#!/bin/bash

# Copyright (c) 2020 jm1hey
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

# Version
script_version="1.5"

# The purpose of this script is described in the 'printhelp' function defined below.

# define command name -- this should be the same as the script file name
cmdname="randstr"

# define usage and help functions
function printusage {
	echo \
"
Usage: $cmdname [OPTION(s)]

Options:
	--help
		Print help information and exit

	--version
		Print version information and exit

	(--length | -l) [LENGTH IN CHARACTERS OF EACH STRING]
		Default: 15

	(--number | -n) [NUMBER OF STRINGS TO PRODUCE]
		Default: 1

	(--delimiter | -d) [(space | s) | (line | l)]
		Default: space
	
	(--type | -t) [(alpha | a) | (numeric | n) | (alphanumeric | an)]
		Default: alphanumeric
	
	(--case | -c) [(upper | u) | (lower | l) | (both | b)]
		Default: both

"
}

function printhelp {
	echo \
"
$cmdname is a Bash script that prints random alphanumeric
character strings. It uses only commands that are commonly
included in Unix-like systems."
	printusage
}

function printversion {
	echo "$script_version"
}

# check for "--help" argument
for i in "$@"
do
	if [ "$i" == "--help" ]
	then
		printhelp
		exit 0
	fi
done

# check for "--version" argument
for i in "$@"
do
	if [ "$i" == "--version" ]
	then
		printversion
		exit 0
	fi
done

# check for 'tr'
which tr > /dev/null
if [ $? != 0 ]
then
	echo "Error: 'tr' not found"
	exit 1
fi
printf "\xFF" | tr -dc "A-Za-z0-9" > /dev/null 2>&1
if [ $? != 0 ]
then
	echo "Error: unsupported version of 'tr' installed"
	exit 1
fi

# options will be kept at default values if not set by user
length_set="0"
number_set="0"
delimiter_set="0"
type_set="0"
alpha_case_set="0"

i=1
for arg in "$@"
do
	# assume for now that all arguments are invalid
	argvalid[$i]=0
	i=$((i+1))
done

