feat: file explorer

backend/internal/application/dto/dto.go

@@ -59,16 +59,28 @@ type CreateAuthProviderRequest struct {
 
 // FeatureFlagsDTO represents app-wide feature flags in API responses.
 type FeatureFlagsDTO struct {
-	RegistrationEnabled  bool `json:"registration_enabled"`
-	ProviderLoginEnabled bool `json:"provider_login_enabled"`
-	PublicSharingEnabled bool `json:"public_sharing_enabled"`
+	RegistrationEnabled  bool   `json:"registration_enabled"`
+	ProviderLoginEnabled bool   `json:"provider_login_enabled"`
+	PublicSharingEnabled bool   `json:"public_sharing_enabled"`
+	FileExplorerEnabled  bool   `json:"file_explorer_enabled"`
+	S3Endpoint           string `json:"s3_endpoint,omitempty"`
+	S3Bucket             string `json:"s3_bucket,omitempty"`
+	S3Region             string `json:"s3_region,omitempty"`
+	S3AccessKey          string `json:"s3_access_key,omitempty"`
+	S3SecretKeySet       bool   `json:"s3_secret_key_set"`
 }
 
 // UpdateFeatureFlagsRequest represents admin payload for feature flag updates.
 type UpdateFeatureFlagsRequest struct {
-	RegistrationEnabled  bool `json:"registration_enabled"`
-	ProviderLoginEnabled bool `json:"provider_login_enabled"`
-	PublicSharingEnabled bool `json:"public_sharing_enabled"`
+	RegistrationEnabled  bool   `json:"registration_enabled"`
+	ProviderLoginEnabled bool   `json:"provider_login_enabled"`
+	PublicSharingEnabled bool   `json:"public_sharing_enabled"`
+	FileExplorerEnabled  bool   `json:"file_explorer_enabled"`
+	S3Endpoint           string `json:"s3_endpoint"`
+	S3Bucket             string `json:"s3_bucket"`
+	S3Region             string `json:"s3_region"`
+	S3AccessKey          string `json:"s3_access_key"`
+	S3SecretKey          string `json:"s3_secret_key"` // empty = keep existing encrypted value
 }
 
 // UserDTO represents a user in API responses
@@ -206,6 +218,12 @@ func NewFeatureFlagsDTO(flags *entities.FeatureFlags) *FeatureFlagsDTO {
 		RegistrationEnabled:  flags.RegistrationEnabled,
 		ProviderLoginEnabled: flags.ProviderLoginEnabled,
 		PublicSharingEnabled: flags.PublicSharingEnabled,
+		FileExplorerEnabled:  flags.FileExplorerEnabled,
+		S3Endpoint:           flags.S3Endpoint,
+		S3Bucket:             flags.S3Bucket,
+		S3Region:             flags.S3Region,
+		S3AccessKey:          flags.S3AccessKey,
+		S3SecretKeySet:       flags.S3SecretKey != "",
 	}
 }
 

backend/internal/application/services/admin_service.go

@@ -10,6 +10,7 @@ import (
 	"github.com/noteapp/backend/internal/application/dto"
 	"github.com/noteapp/backend/internal/domain/entities"
 	"github.com/noteapp/backend/internal/domain/repositories"
+	"github.com/noteapp/backend/internal/infrastructure/security"
 )
 
 // AdminService handles admin-level operations
@@ -22,6 +23,7 @@ type AdminService struct {
 	categoryRepo      repositories.CategoryRepository
 	featureFlagRepo   repositories.FeatureFlagRepository
 	permissionService *PermissionService
+	encryptor         *security.Encryptor
 }
 
 // NewAdminService creates a new AdminService
@@ -34,6 +36,7 @@ func NewAdminService(
 	categoryRepo repositories.CategoryRepository,
 	featureFlagRepo repositories.FeatureFlagRepository,
 	permissionService *PermissionService,
+	encryptor *security.Encryptor,
 ) *AdminService {
 	return &AdminService{
 		userRepo:          userRepo,
@@ -44,6 +47,7 @@ func NewAdminService(
 		categoryRepo:      categoryRepo,
 		featureFlagRepo:   featureFlagRepo,
 		permissionService: permissionService,
+		encryptor:         encryptor,
 	}
 }
 
@@ -299,10 +303,31 @@ func (s *AdminService) UpdateFeatureFlags(ctx context.Context, req *dto.UpdateFe
 		return nil, errors.New("feature flags are unavailable")
 	}
 
