jd-book-uploader-backend/services/firebase.go

package services

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"jd-book-uploader/config"

	firebase "firebase.google.com/go/v4"
	"firebase.google.com/go/v4/storage"
	"google.golang.org/api/option"
)

var (
	FirebaseApp    *firebase.App
	FirebaseClient *storage.Client
)

// InitFirebase initializes Firebase Admin SDK and Storage client
func InitFirebase(cfg *config.Config) (*storage.Client, error) {
	ctx := context.Background()

	// Determine credentials file path
	credentialsFile := cfg.FirebaseCredentialsFile
	if credentialsFile == "" {
		// Fallback to GOOGLE_APPLICATION_CREDENTIALS env var
		credentialsFile = os.Getenv("GOOGLE_APPLICATION_CREDENTIALS")
	}

	// Check if credentials file exists
	if credentialsFile != "" {
		if _, err := os.Stat(credentialsFile); os.IsNotExist(err) {
			return nil, fmt.Errorf("firebase credentials file not found: %s", credentialsFile)
		}
		// Convert relative path to absolute
		if !filepath.IsAbs(credentialsFile) {
			credentialsFile, _ = filepath.Abs(credentialsFile)
		}
	}

	// Build Firebase config
	firebaseConfig := &firebase.Config{
		ProjectID:     cfg.FirebaseProjectID,
		StorageBucket: cfg.FirebaseStorageBucket,
	}

	// Initialize Firebase app
	var app *firebase.App
	var err error

	if credentialsFile != "" {
		// Use credentials file
		opt := option.WithCredentialsFile(credentialsFile)
		app, err = firebase.NewApp(ctx, firebaseConfig, opt)
	} else {
		// Use default credentials (from environment)
		app, err = firebase.NewApp(ctx, firebaseConfig)
	}

	if err != nil {
		return nil, fmt.Errorf("failed to initialize Firebase app: %w", err)
	}

	// Create Storage client
	client, err := app.Storage(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to create Firebase Storage client: %w", err)
	}

	FirebaseApp = app
	FirebaseClient = client

	return client, nil
}

// UploadImage uploads an image to Firebase Storage and returns the public URL
// folderPath: storage folder path (e.g., "/jd-bookshop/books" or "/jd-bookshop/stationery")
// filename: image filename (should be the slug with .png extension)
func UploadImage(ctx context.Context, imageData []byte, folderPath string, filename string) (string, error) {
	if FirebaseClient == nil {
		return "", fmt.Errorf("firebase client not initialized")
	}

	// Build object path: {folderPath}/{filename}
	// Use provided path strictly without adding year/month
	objectPath := fmt.Sprintf("%s/%s", folderPath, filename)

	// Get bucket handle
	bucket, err := FirebaseClient.DefaultBucket()
	if err != nil {
		return "", fmt.Errorf("failed to get default bucket: %w", err)
	}

	// Create object handle
	obj := bucket.Object(objectPath)

	// Create writer
	writer := obj.NewWriter(ctx)
	writer.ContentType = "image/png"
	writer.CacheControl = "public, max-age=31536000" // 1 year cache

	// Write image data with retry logic
	maxRetries := 3
	var writeErr error
	for i := 0; i < maxRetries; i++ {
		if i > 0 {
			// Wait before retry (exponential backoff)
			time.Sleep(time.Duration(i) * time.Second)
		}

		// Write data
		_, writeErr = writer.Write(imageData)
		if writeErr == nil {
			break
		}
	}

	if writeErr != nil {
		writer.Close()
		return "", fmt.Errorf("failed to write image data after %d attempts: %w", maxRetries, writeErr)
	}

	// Close writer to finalize upload
	if err := writer.Close(); err != nil {
		return "", fmt.Errorf("failed to close writer: %w", err)
	}

	// Get public URL from Firebase
	attrs, err := obj.Attrs(ctx)
	if err != nil {
		return "", fmt.Errorf("failed to get object attributes: %w", err)
	}

	// Use Firebase's original download link (MediaLink)
	publicURL := attrs.MediaLink

	return publicURL, nil
}