feat: make webhook headers case insensitive (#256)

src/core.ts

@@ -1053,16 +1053,33 @@ export const isHeadersProtocol = (headers: any): headers is HeadersProtocol => {
   return typeof headers?.get === 'function';
 };
 
-export const getHeader = (headers: HeadersLike, key: string): string | null | undefined => {
-  const lowerKey = key.toLowerCase();
-  if (isHeadersProtocol(headers)) return headers.get(key) || headers.get(lowerKey);
-  const value = headers[key] || headers[lowerKey];
-  if (Array.isArray(value)) {
-    if (value.length <= 1) return value[0];
-    console.warn(`Received ${value.length} entries for the ${key} header, using the first entry.`);
-    return value[0];
+export const getRequiredHeader = (headers: HeadersLike, header: string): string => {
+  const lowerCasedHeader = header.toLowerCase();
+  if (isHeadersProtocol(headers)) {
+    // to deal with the case where the header looks like Finch-Event-Id
+    const intercapsHeader =
+      header[0]?.toUpperCase() +
+      header.substring(1).replace(/([^\w])(\w)/g, (_m, g1, g2) => g1 + g2.toUpperCase());
+    for (const key of [header, lowerCasedHeader, header.toUpperCase(), intercapsHeader]) {
+      const value = headers.get(key);
+      if (value) {
+        return value;
+      }
+    }
   }
-  return value;
+
+  for (const [key, value] of Object.entries(headers)) {
+    if (key.toLowerCase() === lowerCasedHeader) {
+      if (Array.isArray(value)) {
+        if (value.length <= 1) return value[0];
+        console.warn(`Received ${value.length} entries for the ${header} header, using the first entry.`);
+        return value[0];
+      }
+      return value;
+    }
+  }
+
+  throw new Error(`Could not find ${header} header`);
 };
 
 /**

src/resources/webhooks.ts

@@ -3,7 +3,7 @@
 import { APIResource } from 'modern-treasury/resource';
 import { createHmac } from 'crypto';
 import type { HeadersLike } from 'modern-treasury/core';
-import { getHeader } from 'modern-treasury/core';
+import { getRequiredHeader } from 'modern-treasury/core';
 
 export class Webhooks extends APIResource {
   /**
@@ -40,8 +40,9 @@ export class Webhooks extends APIResource {
     opts?: { key?: string | null | undefined },
   ): boolean {
     const signature = this.getSignature(payload, opts);
-    const expectedSignature = typeof headers === 'string' ? headers : getHeader(headers, 'X-Signature');
-    if (!expectedSignature) throw new Error('Could not find an X-Signature header');
+    const expectedSignature =
+      typeof headers === 'string' ? headers : getRequiredHeader(headers, 'X-Signature');
+    if (!expectedSignature) throw new Error('Could not find X-Signature header');
     return signature === expectedSignature;
   }
 }

tests/api-resources/webhooks.test.ts

@@ -52,7 +52,7 @@ describe('resource webhooks', () => {
   it('validateSignature: Throws an error when the X-Signature header is not present', () => {
     expect(() =>
       modernTreasury.webhooks.validateSignature('bar', /* headers */ {}, { key: 'foo' }),
-    ).toThrowError('Could not find an X-Signature header');
+    ).toThrowError('Could not find X-Signature header');
   });
 
   it('validateSignature: Correctly verifies against the expected signature', () => {