Make indexer update light client until the parent of the best block

Since querying the current best block's seal is difficult, our PoC
implementation does not implement it. Make the relayer use the
information.

Author: Park Juhyung

ibc.ts/src/relayer/index.ts

@@ -77,8 +77,8 @@ async function pendingDatagrams({
     chain: Chain;
     counterpartyChain: Chain;
 }): Promise<{ localDatagrams: Datagram[]; counterpartyDatagrams: Datagram[] }> {
-    const height = await chain.latestHeight();
-    const counterpartyChainHeight = await counterpartyChain.latestHeight();
+    let height = await chain.latestHeight();
+    let counterpartyChainHeight = await counterpartyChain.latestHeight();
     let localDatagrams: Datagram[] = [];
     let counterpartyDatagrams: Datagram[] = [];
 
@@ -100,6 +100,10 @@ async function pendingDatagrams({
         })
     );
 
+    // FIXME: We can't update light client upto the best block.
+    height = height - 1;
+    counterpartyChainHeight = counterpartyChainHeight - 1;
+
     const {
         localDatagrams: localDatagramsForConnection,
         counterpartyDatagrams: counterpartyDatagramsForConnection
@@ -138,7 +142,8 @@ async function updateLightClient({
         );
     }
     let currentBlockNumber = clientState!.data!.number;
-    while (currentBlockNumber < counterpartyChainHeight) {
+    // FIXME: We can't get the best block's IBC header
+    while (currentBlockNumber < counterpartyChainHeight - 1) {
         const header = (await counterpartyChain.queryIBCHeader(
             currentBlockNumber + 1
         ))!;