num_i=1
i_next=2
for arg in "$@"
do
	if [ "$arg" == "-l" ] || [ "$arg" == "--length" ]
	then
		if [ "$length_set" == "1" ]
		then
			echo "Error: do not set the same option more than once"
			exit 1
		elif [ -z "${!i_next}" ]
		then
			printf "%s\"%s\"\n" "Error: missing argument for option " "$arg"
			exit 1
		elif [ "${!i_next:0:1}" == "-" ]
		then
			printf "%s\"%s\"%s\n" "Error: argument for option " "$arg" " must be a positive integer"
			exit 1
		elif ! [[ "${!i_next}" =~ ^[0-9]+$ ]]
		then
			printf "%s\"%s\"%s\n" "Error: argument for option " "$arg" " must be a positive integer"
			exit 1
		else
			length="${!i_next}"
			length_set=1
			argvalid[$num_i]=1
			argvalid[$i_next]=1
		fi
	elif [ "$arg" == "-n" ] || [ "$arg" == "--number" ]
	then
		if [ "$number_set" == "1" ]
		then
			echo "Error: do not set the same option more than once"
			exit 1
		elif [ -z "${!i_next}" ]
		then
			printf "%s\"%s\"\n" "Error: missing argument for option " "$arg"
			exit 1
		elif [ "${!i_next:0:1}" == "-" ]
		then
			printf "%s\"%s\"%s\n" "Error: argument for option " "$arg" " must be a positive integer"
			exit 1
		elif ! [[ "${!i_next}" =~ ^[0-9]+$ ]]
		then
			printf "%s\"%s\"%s\n" "Error: argument for option " "$arg" " must be a positive integer"
			exit 1
		else
			number="${!i_next}"
			number_set=1
			argvalid[$num_i]=1
			argvalid[$i_next]=1
		fi
	elif [ "$arg" == "-d" ] || [ "$arg" == "--delimiter" ]
	then
		if [ "$delimiter_set" == "1" ]
		then
			echo "Error: do not set the same option more than once"
			exit 1
		elif [ -z "${!i_next}" ]
		then
			printf "%s\"%s\"\n" "Error: missing argument for option " "$arg"
			exit 1
		elif [ "${!i_next}" != "s" ] && [ "${!i_next}" != "space" ] && [ "${!i_next}" != "l" ] && [ "${!i_next}" != "line" ]
		then
			printf "%s\"%s\"\n" "Error: invalid argument for option " "$arg"
			exit 1
		else
			if [ "${!i_next}" == "s" ] || [ "${!i_next}" == "space" ]
			then
				delimiter=" "
			elif [ "${!i_next}" == "l" ] || [ "${!i_next}" == "line" ]
			then
				delimiter="\n"
			fi
			delimiter_set=1
			argvalid[$num_i]=1
			argvalid[$i_next]=1
		fi
	elif [ "$arg" == "-t" ] || [ "$arg" == "--type" ]
	then
		if [ "$type_set" == "1" ]
		then
			echo "Error: do not set the same option more than once"
			exit 1
		elif [ -z "${!i_next}" ]
		then
			printf "%s\"%s\"\n" "Error: missing argument for option " "$arg"
			exit 1
		elif [ "${!i_next}" != "a" ] && [ "${!i_next}" != "alpha" ] &&
			[ "${!i_next}" != "n" ] && [ "${!i_next}" != "numeric" ] &&
			[ "${!i_next}" != "an" ] && [ "${!i_next}" != "alphanumeric" ]
		then
			printf "%s\"%s\"\n" "Error: invalid argument for option " "$arg"
			exit 1
		else
			if [ "${!i_next}" == "a" ] || [ "${!i_next}" == "alpha" ]
			then
				type="alpha"
			elif [ "${!i_next}" == "n" ] || [ "${!i_next}" == "numeric" ]
			then
				type="numeric"
			elif [ "${!i_next}" == "an" ] || [ "${!i_next}" == "alphanumeric" ]
			then
				type="alphanumeric"
			fi
			type_set=1
			argvalid[$num_i]=1
			argvalid[$i_next]=1
		fi
	elif [ "$arg" == "-c" ] || [ "$arg" == "--case" ]
	then
		if [ "$alpha_case_set" == "1" ]
		then
			echo "Error: do not set the same option more than once"
			exit 1
		elif [ -z "${!i_next}" ]
		then
			printf "%s\"%s\"\n" "Error: missing argument for option " "$arg"
			exit 1
		elif [ "${!i_next}" != "u" ] && [ "${!i_next}" != "upper" ] &&
			[ "${!i_next}" != "l" ] && [ "${!i_next}" != "lower" ] &&
			[ "${!i_next}" != "b" ] && [ "${!i_next}" != "both" ]
		then
			printf "%s\"%s\"\n" "Error: invalid argument for option " "$arg"
			exit 1
		else
			if [ "${!i_next}" == "u" ] || [ "${!i_next}" == "upper" ]
			then
				alpha_case="upper"
			elif [ "${!i_next}" == "l" ] || [ "${!i_next}" == "lower" ]
			then
				alpha_case="lower"
			elif [ "${!i_next}" == "b" ] || [ "${!i_next}" == "both" ]
			then
				alpha_case="both"
			fi
			alpha_case_set=1
			argvalid[$num_i]=1
			argvalid[$i_next]=1
		fi
	fi
	num_i=$((num_i+1))
	i_next=$((i_next+1))
done

# reject any unrecognized arguments
num_i=1
for arg in "$@"
do
	if [ "${argvalid[$num_i]}" != "1" ]
	then
		printf "%s\"%s\"\n" "Error: unrecognized argument: " "$arg"
		exit 1
	fi
	num_i=$((num_i+1))
done

# set any unset arguments to their default values
if [ "$length_set" == "0" ]
then
	length=15
fi
if [ "$number_set" == "0" ]
then
	number=1
fi
if [ "$delimiter_set" == "0" ]
then
	delimiter=" "
fi
if [ "$type_set" == "0" ]
then
	type="alphanumeric"
fi
if [ "$alpha_case_set" == "0" ]
then
	alpha_case="both"
fi

# set character set
if [ "$type" == "alpha" ]
then
	if [ "$alpha_case" == "upper" ]
	then
		charset="A-Z"
	elif [ "$alpha_case" == "lower" ]
	then
		charset="a-z"
	else
		charset="A-Za-z"
	fi
elif [ "$type" == "numeric" ]
then
	charset="0-9"
else
	if [ "$alpha_case" == "upper" ]
	then
		charset="A-Z0-9"
	elif [ "$alpha_case" == "lower" ]
	then
		charset="a-z0-9"
	else
		charset="A-Za-z0-9"
	fi
fi

# print random strings
i=1
while [ "$i" -lt "$number" ]
do
	tr -dc "$charset" </dev/urandom | head -c "$length"
	printf "$delimiter"
	i=$((i+1))
done
tr -dc "$charset" </dev/urandom | head -c "$length"
printf "\n"