+	// Load existing flags so we can preserve the encrypted S3 secret when not updated
+	existing, err := s.featureFlagRepo.GetFeatureFlags(ctx)
+	if err != nil {
+		existing = entities.NewDefaultFeatureFlags()
+	}
+
 	flags := &entities.FeatureFlags{
 		RegistrationEnabled:  req.RegistrationEnabled,
 		ProviderLoginEnabled: req.ProviderLoginEnabled,
 		PublicSharingEnabled: req.PublicSharingEnabled,
+		FileExplorerEnabled:  req.FileExplorerEnabled,
+		S3Endpoint:           strings.TrimSpace(req.S3Endpoint),
+		S3Bucket:             strings.TrimSpace(req.S3Bucket),
+		S3Region:             strings.TrimSpace(req.S3Region),
+		S3AccessKey:          strings.TrimSpace(req.S3AccessKey),
+		S3SecretKey:          existing.S3SecretKey, // keep encrypted secret by default
+	}
+
+	// Only re-encrypt if a new secret was supplied
+	if s.encryptor != nil && strings.TrimSpace(req.S3SecretKey) != "" {
+		encrypted, err := s.encryptor.Encrypt(strings.TrimSpace(req.S3SecretKey))
+		if err != nil {
+			return nil, err
+		}
+		flags.S3SecretKey = encrypted
 	}
 
