fix(*): refactor code structure

multipart_reader.go

@@ -0,0 +1,128 @@
+package multipart
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/textproto"
+)
+
+var ErrClosed = func(err error) error {
+	return fmt.Errorf("pipe is closed before writing %s", err)
+}
+
+type MultipartReader struct {
+	src           ReadSeekCloser
+	outputHeaders bool
+	contentLen    int64
+	parts         []*Part
+	boundary      string
+	w             *io.PipeWriter
+	r             *io.PipeReader
+	transformer   *Transformer
+}
+
+func NewMultipartReader(src ReadSeekCloser, parts []*Part) (*MultipartReader, error) {
+	return NewMultipartReaderWithBoudary(src, parts, randomBoundary())
+}
+
+func NewMultipartReaderWithBoudary(src ReadSeekCloser, parts []*Part, boundary string) (*MultipartReader, error) {
+	r, w := io.Pipe()
+	mpReader := &MultipartReader{
+		src:         src,
+		parts:       parts,
+		boundary:    boundary,
+		w:           w,
+		r:           r,
+		transformer: NewTransformerWithBoundary(src, parts, boundary),
+	}
+
+	switch len(parts) {
+	case 0:
+		return nil, errors.New("no part to write")
+	case 1:
+		// rw.reader, rw.pw = io.Pipe()
+		mpReader.contentLen = int64(parts[0].rangeEndInt - parts[0].rangeStartInt + 1)
+	default:
+		// rw.reader, rw.mw = mw, mw
+		mpReader.contentLen = mpReader.transformer.ContentLength()
+	}
+
+	return mpReader, nil
+}
+
+func (mr *MultipartReader) ContentLength() int64 {
+	return mr.contentLen
+}
+
+func (mr *MultipartReader) SetOutputHeaders(val bool) {
+	mr.outputHeaders = val
+}
+
+func (mr *MultipartReader) Start() {
+	var err error
+	headerBuf := new(bytes.Buffer)
+
+	if len(mr.parts) == 1 {
+		if mr.outputHeaders {
+			if err := writeStatus(headerBuf, 206); err != nil {
+				mr.w.CloseWithError(err)
+			}
+
+			headers := textproto.MIMEHeader{}
+			headers.Add("Content-Range", fmt.Sprintf("bytes %s-%s/%s", mr.parts[0].rangeStart, mr.parts[0].rangeEnd, mr.parts[0].fileSize))
+			if err = writeHeaders(headerBuf, headers); err != nil {
+				mr.w.CloseWithError(err)
+			}
+		}
+
+		_, err = io.Copy(mr.w, headerBuf)
+		if err != nil {
+			mr.w.CloseWithError(err)
+			return
+		}
+		_, err = mr.w.Write([]byte("\r\n"))
+		if err != nil {
+			mr.w.CloseWithError(err)
+		}
+		if err = writePartBody(mr.src, mr.w, mr.parts[0]); err != nil {
+			mr.w.CloseWithError(err)
+			return
+		}
+	} else {
+		if mr.outputHeaders {
+			if err := writeStatus(headerBuf, 206); err != nil {
+				mr.w.CloseWithError(err)
+			}
+
+			headers := textproto.MIMEHeader{}
+			headers.Add("Content-Type", fmt.Sprintf("multipart/byteranges; boundary=%s", mr.boundary))
+			if err = writeHeaders(headerBuf, headers); err != nil {
+				mr.w.CloseWithError(err)
+			}
+		}
+
+		_, err = io.Copy(mr.w, headerBuf)
+		if err != nil {
+			mr.w.CloseWithError(err)
+			return
+		}
+
+		if err = mr.transformer.WriteMultiParts(mr.w); err != nil {
+			mr.w.CloseWithError(err)
+			return
+		}
+	}
+
+	// source file should be closed by user
+	mr.w.CloseWithError(nil) // TODO: log error
+}
+
+func (mr *MultipartReader) Read(p []byte) (n int, err error) {
+	return mr.r.Read(p)
+}
+
+func (mr *MultipartReader) Close() error {
+	return mr.r.Close()
+}