#!/bin/sh

# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the Free
# Software Foundation, either version 3 of the License, or (at your option) any
# later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
# details.

readonly ROOTDIR="$(CDPATH="" cd -- "$(dirname -- "$0")/.." && pwd -P)"

main()
{
	# Handle opts
	while getopts ":h" opt
	do
		case "$opt" in
			h) usage && exit 0 ;;
			*)
				printf "Invalid option passed: %s\n" "$OPTARG" >&2
				;;
		esac
	done

	shift $(( OPTIND - 1 ))

	# Make a list of all unique tags
	tags="$(mktemp)"
	awk '/^tags:/ { for (i=2; i<=NF; i++) print $i }' "$ROOTDIR/src/_posts/"* \
		| sort \
		| uniq \
		> "$tags"

	# Create a feed for each tag
	mkdir -p -- "$ROOTDIR/src/feed"
	mkdir -p -- "$ROOTDIR/src/atom"

	while read -r tag
	do
		lc_tag="$(printf "%s" "$tag" | tr "[:upper:]" "[:lower:]")"

		echo "Creating RSS 2.0 feed for $lc_tag"
		TAG="$tag" envsubst < "$ROOTDIR/share/feed-rss2.xml" > "$ROOTDIR/src/feed/$lc_tag.xml"

		echo "Creating Atom feed for $lc_tag"
		TAG="$tag" envsubst < "$ROOTDIR/share/feed-atom.xml" > "$ROOTDIR/src/atom/$lc_tag.xml"

		unset lc_tag
	done < "$tags"

	# Clean up
	rm -f -- "$tags"
}

usage()
{
	cat <<EOF
Usage:
	${0##*/} -h

Generate all the seperate feeds for each tag used in posts.

Options:
	-h  Show this help text and exit.
EOF
}

main "$@"