#!/usr/bin/env bash
# Filename:      makepass.bash
# Purpose:       Creating random passwords.
# Authors:       Dennis Eriksen <d@ennis.no>
# Bug-Reports:   Email <git@dnns.no>
# License:       This file is licensed under the BSD 3-Clause license.
################################################################################
# This script generates random passwords.
################################################################################
# Copyright (c) 2018-2023 Dennis Eriksen • d@ennis.no

MAX=255         # max length of passwords
RANGE_MAX=42    # max length when using random length
RANGE_MIN=8     # min length when using random length
PASS_WORDS=8    # number of words in passphrases

LOWER='abcdefghijklmnopqrstuvwxyz'
UPPER='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
DIGIT='0123456789'
OTHER='!#$%&/()=?+-_,.;:<>[]{}|@*'
ALPHA=${LOWER}${UPPER}
ALNUM=${ALPHA}${DIGIT}
EVERY=${ALNUM}${OTHER}

LENGTH=${MAKEPASS_LENGTH:-0}     # length of passwords. 0 means "random number between RANGE_MIN and RANGE_MAX"
NUMBER=${MAKEPASS_NUMBER:-10}    # number of passwords
PRINTLEN=${MAKEPASS_PRINTLEN:-0} # print length of passwords
NORMAL=${MAKEPASS_NORMAL:-$ALNUM'-_'}
SPECIAL=${MAKEPASS_SPECIAL:-$EVERY}
WORDLIST=${MAKEPASS_WORDLIST:-/usr/share/dict/words}
XWIDTH=$(tput cols)
WORDS=()

#
# Functions
#

# makepass-function
function main {

  # Getopts
  while getopts 'hl:n:p' opt; do
    case $opt in
      h)
        help && return 0;;
      l)
        if ! int_in_range "$OPTARG" 0 "$MAX"; then die "-l takes a number between 0 and $MAX"; fi
        LENGTH=$OPTARG;;
      n)
        if ! int_in_range "$OPTARG" 1 "$MAX"; then die "-n takes a number between 1 and $MAX"; fi
        NUMBER=$OPTARG;;
      p)
        PRINTLEN=1;;
      *)
        die "Unknown argument";;
    esac
  done
  shift $((OPTIND - 1))


  #
  # Some error-checking
  #

  if [[ $# -gt 1 ]]; then die "only one argument"; fi

  if [[ -n $1 ]]; then LENGTH=$1; fi

  # Check $LENGTH and $NUMBER
  if ! int_in_range "$LENGTH" 0 "$MAX"; then die "length must be a number between 0 and $MAX"; fi
  if ! int_in_range "$NUMBER" 0 "$MAX"; then die "number-argument must be between and $MAX"; fi


  #
  # Some other work
  #

  if (( PRINTLEN )); then PRINTLEN=$((LENGTH < 100 ? 2 : 3)); fi

  COL_WIDTH=$(( ( LENGTH ? LENGTH : RANGE_MAX ) + 2 ))
  COL_NUM=$(( XWIDTH / ( COL_WIDTH + ( PRINTLEN ? PRINTLEN + 1 : 0 )) ))



  #
  # Print!
  #

  print_columns "Normal passwords" "$NUMBER" "$NORMAL"

  echo ""

  print_columns "Passwords with special characters" "$((NUMBER*2/3))" "$SPECIAL"

  if [ -r "${MAKEPASS_WORDLIST}" ]; then
    echo ""
    echo "Passphrases:"

    mapfile -t WORDS < "${WORDLIST}"

    for ((i=0; i < (NUMBER / 2); i++)); do
      passphrase
    done;
  fi


}

# Function to print passwords in neat columns
function print_columns {
  local title=$1
  local num=$2
  local chars=$3
  local i

  local strings=()
  for ((i=0; i < num; i++)); do
    strings+=("$(randstring "$chars")")
  done

  echo "${title}:"

  i=0
  for s in "${strings[@]}"; do
    ((i++))
    if (( PRINTLEN )); then printf "%0${PRINTLEN}i " "${#s}"; fi
    printf "%-${COL_WIDTH}s" "$s"
    if ((i % COL_NUM == 0 || (i == num && i % COL_NUM > 0) )); then echo ""; fi
  done
}

