#!/usr/bin/env bash
#
# @(#) : display shell script usage
#
# @version 1.0.0
# @author  Furukawa, Atsushi <atsushifx@aglabo.com>
# @date    2023-12-27
# @license MIT
#
# @description <<
#
# what <file>
#  print shell script usage
#
# -d    print usage created by header
# -v    print version
# -h -? print this usage
#
#
###
#
# THIS CODE IS MADE AVAILABLE AS IS, WITHOUT WARRANTY OF ANY KIND.
# THE ENTIRE RISK OF THE USE OR THE RESULTS FROM THE USE OF THIS CODE REMAINS WITH THE USER.
#
#<<

### initialize
set -euC -o pipefail
readonly THISCMD="$0"

readonly SCRIPTDIR=$(
	cd "$(dirname "$0")"
	pwd
)
readonly WORKINGDIR="$(pwd)"
readonly LIBDIR="${SCRIPTDIR}/inc"

# cd "$SCRIPTDIR"

### linrary read

### Global Variables
# @global filenames from command line
INPUT_FILES=

# @global command flag (0:what/ 1:header)
FLAG_HEADER=0

## utility functionis

#
# _isBinary : check if filetype is text / binary
#
# @param filename
# @return text : file is text filea / binary : file is binary(ELF exe, ...)
#
#@desciription <<
#
##<<
_isBinary() {
	local _filetype
	_filetype=$(file "$1")
	if [[ "${_filetype}" =~ "text" ]]; then
		echo "text"
	else
		echo "binary"
	fi
}

### command functions

#
# what
#  print oneline usage created bt '@(#)' comment
what() {
	local _file
	local _cmd _ver _desc

	_file="$*"
	_cmd=$(basename "$_file")
	_ver=$(strings "$_file" | grep '@version' | head -1 | awk '{print $3}')
	_desc=$(strings "$_file" | grep '@(#)' | head -1 | sed -e 's/[^.]*#)[ :]*//')

	echo "${_cmd} ( v$_ver ) : ${_desc}"
	return 0
}

##
# header : print usage created by header comment
#
# @param nil
# @return usage message
#
# @desc<<
# print usage created by header commeny
# message begins @help, @usage, @desc(ription) and
# ends by null line or '<<'(for binary)
#
#<<
header() {
	local _file _type

	_file="$*"
	_type=$(_isBinary "$_file")

	if [[ "$_type" == "text" ]]; then
		cat "${_file}" \
		| sed -r 1,"/^#[@ ]*(usage|help|desc)/d" \
		|	sed -r '/^$/,${ d; }' \
		| sed -r 's/^[#< ]*//' \
		| cat -s
	else
		strings -w "${_file}" |
			sed -r '1,/^#[ ]*@(usage|help|desc)/d' |
			sed -r '/^$/,${ d; }' |
			sed -e 's/^[#< ]*//' |
			cat -s
	fi
}

### main block (call this script as command)]
if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then

	## main functions

	#
	# usage : print usage messages from this command
	#
	usage() {
		header "${THISCMD}"
		exit 1
	}

	#
	# print this command's version
	#
	version() {
		what "${THISCMD}"
		exit 0
	}

	#
	# parse_args : check option and file from commanf line
	#
	parse_args() {
		while getopts "dvh?" OPT; do
			case $OPT in
			d) FLAG_HEADER=1 ;;
			v) version ;;
			h | ?) usage ;;
			esac
		done
		shift $((OPTIND - 1))
		INPUT_FILES="$*"
	}

fi
### end OF main functions

### mai roution
main() {
	local _file

	for _file in "${@}"; do
		if [[ ! -f "${_file}" ]]; then
			_file=$(which "${_file}")
		fi
		if [[ $FLAG_HEADER -ne 1 ]]; then
			what "${_file}"
		else
			header "${_file}"
		fi
	done
}

if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then
	parse_args "$@"

	if [[ "${INPUT_FILES}" == "" ]]; then
		version
	else
		main "${INPUT_FILES}"
	fi
fi