package garage

import "io"

type infiniteReader struct {
	b []byte
	i int
}

// NewInfiniteReader returns a reader which will produce the given bytes in
// repetition. len(b) must be greater than 0.
func NewInfiniteReader(b []byte) io.Reader {

	if len(b) == 0 {
		panic("len(b) must be greater than 0")
	}

	return &infiniteReader{b: b}
}

func (r *infiniteReader) Read(b []byte) (int, error) {

	// here, have a puzzle

	var n int

	for {

		n += copy(b[n:], r.b[r.i:])

		if r.i > 0 {
			n += copy(b[n:], r.b[:r.i])
		}

		r.i = (r.i + n) % len(r.b)

		if n >= len(b) {
			return n, nil
		}
	}
}