fixed production deduplication

Author: yb175

frontend/src/lib/api.ts

@@ -1 +1,36 @@
-export const API_BASE_URL = import.meta.env.VITE_BACKEND_URL ?? "http://localhost:3000";
+const DEFAULT_API_BASE_URL = "http://localhost:3000";
+
+const normalizeApiBaseUrl = (rawBaseUrl: string): string => {
+	const baseWithoutTrailingSlash = rawBaseUrl.replace(/\/+$/, "");
+
+	try {
+		const parsed = new URL(baseWithoutTrailingSlash);
+		const duplicatedHostPrefix = `/${parsed.hostname}`;
+
+		// Handle accidental base URLs like http://host/host/api
+		if (
+			parsed.pathname === duplicatedHostPrefix ||
+			parsed.pathname.startsWith(`${duplicatedHostPrefix}/`)
+		) {
+			parsed.pathname = parsed.pathname.slice(duplicatedHostPrefix.length) || "/";
+		}
+
+		parsed.pathname = parsed.pathname.replace(/\/+$/, "") || "/";
+		return `${parsed.origin}${parsed.pathname === "/" ? "" : parsed.pathname}`;
+	} catch {
+		return baseWithoutTrailingSlash;
+	}
+};
+
+export const API_BASE_URL = normalizeApiBaseUrl(
+	import.meta.env.VITE_BACKEND_URL ?? DEFAULT_API_BASE_URL
+);
+
+export const buildApiUrl = (endpoint: string): string => {
+	if (/^https?:\/\//i.test(endpoint)) {
+		return endpoint;
+	}
+
+	const normalizedEndpoint = endpoint.replace(/^\/+/, "");
+	return new URL(normalizedEndpoint, `${API_BASE_URL}/`).toString();
+};

frontend/src/lib/fetcher.ts

@@ -1,7 +1,7 @@
 // src/lib/fetcher.ts
 
 import { useAuth } from "@clerk/react";
-import { API_BASE_URL } from "./api";
+import { buildApiUrl } from "./api";
 
 export const useApi = () => {
   const { getToken } = useAuth();
@@ -12,7 +12,7 @@ export const useApi = () => {
   ) => {
     const token = await getToken();
 
-    const res = await fetch(`${API_BASE_URL}${endpoint}`, {
+    const res = await fetch(buildApiUrl(endpoint), {
       ...options,
       headers: {
         ...(options.headers || {}),

frontend/src/pages/DashboardPage.tsx

@@ -1,5 +1,6 @@
 import { useUser, useClerk, useAuth } from '@clerk/react'
 import { useState } from 'react'
+import { buildApiUrl } from '../lib/api'
 
 export function DashboardPage() {
   const { user } = useUser()
@@ -15,8 +16,7 @@ export function DashboardPage() {
     try {
       const authToken = await getToken()
 
-      const backendUrl = import.meta.env.VITE_BACKEND_URL || "http://localhost:3000"
-      const res = await fetch(`${backendUrl}/preferences`, {
+      const res = await fetch(buildApiUrl('/preferences'), {
         headers: {
           'Authorization': `Bearer ${authToken}`,
           'Content-Type': 'application/json'