#!/hint/bash
# Copyright (C) 2018  Luke Shumaker
# Copyright (C) 2023-2024  Umorpha Systems
# SPDX-License-Identifier: AGPL-3.0-or-later

opt_specs=()

# Usage:
#
#	argparse MYDEFAULT "$@"
#	case "$opt_mode" in
#		error)
#			print "Try '%q --help' for more information" "${0##*/}" >&2
#			return $EXIT_INVALIDARGUMENT
#			;;
#		version)
#			print "%s %s" "$NAME" "$VERSION"
#			return $EXIT_SUCCESS
#			;;
#		help)
#			print 'Usage: %s [OPTIONS]' "${0##*/}"
#			print 'One line description'
#			echo
#			print 'Longer description.'
#			echo
#			print 'OPTIONS:'
#			echo "${opt_flaghelp}"
#			return $EXIT_SUCCESS
#			;;
#		MYDEFAULT)
#	...
#
# Inputs:
#
#	variable:   opt_specs
#
# Callbacks:
#
#	functions:  opt_visit:${longname} [OPTARG]
#	function:   opt_positional [POSITONAL_ARGS...]
#	functions:  opt_final:${longname}
#
# Outputs:
#
#	variable: opt_mode
#	variable: opt_flaghelp
argparse() {
	local IFS

	local _a_mode_default
	_a_mode_default="$1"
	shift

	# Augment opt_specs.

	if [[ ${#opt_specs[@]} -gt 0 ]]; then
		opt_specs+=('')
	fi

	opt_specs+=('-h : --help : : display this help')
	# shellcheck disable=SC2317
	opt_visit:help() { argparse:setmode help; }
	# shellcheck disable=SC2317
	opt_final:help() { :; }

	opt_specs+=('-V : --version : : output version information')
	# shellcheck disable=SC2317
	opt_visit:version() { argparse:setmode version; }
	# shellcheck disable=SC2317
	opt_final:version() { :; }

	# These 4 variables control the flag parsing and opt_flaghelp text.
	local _getopt_short=''           # ex: 'a::b:c'
	local _getopt_long=()            # ex: ('airplane::' 'boat:' 'car')
	declare -A _getopt_short2long=() # ex: ([a]=airplane [b]=boat [c]=car)
	declare -A _getopt_optarg=()     # ex: ([airplane]=maybe [boat]=yes [car]=no)
	local _help_specs=()

	# Parse ${opt_specs[@]} to adjust those 5 variables.
	local _spec
	for _spec in "${opt_specs[@]}"; do
		# Normalize whitespace
		_spec="$(sed -e 's/^\s*//' -e 's/\s*:\s*/:/g' -e 's/\s*$//' <<<"$_spec")"
		if [[ -z "${_spec}" ]]; then
			_help_specs+=('')
			continue
		fi

		local _spec_short _spec_long _spec_optarg _spec_desc
		IFS=':'
		# shellcheck disable=SC2162 # I want int to mangle backslashes.
		read _spec_short _spec_long _spec_optarg _spec_desc <<<"${_spec}"
		if [[ $_spec_long != --* ]]; then
			error "$EXIT_FAILURE" 'Internal error.  The programmer writing this tool screwed up.'
		fi

		local _g_suffix='' _s_suffix='' _l_suffix=''
		case "$_spec_optarg" in
			'')      _getopt_optarg["${_spec_long#'--'}"]=no   ; ;;
			'['*']') _getopt_optarg["${_spec_long#'--'}"]=maybe; _g_suffix='::'; _s_suffix="$_spec_optarg" ; _l_suffix="[=${_spec_optarg#'['}";;
			*)       _getopt_optarg["${_spec_long#'--'}"]=yes  ; _g_suffix=':' ; _s_suffix=" $_spec_optarg"; _l_suffix="=${_spec_optarg}";;
		esac
		_getopt_long+=("${_spec_long#'--'}${_g_suffix}")
		local _h_short=''
		if [[ -n "$_spec_short" ]]; then
			_getopt_short+="${_spec_short#'-'}${_g_suffix}"
			_getopt_short2long["${_spec_short#'-'}"]="${_spec_long#'--'}"
			_h_short="${_spec_short}${_s_suffix},"
		fi
		local _h_long _h_desc
		_h_long="${_spec_long}${_l_suffix}"
		_h_desc="$(gettext -- "${_spec_desc}")"
		_help_specs+=($'\t\t'"${_h_short}"$'\t'"${_h_long}"$'\t\t'"${_h_desc}")
	done
	
	# Do the actual flag parsing.
	local _l_arg_str
	local _l_mode=()
	if ! _l_arg_str="$(IFS=','; getopt -n "${0##*/}" -o "$_getopt_short" -l "${_getopt_long[*]}" -- "$@")"; then
		_l_mode=('error')
	fi
	eval "set -- $_l_arg_str"
	local _l_longname
	while true; do
		if [[ $1 == -? && $1 != '--' ]]; then
			set -- "--${_getopt_short2long["${1#'-'}"]}" "${@:2}"
		fi
		case "$1" in
			--)
				shift
				break
				;;
			--*)
				_l_longname=${1#'--'}
				if [[ ${_getopt_optarg["$_l_longname"]} == no ]]; then
					opt_visit:"$_l_longname"
					shift 1
				else
					opt_visit:"$_l_longname" "$2"
					shift 2
				fi
				;;
		esac
	done

	# Call the opt_positional() and opt_final:*() callbacks with
	# opt_mode set to a preliminary value.
	declare -g opt_mode
	opt_mode=${_l_mode[0]:-"$_a_mode_default"}
	if [[ $opt_mode != help && $opt_mode != version ]]; then
		opt_positional "$@"
		for _l_longname in "${!_getopt_optarg[@]}"; do
			opt_final:"$_l_longname"
		done
	fi

	# Set the opt_mode and opt_flaghelp outputs.
	# shellcheck disable=SC2034
	opt_mode=${_l_mode[0]:-"$_a_mode_default"}
	declare -g opt_flaghelp
	# shellcheck disable=SC2034
	opt_flaghelp=$(printf '%s\n' "${_help_specs[@]}" | column --table --keep-empty-lines --separator=$'\t' --output-separator=' ' | sed 's/\s*$//')
}

# Usage: argparse:setmode MODE
#
# Use argparse:setmode in your opt_* callback functions to set the
# returned opt_mode.  Don't use this for the 'error' mode, use
# argparse:error for that.
argparse:setmode() {
	_l_mode+=("$1")
}

# Usage: argparse:error PRINTF_STRING [ARGS...]
#
# Use argparse:error in your opt_* callback functions to signal that
# the end-user passed in an invalid argument.
argparse:error() {
	_l_mode=('error')
	error 0 "$@"
}