add a tagging system to the website

src/feed.rs

@@ -0,0 +1,59 @@
+use chrono::{DateTime, Utc};
+
+use crate::sources::Sources;
+
+#[derive(Debug, Clone)]
+pub struct FeedEntry {
+    pub id: String,
+    pub updated: Option<DateTime<Utc>>,
+    pub url: String,
+    pub title: String,
+    pub tags: Vec<String>,
+}
+
+pub fn generate(sources: &Sources, tag_name: &str) -> Option<Vec<FeedEntry>> {
+    let mut entries = vec![];
+
+    let tag = sources.treehouse.tags.get(tag_name)?;
+    for file_id in &tag.files {
+        if let Some(roots) = sources.treehouse.roots.get(file_id)
+            && let Some(id) = roots.attributes.id.clone()
+        {
+            entries.push(FeedEntry {
+                id,
+                updated: roots.attributes.timestamps.map(|ts| ts.updated),
+                url: format!(
+                    "{}/{}.tree",
+                    sources.config.site,
+                    sources.treehouse.tree_path(*file_id).unwrap()
+                ),
+                title: roots.attributes.title.clone(),
+                tags: roots.attributes.tags.clone(),
+            });
+        } else if let Some(doc) = sources.treehouse.docs.get(file_id)
+            && !doc.attributes.id.is_empty()
+        {
+            entries.push(FeedEntry {
+                id: doc.attributes.id.clone(),
+                updated: doc.attributes.updated,
+                url: format!(
+                    "{}/{}",
+                    sources.config.site,
+                    sources.treehouse.path(*file_id).with_extension("")
+                ),
+                title: doc.attributes.title.clone(),
+                tags: doc.attributes.tags.clone(),
+            });
+        } else {
+            unreachable!(
+                "{file_id:?} registered in tag #{tag_name} is not actually in the treehouse"
+            );
+            // Well... either that, or unknown variant.
+        }
+    }
+
+    entries.sort_by_key(|entry| entry.updated);
+    entries.reverse();
+
+    Some(entries)
+}