// SPDX-License-Identifier: Unlicense

// Package test contains helpers for testing parsers.
package test

import (
	"io"

	"git.codemonkeysoftware.net/b/gigaparsec"
	"github.com/shoenig/test"
)

type errReaderAt struct {
	err error
}

func (r errReaderAt) ReadAt([]byte, int64) (int, error) {
	return 0, r.err
}

// ErrReaderAt returns an [io.ReaderAt] with a ReadAt method that always returns err.
func ErrReaderAt(err error) io.ReaderAt {
	return errReaderAt{err: err}
}

func StateIsAt[Input any](t test.T, s gigaparsec.State[Input], pos uint64) {
	test.EqOp(t, pos, s.Pos(), test.Sprintf("expected parser state to be at position %d, got %d", pos, s.Pos()))
}