feat(parser): add xml:lang tracking and license field support

crates/feedparser-rs-core/src/parser/atom.rs

@@ -136,6 +136,10 @@ fn parse_feed_element(
                             {
                                 feed.feed.link = Some(link.href.clone());
                             }
+                            if feed.feed.license.is_none() && link.rel.as_deref() == Some("license")
+                            {
+                                feed.feed.license = Some(link.href.clone());
+                            }
                             feed.feed
                                 .links
                                 .try_push_limited(link, limits.max_links_per_feed);
@@ -305,6 +309,9 @@ fn parse_entry(
                             if entry.link.is_none() && link.rel.as_deref() == Some("alternate") {
                                 entry.link = Some(link.href.clone());
                             }
+                            if entry.license.is_none() && link.rel.as_deref() == Some("license") {
+                                entry.license = Some(link.href.clone());
+                            }
                             entry
                                 .links
                                 .try_push_limited(link, limits.max_links_per_entry);
@@ -926,4 +933,45 @@ mod tests {
         assert_eq!(feed.feed.links.len(), 1);
         assert_eq!(feed.feed.tags.len(), 1);
     }
+
+    #[test]
+    fn test_parse_atom_license_feed() {
+        let xml = br#"<?xml version="1.0"?>
+        <feed xmlns="http://www.w3.org/2005/Atom">
+            <title>Test Feed</title>
+            <link rel="license" href="https://creativecommons.org/licenses/by/4.0/"/>
+            <link rel="alternate" href="https://example.com/"/>
+        </feed>"#;
+
+        let feed = parse_atom10(xml).unwrap();
+        assert_eq!(
+            feed.feed.license.as_deref(),
+            Some("https://creativecommons.org/licenses/by/4.0/")
+        );
+        assert_eq!(feed.feed.link.as_deref(), Some("https://example.com/"));
+    }
+
+    #[test]
+    fn test_parse_atom_license_entry() {
+        let xml = br#"<?xml version="1.0"?>
+        <feed xmlns="http://www.w3.org/2005/Atom">
+            <entry>
+                <title>Licensed Entry</title>
+                <id>urn:uuid:1</id>
+                <link rel="license" href="https://creativecommons.org/licenses/by-sa/3.0/"/>
+                <link rel="alternate" href="https://example.com/entry/1"/>
+            </entry>
+        </feed>"#;
+
+        let feed = parse_atom10(xml).unwrap();
+        assert_eq!(feed.entries.len(), 1);
+        assert_eq!(
+            feed.entries[0].license.as_deref(),
+            Some("https://creativecommons.org/licenses/by-sa/3.0/")
+        );
+        assert_eq!(
+            feed.entries[0].link.as_deref(),
+            Some("https://example.com/entry/1")
+        );
+    }
 }

crates/feedparser-rs-core/src/parser/common.rs

@@ -285,6 +285,47 @@ pub fn extract_xml_base(
         .map(|s| s.to_string())
 }
 
+/// Extract xml:lang attribute from element
+///
+/// Returns the language code if xml:lang or lang attribute exists.
+/// Respects `max_attribute_length` limit for `DoS` protection.
+///
+/// # Arguments
+///
+/// * `element` - The XML element to extract xml:lang from
+/// * `max_attr_length` - Maximum allowed attribute length (`DoS` protection)
+///
+/// # Returns
+///
+/// * `Some(String)` - The xml:lang value if found and within length limit
+/// * `None` - If attribute not found or exceeds length limit
+///
+/// # Examples
+///
+/// ```ignore
+/// use feedparser_rs::parser::common::extract_xml_lang;
+///
+/// let element = /* BytesStart from quick-xml */;
+/// if let Some(lang) = extract_xml_lang(&element, 1024) {
+///     println!("Language: {}", lang);
+/// }
+/// ```
+pub fn extract_xml_lang(
+    element: &quick_xml::events::BytesStart,
+    max_attr_length: usize,
+) -> Option<String> {
+    element
+        .attributes()
+        .flatten()
+        .find(|attr| {
+            let key = attr.key.as_ref();
+            key == b"xml:lang" || key == b"lang"
+        })
+        .filter(|attr| attr.value.len() <= max_attr_length)
+        .and_then(|attr| attr.unescape_value().ok())
+        .map(|s| s.to_string())
+}
+
 /// Read text content from current XML element (handles text and CDATA)
 pub fn read_text(
     reader: &mut Reader<&[u8]>,