ipx-feed's lib.rs splits into leaf modules (#356)

lib.rs held 2,000 lines: fetching, parsing, OPML, Patreon, discovery,
artwork, categories, Jev and redaction, and their tests. It is now the
module list and the re-exports, so ipx and the directory call
feed::fetch, feed::parse and the rest as before:

  fetch.rs      fetch and its limits    parse.rs     RSS and Atom
  outlines.rs   OPML (not opml.rs, which would shadow the opml crate)
  patreon.rs    a creator's shows       discover.rs  finding a feed
  wordpress.rs  WordPress.com's API     failure.rs   failures in words
  privacy.rs    redact, looks_private   artwork.rs   https art, icons
  category.rs   Apple's categories      jev.rs       Jev's category

Moved verbatim, private items pub(crate) where a sibling calls them,
calls across modules module::function. Every definition and doc comment
line of the old lib.rs is in exactly one of the new files; each test
went with what it tests, and all 40 run.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/feed/src/privacy.rs

@@ -0,0 +1,105 @@
+//! Addresses that carry someone's access: taking it out of what is logged, and keeping such feeds private.
+
+/// Conditional GET, following redirects itself: `client` must follow none (`feed_client`), so
+/// each hop is seen. The second value is where the feed now is when every hop said so for good
+/// (301 or 308): a publisher that moved its feed, which the catalogue should follow rather
+/// than be redirected on every read. A temporary redirect (302, 307) moves nothing.
+/// `system-proxy` reads http_proxy/https_proxy.
+/// `auth` is a username and password, sent only to the feed's own host.
+/// An address as a trace may keep it: without its query or user and password, where a private
+/// feed carries its credential (Patreon's `?auth=`), which Tempo kept for anyone reading it (#225).
+/// shortcut: a token in the path (`/feed/<token>.xml`) stays; strip paths too if a feed does that.
+#[must_use]
+pub fn redact(url: &str) -> String {
+    match url::Url::parse(url) {
+        Ok(mut u) => {
+            u.set_query(None);
+            u.set_fragment(None);
+            let _ = u.set_username("");
+            let _ = u.set_password(None);
+            u.to_string()
+        }
+        // Not an address ipx could fetch; keep what comes before anything that could be a query.
+        Err(_) => url.split(['?', '#', '@']).next().unwrap_or_default().to_owned(),
+    }
+}
+
+/// Text with each address in it redacted, for what is logged and sent to every open page: an
+/// error from reqwest names the whole address it fetched, a private feed's key with it (#238).
+#[must_use]
+pub fn redact_text(text: &str) -> String {
+    let mut out = String::with_capacity(text.len());
+    let mut rest = text;
+    while let Some(i) = rest.find("http://").into_iter().chain(rest.find("https://")).min() {
+        out.push_str(&rest[..i]);
+        let end = rest[i..].find(|c: char| c.is_whitespace() || "()<>\"'".contains(c)).map_or(rest.len(), |n| i + n);
+        out.push_str(&redact(&rest[i..end]));
+        rest = &rest[end..];
+    }
+    out.push_str(rest);
+    out
+}
+
+/// An address that carries a subscriber's own access: a paid-feed host, credentials in the URL,
+/// or a key in the query. ipx leaves such a feed out of anything others see, and the directory
+/// refuses one sent to it (#202).
+///
+/// ponytail: a heuristic. A key hidden in the path of a host not in `PAID_HOSTS` gets
+/// through; a per-feed private flag is the upgrade (#205).
+#[must_use]
+pub fn url_looks_private(feed_url: &str) -> bool {
+    let Ok(u) = url::Url::parse(feed_url) else { return true };
+    // Paid-feed services put the subscriber's key in the path as often as in the query, and a
+    // long path segment alone proves nothing (acast's public show ids look the same). So a
+    // feed from one of them is private whatever its URL looks like. Supercast is why this
+    // exists: `feeds.supercast.com/feeds/<key>` reached the directory before it did.
+    let host = u.host_str().unwrap_or("");
+    PAID_HOSTS.iter().any(|h| host == *h || host.ends_with(&format!(".{h}")))
+        || !u.username().is_empty()
+        || u.password().is_some()
+        || u.query_pairs().any(|(k, _)| {
+            let k = k.to_ascii_lowercase();
+            ["auth", "token", "key", "secret", "pass", "sig", "session", "user", "uid"].iter().any(|w| k.contains(w))
+        })
+}
+
+/// Services whose feeds are always one subscriber's own.
+pub(crate) const PAID_HOSTS: &[&str] =
+    &["patreon.com", "supercast.com", "supportingcast.fm", "glow.fm", "memberful.com"];
+
+#[cfg(test)]
+mod tests {
+
+    #[test]
+    fn redact_drops_what_carries_a_credential() {
+        assert_eq!(super::redact("https://www.patreon.com/rss/x?auth=SECRET&show=1"), "https://www.patreon.com/rss/x");
+        assert_eq!(super::redact("https://me:pw@example.com/feed.xml#top"), "https://example.com/feed.xml");
+        assert_eq!(super::redact("https://example.com/feed.xml"), "https://example.com/feed.xml");
+        assert_eq!(super::redact("not a url?token=SECRET"), "not a url");
+        // As reqwest words a failure, and with two addresses and none.
+        assert_eq!(
+            super::redact_text(
+                "connecting: error sending request for url (https://www.patreon.com/rss/x?auth=SECRET&show=1): operation timed out"
+            ),
+            "connecting: error sending request for url (https://www.patreon.com/rss/x): operation timed out"
+        );
+        assert_eq!(super::redact_text("from http://a/f?k=1 to https://u:p@b/g"), "from http://a/f to https://b/g");
+        assert_eq!(super::redact_text("HTTP 404 Not Found"), "HTTP 404 Not Found");
+    }
+
+    #[test]
+    fn an_address_carrying_someones_access_looks_private() {
+        let private = super::url_looks_private;
+        assert!(!private("https://feeds.twit.tv/twit.xml"));
+        // Patreon's shape: the key is a query parameter.
+        assert!(private("https://www.patreon.com/rss/x?auth=abc123&show=2073588"));
+        assert!(private("https://example.com/rss?api_key=abc"));
+        // Paid-feed services put the key in the path; the host gives them away.
+        assert!(private("https://feeds.supercast.com/feeds/abcdefghijklmnopqrstuvwx"));
+        assert!(private("https://someshow.supportingcast.fm/content/abc123.rss"));
+        // A long path segment alone is not a key: acast's public show ids look the same.
+        assert!(!private("https://feeds.acast.com/public/shows/0123456789abcdef01234567"));
+        assert!(private("https://ray:hunter2@example.com/rss"));
+        assert!(private("not a url"), "unparseable is not safe to list");
+    }
+}