#!/bin/sh
set -eu


usage() {
	cat <<-'EOF'
		Usage:
		  extract -t TYPE < STDIN
		  extract -h
	EOF
}

help() {
	cat <<-'EOF'

		Options:
		  -t TYPE       the type of extraction to perform ("content" or "env")
		  -h, --help    show this message


		Separate the content from the "frontmatter", and emit the
		selected one.


		Examples:

		  Get the content:

		    $ extract -t content < src/file.md > src/file.entry-content


		  Get the "frontmatter":

		    $ extract -t env < src/f.md > src/f.entry-env
	EOF
}


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

TYPE=''
while getopts 't:h' flag; do
	case "$flag" in
		t)
			TYPE="$OPTARG"
			;;
		h)
			usage
			help
			exit
			;;
		*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))


eval "$(assert-arg "$TYPE" '-t TYPE')"


case "$TYPE" in
	content)
		awk '
			separator >= 2
			/^---$/ { separator++ }
		'
		;;
	env)
		awk '
			/^---$/ {
				if (++separator > 1) {
					exit
				} else {
					next
				}
			}

			{ print }
		'
		;;
	*)
		printf 'Bad value for TYPE: "%s".\n\n' \
			"$TYPE" >&2
		usage >&2
		exit 2
		;;
esac