From 3d5b071ef727e4bfef18ca3916c6ba1a054a12b1 Mon Sep 17 00:00:00 2001
From: Rohan Verma <hello@rohanverma.net>
Date: Fri, 18 Oct 2019 13:15:03 +0530
Subject: [PATCH] fix: change multipart.File -> io.ReadSeeker

---
 simples3.go | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/simples3.go b/simples3.go
index 6296aee..14afca4 100644
--- a/simples3.go
+++ b/simples3.go
@@ -38,7 +38,7 @@ type UploadInput struct {
 	ObjectKey   string
 	FileName    string
 	ContentType string
-	Body        multipart.File
+	Body        io.ReadSeeker
 }
 
 // UploadResponse receives the following XML
@@ -143,19 +143,18 @@ func (s3 *S3) getClient() *http.Client {
 	return s3.Client
 }
 
-func detectFileSize(body multipart.File) int64 {
-	switch r := body.(type) {
-	case io.Seeker:
-		pos, _ := r.Seek(0, 1)
-		defer r.Seek(pos, 0)
-
-		n, err := r.Seek(0, 2)
-		if err != nil {
-			return -1
-		}
-		return n
+func detectFileSize(body io.Seeker) (int64, error) {
+	pos, err := body.Seek(0, 1)
+	if err != nil {
+		return -1, err
 	}
-	return -1
+	defer body.Seek(pos, 0)
+
+	n, err := body.Seek(0, 2)
+	if err != nil {
+		return -1, err
+	}
+	return n, nil
 }
 
 // SetClient can be used to set the http client to be
@@ -173,12 +172,16 @@ func (s3 *S3) SetClient(client *http.Client) *S3 {
 // FileUpload makes a POST call with the file written as multipart
 // and on successful upload, checks for 200 OK.
 func (s3 *S3) FileUpload(u UploadInput) (UploadResponse, error) {
+	fSize, err := detectFileSize(u.Body)
+	if err != nil {
+		return UploadResponse{}, err
+	}
 	policies, err := s3.CreateUploadPolicies(UploadConfig{
 		UploadURL:   fmt.Sprintf(s3.URIFormat, s3.Region, u.Bucket),
 		BucketName:  u.Bucket,
 		ObjectKey:   u.ObjectKey,
 		ContentType: u.ContentType,
-		FileSize:    detectFileSize(u.Body),
+		FileSize:    fSize,
 		MetaData: map[string]string{
 			"success_action_status": "201", // returns XML doc on success
 		},