refactor(relayer): Defer deposit MDCs check (#1329)

Rather than duplicating the array of unfilled deposits, just check it as
the first conditional in the subsequent loop. This allows the entire
function to be subsequently factored away, which will occur in a
follow-up commit.

src/relayer/Relayer.ts

@@ -258,37 +258,47 @@ export class Relayer {
     // Fetch unfilled deposits and filter out deposits upfront before we compute the minimum deposit confirmation
     // per chain, which is based on the deposit volume we could fill.
     const unfilledDeposits = await this._getUnfilledDeposits();
-
-    const mdcPerChain = this.computeRequiredDepositConfirmations(
-      Object.values(unfilledDeposits.map(({ deposit }) => deposit))
-    );
-
-    // Filter out deposits whose block time does not meet the minimum number of confirmations for the origin chain.
-    const confirmedUnfilledDeposits = unfilledDeposits
-      .filter(
-        ({ deposit: { originChainId, blockNumber } }) =>
-          blockNumber <= spokePoolClients[originChainId].latestBlockSearched - mdcPerChain[originChainId]
-      )
-      .map(({ deposit }) => deposit);
+    const allUnfilledDeposits = Object.values(unfilledDeposits.map(({ deposit }) => deposit));
     this.logger.debug({
-      at: "Relayer::checkForUnfilledDepositsAndFill",
-      message: `${confirmedUnfilledDeposits.length} unfilled deposits found`,
+      at: "Relayer#checkForUnfilledDepositsAndFill",
+      message: `${allUnfilledDeposits.length} unfilled deposits found.`,
     });
+    if (allUnfilledDeposits.length === 0) {
+      return;
+    }
+
+    const mdcPerChain = this.computeRequiredDepositConfirmations(allUnfilledDeposits);
 
-    // Iterate over all unfilled deposits. For each unfilled deposit: a) check that the token balance client has enough
-    // balance to fill the unfilled amount. b) the fill is profitable. If both hold true then fill the unfilled amount.
-    // If not enough ballance add the shortfall to the shortfall tracker to produce an appropriate log. If the deposit
-    // is has no other fills then send a 0 sized fill to initiate a slow relay. If unprofitable then add the
-    // unprofitable tx to the unprofitable tx tracker to produce an appropriate log.
+    // Iterate over all unfilled deposits. For each unfilled deposit, check that:
+    // a) it exceeds the minimum number of required block confirmations,
+    // b) the token balance client has enough tokens to fill it,
+    // c) the fill is profitable.
+    // If all hold true then complete the fill. If there is insufficient balance to complete the fill and slow fills are
+    // enabled then request a slow fill instead.
     const { slowDepositors } = config;
-    for (const deposit of confirmedUnfilledDeposits) {
-      const { depositor, recipient, destinationChainId, originChainId, inputToken, outputAmount } = deposit;
+    for (const deposit of allUnfilledDeposits) {
+      const { depositId, depositor, recipient, destinationChainId, originChainId, inputToken, outputAmount } = deposit;
+
+      // If the deposit does not meet the minimum number of block confirmations, skip it.
+      const maxBlockNumber = spokePoolClients[originChainId].latestBlockSearched - mdcPerChain[originChainId];
+      if (deposit.blockNumber > maxBlockNumber) {
+        const chain = getNetworkName(originChainId);
+        this.logger.debug({
+          at: "Relayer#checkForUnfilledDepositsAndFill",
+          message: `Skipping ${chain} deposit ${depositId} due to insufficient deposit confirmations.`,
+          depositId,
+          blockNumber: deposit.blockNumber,
+          maxBlockNumber,
+          transactionHash: deposit.transactionHash,
+        });
+        continue;
+      }
 
       // If depositor is on the slow deposit list, then send a zero fill to initiate a slow relay and return early.
       if (slowDepositors?.includes(depositor)) {
         if (sendSlowRelays) {
           this.logger.debug({
-            at: "Relayer",
+            at: "Relayer#checkForUnfilledDepositsAndFill",
             message: "Initiating slow fill for grey listed depositor",
             depositor,
           });

test/Relayer.BasicFill.ts

@@ -372,7 +372,7 @@ describe("Relayer: Check for Unfilled Deposits and Fill", async function () {
 
       await updateAllClients();
       await relayerInstance.checkForUnfilledDepositsAndFill();
-      expect(lastSpyLogIncludes(spy, "0 unfilled deposits")).to.be.true;
+      expect(lastSpyLogIncludes(spy, "due to insufficient deposit confirmations")).to.be.true;
     });
 
     it("Ignores deposits with quote times in future", async function () {