1 files changed, 63 insertions, 0 deletions
diff --git a/third_party/rust/relevancy/src/url_hash.rs b/third_party/rust/relevancy/src/url_hash.rs
new file mode 100644
index 0000000000..d31a45d06b
--- /dev/null
+++ b/third_party/rust/relevancy/src/url_hash.rs
@@ -0,0 +1,63 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use md5::{Digest, Md5};
+use url::{Host, Url};
+
+pub type UrlHash = [u8; 16];
+
+/// Given a URL, extract the part of it that we want to use to identify it.
+///
+/// We currently use the final 3 components of the URL domain.
+///
+/// TODO: decide if this should be 3 or 3 components.
+pub fn url_hash_source(url: &str) -> Option<String> {
+    let url = Url::parse(url).ok()?;
+    let domain = match url.host() {
+        Some(Host::Domain(d)) => d,
+        _ => return None,
+    };
+    // This will store indexes of `.` chars as we search backwards.
+    let mut pos = domain.len();
+    for _ in 0..3 {
+        match domain[0..pos].rfind('.') {
+            Some(p) => pos = p,
+            // The domain has less than 3 dots, return it all
+            None => return Some(domain.to_owned()),
+        }
+    }
+    Some(domain[pos + 1..].to_owned())
+}
+
+pub fn hash_url(url: &str) -> Option<UrlHash> {
+    url_hash_source(url).map(|hash_source| {
+        let mut hasher = Md5::new();
+        hasher.update(hash_source);
+        let result = hasher.finalize();
+        result.into()
+    })
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_url_hash_source() {
+        let table = [
+            ("http://example.com/some-path", Some("example.com")),
+            ("http://foo.example.com/some-path", Some("foo.example.com")),
+            (
+                "http://foo.bar.baz.example.com/some-path",
+                Some("baz.example.com"),
+            ),
+            ("http://foo.com.uk/some-path", Some("foo.com.uk")),
+            ("http://amazon.com/some-path", Some("amazon.com")),
+            ("http://192.168.0.1/some-path", None),
+        ];
+        for (url, expected) in table {
+            assert_eq!(url_hash_source(url).as_deref(), expected)
+        }
+    }
+}