#!/usr/bin/bash
# SPDX-License-Identifier: BlueOak-1.0.0
# SPDX-FileCopyrightText: © 2021-2023 Alexander Klang <a.klang@icloud.com>
# SPDX-FileNotice: License Terms <https://blueoakcouncil.org/license/1.0.0>


# PWGEN.SH VERSION 2.2 INHUMAN
# ------------------------------------------------------------------------------
# Generates 48 character passwords and prints them to "STDOUT"
#
# Usage: pwgen.sh [<number>]
# Where <number> is the amount of passwords to generate (1-1000)
#
# Dependency: GNU Bash Shell Version 5.1 or newer


# SAFEGUARDS
# ------------------------------------------------------------------------------

# Abort with an error if "bash" is too old for the upcoming code
if [[ -z ${BASH_VERSINFO[*]} ]] \
   || (( BASH_VERSINFO[0] < 5 )) \
   || (( BASH_VERSINFO[0] == 5 && BASH_VERSINFO[1] < 1 )); then
  echo "${0}: GNU Bash Shell Version 5.1 or newer required!" >&2
  exit 1
fi

# Dealing with arguments:
# - Given the 1st argument is a number, it becomes "N_AMOUNT"
# - If "N_AMOUNT" is too large/small, abort with an error
# - When no argument is given at all, generate 1 password ("N_AMOUNT=1")
# - Abort with help if anything but a number is given as 1st argument
# - Any arguments but the 1st are politely ignored
if [[ ${1} =~ ^[[:digit:]]+$ ]]; then
  # Reminder: Set number to "base 10" to strip leading 0's irritating the shell
  N_AMOUNT=$(( 10#${1} ))
  if (( N_AMOUNT < 1 || N_AMOUNT > 1000 )); then
    echo "${0}: The number given must be between 1 and 1000!" >&2
    exit 1
  fi
elif [[ -z ${1} ]]; then
  N_AMOUNT=1
else
  echo "${0} generates random passwords with an easy to type structure."
  echo "Usage: ${0} [<number>]"
  echo 'Where <number> is the amount of passwords to generate (1-1000).'
  exit 0
fi


# MAIN CODE
# ------------------------------------------------------------------------------


a_characters=( a b c d e f g h i j k l m n o p q r s t u v w x y z )
a_characters+=( 0 1 2 3 4 5 6 7 8 9 ',' '.' ':' '-' '_' )

# Run the following as often as defined in "N_AMOUNT"
while (( ${n_run:=0} < N_AMOUNT )); do

  # Run the following 48 times
  until (( ${n_position:=0} == 48 )); do
    # Pick a random character from the pool defined in 'a_characters'
    n_element="$(( SRANDOM % ${#a_characters[@]} ))"
    # Randomly turn the chosen character into uppercase or lowercase
    # and add it to the password
    if (( SRANDOM % 2 )); then
      v_password+="${a_characters[${n_element}]^^}"
    else
      v_password+="${a_characters[${n_element}],,}"
    fi
    (( ++n_position ))
  done
  # Print the generated password
  echo "${v_password}"

  # Clean up lingering variables
  unset n_{element,position} v_password
  # Increment the loop's counter
  (( ++n_run ))

done