Fix distance evaluation client

• Fix owner key retrieval in distance client
  • I could not find how to decode the StorageMap cleanly so I used byte ranges with the help of this article. I'm not sure it can't break in the future.
• Fix modulo in evaluation result filename in distance oracle
• Fix evaluation result file deletion
  • If you want to name the files using pool indices instead of a strictly increasing sequence, you run into problems (this is the reason why it was not the case, btw). It should work now, but if the node can't publish (i.e. crash or network error for this block) after the file is deleted, the evaluation result is lost.

Fixes #261 (closed)

client/distance/src/lib.rs

@@ -87,34 +87,33 @@ where
     // Have we already published a result for this period?
     if let Some(results) = published_results {
         // Find the account associated with the BABE key that is in our owner keys.
-        let Some((_key, local_account)) = client
-            .storage_pairs(
-                parent,
-                Some(&StorageKey(
-                    frame_support::storage::storage_prefix(b"Session", b"KeyOwner").to_vec(),
-                )),
-                None,
-            )?
-            .filter_map(|(raw_key, raw_data)| {
-                if &raw_key.0[40..44] == b"babe" {
-                    Some((
-                        sp_core::sr25519::Public::from_raw(
-                            raw_key.0[45..45 + 32].try_into().unwrap(),
-                        ),
-                        AccountId32::decode(&mut &raw_data.0[..]).ok()?,
-                    ))
+        let mut local_account = None;
+        for key in owner_keys {
+            // Session::KeyOwner is StorageMap<_, Twox64Concat, (KeyTypeId, Vec<u8>), AccountId32, OptionQuery>
+            // Slices (variable length) and array (fixed length) are encoded differently, so the `.as_slice()` is needed
+            let item_key = (sp_runtime::KeyTypeId(*b"babe"), key.0.as_slice()).encode();
+            let mut storage_key =
+                frame_support::storage::storage_prefix(b"Session", b"KeyOwner").to_vec();
+            storage_key.extend_from_slice(&sp_core::twox_64(&item_key));
+            storage_key.extend_from_slice(&item_key);
+
+            if let Some(raw_data) = client.storage(parent, &StorageKey(storage_key))? {
+                if let Ok(key_owner) = AccountId32::decode(&mut &raw_data.0[..]) {
+                    local_account = Some(key_owner);
+                    break;
                 } else {
-                    None
+                    log::warn!("🧙 [distance oracle] Cannot decode key owner value");
                 }
-            })
-            .find(|(key, _data)| owner_keys.contains(key))
-        else {
+            }
+        }
+        if let Some(local_account) = local_account {
+            if results.evaluators.contains(&local_account) {
+                log::debug!("🧙 [distance oracle] Already published a result for this period");
+                return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(None));
+            }
+        } else {
             log::error!("🧙 [distance oracle] Cannot find our BABE owner key");
             return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(None));
-        };
-        if results.evaluators.contains(&local_account) {
-            log::debug!("🧙 [distance oracle] Already published a result for this period");
-            return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(None));
         }
     }