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

@@ -85,24 +85,46 @@ where
         });
 
     // Have we already published a result for this period?
-    // The block author is guaranteed to be in the owner_keys.
     if let Some(results) = published_results {
-        if owner_keys
-            .iter()
-            .map(|&key| sp_runtime::AccountId32::new(key.0))
-            .any(|key| results.evaluators.contains(&key))
-        {
+        // 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()?,
+                    ))
+                } else {
+                    None
+                }
+            })
+            .find(|(key, _data)| owner_keys.contains(key))
+        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));
         }
     }
 
-    // Read evaluation result from file, if it exists
+    // Read evaluation result from file, if it exists, then remove it
     log::debug!(
         "🧙 [distance oracle] Reading evaluation result from file {:?}",
         distance_dir.clone().join(pool_index.to_string())
     );
-    let evaluation_result = match std::fs::read(distance_dir.join(pool_index.to_string())) {
+    let evaluation_result_file_path = distance_dir.join(pool_index.to_string());
+    let evaluation_result = match std::fs::read(&evaluation_result_file_path) {
         Ok(data) => data,
         Err(e) => {
             match e.kind() {
@@ -118,6 +140,9 @@ where
             return Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(None));
         }
     };
+    std::fs::remove_file(&evaluation_result_file_path).unwrap_or_else(move |e| {
+        log::warn!("🧙 [distance oracle] Cannot remove old result file `{evaluation_result_file_path:?}`: {e:?}")
+    });
 
     log::info!("🧙 [distance oracle] Providing evaluation result");
     Ok(sp_distance::InherentDataProvider::<IdtyIndex>::new(Some(