subscriber.go

package subscriber

import (
	"context"
	"github.com/ethereum/go-ethereum/core/types"
	"github.com/ethereum/go-ethereum/ethclient"
	"github.com/go-redis/redis/v8"
	"github.com/sirupsen/logrus"
	"github.com/spf13/cobra"
)

type Subscriber struct {
	Endpoint      string
	Chain         string
	RedisAddress  string
	RedisPassword string

	ctx            context.Context
	redisClient    *redis.Client
	ethereumClient *ethclient.Client
}

func (s *Subscriber) InitializeRedisClient() error {
	redisClient := redis.NewClient(&redis.Options{
		Addr:     s.RedisAddress,
		Password: s.RedisPassword,
	})
	if _, err := redisClient.Ping(context.Background()).Result(); err != nil {
		return err
	}
	s.redisClient = redisClient
	logrus.Infoln("Connected to Redis")
	return nil
}

func (s *Subscriber) InitializeEthereumClient() error {
	ethereumClient, err := ethclient.Dial(s.Endpoint)
	if err != nil {
		return err
	}
	s.ethereumClient = ethereumClient
	logrus.Infoln("Connected to Ethereum WebSocket provider")
	return nil
}

func (s *Subscriber) Run() error {
	headerCh := make(chan *types.Header)
	subscription, err := s.ethereumClient.SubscribeNewHead(s.ctx, headerCh)
	if err != nil {
		return err
	}
	defer subscription.Unsubscribe()
	for {
		select {
		case err := <-subscription.Err():
			return err
		case header := <-headerCh:
			block, err := s.ethereumClient.BlockByHash(s.ctx, header.Hash())
			if err != nil {
				logrus.Errorln(err)
				continue
			}
			logrus.Infoln(block.Number())
		}
	}
}

func NewSubscriberCommand(ctx context.Context) *cobra.Command {
	subscriber := &Subscriber{
		ctx: ctx,
	}
	command := &cobra.Command{
		Use: "subscriber",
		Run: func(cmd *cobra.Command, args []string) {
			if err := subscriber.InitializeRedisClient(); err != nil {
				logrus.Fatalln(err)
			}
			if err := subscriber.InitializeEthereumClient(); err != nil {
				logrus.Fatalln(err)
			}
			if err := subscriber.Run(); err != nil {
				logrus.Fatalln(err)
			}
		},
	}
	command.Flags().StringVar(&subscriber.Chain, "chain", "ethereum-main", "")
	command.Flags().StringVar(&subscriber.Endpoint, "endpoint", "", "")
	command.Flags().StringVar(&subscriber.RedisAddress, "redis-address", "127.0.0.1:6379", "")
	command.Flags().StringVar(&subscriber.RedisPassword, "redis-password", "", "")
	return command
}