rc/sh/feud

#!/usr/bin/env sh
# compat: +ash +bash +dash -hush +ksh +mksh +oksh +osh +posh +yash +zsh

### @feud - parse command-line arguments, mapping short-flags to variable names.
### **NOTE:** the API is still experimental and will undergo major changes.

__feud_invalid() {
	#v(){ case "$1" in (*[!_A-Za-z0-9]*) :;;([_A-Za-z]*) [ ];esac;}
	case "$1" in (*[!_A-Za-z0-9]*) true;; ([_A-Za-z]*) false;; (*) true;; esac
}

feud_new_program() {
	if [ $# != 2 ]; then
		printf >&2 %s\\n "usage: feud_new_program {program name} {callback name}"
		return 64
	elif __feud_invalid "$2"; then
		printf >&2 %s\\n "feud_new_program: callback name must be a valid identifier"
		return 64
	fi

	__feud_program="$1" __feud_callback="$2"
	__feud_switches= __feud_options= __feud_matches=
}

feud_add_option() {
	if [ $# != 2 ] || [ "${#1}" != 1 ] || [ "${#2}" = 0 ]; then
		# TODO: improve error message, especially when running from __feud_dispatch!
		[ "${#1}"  = 1 ] || printf >&2 %s\\n "feud_add_option: invalid argument: \"$1\""
		[ "${#2}" != 0 ] || printf >&2 %s\\n "feud_add_option: invalid argument: \"$2\""
		printf >&2 %s\\n "usage: feud_add_option {single character} {variable name}"
		return 64
	elif __feud_invalid "$2"; then
		printf >&2 %s\\n "feud_add_option: invalid argument: \"$2\""
		printf >&2 %s\\n "feud_add_option: variable name must be a valid identifier"
		return 64
	fi

	__feud_options="$__feud_options$1"
	__feud_matches="$__feud_matches ($1) $2=\"\$2\";;"
}

feud_add_switch() {
	if { [ $# != 2 ] && [ $# != 3 ] ;} || [ "${#1}" != 1 ] || [ "${#2}" = 0 ]; then
		# TODO: improve error message, especially when running from __feud_dispatch!
		[ "${#1}"  = 1 ] || printf >&2 %s\\n "feud_add_switch: invalid argument: \"$1\""
		[ "${#2}" != 0 ] || printf >&2 %s\\n "feud_add_switch: invalid argument: \"$2\""
		printf >&2 %s\\n "usage: feud_add_switch {single character} {variable name} [value]"
		return 64
	elif __feud_invalid "$2"; then
		printf >&2 %s\\n "feud_add_switch: invalid argument: \"$2\""
		printf >&2 %s\\n "feud_add_switch: variable name must be a valid identifier"
		return 64
	elif [ $# = 3 ] && [ -z "${3##*[!0-9]*}" ]; then
		# TODO: lift this restriction?
		printf >&2 %s\\n "feud_add_switch: value must be a non-negative integer"
		return 64
	fi

	__feud_switches="$__feud_switches$1"
	if [ $# = 2 ]; then
		eval "$2=0"
		__feud_matches="$__feud_matches ($1) : \$(($2+=1));;"
	else
		__feud_matches="$__feud_matches ($1) $2=$3;;"
	fi
}

__feud_dispatch() {
	# NOTE: temporarily using 2>/dev/null instead of 2>&- until OSH bug gets fixed.
	PATH=: setopt local_options sh_word_split 2>/dev/null
	case $- in (*f*) set -- $1${1:+,};; (*) set -f; set -- $1${1:+,}; set +f;; esac
	for arg; do
		set -- "${arg##*-}" "${arg%-*}"
		case "$arg" in
		(?*=?*-?*)
			"$__feud_c" "$1" "${2%%=*}" "${2#*=}";;
		(?*-?*)
			"$__feud_c" "$1" "$2";;
		# TODO: handle (*=*) to give a contextual error message.
		(*) # TODO: catch this case as well: "c=-d"
			printf >&2 %s\\n "feud_configure: expected two hyphen-separated parameters: \"$arg\""
			__feud_error=64;;
		esac || {
			__feud_error=$?
			printf >&2 %s\\n "feud_configure: the above error is due to this substring: \"$arg\""
		}
	done
}

