feat(BE): add function read and download in document

internal/common/service/common.document.service.go

@@ -8,6 +8,7 @@ import (
 	"mime/multipart"
 	"path/filepath"
 	"strings"
+	"time"
 
 	commonRepo "gitlab.com/mbugroup/lti-api.git/internal/common/repository"
 	"gitlab.com/mbugroup/lti-api.git/internal/config"
@@ -29,6 +30,7 @@ type DocumentService interface {
 	DeleteDocuments(ctx context.Context, ids []uint, removeFromStorage bool) error
 	DeleteByTarget(ctx context.Context, documentableType string, documentableID uint64, removeFromStorage bool) error
 	PublicURL(document entity.Document) string
+	PresignURL(ctx context.Context, document entity.Document, expires time.Duration) (string, error)
 }
 
 type DocumentUploadRequest struct {
@@ -293,6 +295,16 @@ func (s *documentService) PublicURL(document entity.Document) string {
 	return s.storage.URL(document.Path)
 }
 
+func (s *documentService) PresignURL(ctx context.Context, document entity.Document, expires time.Duration) (string, error) {
+	if s.storage == nil {
+		return "", errors.New("document storage not configured")
+	}
+	if strings.TrimSpace(document.Path) == "" {
+		return "", errors.New("document path is required")
+	}
+	return s.storage.PresignURL(ctx, document.Path, expires)
+}
+
 func (s *documentService) generateObjectKey(ext string) (string, error) {
 	normalizedExt := strings.TrimSpace(ext)
 	if normalizedExt != "" && !strings.HasPrefix(normalizedExt, ".") {

internal/common/service/common.document.storage.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"strings"
+	"time"
 
 	"github.com/aws/aws-sdk-go-v2/aws"
 	awsconfig "github.com/aws/aws-sdk-go-v2/config"
@@ -17,6 +18,7 @@ type DocumentStorage interface {
 	Upload(ctx context.Context, key string, body io.Reader, size int64, contentType string) (DocumentStorageUploadResult, error)
 	Delete(ctx context.Context, key string) error
 	URL(key string) string
+	PresignURL(ctx context.Context, key string, expires time.Duration) (string, error)
 }
 
 type DocumentStorageUploadResult struct {
@@ -36,9 +38,10 @@ type S3DocumentStorageConfig struct {
 }
 
 type s3DocumentStorage struct {
-	client *s3.Client
-	bucket string
-	base   string
+	client        *s3.Client
+	presignClient *s3.PresignClient
+	bucket        string
+	base          string
 }
 
 func NewS3DocumentStorage(ctx context.Context, cfg S3DocumentStorageConfig) (DocumentStorage, error) {
@@ -86,6 +89,7 @@ func NewS3DocumentStorage(ctx context.Context, cfg S3DocumentStorageConfig) (Doc
 	client := s3.NewFromConfig(awsCfg, func(o *s3.Options) {
 		o.UsePathStyle = cfg.ForcePathStyle
 	})
+	presignClient := s3.NewPresignClient(client)
 
 	baseURL := strings.TrimSuffix(strings.TrimSpace(cfg.BaseURL), "/")
 	if baseURL == "" {
@@ -97,9 +101,10 @@ func NewS3DocumentStorage(ctx context.Context, cfg S3DocumentStorageConfig) (Doc
 	}
 
 	return &s3DocumentStorage{
-		client: client,
-		bucket: bucket,
-		base:   baseURL,
+		client:        client,
+		presignClient: presignClient,
+		bucket:        bucket,
+		base:          baseURL,
 	}, nil
 }
 
@@ -158,3 +163,23 @@ func (s *s3DocumentStorage) URL(key string) string {
 	}
 	return fmt.Sprintf("%s/%s", s.base, key)
 }
+
+func (s *s3DocumentStorage) PresignURL(ctx context.Context, key string, expires time.Duration) (string, error) {
+	key = strings.TrimPrefix(strings.TrimSpace(key), "/")
+	if key == "" {
+		return "", errors.New("storage key is required")
+	}
+	if expires <= 0 {
+		expires = 15 * time.Minute
+	}
+
+	out, err := s.presignClient.PresignGetObject(ctx, &s3.GetObjectInput{
+		Bucket: aws.String(s.bucket),
+		Key:    aws.String(key),
+	}, s3.WithPresignExpires(expires))
+	if err != nil {
+		return "", err
+	}
+
+	return out.URL, nil
+}