refactor: make content type header case-insensitive (#135)

* refactor: make content type header case-insensitive

* format

* fix

* fix

* make test more clear

lambda/parse-request-body.ts

@@ -17,7 +17,7 @@ import { bodySchema, CONTENT_TYPES, headersSchema } from './schema';
 
 export function parseRequestBody(body: string, headers: IncomingHttpHeaders) {
   const headersResult = headersSchema.parse(headers);
-  const contentType = headersResult['content-type'] || headersResult['Content-Type'];
+  const contentType = headersResult['content-type'];
   switch (contentType) {
     case CONTENT_TYPES.JSON:
       return JSON.parse(body);

lambda/proxy.test.ts

@@ -123,9 +123,9 @@ describe('proxy', () => {
     const event: APIGatewayProxyWithLambdaAuthorizerEvent<any> = {
       ...baseEvent,
       headers: {
-        ...baseEvent.headers,
-        'content-type': undefined,
-        'Content-Type': 'application/json'
+        Accept: '*/*',
+        'Content-Type': 'application/json',
+        Host: 'some-api.us-west-2.amazonaws.com'
       },
       body: JSON.stringify(VALID_PUSH_PAYLOAD),
       pathParameters: {

lambda/proxy.ts

@@ -61,6 +61,6 @@ export async function handler(event: APIGatewayProxyWithLambdaAuthorizerEvent<an
     }
 
     console.error('An unknown error occurred.', error);
-    return { statusCode: 500, body: 'Internal server error' };
+    return { statusCode: 500, body: `Internal server error: ${error}` };
   }
 }

lambda/schema.ts

@@ -1,4 +1,5 @@
 import { z } from 'zod';
+import mapKeys from 'lodash.mapkeys';
 
 export const urlSchema = z.string().url();
 
@@ -11,19 +12,16 @@ export const CONTENT_TYPES = {
   URL_ENCODED: 'application/x-www-form-urlencoded'
 } as const;
 
-export const headersSchema = z
-  .object({
-    'content-type': z.string().optional(),
-    'Content-Type': z.string().optional()
-  })
-  .refine(
-    headers => {
-      return headers['content-type'] || headers['Content-Type'];
-    },
-    {
-      message: 'Missing Content-Type header'
+export const headersSchema = z.preprocess(
+  obj => {
+    if (obj && typeof obj == 'object') {
+      return mapKeys(obj, (_, key) => key.toLowerCase());
     }
-  );
+  },
+  z.object({
+    'content-type': z.nativeEnum(CONTENT_TYPES)
+  })
+);
 
 export const axiosErrorSchema = z.object({
   response: z.object({

package.json

@@ -10,6 +10,7 @@
   "dependencies": {
     "@types/node": "20.1.1",
     "axios": "1.6.1",
+    "lodash.mapkeys": "4.6.0",
     "query-string": "7.1.3",
     "typescript": "5.2.2",
     "zod": "3.22.4"
@@ -19,6 +20,7 @@
     "@swc/jest": "0.2.29",
     "@types/aws-lambda": "8.10.107",
     "@types/jest": "29.5.8",
+    "@types/lodash.mapkeys": "4.6.9",
     "jest": "29.7.0",
     "prettier": "3.1.0"
   },