package app

import (
	"context"
	"errors"
	"net"
	"sync"
	"time"

	"google.golang.org/grpc"
	healthgrpc "google.golang.org/grpc/health/grpc_health_v1"
	walletv1 "hyapp.local/api/proto/wallet/v1"
	"hyapp/pkg/grpchealth"
	"hyapp/pkg/logx"
	"hyapp/services/wallet-service/internal/config"
	walletservice "hyapp/services/wallet-service/internal/service/wallet"
	mysqlstorage "hyapp/services/wallet-service/internal/storage/mysql"
	grpcserver "hyapp/services/wallet-service/internal/transport/grpc"
)

// App 装配 wallet-service gRPC 入口。
type App struct {
	server    *grpc.Server
	listener  net.Listener
	health    *grpchealth.ServingChecker
	mysqlRepo *mysqlstorage.Repository
	closeOnce sync.Once
}

// New 初始化 wallet-service。
func New(cfg config.Config) (*App, error) {
	startupCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	// wallet-service 的账户、交易、分录和 outbox 必须共享同一个 MySQL 事务边界。
	repository, err := mysqlstorage.Open(startupCtx, cfg.MySQLDSN)
	if err != nil {
		return nil, err
	}

	listener, err := net.Listen("tcp", cfg.GRPCAddr)
	if err != nil {
		_ = repository.Close()
		return nil, err
	}

	server := grpc.NewServer(grpc.UnaryInterceptor(logx.UnaryServerInterceptor("wallet-service")))
	svc := walletservice.New(repository)
	walletv1.RegisterWalletServiceServer(server, grpcserver.NewServer(svc))
	health := grpchealth.NewServingChecker("wallet-service")
	healthgrpc.RegisterHealthServer(server, grpchealth.NewServer(health))

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

// Run 启动 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 gRPC 服务。
func (a *App) Close() {
	a.closeOnce.Do(func() {
		a.health.MarkDraining()
		a.server.GracefulStop()
		if a.mysqlRepo != nil {
			// MySQL 连接池最后关闭，避免正在 drain 的扣费请求丢失提交能力。
			_ = a.mysqlRepo.Close()
		}
	})
}