#!/bin/sh

MD_URL="http://169.254.169.254/latest"
OIFS="$IFS"
TIMEOUT=10
CR="
"

Usage() {
	cat <<EOF
Usage: ${0##*/} [options]
  -u | --url URL    use URL (default: $MD_URL)
  -h | --help       display usage

       --user-data  dump user data
       --<item>     dump 'item' from the metadata service

  Special items:
   --block-device-mappings   dump the block device mappings, space delimited
   --public-keys             dump the public keys

  with no options given, metadata service will be crawled and
  dumped.  This will not include user-data.
EOF
}

error() { echo "$@" 1>&2; }
fail() { [ $# -eq 0 ] || error "$@"; exit 1; }

get_field_list() {
	local under="$1" x="" out="" found=""
	mdget "$under"
	out="$_RET"
	for x in $out; do
		case "$x" in
			*/) get_field_list "${under:+${under}/}${x%/}"
				found="${found} $_RET";;
			*) found="${found} ${under:+$under/}$x";;
		esac
	done
	_RET="${found# }"
}

caturl() {
	curl --fail --silent --max-time "${TIMEOUT}" "$1"
}

mdget() {
	local u="$1" t1="" t2="" out=""
	case "$u" in
		user-data) :;;
		public-keys|public-keys/)
			out=$(caturl "$MD_URL/meta-data/$u") ||
				fail "failed to get $MD_URL/meta-data/$u";
			# output of public-keys is lines of 'X=keyname'
			# so we return a carriage return list of the tokens before =
			_RET=""
			IFS="$CR"
			for t1 in $out; do
				t1="${t1%%=*}"
				_RET="${_RET:+${_RET}${CR}}${t1%/}"
			done
			IFS="$OIFS"
			return
			;;
		public-keys/*)
			t1=${u#public-keys/[0-9]} 
			# t2 will now have 'public-keys/[0-9]'
			t2=${u%${t1}}
			# if t1 has a / (ie, u=public-keys/0=brickies/openssh-keys)
			# then set t1 to just "/openssh-keys". if not, set it to ""
			[ "${t1#*/}" = "${t1}" ] && t1="" || t1="/${t1#*/}"
			u="meta-data/${t2}${t1}"
			;;
		*) u="meta-data/$u";;
	esac
	_RET=$(caturl "$MD_URL/$u") ||
		fail "failed to get ${MD_URL}/$u"
}
special() {
	local out="" x="" t="" ret=""
	case "$1" in
		availability-zone)
			mdget "placement/availability-zone";;
		public-keys)
			mdget public-keys
			out="$_RET"
			IFS="$CR"
			for x in ${out}; do
				IFS="$OIFS" mdget \
					"public-keys/${x}/openssh-key" &&
				ret="${ret:+${ret}${CR}}${_RET}"
			done
			IFS="$OIFS"
			_RET="$ret"
			;;
		block-device-mappings)
			mdget block-device-mapping
			out="$_RET"
			for x in ${out}; do
				mdget "block-device-mapping/$x"
				ret="${ret:+${ret} }${x}=$_RET";
			done
			_RET="$ret"
	esac
}

fields=""
while [ $# -ne 0 ]; do
	cur=${1}; next=${2};
	case "$cur" in
		-h|--help) Usage ; exit 0;;
		--url=*) MD_URL=${cur#*=}; MD_URL=${MD_URL%/};;
		--url|-u) MD_URL="${next%/}"; shift;;
		--availability-zone|--public-keys|--block-device-mappings)
			fields="$fields special_${cur#--}";;
		--*) fields="$fields ${cur#--}";;
	esac
	shift;
done

fields="${fields# }"
if [ -z "$fields" ]; then
	get_field_list ""
	fields="${_RET}"
	prefix=true
else
	prefix=false
fi

for f in $fields; do
	case "$f" in
		special_*) special "${f#special_}";;
		*) mdget "$f";;
	esac
	ret=$?
	[ $ret -eq 0 ] || fail "failed to get $f"
	if $prefix; then
		if [ "${_RET#*${CR}}" != "${_RET}" ]; then
			_RET=$(echo "$_RET" | sed 's,^,|,g')
			_RET="${_RET#|}"
		fi
		echo "${f#special_}: $_RET"
	else
		echo "$_RET"
	fi
done

exit 0

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