refactor: better error handling when parsing events (#8)

src/index.ts

@@ -1,9 +1,12 @@
+import assert from "assert/strict";
+
 // Types
 import type {
   HttpFunction,
   Request,
   Response,
 } from "@google-cloud/functions-framework";
+import { EventType } from "./types.js";
 import parseTransactionReceipts from "./parse-transaction-receipts";
 import sendDiscordNotification from "./send-discord-notification";
 import sendTelegramNotification from "./send-telegram-notification";
@@ -17,16 +20,19 @@ export const watchdogNotifier: HttpFunction = async (
 
     for (const parsedEvent of parsedEvents) {
       switch (parsedEvent.event.eventName) {
-        case "ProposalCreated":
+        case EventType.ProposalCreated:
           await sendDiscordNotification(parsedEvent.event, parsedEvent.txHash);
           await sendTelegramNotification(parsedEvent.event, parsedEvent.txHash);
           break;
-        case "MedianUpdated":
+        case EventType.MedianUpdated:
           // Acts a health check/heartbeat for the service, as it's a frequently emitted event
           console.info("[HealthCheck]: Block", parsedEvent.block);
           break;
         default:
-          throw new Error("Unknown event type", parsedEvent.event);
+          assert(
+            false,
+            `Unknown event type from payload: ${JSON.stringify(req.body)}`,
+          );
       }
     }
 

src/parse-transaction-receipts.ts

@@ -1,10 +1,13 @@
+import assert from "assert/strict";
+
 // External
 import { decodeEventLog } from "viem";
 
 // Internal
 import GovernorABI from "./governor-abi.js";
-import { HealthCheckEvent, ProposalCreatedEvent } from "./types.js";
+import { EventType, HealthCheckEvent, ProposalCreatedEvent } from "./types.js";
 import hasLogs from "./utils/has-logs.js";
+import getEventByTopic from "./utils/get-event-by-topic.js";
 import isHealthCheckEvent from "./utils/is-health-check-event.js";
 import isProposalCreatedEvent from "./utils/is-proposal-created-event.js";
 import isTransactionReceipt from "./utils/is-transaction-receipt.js";
@@ -45,48 +48,59 @@ export default function parseTransactionReceipts(
     }
 
     for (const log of receipt.logs) {
-      if (!log.topics) {
-        throw new Error("No topics found in log");
-      }
+      assert(log.topics && log.topics.length > 0, "No topics found in log");
 
-      try {
-        const event = decodeEventLog({
-          abi: GovernorABI,
-          data: log.data as `0x${string}`,
-          topics: log.topics as [
-            signature: `0x${string}`,
-            ...args: `0x${string}`[],
-          ],
-        });
+      const eventSignature = log.topics[0];
+      const eventType = getEventByTopic(eventSignature);
 
-        if (isProposalCreatedEvent(event)) {
-          result.push({
-            event,
-            txHash: log.transactionHash,
+      switch (eventType) {
+        case EventType.Unknown:
+          // It can happen that a single transaction fires multiple events,
+          // some of which we are not interested in
+          continue;
+        case EventType.ProposalCreated: {
+          const event = decodeEventLog({
+            abi: GovernorABI,
+            data: log.data as `0x${string}`,
+            topics: log.topics as [
+              signature: `0x${string}`,
+              ...args: `0x${string}`[],
+            ],
           });
-        }
-        // eslint-disable-next-line no-empty
-      } catch {}
-
-      try {
-        const event = decodeEventLog({
-          abi: SortedOraclesABI,
-          data: log.data as `0x${string}`,
-          topics: log.topics as [
-            signature: `0x${string}`,
-            ...args: `0x${string}`[],
-          ],
-        });
 
-        if (isHealthCheckEvent(event)) {
-          result.push({
-            block: Number(receipt.blockNumber),
-            event,
-            txHash: log.transactionHash,
+          if (isProposalCreatedEvent(event)) {
+            result.push({
+              event,
+              txHash: log.transactionHash,
+            });
+          }
+          break;
+        }
+        case EventType.MedianUpdated: {
+          const event = decodeEventLog({
+            abi: SortedOraclesABI,
+            data: log.data as `0x${string}`,
+            topics: log.topics as [
+              signature: `0x${string}`,
+              ...args: `0x${string}`[],
+            ],
           });
+
+          if (isHealthCheckEvent(event)) {
+            result.push({
+              block: Number(receipt.blockNumber),
+              event,
+              txHash: log.transactionHash,
+            });
+          }
+          break;
         }
-        // eslint-disable-next-line no-empty
-      } catch {}
+        default:
+          assert(
+            false,
+            `Unknown event type. Did you forget to add a new event?`,
+          );
+      }
     }
   }
 

src/types.ts

@@ -26,8 +26,14 @@ export interface LogsEntity {
   transactionIndex: string;
 }
 
+export enum EventType {
+  Unknown = "Unknown",
+  ProposalCreated = "ProposalCreated",
+  MedianUpdated = "MedianUpdated",
+}
+
 export interface ProposalCreatedEvent {
-  eventName: "ProposalCreated";
+  eventName: EventType.ProposalCreated;
   args: {
     calldatas: readonly `0x${string}`[];
     description: string;
@@ -43,7 +49,7 @@ export interface ProposalCreatedEvent {
 }
 
 export interface HealthCheckEvent {
-  eventName: "MedianUpdated";
+  eventName: EventType.MedianUpdated;
   block: number;
   args: {
     token: `0x${string}`;

src/utils/get-event-by-topic.ts

@@ -0,0 +1,14 @@
+import { EventType } from "../types";
+
+export default function getEventByTopic(topic: string): EventType {
+  switch (topic) {
+    // keccak256(abi.encodePacked("ProposalCreated(uint256,address,address[],uint256[],string[],bytes[],uint256,uint256,string)"))
+    case "0x7d84a6263ae0d98d3329bd7b46bb4e8d6f98cd35a7adb45c274c8b7fd5ebd5e0":
+      return EventType.ProposalCreated;
+    // keccak256(abi.encodePacked("MedianUpdated(address,uint256)"))
+    case "0xa9981ebfc3b766a742486e898f54959b050a66006dbce1a4155c1f84a08bcf41":
+      return EventType.MedianUpdated;
+    default:
+      return EventType.Unknown;
+  }
+}