added atom feed

1 files changed, 57 insertions, 6 deletions

diff --git a/feed.typ b/feed.typ
index 75639e0..3a5fd21 100644
--- a/feed.typ
+++ b/feed.typ
@@ -1,5 +1,6 @@
-// RSS 2.0 feed for the blog posts, emitted as feed.xml by main.typ.
-// Items are built from the metadata in site-info.pages (newest first).
+// RSS 2.0 and Atom feeds for the blog posts, emitted as feed.xml and
+// atom.xml by main.typ. Entries are built from the metadata in
+// site-info.pages (newest first).
 
 #import "/global/common.typ": baseurl
 
@@ -13,16 +14,25 @@
     )
 }
 
-#let feed-xml(site-info) = {
+// ISO date ("2026-07-28") to RFC 3339 ("2026-07-28T00:00:00Z").
+#let rfc3339(iso) = iso + "T00:00:00Z"
+
+#let _entries(site-info, item-fn) = {
     let pages = site-info.pages
     let ids = pages.keys().filter(k => k.starts-with("post/"))
 
-    let items = ()
+    let entries = ()
     for id in ids {
         let p = pages.at(id)
         let title = if "long-title" in p { p.long-title } else { p.title }
         let url = baseurl + "/" + id + ".html"
+        entries.push(item-fn(title, url, p))
+    }
+    entries
+}
 
+#let feed-xml(site-info) = {
+    let items = _entries(site-info, (title, url, p) => {
         let lines = (
             "  <item>",
             "    <title>" + xml-escape(title) + "</title>",
@@ -36,8 +46,8 @@
             lines.push("    <description>" + xml-escape(p.description) + "</description>")
         }
         lines.push("  </item>")
-        items.push(lines.join("\n"))
-    }
+        lines.join("\n")
+    })
 
     (
         "<?xml version=\"1.0\" encoding=\"UTF-8\"?>",
@@ -52,3 +62,44 @@
         "",
     ).join("\n")
 }
+
+// Atom (RFC 4287) feed, emitted as atom.xml by main.typ.
+#let atom-xml(site-info) = {
+    let entries = _entries(site-info, (title, url, p) => {
+        let lines = (
+            "  <entry>",
+            "    <title>" + xml-escape(title) + "</title>",
+            "    <link href=\"" + url + "\"/>",
+            "    <id>" + url + "</id>",
+        )
+        if "date" in p {
+            lines.push("    <updated>" + rfc3339(p.date) + "</updated>")
+        }
+        if "description" in p {
+            lines.push("    <summary>" + xml-escape(p.description) + "</summary>")
+        }
+        lines.push("  </entry>")
+        lines.join("\n")
+    })
+
+    // newest post first, so its date is the feed's last-update time
+    let updated = rfc3339(site-info.pages.at(
+        site-info.pages.keys().filter(k => k.starts-with("post/")).first()
+    ).date)
+
+    (
+        "<?xml version=\"1.0\" encoding=\"UTF-8\"?>",
+        "<feed xmlns=\"http://www.w3.org/2005/Atom\">",
+        "  <title>" + xml-escape(site-info.title) + "</title>",
+        "  <link href=\"" + baseurl + "/\"/>",
+        "  <link rel=\"self\" href=\"" + baseurl + "/atom.xml\"/>",
+        "  <id>" + baseurl + "/</id>",
+        "  <updated>" + updated + "</updated>",
+        "  <author>",
+        "    <name>Kumar</name>",
+        "  </author>",
+        entries.join("\n"),
+        "</feed>",
+        "",
+    ).join("\n")
+}