package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"os"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
	healthpb "google.golang.org/grpc/health/grpc_health_v1"
)

// main 是本地容器 healthcheck 使用的最小 gRPC health probe。
func main() {
	addr := flag.String("addr", "", "gRPC address to probe")
	service := flag.String("service", "", "gRPC health service name")
	timeout := flag.Duration("timeout", 800*time.Millisecond, "probe timeout")
	flag.Parse()

	if *addr == "" {
		log.Fatal("-addr is required")
	}

	ctx, cancel := context.WithTimeout(context.Background(), *timeout)
	defer cancel()

	conn, err := grpc.DialContext(ctx, *addr, grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithBlock())
	if err != nil {
		log.Fatal(err)
	}
	defer conn.Close()

	resp, err := healthpb.NewHealthClient(conn).Check(ctx, &healthpb.HealthCheckRequest{Service: *service})
	if err != nil {
		log.Fatal(err)
	}

	if resp.GetStatus() != healthpb.HealthCheckResponse_SERVING {
		_, _ = fmt.Fprintf(os.Stderr, "service %q is %s\n", *service, resp.GetStatus())
		os.Exit(1)
	}
}