package minio

import "io"

// ReadSeekCloser wraps an io.Reader returning a ReaderSeekerCloser
func ReadSeekCloser(r io.Reader) ReaderSeekerCloser {
	return ReaderSeekerCloser{r}
}

// ReaderSeekerCloser represents a reader that can also delegate io.Seeker and
// io.Closer interfaces to the underlying object if available.
type ReaderSeekerCloser struct {
	r io.Reader
}

// Read reads up to len(p) bytes into p.  It returns the number of bytes
// read (0 <= n <= len(p)) and any error encountered.  Even if Read
// returns n < len(p), it may use all of p as scratch space during the call.
// If some data is available but not len(p) bytes, Read conventionally
// returns what is available instead of waiting for more.
//
// When Read encounters an error or end-of-file condition after
// successfully reading n > 0 bytes, it returns the number of
// bytes read.  It may return the (non-nil) error from the same call
// or return the error (and n == 0) from a subsequent call.
// An instance of this general case is that a Reader returning
// a non-zero number of bytes at the end of the input stream may
// return either err == EOF or err == nil.  The next Read should
// return 0, EOF.
func (r ReaderSeekerCloser) Read(p []byte) (int, error) {
	switch t := r.r.(type) {
	case io.Reader:
		return t.Read(p)
	}
	return 0, nil
}

// Seek sets the offset for the next Read or Write to offset,
// interpreted according to whence: 0 means relative to the start of
// the file, 1 means relative to the current offset, and 2 means
// relative to the end. Seek returns the new offset relative to the
// start of the file and an error, if any.
//
// Seeking to an offset before the start of the file is an error.
//
// If the ReaderSeekerCloser is not an io.Seeker nothing will be done.
func (r ReaderSeekerCloser) Seek(offset int64, whence int) (int64, error) {
	switch t := r.r.(type) {
	case io.Seeker:
		return t.Seek(offset, whence)
	}
	return int64(0), nil
}

// Close closes the ReaderSeekerCloser.
//
// The behavior of Close after the first call is undefined.
// Specific implementations may document their own behavior.
//
// If the ReaderSeekerCloser is not an io.Closer nothing will be done.
func (r ReaderSeekerCloser) Close() error {
	switch t := r.r.(type) {
	case io.Closer:
		return t.Close()
	}
	return nil
}