package main

import (
	"context"
	"log"
	"net"

	"google.golang.org/grpc"
	"google.golang.org/grpc/reflection"

	pb "grpc-ping/ping"
)

const (
	port = ":50051"
)

type server struct {
	pb.UnimplementedPingServer
}

func Reverse(s string) string {
	runes := []rune(s)
	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]
	}
	return string(runes)
}

func (s *server) Ping(ctx context.Context, req *pb.PingRequest) (*pb.PingResponse, error) {
	log.Printf("Received: %v seq=%d", req.Data, req.Seq)
	log.Printf("Sent: %v seq=%d", Reverse(req.Data), req.Seq)
	return &pb.PingResponse{Data: Reverse(req.Data), Seq: req.Seq}, nil
}

func main() {
	lis, err := net.Listen("tcp", port)
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}

	s := grpc.NewServer()
	pb.RegisterPingServer(s, &server{})
	log.Printf("server listening at %v", lis.Addr())
	reflection.Register(s)
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}