feat: default web API calls to same origin

apps/web/package.json

@@ -7,7 +7,8 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "test": "bun test ./test"
   },
   "dependencies": {
     "@codexdash/shared-types": "workspace:*",

apps/web/src/lib/api-base.ts

@@ -0,0 +1,22 @@
+const LOCALHOST_API_ORIGIN = 'http://localhost:3001';
+
+function trimTrailingSlashes(value: string): string {
+  return value.replace(/\/+$/, '');
+}
+
+export function getApiBaseUrl(
+  configuredApiBaseUrl?: string,
+  windowOrigin?: string,
+): string {
+  const configured = configuredApiBaseUrl?.trim();
+  if (configured) {
+    return trimTrailingSlashes(configured);
+  }
+
+  const origin = windowOrigin?.trim();
+  if (origin) {
+    return trimTrailingSlashes(origin);
+  }
+
+  return LOCALHOST_API_ORIGIN;
+}

apps/web/src/lib/api.ts

@@ -10,9 +10,13 @@ import type {
   UsageSummary,
   UserProfile,
 } from '@codexdash/shared-types';
+import { getApiBaseUrl } from './api-base';
 import { clearToken, getToken } from './storage';
 
-const API_BASE_URL = import.meta.env.VITE_API_BASE_URL ?? 'http://localhost:3001';
+const API_BASE_URL = getApiBaseUrl(
+  import.meta.env.VITE_API_BASE_URL,
+  typeof window === 'undefined' ? undefined : window.location.origin,
+);
 
 async function request<T>(path: string, init?: RequestInit): Promise<T> {
   const token = getToken();

apps/web/test/api-base.test.js

@@ -0,0 +1,20 @@
+import { describe, expect, test } from 'bun:test';
+import { getApiBaseUrl } from '../src/lib/api-base.ts';
+
+describe('getApiBaseUrl', () => {
+  test('uses the configured API base when provided', () => {
+    expect(getApiBaseUrl('https://api.example.com/', 'https://app.example.com')).toBe(
+      'https://api.example.com',
+    );
+  });
+
+  test('defaults to the current window origin when no API base is configured', () => {
+    expect(getApiBaseUrl(undefined, 'https://app.example.com/')).toBe(
+      'https://app.example.com',
+    );
+  });
+
+  test('falls back to localhost in non-browser contexts without configuration', () => {
+    expect(getApiBaseUrl(undefined, undefined)).toBe('http://localhost:3001');
+  });
+});