1 files changed, 65 insertions, 0 deletions
diff --git a/src/frontend/rss_conversion.rs b/src/frontend/rss_conversion.rs
new file mode 100644
index 0000000..3448bf0
--- /dev/null
+++ b/src/frontend/rss_conversion.rs
@@ -0,0 +1,65 @@
+//! Conversion of MF2-JSON posts into RSS items.
+
+/// TTL of the RSS feeds generated by Kittybox. Compliant RSS
+/// consumers must avoid refetching the feed before its TTL expires.
+const RSS_TTL: std::time::Duration = std::time::Duration::from_secs(600);
+
+/// Convert a single MF2 post to an RSS item.
+///
+/// Posts must have a UID.
+pub fn post_to_rss(mut post: serde_json::Value) -> Option<rss::Item> {
+    let mut builder = rss::ItemBuilder::default();
+
+    let date = match post["properties"]["published"][0].take() {
+        serde_json::Value::String(d) => chrono::DateTime::<chrono::FixedOffset>::parse_from_rfc3339(&d).ok(),
+        _ => None
+    };
+    if let Some(date) = date {
+        builder.pub_date(date.to_rfc2822());
+    }
+    if let serde_json::Value::String(title) = post["properties"]["title"][0].take() {
+        builder.title(title);
+    }
+    if let serde_json::Value::String(summary) = post["properties"]["summary"][0].take() {
+        builder.description(summary);
+    }
+    // Do not emit posts that do not have GUIDs.
+    match post["properties"]["uid"][0].take() {
+        serde_json::Value::String(uid) => {
+            builder.guid(rss::GuidBuilder::default().value(uid).permalink(true).build());
+        },
+        _ => { return None; },
+    }
+    // TODO: enclosures for u-photo, u-video, u-audio
+    // requires knowing MIME type for the included media file
+    // can enrich from media endpoint
+
+    let item = builder.build();
+    if item.title.is_some() || item.description.is_some() {
+        Some(item)
+    } else {
+        None
+    }
+}
+
+/// Convert an entire MF2 h-feed into an RSS channel.
+/// Fairly opinionated. Provided MF2-JSON object must be a feed.
+pub fn feed_to_rss(mut post: serde_json::Value) -> rss::Channel {
+    let children: Vec<serde_json::Value> = match post["children"].take() {
+        serde_json::Value::Array(children) => children,
+        _ => Vec::default(),
+    };
+    rss::ChannelBuilder::default()
+        .title(post["properties"]["name"][0].as_str().unwrap())
+        .link(post["properties"]["uid"][0].as_str().unwrap())
+        .generator(Some(concat!(
+            env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION")
+        ).to_string()))
+        .ttl((RSS_TTL.as_secs() / 60).to_string())
+        .items(children
+            .into_iter()
+            .filter_map(post_to_rss)
+            .collect::<Vec<rss::Item>>()
+        )
+        .build()
+}