array_remove

#!/usr/bin/env bash

##region########################################### HELP & VERSION ###########################################
_show_help() {
	# -f, --first, --forward[s]: Search from the beginning of the list. Mutually exclusive with -l. Default.
	# -l, --last, -b, --backward[s]: Search from the end of the list. Mutually exclusive with -f.
	cat << __EOF__
Removes the specified values from the list.

Usage:	$0 [-sar] [--] VALUE ENTRY1 ENTRY2...
	or:	$0 --value VALUE [-sar] [--] ENTRY1 ENTRY2...
	or:	$0 --index VALUE [-sar] [--] ENTRY1 ENTRY2...
	or:	$0 --index [-sar] [--] VALUE ENTRY1 ENTRY2...
	or:	$0 [--last|first] [--] VALUE ENTRY1 ENTRY2...
	or:	$0 --help
	or:	$0 --version

Options:
	-h, --help: Shows this help text.
	--version: Shows version info.
	-i, --index[-at/_at], --at[-index/_index] [VALUE]: The index of the value to remove. If value wasn't assigned by a preceding option & the following token is an integer, that token will be used as 'VALUE'. If value wasn't assigned by a preceding option & the following token is not an integer, value will be assigned by a later '--value' option, the first argument after a terminating --, or the first argument to not match a parameter nor follow a named parameter.
	-v, --value VALUE: The value to remove. Can be an empty string.
	-r, --regex: Treat 'VALUE' as an extended regex.
	-I, --invert: Instead of searching for matching values, searches for non-matching values. Mainly useful for filtering a list into matching and non-matching members.
	-a, --all: Remove all matching values.
	-d, --delim, --delimiter DELIMITER: A string literal to be placed in between each element in the returned list & after the last element. If the input may contain spaces and/or newlines, use a value like \$'\\003' (ASCII ETX) & mapfile to break the output back into an array.
	-c, --count [DELIMITER]: Print the number of elements in the returned list before the list itself. Separated from the first element by DELIMITER. If the token after the flag doesn't match any options, it will be used as the count delimiter. Defaults to a single newline.
	--: Stop processing arguments. If 'VALUE' isn't assigned to yet, the next token will be used.

Exit Status:
	0 if found, 1 if not found, 255 for undefined execution error.
__EOF__
}
_show_version() {
	cat << __EOF__
$0 3.0.0

Copyright (C) 2025 Justin Morris
__EOF__
}
##endregion######################################## HELP & VERSION ###########################################
set -e
declare -r numericMatcher='^[-+]?[[:digit:]]+$'
declare fInvert='false'
declare fAll='false'
declare fAt='false'
declare fRegex='false'
declare fCount='false'
# declare countDelim=
declare delim=$'\n' # declare delim=$'\003'
shopt -s extglob globasciiranges
# TODO: Forwards & Backwards options?
# while (($# > 0)); do
while true; do
	case "$1" in
		-c | --count) declare -r fCount='true'; shift; continue;;
		-d | --delim | --delimiter) shift; declare -r delim="$1";;
		-s | --single | -o | --one) declare -r fAll='false';;
		-a | --all) declare -r fAll='true';;
		-I | --invert) declare -r fInvert='true';;
		-r | --regex) declare -r fRegex='true';;
		-i | --index | --index[-_]at | --at | --at[-_]index)
			declare -r fAt='true'
			if ! [ -v toRemove ] && [[ "$2" =~ $numericMatcher ]]; then
				shift
				declare toRemove="$1"
			fi
			;;
		# TODO: Warn if value overwritten?
		-v | --value) shift; declare toRemove="$1";;
		-h | --help) _show_help; exit 0;;
		--version) _show_version; exit 0;;
		*)
			if eval "$fCount" && ! [ -v countDelim ]; then
				declare -r countDelim="$1"
				shift
				continue
			fi
			if ! [ -v toRemove ]; then
				declare toRemove="$1"
				if ! shift; then
					echo "No array elements" 1>&2
					exit 1
				fi
			fi
			break
			;;
	esac
	shift
	if eval "$fCount" && ! [ -v countDelim ]; then declare -r countDelim=$'\n'; fi
done
if ! [ -v toRemove ]; then
	echo "toRemove Undefined" 1>&2
	exit 1
fi
if eval "$fCount" && ! [ -v countDelim ]; then
	echo "countDelim Undefined" 1>&2
	exit 1
fi
declare -r toRemove="$toRemove" fAll fAt delim fRegex fInvert
declare -a result=()
if eval "$fAt"; then
	# TODO: account for octal & such https://www.gnu.org/software/bash/manual/bash.html#Shell-Arithmetic
	if ! [[ "$toRemove" =~ $numericMatcher ]]; then
		echo "Cannot remove non-numeric index $toRemove" 1>&2
		exit 1
	else
		declare -i toRemove # If octal or whatever, fixes it for upcoming error messages
		if ((toRemove >= $#)); then
			echo "Cannot remove index $toRemove that exceeds array length of $#" 1>&2
			exit 1
		elif ((toRemove < 0 && toRemove * 1 >= $#)); then
			echo "Cannot remove negative index $toRemove that exceeds array length of $#" 1>&2
			exit 1
		fi
	fi
	result=("$@")
	unset "result[$toRemove]"
	# result=("${result[@]}") # Fixes indices
else
	function _regexMatch() { if eval "$fInvert"; then ! [[ "$1" =~ $toRemove ]] && return 0 || return 1; else [[ "$1" =~ $toRemove ]] && return 0 || return 1; fi }
	function _literalMatch() { if eval "$fInvert"; then ! [ "$1" = "$toRemove" ] && return 0 || return 1; else [ "$1" = "$toRemove" ] && return 0 || return 1; fi }
	while (($# > 0)); do
		if (eval "$fRegex" && _regexMatch "$1") ||
			(! eval "$fRegex" && _literalMatch "$1"); then
			if eval "$fAll"; then
				shift
				continue
			fi
			if shift; then
				result+=("$@")
			fi
			break
		fi
		result+=("$1")
		shift
	done
fi
IFS="$delim"
if eval "$fCount"; then
	echo -nE "${#result[*]}$countDelim${result[*]}$delim"
else
	echo -nE "${result[*]}$delim"
fi
exit