package textedit

func replaceEdit(match, replacement []rune) func(rune, []rune) ([]rune, []rune) {
	return func(r rune, state []rune) ([]rune, []rune) {
		state = append(state, r)
		if len(state) > len(match) {
			return state, nil
		}

		if r != match[len(state)-1] {
			return state, nil
		}

		if len(state) == len(match) {
			return replacement, nil
		}

		return nil, state
	}
}

func replaceRelease(state []rune) []rune {
	return state
}

func replaceOne(match, replacement string) Editor {
	return Func(
		replaceEdit([]rune(match), []rune(replacement)),
		replaceRelease,
	)
}

func replace(a ...string) Editor {
	if len(a)%2 != 0 {
		a = append(a, "")
	}

	var e []Editor
	for i := 0; i < len(a); i += 2 {
		e = append(
			e,
			replaceOne(a[i], a[i+1]),
		)
	}

	return sequence(e...)
}

func escape(esc rune, chars ...rune) Editor {
	r := []string{string(esc), string([]rune{esc, esc})}
	for _, c := range chars {
		r = append(r, string(c), string([]rune{esc, c}))
	}

	return replace(r...)
}