) error {
		var body map[string]string

		if err := json.Unmarshal(msg.Body, &body); err != nil {
			return err
		}

		b.GossipHandler([]byte(body[messageBodyKey]))

		return nil
	})

	n.Handle(bmmc.SolicitationRoute, func(msg maelstrom.Message) error {
		var body map[string]string

		if err := json.Unmarshal(msg.Body, &body); err != nil {
			return err
		}

		b.SolicitationHandler([]byte(body[messageBodyKey]))

		return nil
	})

	n.Handle(bmmc.SynchronizationRoute, func(msg maelstrom.Message) error {
		var body map[string]string

		if err := json.Unmarshal(msg.Body, &body); err != nil {
			return err
		}

		b.SynchronizationHandler([]byte(body[messageBodyKey]))

		return nil
	})

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

		if err := b.AddMessage(body[messageBodyKey], bmmc.NOCALLBACK); err != nil {
			logger.Error("cannot add message to bmmc", "err", err, "msg", body[messageBodyKey])
		}

		return n.Reply(msg, map[string]any{
			typeBodyKey: "broadcast_ok",
		})
	})

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

		body[typeBodyKey] = "read_ok"
		body["messages"] = b.GetMessages()

		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"]

		convTopology, convOk := topology.(map[string]any)
		if !convOk {
			return errCannotCast
		}

		peers := convTopology[n.ID()]

		convPeers, convOk := peers.([]any)
		if !convOk {
			return errCannotCast
		}

		for _, peer := range convPeers {
			convPeer, convOk := peer.(string)
			if !convOk {
				return errCannotCast
			}

			if err := b.AddPeer(convPeer); err != nil {
				return err
			}
		}

		return n.Reply(msg, map[string]any{
			typeBodyKey: "topology_ok",
		})
	})

	if err := n.Run(); err != nil {
		logger.Error("cannot start maelstrom server", "err", err)
	}
}