#!/usr/bin/bash

function usage()
{
	local just_help=$1
	local missing_required=$2
	local invalid_argument=$3
	local invalid_option=$4

	local help="Usage: genpass -c COUNT [OPTION] [SET]

Generate random password from /dev/urandom using the character set chosen

Option (pick one character set):"
local help_options="\t\-a ,\--all\ all printable characters, not including space
	\t\-lt ,\--limited\ all except special characters [A-Za-z0-9%+,-./:=@^_]
	\t\-b32 ,\--base32\ all valid base32 characters [A-Z2-7=]
	\t\-b64 ,\--base64\ all valid base64 characters [A-Za-z0-9+/]
	\t\-an ,\--alphanumeric\ letters and digits
	\t\-al ,\--alpha\ letters
	\t\-u ,\--upper\ upper case letters
	\t\-l ,\--lower\ lower case letters
	\t\-n ,\--numeric\ digits
	\t\-h ,\--hex\ hexadecimal digits
	\t\-c ,\--count <length>\ Length of password to generate
	\t\[SET]\ \ Other character SET compatible with tr
"

	if [ "$missing_required" != "" ]
	then
		echo "Missing required argument: $missing_required"
	fi

	if [ "$invalid_option" != "" ] && [ "$invalid_value" = "" ]
	then
		echo "Invalid option: $invalid_option"
	elif [ "$invalid_value" != "" ]
	then
		echo "Invalid value: $invalid_value for option: --$invalid_option"
	fi

	echo -e "
"
	echo "$help"
	echo "$help_options" | column -t -s'\'
	return
}
function init_args()
{
REQ_ARGS=("count" )

# get command line arguments
POSITIONAL=()
while [[ $# -gt 0 ]]
do
key="$1"

case $key in
	-a|--all)
		characters="[:graph:]"
		shift
		;;
	-lt|--limited)
		characters="A-Za-z0-9%+,-./:=@^_"
		shift
		;;
	-b32|--base32)
		characters="A-Z2-7="
		shift
		;;
	-b64|--base64)
		characters="A-Za-z0-9+/"
		shift
		;;
	-an|--alphanumeric)
		characters="[:alnum:]"
		shift
		;;
	-al|--alpha)
		characters="[:alpha:]"
		shift
		;;
	-u|--upper)
		characters="[:upper:]"
		shift
		;;
	-l|--lower)
		characters="[:lower:]"
		shift
		;;
	-n|--numeric)
		characters="[:digit:]"
		shift
		;;
	-h|--hex)
		characters="0-9a-f"
		shift
		;;
	-c|--count)
		count="$2"
		shift 2
		;;
	*)
		POSITIONAL+=("$1") # saves unknown option in array
		shift
		;;
esac
done

for i in "${REQ_ARGS[@]}"; do
	# $i is the string of the variable name
	# ${!i} is a parameter expression to get the value
	# of the variable whose name is i.
	req_var=${!i}
	if [ "$req_var" = "" ]
	then
		usage "" "--$i"
		exit
	fi
done
}

init_args $@

if [ -z $characters ]; then
	if [ -z $POSITIONAL ]; then
		echo "Missing at least one character set"
		exit 2
	else
		characters=$POSITIONAL
	fi
fi

< /dev/urandom tr -dc $characters | head -c $count