__feud_dispatch_both() {
	# FIXME? on shells that don't support locals (ksh), IFS never gets reset.
	__feud_c=feud_add_option IFS=, __feud_dispatch "$1"
	__feud_c=feud_add_switch IFS=, __feud_dispatch "$2"
	return $__feud_error
}

feud_configure() {
	if [ $# != 1 ]; then
		printf >&2 %s\\n 'usage: feud_configure {string of options:switches}'
		printf >&2 %s\\n 'example: `feud_configure input-i,output-o:always-a,yes-y`'
		return 64
	fi

	case "$1" in
	(*:*:*)
		printf >&2 %s\\n 'feud_configure: too many colons, expected one'
		printf >&2 %s\\n 'feud_configure: (hint) "switch,switch:option,option"'
		return 64;;
	(*:*) :;; # no-op
	(*)
		printf >&2 %s\\n 'feud_configure: expected one colon'
		return 64;;
	esac

	__feud_error=0 \
	__feud_old_options="$__feud_options" \
	__feud_old_switches="$__feud_switches" \
	__feud_old_matches="$__feud_matches" \
	__feud_dispatch_both "${1%:*}" "${1#*:}"
}

feud_match_flag() {
	false
}

__feud_help() {
	"${__feud_callback}_help"
}

feud() {
	# locals: __feud_n, __feud_f

	if [ -z "$__feud_callback" ]; then
		printf >&2 %s\\n "feud: missing initialization -- call feud_new_program first!"
		return 64
	fi
	eval "feud_match_flag() { case \"\$1\" in $__feud_matches (*) false; esac ;}"

	__feud_n=$#
	while [ $((__feud_n-=1)) -ge 0 ]; do
		__feud_f="$1"
		case "$__feud_f" in

		# TODO: don't check for -h here if the user configured their own.
		(/\?|-h|-help|--help)
			__feud_help
			return 0;;

		(--)
			shift
			while [ $((__feud_n-=1)) -ge 0 ]; do
				set -- "$@" "$1"
				shift
			done
			break;;

		(-*)
			shift
			case "${__feud_f#-}" in
			(["$__feud_switches"])
				feud_match_flag "${__feud_f#-}" || printf >&2 '%s: %s\n' feud "internal error"
				:;;
			(["$__feud_options"])
				if [ $__feud_n = 0 ]; then
					printf >&2 '%s: %s\n' "$__feud_program" "missing argument for $__feud_f"
					__feud_help >&2
					return 64
				fi
				: $((__feud_n-=1))
				feud_match_flag "${__feud_f#-}" "$1" || printf '%s: %s\n' feud "internal error"
				shift;;
			(-*|?)
				printf >&2 '%s: %s\n' "$__feud_program" "unknown flag: $__feud_f"
				__feud_help >&2
				return 64;;
			(*)
				if case "$__feud_f" in
				(-["$__feud_options"]*) true;;
				(*) false;;
				esac; then
					set -- "${__feud_f%"${__feud_f#-?}"}" "${__feud_f#-?}" "$@"
				else
					set -- "${__feud_f%"${__feud_f#-?}"}" "-${__feud_f#-?}" "$@"
				fi
				: $((__feud_n+=2))
				continue;;
			esac;;

		(*)
			shift
			set -- "$@" "$__feud_f";;
		esac
	done

	"$__feud_callback" "$@"
}

feud_cleanup() { # optional
	unset \
	__feud_program __feud_callback __feud_switches __feud_options __feud_matches \
	__feud_c __feud_f __feud_n __feud_error \
	__feud_old_options __feud_old_switches __feud_old_matches
	feud_match_flag() { false; }
}

[ -n "${preload+-}" ] || feud "$@"

# cursed modeline:
# vim:ft=bash ts=3 sw=3 noet sts=3