move chainId parsing to function

lib/handlers/get-orders/handler.ts

@@ -15,6 +15,7 @@ import {
   ErrorResponse,
   Response,
 } from '../base/index'
+import { tryParseChainIdFromBody } from '../post-order/handler'
 import { ContainerInjected, RequestInjected } from './injector'
 import { GetDutchV2OrderResponse } from './schema/GetDutchV2OrderResponse'
 import { GetOrdersResponse, GetOrdersResponseJoi } from './schema/GetOrdersResponse'
@@ -102,14 +103,7 @@ export class GetOrdersHandler extends APIGLambdaHandler<
   protected afterResponseHook(event: APIGatewayProxyEvent, _context: Context, response: APIGatewayProxyResult): void {
     const { statusCode } = response
 
-    // Try and extract the chain id from the raw json.
-    let chainId = '0'
-    try {
-      const rawBody = JSON.parse(event.body || '')
-      chainId = rawBody.chainId ?? chainId
-    } catch (err) {
-      // no-op. If we can't get chainId still log the metric as chain 0
-    }
+    const chainId = tryParseChainIdFromBody(event)
     const statusCodeMod = (Math.floor(statusCode / 100) * 100).toString().replace(/0/g, 'X')
 
     const getOrdersByChainMetricName = `GetOrdersChainId${chainId.toString()}Status${statusCodeMod}`

lib/handlers/post-order/handler.ts

@@ -22,6 +22,20 @@ import {
 import { PostOrderBodyParser } from './PostOrderBodyParser'
 import { PostOrderRequestBody, PostOrderRequestBodyJoi, PostOrderResponse, PostOrderResponseJoi } from './schema'
 
+export function tryParseChainIdFromBody(event: APIGatewayProxyEvent) {
+  // Try and extract the chain id from the raw json.
+  if (!event || !event.body) {
+    return '0'
+  }
+
+  try {
+    const rawBody = JSON.parse(event.body)
+    const chainId = rawBody.chainId ?? '0'
+    return chainId
+  } catch (err) {
+    return '0'
+  }
+}
 export class PostOrderHandler extends APIGLambdaHandler<
   unknown,
   ApiRInj,
@@ -119,14 +133,7 @@ export class PostOrderHandler extends APIGLambdaHandler<
   protected afterResponseHook(event: APIGatewayProxyEvent, _context: Context, response: APIGatewayProxyResult): void {
     const { statusCode } = response
 
-    // Try and extract the chain id from the raw json.
-    let chainId = '0'
-    try {
-      const rawBody = JSON.parse(event.body || '')
-      chainId = rawBody.chainId ?? chainId
-    } catch (err) {
-      // no-op. If we can't get chainId still log the metric as chain 0
-    }
+    const chainId = tryParseChainIdFromBody(event)
 
     const statusCodeMod = (Math.floor(statusCode / 100) * 100).toString().replace(/0/g, 'X')
 

test/unit/handlers/post-order/post-order.test.ts

@@ -1,6 +1,7 @@
 import { Logger } from '@aws-lambda-powertools/logger'
 import { SFNClient, StartExecutionCommand } from '@aws-sdk/client-sfn'
 import { OrderType, OrderValidation, OrderValidator, RelayOrderValidator } from '@uniswap/uniswapx-sdk'
+import { APIGatewayEvent } from 'aws-lambda'
 import { mockClient } from 'aws-sdk-client-mock'
 import { mock } from 'jest-mock-extended'
 import { ORDER_STATUS, UniswapXOrderEntity } from '../../../../lib/entities'
@@ -519,4 +520,26 @@ describe('Testing post order handler.', () => {
       })
     })
   })
+
+  describe('tryParseChainIdFromBody', () => {
+    test('should return 0 when no chainId', () => {
+      const response = postOrderHandler.tryParseChainIdFromBody({ body: '{}' } as APIGatewayEvent)
+      expect(response).toEqual('0')
+    })
+
+    test('should return 0 when no body', () => {
+      const response = postOrderHandler.tryParseChainIdFromBody({} as APIGatewayEvent)
+      expect(response).toEqual('0')
+    })
+
+    test('should return 0 when JSON.parse errors', () => {
+      const response = postOrderHandler.tryParseChainIdFromBody({ body: '{;}' } as APIGatewayEvent)
+      expect(response).toEqual('0')
+    })
+
+    test('should return chainId', () => {
+      const response = postOrderHandler.tryParseChainIdFromBody({ body: '{"chainId":1}' } as APIGatewayEvent)
+      expect(response).toEqual(1)
+    })
+  })
 })