#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  feed FILENAME
		  feed -h
	EOF
}

help() {
	cat <<-'EOF'


		Options:
		  -h, --help    show this message

		  FILENAME      the target feed to be generated


		Generate FILENAME as an Atom feed.  The collection type and
		language are inferred by the name of FILENAME.


		Examples:

		  Generate a feed for TILs:

		    $ feed src/en/til/feed.xml
	EOF
}


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

while getopts 'h' flag; do
	case "$flag" in
		h)
			usage
			help
			exit
			;;
		*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))

. src/lib.sh

FILENAME="${1:-}"
eval "$(assert_arg "$FILENAME" 'FILENAME')"


. src/lib/base.conf
# shellcheck source=/dev/null
. src/lib/base."$(lang-for "$FILENAME")".conf


now="$(date -uIs)"
url_absolute="$(url-for "${FILENAME#"$CONTENT_PREFIX"/}" | absolute)"
site_name_html="$(htmlesc "${site_name:?}")"
collection="$(collection-for "$FILENAME")"
coll_path="$(coll2path "${lang:?}" "$collection")"
collection_url_absolute="$(url-for "${lang:?}/$coll_path" | absolute)"
feed_title_html="$(eval "echo \"\$feed_${collection}_title\"" | htmlesc)"
export now url_absolute site_name_html collection_url_absolute feed_title_html

DIR="$(dirname "$FILENAME")"
mkdir -p "$DIR"
{
	envsubst < src/lib/feed.xml
	find "$DIR"/*.sortdata 2>/dev/null |
		sort -nr |
		xargs cat |
		sed 's|\.md$|.xmlentry|' |
		xargs cat
	printf '</feed>\n'
} > "$FILENAME"

printf '' > "$DIR"/index.extrafeeds
while read -r category; do
	url_absolute="$(url-for "${DIR#"$CONTENT_PREFIX"/}/feed.$category.xml" | absolute)"
	collection_url_absolute="$(url-for "${DIR#"$CONTENT_PREFIX"/}/${by_category_url_name:?}#$category" | absolute)"
	feed_title_html="$(eval "echo \"\$index_category_${collection}_title\"" | htmlesc)"
	export url_absolute collection_url_absolute feed_title_html

	{
		envsubst < src/lib/feed.xml
		< "$DIR/$category.category" \
			sed 's|\.md$|.xmlentry|' |
			xargs cat
		printf '</feed>\n'
	} > "$DIR/feed.$category.xml"
	echo "$DIR/feed.$category.xml" >> "$DIR"/index.extrafeeds
done < "$DIR"/index.categories