package app

import (
	"errors"
	"net"
	"sync"

	"google.golang.org/grpc"
	healthgrpc "google.golang.org/grpc/health/grpc_health_v1"
	"hyapp/pkg/grpchealth"
	"hyapp/services/activity-service/internal/config"
)

// App 只提供 activity-service 的占位进程骨架。
type App struct {
	server    *grpc.Server
	listener  net.Listener
	health    *grpchealth.ServingChecker
	closeOnce sync.Once
}

// New 初始化 activity-service 占位应用。
func New(cfg config.Config) (*App, error) {
	listener, err := net.Listen("tcp", cfg.GRPCAddr)
	if err != nil {
		return nil, err
	}

	server := grpc.NewServer()
	health := grpchealth.NewServingChecker("activity-service")
	healthgrpc.RegisterHealthServer(server, grpchealth.NewServer(health))

	return &App{
		server:   server,
		listener: listener,
		health:   health,
	}, nil
}

// Run 启动占位 gRPC 服务。
func (a *App) Run() error {
	a.health.MarkServing()
	err := a.server.Serve(a.listener)
	a.health.MarkStopped()
	if errors.Is(err, grpc.ErrServerStopped) {
		return nil
	}

	return err
}

// Close 关闭占位 gRPC 服务。
func (a *App) Close() {
	a.closeOnce.Do(func() {
		a.health.MarkDraining()
		a.server.GracefulStop()
	})
}