package app

import (
	"context"
	"fmt"
	"io"
	"log/slog"

	gatewaypb "chatappgateway/api/proto"
	"chatappgateway/internal/config"
	"chatappgateway/internal/integration/paygrpc"
	"chatappgateway/internal/integration/usergrpc"
	"chatappgateway/internal/service/auth"
	"chatappgateway/internal/service/pay"
	httpserver "chatappgateway/internal/transport/http"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
)

// Application 组合网关运行所需的全部组件。
type Application struct {
	server  *httpserver.Server
	closers []io.Closer
}

// New 构造完整应用，包括 gRPC 连接、业务服务和 HTTP 服务。
func New(ctx context.Context, cfg config.Config, logger *slog.Logger) (*Application, error) {
	userConn, err := dialGRPC(ctx, cfg.GRPC.User.Target)
	if err != nil {
		return nil, fmt.Errorf("dial ChatAppUser: %w", err)
	}

	payConn, err := dialGRPC(ctx, cfg.GRPC.Pay.Target)
	if err != nil {
		_ = userConn.Close()
		return nil, fmt.Errorf("dial ChatAppPay: %w", err)
	}

	userClient := usergrpc.New(gatewaypb.NewChatAppUserClient(userConn), cfg.GRPC.User.Timeout)
	payClient := paygrpc.New(gatewaypb.NewChatAppPayClient(payConn), cfg.GRPC.Pay.Timeout)

	authService := auth.New(userClient)
	payService := pay.New(payClient)
	readinessChecker := newReadinessGroup(
		namedChecker{
			name:  "ChatAppUser",
			check: grpcConnectionReady(userConn),
		},
		namedChecker{
			name:  "ChatAppPay",
			check: grpcConnectionReady(payConn),
		},
	)
	server := httpserver.New(cfg.App.Name, cfg.App.HTTPAddr, cfg.App.ShutdownTimeout, logger, authService, payService, readinessChecker)

	return &Application{
		server:  server,
		closers: []io.Closer{userConn, payConn},
	}, nil
}

// Run 启动 HTTP 服务。
func (a *Application) Run(ctx context.Context) error {
	return a.server.Run(ctx)
}

// Close 关闭底层 gRPC 连接。
func (a *Application) Close() error {
	var firstErr error
	for _, closer := range a.closers {
		if err := closer.Close(); err != nil && firstErr == nil {
			firstErr = err
		}
	}
	return firstErr
}

func dialGRPC(ctx context.Context, target string) (*grpc.ClientConn, error) {
	// 网关只做自身健康检查，因此这里使用懒连接，避免下游暂时不可用时阻塞启动。
	return grpc.DialContext(
		ctx,
		target,
		grpc.WithTransportCredentials(insecure.NewCredentials()),
	)
}