package aprs

import (
	"fmt"
	"slices"
)

func base91Decode(s string) (n int, err error) {
	for i, l := 0, len(s); i < l; i++ {
		c := s[i]
		if c < 33 || c > 122 {
			//			panic(fmt.Sprintf("aprs: invalid base-91 encoding char %q (%d)", c, c))
			return 0, fmt.Errorf("aprs: invalid base-91 encoding char %q (%d)", c, c)
		}

		n *= 91
		n += int(c) - 33
	}
	return
}

func base91Encode(b []byte, n int) {
	i := 0
	for n > 1 {
		x := n % 91
		n /= 91
		b[i] = byte(x) + 33
		i++
	}
	slices.Reverse(b[:i])
}