# Function to create random strings
function randstring {
  local chars=${1:-$NORMAL}
  local string
  local len=$(( LENGTH ? LENGTH : RANDOM % (RANGE_MAX - RANGE_MIN + 1) + RANGE_MIN ))

  string+="${ALPHA:$((RANDOM % ${#ALPHA})):1}"
  while (( ${#string} <= len - 2 )); do string+="${chars:$((RANDOM % ${#chars})):1}"; done
  if (( len >= 2 )); then string+="${ALNUM:$((RANDOM % ${#ALNUM})):1}"; fi

  echo "$string"
}

# PASSPHRASE!!
function passphrase {
  local string
  local i
  for ((i=0; i < PASS_WORDS; i++)); do
    string+="${WORDS[$((RANDOM % ${#WORDS[@]}))]}-"
  done
  string="${string:0:-1}"

  echo "$string"
}

# Check if int and if in range
function int_in_range {
  local num=$1
  local min=$2
  local max=$3

  if [[ $num =~ ^[0-9]+$ && $min -le $num && $num -le $max ]]; then
    return 0
  fi
  return 1
}

# Function to die
function die() {
  echo -- "$@"
  echo -- "Maybe try running \`makepass -h\` for help"
  exit 1
}

# Help-function
function help {
  echo $'NAME
    makepass - create several random passwords

SYNOPSIS
    makepass [OPTIONS] [NUM]

    If a NUM is provided, passwords will be NUM characters long.

    By default `makepass` will output passwords from the three following classes:

    - Normal passwords - random strings with letters (both lower and upper
      case), numbers, and dashes and underscores.

    - Passwords with special characters - random strings generated from lower
      and upper case letters, numbers, and the following characters:
      !#$%&/()=?+-_,.;:<>[]{}|@*

    - Passphrases - if we find a dictionary, a series of eight random words
      from the dictionary, separated by dashes. The number of words can not be
      changed, but you do not have to use all of them. Use as mane as you want.

    The first character will always be alphabetic, and the last will always be
    alphanumeric.

DESCRIPTION
    makepass has the following options:

    -h
        output this help-text
    -l
        length of passwords. See MAKEPASS_LENGTH below
    -n
        number of passwords. See MAKEPASS_NUMBER below
    -p
        print length of number

ENVIRONMENT
    makepass examines the following environmental variables.

    MAKEPASS_LENGTH
        Specifies the length of passwords. Valid values are 0-255. If 0, a
        random value between 8 and 42 will be used for each password. -l
        overrides this environmental variable, and the argument NUM overrides
        that again. So `MAKEPASS_LENGTH=10 makepass -l 12 14` will give
        passwords that are 14 characters long, even though both -l and
        MAKEPASS_LENGTH also specifies a length.

    MAKEPASS_NUMBER
        The number of passwords to generate. This formula is used to determine
        how many passwords from each group should be generated:
        - (n) normal passwords
        - (n / 3 * 2 + 1) special passwords
        - (n / 2) passphrases
        Where n is 10 by default. Valid values for n are 1-255. Floating-poing
        math is not used, so results may vary.

    MAKEPASS_PRINTLEN
        If 1, print length of all passwords. If 0, don\'t.

    MAKEPASS_NORMAL
        String of characters from which to generate "normal" passwords.
        Defaults to:
        abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_

    MAKEPASS_SPECIAL
        String of characters from which to generate passwords with special
        characters. Defaults to the same characters as in MAKEPASS_NORMAL, plus
        these:
        !#$%&/()=?+-_,.;:<>[]{}|@*

    MAKEPASS_WORDLIST
        Specifies the dictionary we find words for passphrases in. If this is
        unset or empty, we try "/usr/share/dict/words". If that file does not
        exist, no passphrases will be provided.

NOTES
    This scripts makes use of $RANDOM - a builtin in bash which produces a
    pseudo-random integer, newly generated each time the parameter is
    referenced. This should provide enough randomnes to generate sufficiently
    secure passwords.

AUTHOR
    Dennis Eriksen <https://dnns.no>'

  return 0
}

# RUN IT!
main "${@:-}"

## END OF FILE #################################################################