feat: add file download and preview

api_file.go

@@ -1,6 +1,9 @@
 package main
 
 import (
+	"fmt"
+	"time"
+
 	"gosvc/httpserver"
 	"gosvc/logger"
 	"gosvc/validator"
@@ -88,15 +91,20 @@ func (s *Service) HandleDownloadFile(
 	resp *httpserver.Response,
 ) *httpserver.Response {
 	path := req.QueryString("path")
+	preview := req.QueryBool("preview")
 	newPath := utils.NormalizePath(path)
 
-	_, _, err := s.FileSystemManager.DownloadFile(req.Context(), utils.FullPath(newPath))
+	entry, downloader, err := s.FileSystemManager.DownloadFile(req.Context(), utils.FullPath(newPath))
 	if err != nil {
 		logger.Error("download %s: %v", path, err)
 		return resp.InternalServerError("download file failed, " + err.Error())
 	}
 
-	return resp.NoContent()
+	if !preview {
+		resp.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%s", entry.FullPath.Name()))
+	}
+
+	return resp.ServeContent(entry.FullPath.Name(), time.Unix(entry.LastModificationTime, 0), downloader)
 }
 
 func (s *Service) HandleDeleteFile(

engine/filesystem_manager.go

@@ -158,7 +158,7 @@ func (f *FileSystemManager) CreateFile(ctx context.Context, path utils.FullPath,
 	return nil
 }
 
-func (f *FileSystemManager) DownloadFile(ctx context.Context, path utils.FullPath) ([]byte, *utils.Entry, error) {
+func (f *FileSystemManager) DownloadFile(ctx context.Context, path utils.FullPath) (*utils.Entry, io.ReadSeeker, error) {
 	f.RLock()
 	defer f.RUnlock()
 
@@ -171,12 +171,12 @@ func (f *FileSystemManager) DownloadFile(ctx context.Context, path utils.FullPat
 		return nil, nil, fmt.Errorf("cannot download directory")
 	}
 
-	content, err := f.storage.ReadObject(entry.S3Key)
+	downloader, err := f.storage.DownloadFile(entry.S3Key)
 	if err != nil {
 		return nil, nil, fmt.Errorf("read s3 object failed: %v", err)
 	}
 
-	return content, entry, nil
+	return entry, downloader, nil
 }
 
 func (f *FileSystemManager) DeleteFile(ctx context.Context, path utils.FullPath, isDir bool) error {

engine/storage_manager.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"os"
 
 	"robotfs/utils"
 
@@ -122,19 +121,24 @@ func (sm *StorageManager) UploadFile(s3Key string, data io.Reader, contentType s
 	return output, nil
 }
 
-func (sm *StorageManager) DownloadFile(S3Key string, localFilePath string) error {
+func (sm *StorageManager) DownloadFile(S3Key string) (io.ReadSeeker, error) {
-	file, err := os.Create(localFilePath)
+	head, err := sm.s3Client.HeadObject(&s3.HeadObjectInput{
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-
-	_, err = sm.s3Downloader.Download(file, &s3.GetObjectInput{
 		Bucket: aws.String(sm.bucketName),
 		Key:    aws.String(S3Key),
 	})
+	if err != nil {
+		return nil, err
+	}
 
-	return err
+	result, err := sm.s3Client.GetObject(&s3.GetObjectInput{
+		Bucket: aws.String(sm.bucketName),
+		Key:    aws.String(S3Key),
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return utils.NewS3ReadSeeker(sm.s3Client, sm.bucketName, S3Key, result.Body, *head.ContentLength), nil
 }
 
 func (sm *StorageManager) ReadObject(S3Key string) ([]byte, error) {

router.go

@@ -99,6 +99,11 @@ func (s *Service) RegisterRouteRules() {
 						Method:  http.MethodGet,
 						Handler: s.HandleDownloadFile,
 						QueryRules: []*httpserver.QueryRule{
+							{
+								Key:      "preview",
+								Type:     httpserver.QueryTypeBool,
+								Required: true,
+							},
 							{
 								Key:      "path",
 								Type:     httpserver.QueryTypeString,

utils/s3ReadSeeker.go

@@ -0,0 +1,82 @@
+package utils
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/service/s3"
+)
+
+type S3ReadSeeker struct {
+	client     *s3.S3
+	bucket     string
+	key        string
+	offset     int64
+	body       io.ReadCloser
+	contentLen int64
+}
+
+func NewS3ReadSeeker(client *s3.S3, bucket, key string, body io.ReadCloser, contentLen int64) *S3ReadSeeker {
+	return &S3ReadSeeker{
+		client:     client,
+		bucket:     bucket,
+		key:        key,
+		body:       body,
+		contentLen: contentLen,
+	}
+}
+
+func (r *S3ReadSeeker) Read(p []byte) (n int, err error) {
+	if r.body == nil {
+		return 0, io.EOF
+	}
+	return r.body.Read(p)
+}
+
+func (r *S3ReadSeeker) Seek(offset int64, whence int) (int64, error) {
+	if r.body != nil {
+		r.body.Close()
+		r.body = nil
+	}
+
+	var newOffset int64
+	switch whence {
+	case io.SeekStart:
+		newOffset = offset
+	case io.SeekCurrent:
+		newOffset = r.offset + offset
+	case io.SeekEnd:
+		newOffset = r.contentLen + offset
+	default:
+		return 0, fmt.Errorf("invalid whence")
+	}
+
+	if newOffset < 0 {
+		return 0, fmt.Errorf("negative offset")
+	}
+
+	if newOffset >= r.contentLen {
+		return r.contentLen, nil
+	}
+
+	result, err := r.client.GetObject(&s3.GetObjectInput{
+		Bucket: aws.String(r.bucket),
+		Key:    aws.String(r.key),
+		Range:  aws.String(fmt.Sprintf("bytes=%d-", newOffset)),
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	r.body = result.Body
+	r.offset = newOffset
+	return newOffset, nil
+}
+
+func (r *S3ReadSeeker) Close() error {
+	if r.body != nil {
+		return r.body.Close()
+	}
+	return nil
+}