fix #1: add_link without rem_link calls must be idempotent

dubp-wot/src/data/mod.rs

@@ -92,6 +92,8 @@ pub enum NewLinkResult {
     Ok(usize),
     /// All available certifications has been used.
     AllCertificationsUsed(usize),
+    /// Already existing certification (maybe a replay).
+    AlreadyExistingCertification(),
     /// Unknown source.
     UnknownSource(),
     /// Unknown target.

dubp-wot/src/data/rusty.rs

@@ -138,6 +138,8 @@ impl WebOfTrust for RustyWebOfTrust {
             NewLinkResult::UnknownTarget()
         } else if self.nodes[source.0].issued_count >= self.max_links {
             NewLinkResult::AllCertificationsUsed(self.nodes[target.0].links_source.len())
+        } else if self.nodes[target.0].links_source.contains(&source) {
+            NewLinkResult::AlreadyExistingCertification()
         } else {
             self.nodes[source.0].issued_count += 1;
             self.nodes[target.0].links_source.insert(source);

dubp-wot/src/lib.rs

@@ -197,6 +197,16 @@ mod tests {
         // should be able to add some links, cert count is returned
         assert_eq!(wot.add_link(WotId(2), WotId(0)), NewLinkResult::Ok(1));
         assert_eq!(wot.add_link(WotId(4), WotId(0)), NewLinkResult::Ok(2));
+        // Check that certification replay is handled
+        assert_eq!(
+            wot.add_link(WotId(4), WotId(0)),
+            NewLinkResult::AlreadyExistingCertification()
+        );
+        // Check that certification re-replay is handled
+        assert_eq!(
+            wot.add_link(WotId(4), WotId(0)),
+            NewLinkResult::AlreadyExistingCertification()
+        );
         assert_eq!(wot.add_link(WotId(5), WotId(0)), NewLinkResult::Ok(3));
 
         // should exist new links