 	if err := s.featureFlagRepo.UpdateFeatureFlags(ctx, flags); err != nil {

backend/internal/application/services/file_service.go

@@ -0,0 +1,389 @@
+package services
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"io"
+	"path"
+	"strings"
+	"time"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/credentials"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+	"github.com/aws/aws-sdk-go-v2/service/s3/types"
+	"go.mongodb.org/mongo-driver/v2/bson"
+
+	"github.com/noteapp/backend/internal/domain/repositories"
+	"github.com/noteapp/backend/internal/infrastructure/security"
+)
+
+// S3Object represents a file or folder entry with key relative to the space root.
+type S3Object struct {
+	Key          string `json:"key"`
+	Size         int64  `json:"size"`
+	LastModified string `json:"last_modified"`
+	IsFolder     bool   `json:"is_folder"`
+}
+
+// FileService handles S3 file operations scoped to individual spaces.
+type FileService struct {
+	featureFlagRepo repositories.FeatureFlagRepository
+	membershipRepo  repositories.MembershipRepository
+	encryptor       *security.Encryptor
+}
+
+// NewFileService creates a new FileService.
+func NewFileService(
+	featureFlagRepo repositories.FeatureFlagRepository,
+	membershipRepo repositories.MembershipRepository,
+	encryptor *security.Encryptor,
+) *FileService {
+	return &FileService{
+		featureFlagRepo: featureFlagRepo,
+		membershipRepo:  membershipRepo,
+		encryptor:       encryptor,
+	}
+}
+
+type s3Config struct {
+	client *s3.Client
+	bucket string
+}
+
+// buildS3Config loads feature flags, decrypts credentials, and returns an S3 client + bucket name.
+func (s *FileService) buildS3Config(ctx context.Context) (*s3Config, error) {
+	flags, err := s.featureFlagRepo.GetFeatureFlags(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if !flags.FileExplorerEnabled {
+		return nil, errors.New("file explorer is disabled")
+	}
+	if flags.S3Endpoint == "" || flags.S3Bucket == "" {
+		return nil, errors.New("S3 is not configured")
+	}
+
+	secretKey := ""
+	if flags.S3SecretKey != "" && s.encryptor != nil {
+		secretKey, err = s.encryptor.Decrypt(flags.S3SecretKey)
+		if err != nil {
+			return nil, errors.New("failed to decrypt S3 credentials")
+		}
+	}
+
+	region := flags.S3Region
+	if region == "" {
+		region = "us-east-1"
+	}
+
+	cfg := aws.Config{
+		Region:      region,
+		Credentials: credentials.NewStaticCredentialsProvider(flags.S3AccessKey, secretKey, ""),
+	}
+
+	client := s3.NewFromConfig(cfg, func(o *s3.Options) {
+		o.BaseEndpoint = aws.String(flags.S3Endpoint)
+		o.UsePathStyle = true
+	})
+
+	return &s3Config{client: client, bucket: flags.S3Bucket}, nil
+}
+
+// validateAccess ensures file explorer is enabled and the user is a member of the space.
+// Returns a ready S3 config on success.
+func (s *FileService) validateAccess(ctx context.Context, userIDHex, spaceIDHex string) (*s3Config, error) {
+	cfg, err := s.buildS3Config(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	userID, err := bson.ObjectIDFromHex(userIDHex)
+	if err != nil {
+		return nil, errors.New("access denied")
+	}
+	spaceID, err := bson.ObjectIDFromHex(spaceIDHex)
+	if err != nil {
+		return nil, errors.New("access denied")
+	}
+
+	if _, err := s.membershipRepo.GetUserMembership(ctx, userID, spaceID); err != nil {
+		return nil, errors.New("access denied")
+	}
+
+	return cfg, nil
+}
+
+// spaceBase returns the S3 key prefix for a space: "spaces/<spaceIDHex>/".
+func spaceBase(spaceIDHex string) string {
+	return "spaces/" + spaceIDHex + "/"
+}
+
+// resolveRelKey sanitises a relative key and returns the full S3 key,
+// rejecting anything that would escape the space prefix.
+func resolveRelKey(spaceIDHex, relKey string) (string, error) {
+	relKey = strings.TrimLeft(strings.TrimSpace(relKey), "/")
+	cleaned := path.Clean(relKey)
+	if cleaned == "." || cleaned == "" {
+		return "", errors.New("key is empty")
+	}
+	if strings.Contains(cleaned, "..") {
+		return "", errors.New("invalid key")
+	}
+	base := spaceBase(spaceIDHex)
+	full := base + cleaned
+	if !strings.HasPrefix(full, base) {
+		return "", errors.New("invalid key: outside space boundary")
+	}
+	return full, nil
+}
+
+// resolveRelPrefix sanitises a relative folder prefix and returns the full S3 prefix.
+// An empty relPrefix maps to the space root folder.
+func resolveRelPrefix(spaceIDHex, relPrefix string) (string, error) {
+	base := spaceBase(spaceIDHex)
+	relPrefix = strings.TrimLeft(strings.TrimSpace(relPrefix), "/")
+	if relPrefix == "" {
+		return base, nil
+	}
+	cleaned := path.Clean(relPrefix)
+	if cleaned == "." {
+		return base, nil
+	}
+	if strings.Contains(cleaned, "..") {
+		return "", errors.New("invalid prefix")
+	}
+	full := base + cleaned + "/"
+	if !strings.HasPrefix(full, base) {
+		return "", errors.New("invalid prefix: outside space boundary")
+	}
+	return full, nil
+}
+
+// ListObjects returns objects and virtual folders directly under relPrefix within the space.
+// Returned keys are relative to the space root (no "spaces/<spaceId>/" prefix).
+func (s *FileService) ListObjects(ctx context.Context, userIDHex, spaceIDHex, relPrefix string) ([]*S3Object, error) {
+	cfg, err := s.validateAccess(ctx, userIDHex, spaceIDHex)
+	if err != nil {
+		return nil, err
+	}
+
+	fullPrefix, err := resolveRelPrefix(spaceIDHex, relPrefix)
+	if err != nil {
+		return nil, err
+	}
+
+	base := spaceBase(spaceIDHex)
+	result, err := cfg.client.ListObjectsV2(ctx, &s3.ListObjectsV2Input{
+		Bucket:    aws.String(cfg.bucket),
