)

// Reader - JSON record reader for S3Select.
type Reader struct {
	args    *json.ReaderArgs
	input   chan simdjson.Stream
	decoded chan simdjson.Object

	// err will only be returned after decoded has been closed.
	err          *error
	readCloser   io.ReadCloser
	onReaderExit func()

	exitReader chan struct{}
	readerWg   sync.WaitGroup
}

// Read - reads single record.

// and then Reader can be treated as an io.Reader to access the file's data.
type Reader struct {
	r    io.Reader
	pad  int64      // Amount of padding (ignored) after current file entry
	curr fileReader // Reader for current file entry
	blk  block      // Buffer to use as temporary local storage

	// err is a persistent error.

	if cap(dst) < skip {
		dst = make([]byte, 0, skip+1024)
	}
	dst = dst[:skip]
	if skip > 0 {
		n, err := io.ReadFull(r.buf, dst)
		if err != nil && err != io.ErrUnexpectedEOF {
			// If an EOF happens after reading some but not all the bytes,
			// ReadFull returns ErrUnexpectedEOF.
			return dst[:n], err
		}
		dst = dst[:n]
		if err == io.ErrUnexpectedEOF {
			return dst, io.EOF
		}
	}

	if t, ok := r.src.(etag.Tagger); ok {
		return t.ETag()
	}
	return nil
}

// MD5Current returns the MD5 checksum of the content
// that has been read so far.
//
// Calling MD5Current again after reading more data may
// result in a different checksum.
func (r *Reader) MD5Current() []byte {
	if r.disableMD5 {
		return r.checksum
	}
	return r.ETag()[:]
}