firebase/firebase.go

package firebase

import (
	"context"

	fb "firebase.google.com/go/v4"
	"firebase.google.com/go/v4/auth"

	"code.nochebuena.dev/go/health"
	"code.nochebuena.dev/go/launcher"
	"code.nochebuena.dev/go/logz"
	"code.nochebuena.dev/go/xerrors"
)

// Provider is the minimal interface for consumers that only need the firebase App.
type Provider interface {
	App() *fb.App
}

// Component adds lifecycle management and health check to Provider.
type Component interface {
	launcher.Component
	health.Checkable
	Provider
}

// Config holds Firebase configuration.
type Config struct {
	// ProjectID is the Google Cloud Project ID.
	ProjectID string `env:"FIREBASE_PROJECT_ID,required"`
}

type firebaseComponent struct {
	cfg        Config
	logger     logz.Logger
	app        *fb.App
	authClient *auth.Client
}

// New returns a firebase Component. Call lc.Append(fb) to manage its lifecycle.
func New(logger logz.Logger, cfg Config) Component {
	return &firebaseComponent{cfg: cfg, logger: logger}
}

func (f *firebaseComponent) OnInit() error {
	if f.cfg.ProjectID == "" {
		return xerrors.New(xerrors.ErrInvalidInput, "firebase: ProjectID is required")
	}
	f.logger.Info("firebase: initializing app", "project_id", f.cfg.ProjectID)
	app, err := fb.NewApp(context.Background(), &fb.Config{
		ProjectID: f.cfg.ProjectID,
	})
	if err != nil {
		f.logger.Error("firebase: failed to create app", err)
		return xerrors.Wrap(xerrors.ErrInternal, "firebase: create app", err)
	}
	f.app = app
	authClient, err := app.Auth(context.Background())
	if err != nil {
		return xerrors.Wrap(xerrors.ErrInternal, "firebase: get auth client", err)
	}
	f.authClient = authClient
	return nil
}

func (f *firebaseComponent) OnStart() error {
	f.logger.Info("firebase: app ready")
	return nil
}

func (f *firebaseComponent) OnStop() error {
	f.logger.Info("firebase: shutting down")
	return nil
}

func (f *firebaseComponent) App() *fb.App { return f.app }

func (f *firebaseComponent) HealthCheck(ctx context.Context) error {
	if f.authClient == nil {
		return xerrors.New(xerrors.ErrInternal, "firebase: app not initialized")
	}
	_, err := f.authClient.GetUser(ctx, "health-probe-non-existent")
	if err != nil {
		if auth.IsUserNotFound(err) {
			return nil // expected: probe of non-existent UID succeeded
		}
		return err
	}
	return nil
}

func (f *firebaseComponent) Name() string          { return "firebase" }
func (f *firebaseComponent) Priority() health.Level { return health.LevelCritical }