Stream post videos to Spaces (#23)

Pass the spooled video file through instead of buffering it in RAM, and sign Spaces uploads as UNSIGNED-PAYLOAD so the client does not hash the body first.

Reviewed-on: #23
Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/web/post_images.go

@@ -190,13 +190,14 @@ func (s *Server) uploadPostMedia(
 		if err != nil {
 			return store.PostImage{}, "", err
 		}
+		defer prepared.body.Close()
 		mediaID := uuid.NewString()
 		objectKey := path.Join("post-videos", postID, mediaID+prepared.extension)
 		publicURL, err := s.cfg.Blob.Upload(ctx, blob.FileUpload{
 			Key:         objectKey,
-			Body:        bytes.NewReader(prepared.body),
+			Body:        prepared.body,
 			ContentType: prepared.contentType,
-			Size:        int64(len(prepared.body)),
+			Size:        prepared.size,
 		})
 		if err != nil {
 			return store.PostImage{}, "", &postImageRequestError{
@@ -405,7 +406,8 @@ func isWebM(raw []byte) bool {
 }
 
 type preparedPostVideo struct {
-	body        []byte
+	body        io.ReadCloser
+	size        int64
 	extension   string
 	contentType string
 }
@@ -414,6 +416,9 @@ func preparePostVideo(header *multipart.FileHeader) (preparedPostVideo, error) {
 	if header == nil {
 		return preparedPostVideo{}, invalidPostImage("Select a valid video.", nil)
 	}
+	if header.Size == 0 {
+		return preparedPostVideo{}, invalidPostImage("Videos cannot be empty.", nil)
+	}
 	if header.Size > postVideoMaxFileBytes {
 		return preparedPostVideo{}, &postImageRequestError{
 			status:  http.StatusRequestEntityTooLarge,
@@ -424,27 +429,28 @@ func preparePostVideo(header *multipart.FileHeader) (preparedPostVideo, error) {
 	if err != nil {
 		return preparedPostVideo{}, invalidPostImage("Could not read video.", err)
 	}
-	defer file.Close()
-	raw, err := io.ReadAll(io.LimitReader(file, postVideoMaxFileBytes+1))
-	if err != nil {
+	peek := make([]byte, 512)
+	n, err := io.ReadFull(file, peek)
+	if err != nil && !errors.Is(err, io.ErrUnexpectedEOF) && !errors.Is(err, io.EOF) {
+		file.Close()
 		return preparedPostVideo{}, invalidPostImage("Could not read video.", err)
 	}
-	if len(raw) == 0 {
+	if n == 0 {
+		file.Close()
 		return preparedPostVideo{}, invalidPostImage("Videos cannot be empty.", nil)
 	}
-	if int64(len(raw)) > postVideoMaxFileBytes {
-		return preparedPostVideo{}, &postImageRequestError{
-			status:  http.StatusRequestEntityTooLarge,
-			message: "Each video must be 25 MB or smaller.",
-		}
-	}
-	switch mediaKindFromBytes(raw) {
+	switch mediaKindFromBytes(peek[:n]) {
 	case store.MediaKindVideo:
 	default:
+		file.Close()
 		return preparedPostVideo{}, invalidPostImage("Videos must be MP4 or WebM.", nil)
 	}
-	result := preparedPostVideo{body: raw}
-	if isWebM(raw) {
+	if _, err := file.Seek(0, io.SeekStart); err != nil {
+		file.Close()
+		return preparedPostVideo{}, invalidPostImage("Could not read video.", err)
+	}
+	result := preparedPostVideo{body: file, size: header.Size}
+	if isWebM(peek[:n]) {
 		result.extension = ".webm"
 		result.contentType = "video/webm"
 		return result, nil