chore(rln-relay): health check should account for window of roots (#2664

)

* test(rln-relay): health check should account for window of roots

* fix: some type-fu

* fix: widen the type vs narrowing

* fix: add extra parens

waku/waku_rln_relay/group_manager/on_chain/group_manager.nim

@@ -586,7 +586,7 @@ proc getNewBlockCallback(g: OnchainGroupManager): proc =
     g.retryWrapper(handleBlockRes, "Failed to handle new block"):
       await g.getAndHandleEvents(fromBlock, latestBlock)
 
-    # cannot use isOkOr here because results in a compile-time error that 
+    # cannot use isOkOr here because results in a compile-time error that
     # shows the error is void for some reason
     let setMetadataRes = g.setMetadata()
     if setMetadataRes.isErr():
@@ -855,7 +855,8 @@ method isReady*(g: OnchainGroupManager): Future[bool] {.async.} =
   g.retryWrapper(currentBlock, "Failed to get the current block number"):
     cast[BlockNumber](await g.ethRpc.get().provider.eth_blockNumber())
 
-  if g.latestProcessedBlock < currentBlock:
+  # the node is still able to process messages if it is behind the latest block by a factor of the valid roots
+  if u256(g.latestProcessedBlock) < (u256(currentBlock) - u256(g.validRoots.len)):
     return false
 
   return not (await g.isSyncing())