Fix Atom feed (#764)

* Percent-encode URI segments in ap_url

* Fix invalid Atoms

* Remove redundant clone according to cargo clippy

* Revert "Percent-encode URI segments in ap_url"

This reverts commit 8253aa79bd.
ActivityPub(JSON-LD) accepts URI.
See https://github.com/Plume-org/Plume/pull/764#issuecomment-623105734

* Use absolute IRI for IDs in Atom

* Reuse formatted string

* Use parent element's creation date for Atom updated if there's no post

* Remove uncecessary UTC conversion

* Extract routes::build_atom_feed function

src/routes/mod.rs

@@ -1,6 +1,9 @@
 #![warn(clippy::too_many_arguments)]
 use crate::template_utils::Ructe;
-use atom_syndication::{ContentBuilder, Entry, EntryBuilder, LinkBuilder, Person, PersonBuilder};
+use atom_syndication::{
+    ContentBuilder, Entry, EntryBuilder, Feed, FeedBuilder, LinkBuilder, Person, PersonBuilder,
+};
+use chrono::naive::NaiveDateTime;
 use plume_models::{posts::Post, Connection, CONFIG, ITEMS_PER_PAGE};
 use rocket::{
     http::{
@@ -115,13 +118,46 @@ pub struct RemoteForm {
     pub remote: String,
 }
 
-pub fn post_to_atom(post: Post, conn: &Connection) -> Entry {
+pub fn build_atom_feed(
+    entries: Vec<Post>,
+    uri: &str,
+    title: &str,
+    default_updated: &NaiveDateTime,
+    conn: &Connection,
+) -> Feed {
+    let updated = if entries.is_empty() {
+        default_updated
+    } else {
+        &entries[0].creation_date
+    };
+
+    FeedBuilder::default()
+        .title(title)
+        .id(uri)
+        .updated(updated.format("%Y-%m-%d %H:%M:%SZ").to_string())
+        .entries(
+            entries
+                .into_iter()
+                .map(|p| post_to_atom(p, conn))
+                .collect::<Vec<Entry>>(),
+        )
+        .links(vec![LinkBuilder::default()
+            .href(uri)
+            .rel("self")
+            .mime_type("application/atom+xml".to_string())
+            .build()
+            .expect("Atom feed: link error")])
+        .build()
+        .expect("user::atom_feed: Error building Atom feed")
+}
+
+fn post_to_atom(post: Post, conn: &Connection) -> Entry {
+    let formatted_creation_date = post.creation_date.format("%Y-%m-%dT%H:%M:%SZ").to_string();
     EntryBuilder::default()
         .title(format!("<![CDATA[{}]]>", post.title))
         .content(
             ContentBuilder::default()
                 .value(format!("<![CDATA[{}]]>", *post.content.get()))
-                .src(post.ap_url.clone())
                 .content_type("html".to_string())
                 .build()
                 .expect("Atom feed: content error"),
@@ -141,8 +177,9 @@ pub fn post_to_atom(post: Post, conn: &Connection) -> Entry {
         )
         // Using RFC 4287 format, see https://tools.ietf.org/html/rfc4287#section-3.3 for dates
         // eg: 2003-12-13T18:30:02Z (Z is here because there is no timezone support with the NaiveDateTime crate)
-        .published(post.creation_date.format("%Y-%m-%dT%H:%M:%SZ").to_string())
-        .id(post.id.to_string())
+        .published(formatted_creation_date.clone())
+        .updated(formatted_creation_date)
+        .id(post.ap_url.clone())
         .links(vec![LinkBuilder::default()
             .href(post.ap_url)
             .build()