#! /usr/bin/env oksh
# shellcheck shell=ksh

# Copyright (c) 2021, 2024 Stefan Kreutz <mail@skreutz.com>
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

set -o errexit
set -o nounset
set -o pipefail

alphabet=23456789abcdefghijmopqrstwxyzABCDEFGHJKLMNPQRSTUVWXYZ
groups=12
width=4
separator=-
verbosity=0

while getopts :va:g:w:s: option; do
  case "$option" in
    v) verbosity=$((verbosity+1)) ;;
    a) alphabet="$OPTARG" ;;
    g) groups="$OPTARG" ;;
    w) width="$OPTARG" ;;
    s) separator="$OPTARG" ;;
    :) print -u2 -- "missing argument for option -$OPTARG"; exit 1 ;;
    ?) print -u2 -- "illegal option: -$OPTARG"; exit 1 ;;
  esac
done
shift $((OPTIND-1))

# shellcheck disable=SC2046
set -A symbol -- $( echo "$alphabet" | fold -w 1 | sort -u | tr -d '\n' | sed 's/./& /g' )

# shellcheck disable=SC2154
symbols=${#symbol[*]}

jot -r $((groups*width)) 0 $((symbols-1)) |
  while IFS= read -r i; do echo "${symbol[$i]}"; done |
  tr -d '\n' |
  fold -w "$width" |
  paste -s -d "$separator" -

if [ "$( uname )" == "FreeBSD" ] ; then
  # FreeBSD's paste(1) swallows the final newline.
  printf '\n'
fi

if [ $verbosity -gt 0 ]; then
  entropy="$( printf 'e = (%d * %d * l(%d))/l(2); scale = 0; e/1\n' "$groups" "$width" "$symbols" | bc -l )"
  print -u2 -- "The generated password has an entropy of ${entropy} bits."
fi