package textfmt_test

import (
	"errors"
	"io"
)

type failingWriter struct {
	out       io.Writer
	failAfter int
	err       error
}

func (w *failingWriter) Write(p []byte) (int, error) {
	if w.err != nil {
		return 0, w.err
	}

	if w.failAfter <= len(p) {
		p = p[:w.failAfter]
	}

	if len(p) > 0 && w.out != nil {
		if n, err := w.out.Write(p); err != nil {
			w.err = err
			return n, w.err
		}
	}

	w.failAfter -= len(p)
	if w.failAfter == 0 {
		w.err = errors.New("test write error")
	}

	return len(p), w.err
}