#!/bin/sh
set -eu

usage() {
	echo 'Usage: feed FILENAME'
}

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


absolute() {
	printf 'https://domain-here.com/%s' "$(cat -)"
}

feed_article_title=''
site_name=' '
lang=en
now="$(date -uIs)"
url_absolute="$(printf '%s' "${FILENAME#src/}" | absolute)"
site_name_html="$(htmlesc "${site_name:?}")"
collection=article
collection_url_absolute="$(printf '%s' ${lang:?}/ | absolute)"
feed_title_html="$(eval "echo \"\$feed_${collection}_title\"" | htmlesc)"
export now url_absolute site_name_html collection_url_absolute feed_title_html

DIR="$(dirname "$FILENAME")"

author=
email=
cat <<EOF
<feed
    xmlns="http://www.w3.org/2005/Atom"
    xmlns:content="http://purl.org/rss/1.0/modules/content/"
    xml:lang="$lang">
  <link href="$url_absolute" rel="self" type="application/atom+xml" />
  <link href="$collection_url_absolute" rel="alternate" type="text/html" hreflang="$lang" />
  <title>$site_name_html</title>
  <subtitle>$feed_title_html</subtitle>
  <id>$url_absolute</id>
  <updated>$now</updated>

  <author>
    <name>$author</name>
    <email>$email</email>
  </author>
EOF
find "$@" |
	xargs cat |
	sort -nr |
	xargs cat
printf '</feed>\n'