fix: harden alipay direct pay flow

src/__tests__/lib/alipay/codec.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it } from 'vitest';
+import { decodeAlipayPayload, parseAlipayNotificationParams } from '@/lib/alipay/codec';
+
+describe('Alipay codec', () => {
+  it('should normalize plus signs in notify sign parameter', () => {
+    const params = parseAlipayNotificationParams(Buffer.from('sign=abc+def&trade_no=1'), {
+      'content-type': 'application/x-www-form-urlencoded; charset=utf-8',
+    });
+
+    expect(params.sign).toBe('abc+def');
+    expect(params.trade_no).toBe('1');
+  });
+
+  it('should decode payload charset from content-type header', () => {
+    const body = Buffer.from('charset=utf-8&trade_status=TRADE_SUCCESS', 'utf-8');
+
+    const decoded = decodeAlipayPayload(body, {
+      'content-type': 'application/x-www-form-urlencoded; charset=utf-8',
+    });
+
+    expect(decoded).toContain('trade_status=TRADE_SUCCESS');
+  });
+
+  it('should fallback to body charset hint when header is missing', () => {
+    const body = Buffer.from('charset=gbk&trade_no=202603090001', 'utf-8');
+
+    const decoded = decodeAlipayPayload(body);
+
+    expect(decoded).toContain('trade_no=202603090001');
+  });
+});