+		Prefix:    aws.String(fullPrefix),
+		Delimiter: aws.String("/"),
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	var objects []*S3Object
+
+	for _, cp := range result.CommonPrefixes {
+		if cp.Prefix != nil {
+			objects = append(objects, &S3Object{
+				Key:      strings.TrimPrefix(*cp.Prefix, base),
+				IsFolder: true,
+			})
+		}
+	}
+
+	for _, obj := range result.Contents {
+		if obj.Key == nil || *obj.Key == fullPrefix {
+			continue
+		}
+		// Hide virtual .keep placeholder files used for folder creation
+		if path.Base(*obj.Key) == ".keep" {
+			continue
+		}
+		size := int64(0)
+		if obj.Size != nil {
+			size = *obj.Size
+		}
+		lastMod := ""
+		if obj.LastModified != nil {
+			lastMod = obj.LastModified.Format(time.RFC3339)
+		}
+		objects = append(objects, &S3Object{
+			Key:          strings.TrimPrefix(*obj.Key, base),
+			Size:         size,
+			LastModified: lastMod,
+		})
+	}
+
+	return objects, nil
+}
+
+// GetObjectContent streams an S3 object, enforcing space boundary.
+// relKey is relative to the space root.
+func (s *FileService) GetObjectContent(ctx context.Context, userIDHex, spaceIDHex, relKey string) (io.ReadCloser, string, error) {
+	cfg, err := s.validateAccess(ctx, userIDHex, spaceIDHex)
+	if err != nil {
+		return nil, "", err
+	}
+
+	fullKey, err := resolveRelKey(spaceIDHex, relKey)
+	if err != nil {
+		return nil, "", err
+	}
+
+	result, err := cfg.client.GetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(cfg.bucket),
+		Key:    aws.String(fullKey),
+	})
+	if err != nil {
+		return nil, "", err
+	}
+
+	contentType := "application/octet-stream"
+	if result.ContentType != nil {
+		contentType = *result.ContentType
+	}
+
+	return result.Body, contentType, nil
+}
+
+// UploadObject stores a file at relKey within the space.
+func (s *FileService) UploadObject(ctx context.Context, userIDHex, spaceIDHex, relKey, contentType string, body io.Reader, size int64) error {
+	cfg, err := s.validateAccess(ctx, userIDHex, spaceIDHex)
+	if err != nil {
+		return err
+	}
+
+	fullKey, err := resolveRelKey(spaceIDHex, relKey)
+	if err != nil {
+		return err
+	}
+
+	if contentType == "" {
+		contentType = "application/octet-stream"
+	}
+
+	input := &s3.PutObjectInput{
+		Bucket:      aws.String(cfg.bucket),
+		Key:         aws.String(fullKey),
+		Body:        body,
+		ContentType: aws.String(contentType),
+	}
+	if size > 0 {
+		input.ContentLength = aws.Int64(size)
+	}
+
+	_, err = cfg.client.PutObject(ctx, input)
+	return err
+}
+
+// CreateFolder creates a virtual folder by uploading a zero-byte .keep placeholder.
+func (s *FileService) CreateFolder(ctx context.Context, userIDHex, spaceIDHex, relPath string) error {
+	cfg, err := s.validateAccess(ctx, userIDHex, spaceIDHex)
+	if err != nil {
+		return err
+	}
+
+	base := spaceBase(spaceIDHex)
+	relPath = strings.Trim(relPath, "/")
+	cleaned := path.Clean(relPath)
+	if cleaned == "." || cleaned == "" || strings.Contains(cleaned, "..") {
+		return errors.New("invalid folder path")
+	}
+	fullKey := base + cleaned + "/.keep"
+	if !strings.HasPrefix(fullKey, base) {
+		return errors.New("invalid folder path: outside space boundary")
+	}
+
+	zero := int64(0)
+	_, err = cfg.client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket:        aws.String(cfg.bucket),
+		Key:           aws.String(fullKey),
+		Body:          bytes.NewReader(nil),
+		ContentType:   aws.String("application/octet-stream"),
+		ContentLength: aws.Int64(zero),
+	})
+	return err
+}
+
+// DeleteObject removes a single object within the space.
+func (s *FileService) DeleteObject(ctx context.Context, userIDHex, spaceIDHex, relKey string) error {
+	cfg, err := s.validateAccess(ctx, userIDHex, spaceIDHex)
+	if err != nil {
+		return err
+	}
+
+	fullKey, err := resolveRelKey(spaceIDHex, relKey)
+	if err != nil {
+		return err
+	}
+
+	_, err = cfg.client.DeleteObject(ctx, &s3.DeleteObjectInput{
+		Bucket: aws.String(cfg.bucket),
+		Key:    aws.String(fullKey),
+	})
+	return err
+}
+
+// DeleteFolder recursively deletes all objects under relPrefix within the space.
+func (s *FileService) DeleteFolder(ctx context.Context, userIDHex, spaceIDHex, relPrefix string) error {
+	cfg, err := s.validateAccess(ctx, userIDHex, spaceIDHex)
+	if err != nil {
+		return err
+	}
+
+	fullPrefix, err := resolveRelPrefix(spaceIDHex, relPrefix)
+	if err != nil {
+		return err
+	}
+
+	// Safety net: refuse to delete the entire space root
+	if fullPrefix == spaceBase(spaceIDHex) {
+		return errors.New("cannot delete the space root folder")
+	}
+
+	paginator := s3.NewListObjectsV2Paginator(cfg.client, &s3.ListObjectsV2Input{
+		Bucket: aws.String(cfg.bucket),
+		Prefix: aws.String(fullPrefix),
+	})
+
+	var toDelete []types.ObjectIdentifier
+	for paginator.HasMorePages() {
+		page, err := paginator.NextPage(ctx)
+		if err != nil {
+			return err
+		}
+		for _, obj := range page.Contents {
+			if obj.Key != nil {
+				toDelete = append(toDelete, types.ObjectIdentifier{Key: obj.Key})
+			}
+		}
+	}
+
+	if len(toDelete) == 0 {
+		return nil
+	}
+
+	// Delete in batches of 1000 (S3 limit per DeleteObjects call)
+	for i := 0; i < len(toDelete); i += 1000 {
+		end := i + 1000
+		if end > len(toDelete) {
+			end = len(toDelete)
+		}
+		_, err := cfg.client.DeleteObjects(ctx, &s3.DeleteObjectsInput{
+			Bucket: aws.String(cfg.bucket),
+			Delete: &types.Delete{
+				Objects: toDelete[i:end],
+				Quiet:   aws.Bool(true),
+			},
+		})
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}