feat(file): implement file download functionality

internal/router/static_router.go

@@ -22,6 +22,8 @@ package router
 import (
 	"github.com/apache/incubator-answer/internal/service/service_config"
 	"github.com/gin-gonic/gin"
+	"path/filepath"
+	"strings"
 )
 
 // StaticRouter static api router
@@ -39,4 +41,19 @@ func NewStaticRouter(serviceConfig *service_config.ServiceConfig) *StaticRouter
 // RegisterStaticRouter register static api router
 func (a *StaticRouter) RegisterStaticRouter(r *gin.RouterGroup) {
 	r.Static("/uploads", a.serviceConfig.UploadPath)
+
+	r.GET("/download/*filepath", func(c *gin.Context) {
+		// The filePath such as /download/hash/123.png
+		filePath := c.Param("filepath")
+		// The download filename is 123.png
+		downloadFilename := filepath.Base(filePath)
+
+		// After trimming, the downloadLink is /uploads/hash
+		downloadLink := strings.TrimSuffix(filePath, "/"+downloadFilename)
+		// After add the extension, the downloadLink is /uploads/hash.png
+		downloadLink += filepath.Ext(downloadFilename)
+
+		downloadLink = filepath.Join(a.serviceConfig.UploadPath, downloadLink)
+		c.FileAttachment(downloadLink, downloadFilename)
+	})
 }

internal/service/uploader/upload.go

@@ -25,6 +25,7 @@ import (
 	"io"
 	"mime/multipart"
 	"net/http"
+	"net/url"
 	"os"
 	"path"
 	"path/filepath"
@@ -237,7 +238,7 @@ func (us *uploaderService) UploadPostAttachment(ctx *gin.Context) (
 	fileExt := strings.ToLower(path.Ext(fileHeader.Filename))
 	newFilename := fmt.Sprintf("%s%s", uid.IDStr12(), fileExt)
 	avatarFilePath := path.Join(postSubPath, newFilename)
-	return us.uploadAttachmentFile(ctx, fileHeader, avatarFilePath)
+	return us.uploadAttachmentFile(ctx, fileHeader, fileHeader.Filename, avatarFilePath)
 }
 
 func (us *uploaderService) UploadBrandingFile(ctx *gin.Context) (
@@ -304,8 +305,8 @@ func (us *uploaderService) uploadImageFile(ctx *gin.Context, file *multipart.Fil
 	return url, nil
 }
 
-func (us *uploaderService) uploadAttachmentFile(ctx *gin.Context, file *multipart.FileHeader, fileSubPath string) (
-	url string, err error) {
+func (us *uploaderService) uploadAttachmentFile(ctx *gin.Context, file *multipart.FileHeader, originalFilename, fileSubPath string) (
+	downloadUrl string, err error) {
 	siteGeneral, err := us.siteInfoService.GetSiteGeneral(ctx)
 	if err != nil {
 		return "", err
@@ -315,8 +316,16 @@ func (us *uploaderService) uploadAttachmentFile(ctx *gin.Context, file *multipar
 		return "", errors.InternalServer(reason.UnknownError).WithError(err).WithStack()
 	}
 
-	url = fmt.Sprintf("%s/uploads/%s", siteGeneral.SiteUrl, fileSubPath)
-	return url, nil
+	// The original filename is 123.png
+	// The local saved path is /UploadPath/hash.png
+	// The download link wil be /download/hash/123.png.
+	// When downloading, the download link will be redirect to the local saved path. And the download filename will be 123.png.
+	ext := filepath.Ext(fileSubPath)
+	// Need url encode the original filename. Because the filename may contain special characters that conflict with the markdown syntax.
+	originalFilename = url.QueryEscape(originalFilename)
+	downloadPath := strings.TrimSuffix(fileSubPath, ext) + "/" + originalFilename
+	downloadUrl = fmt.Sprintf("%s/download/%s", siteGeneral.SiteUrl, downloadPath)
+	return downloadUrl, nil
 }
 
 func (us *uploaderService) tryToUploadByPlugin(ctx *gin.Context, source plugin.UploadSource) (