[GW-644]: Add simulate tx node extension (#2)

* feat: add simulate tx node extension

* refactor: add jest and node types

* refactor: handle simulate send tx

* feat: add simulate test

* feat: add env examples

Author: dzimiks

.env.example

@@ -0,0 +1 @@
+TENDERLY_WEB3_GATEWAY_ACCESS_TOKEN=

README.md

@@ -7,3 +7,10 @@ Node Extensions is a game-changing enhancement to our existing production node.
 ## How to use
 
 TBD
+
+## Node Extension Examples
+
+Here are examples of Node Extensions that you can use in your projects:
+
+- [chainlink-price-feed](./chainlink-price-feed) - A Node Extension that allows you to query Chainlink Price Feeds
+- [simulate-send-transaction](./simulate-send-transaction) - A Node Extension that allows you to simulate a transaction before sending on-chain

chainlink-price-feed/actions/.env.example

@@ -0,0 +1 @@
+TENDERLY_WEB3_GATEWAY_ACCESS_TOKEN=

simulate-send-transaction/actions/.env.example

@@ -0,0 +1 @@
+TENDERLY_WEB3_GATEWAY_ACCESS_TOKEN=

simulate-send-transaction/actions/.gitignore

@@ -3,3 +3,5 @@ node_modules/
 
 # Ignore tsc output
 out/**/*
+
+.env

simulate-send-transaction/actions/extension.ts

@@ -1,32 +1,46 @@
-import {ActionFn, Context, Event, Network} from '@tenderly/actions';
-
-import {ethers} from 'ethers';
+import { ActionFn, Context, Event, Network, WebhookEvent } from '@tenderly/actions';
+import { ethers } from 'ethers';
 
 export const sendSimulateRawTransaction: ActionFn = async (context: Context, event: Event) => {
-	// Setting a variable that will store the Web3 Gateway RPC URL and secret key
-	const defaultGatewayURL = context.gateways.getGateway(Network.MAINNET);
-
-	// Using the Ethere.js provider class to call the RPC URL
-	const provider = new ethers.JsonRpcProvider(defaultGatewayURL);
-
-	// Decode raw transaction
-	const tx = ethers.Transaction.from(event)
-
-	// Simulate transaction to get execution results
-	const simResponse = await provider.send("tenderly_simulateTransaction", [{
-		"from": tx.from,
-		"to": tx.to,
-		"gas": tx.gasLimit,
-		"gasPrice": tx.gasPrice,
-		"value": tx.value,
-		"data": tx.data,
-	}])
-
-	// If simulation fails, return error
-	if (simResponse.status == false) {
-		return null
-	}
-
-	// Send transaction to the network
-	return provider.send('eth_sendRawTransaction', event)
-}
+  // Casting the event to a WebhookEvent
+  const webhookEvent: WebhookEvent = event as WebhookEvent;
+
+  // Setting a variable that will store the Web3 Gateway RPC URL and secret key
+  const defaultGatewayURL = context.gateways.getGateway(Network.MAINNET);
+
+  // Using the Ethers.js provider class to call the RPC URL
+  const provider = new ethers.providers.JsonRpcProvider(defaultGatewayURL);
+
+  // Getting the raw transaction payload from the webhook event
+  const txPayload = webhookEvent.payload.data;
+
+  // Parsing the transaction payload
+  const tx = ethers.utils.parseTransaction(txPayload);
+
+  // Creating a new transaction object with the parsed transaction
+  // in order to support the tenderly_simulateTransaction RPC call
+  const parsedTransaction = {
+    from: tx.from,
+    to: tx.to,
+    gas: tx.gasLimit?._hex,
+    gasPrice: tx.gasPrice?._hex,
+    value: tx.value?._hex,
+    data: tx.data,
+  };
+
+  // Simulate transaction to get execution results
+  const simulationResponse = await provider.send('tenderly_simulateTransaction', [parsedTransaction, 'latest']);
+
+  // If simulation fails, return error
+  if (simulationResponse.status === false) {
+    console.log('Simulate transaction failed');
+    return Promise.reject({
+      error: 'Simulation failed',
+      simulationResponse,
+    });
+  }
+
+  // If simulation succeeds, send the transaction
+  console.log('Simulate transaction success');
+  return provider.send('eth_sendRawTransaction', [txPayload]);
+};

simulate-send-transaction/actions/jest.config.json

@@ -0,0 +1,4 @@
+{
+  "preset": "ts-jest",
+  "testEnvironment": "node"
+}