#!/bin/sh
set -eu
set -o pipefail

usage() {
	cat <<-'EOF'
	Usage:
	  rfc [-w FORMAT] RFC_NUMBER
	  rfc -h
EOF
}

help() {
	cat <<-'EOF'

	Options:
	  -w FORMAT     Choose between text (txt, the default) and
	                JSON (json)
	  -h, --help    show this message
EOF
}

for flag in "$@"; do
	case "$flag" in
		--)
			break
			;;
		--help)
			usage
			help
			exit
			;;
		*)
			;;
	esac
done

FORMAT='txt'
while getopts 'w:h' flag; do
	case "$flag" in
		w)
			case "$OPTARG" in
				json|txt)
					FORMAT="$OPTARG"
					;;
				*)
					printf 'Bad FORMAT options: %s\n' \
						"$OPTARG" >&2
					exit 2
					;;
			esac
			;;
		h)
			usage
			help
			exit
			;;
		*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))


if [ -z "${1:-}" ]; then
	echo 'Missing argument RFC_NUMBER' >&2
	usage >&2
	exit 2
fi

if [ ! -e "$HOME/.local/share/doc/rfc/rfc$1.$FORMAT" ]; then
	printf 'Given RFC_NUMBER "%s" does not exist\n' "$1" >&2
	exit 2
fi

view() {
	if [ -t 1 ]; then
		$PAGER
	else
		cat -
	fi
}

case "$FORMAT" in
	txt)
		cat "$HOME/.local/share/doc/rfc/rfc$1.txt"   | view
		;;
	json)
		jq < "$HOME/.local/share/doc/rfc/rfc$1.json" | view
		;;
	*)
		printf 'Unreachable: unsupported FORMAT "%s"\n' \
			"$FORMAT" >&2
		exit 2
		;;
esac