feeder rework

src/licence.rs

@@ -0,0 +1,31 @@
+//! Licence-URL → SPDX-style identifier.
+//!
+//! Generic across upstreams: Internet Archive, Jamendo and Wikimedia Commons
+//! all publish a Creative Commons *URL*, while `METADATA_KEYS.md` requires an
+//! SPDX-style identifier — a consumer comparing licences should not be doing
+//! string surgery on `http://` vs `https://` and a trailing slash.
+
+/// `METADATA_KEYS.md` requires an SPDX-style identifier rather than a URL,
+/// because a consumer comparing licences should not be doing string surgery on
+/// `http://` vs `https://` and a trailing slash.
+pub fn licence_from_url(url: &str) -> Option<String> {
+    let u = url.trim().trim_end_matches('/').to_ascii_lowercase();
+    if u.is_empty() {
+        return None;
+    }
+    if u.contains("publicdomain/zero") {
+        return Some("CC0-1.0".to_string());
+    }
+    if u.contains("publicdomain/mark") {
+        return Some("PublicDomain".to_string());
+    }
+    // .../licenses/<variant>/<version>[/<jurisdiction>]
+    let rest = u.split("/licenses/").nth(1)?;
+    let mut parts = rest.split('/');
+    let variant = parts.next()?.to_ascii_uppercase();
+    let version = parts.next().unwrap_or("4.0");
+    if variant.is_empty() {
+        return None;
+    }
+    Some(format!("CC-{variant}-{version}"))
+}