Restore 0.1.5 version from stash

wolai-frontend/src/lib/backend/env.ts

@@ -0,0 +1,48 @@
+const TRAILING_SLASH = /\/$/;
+
+export function getBackendBaseUrl(): string {
+  const raw = process.env.BACKEND_URL ?? process.env.NEXT_PUBLIC_BACKEND_URL;
+  if (!raw) {
+    throw new Error("BACKEND_URL 未配置");
+  }
+  return raw.replace(TRAILING_SLASH, "");
+}
+
+export function tryGetBackendBaseUrl(): string | null {
+  try {
+    return getBackendBaseUrl();
+  } catch {
+    return null;
+  }
+}
+
+type SearchParamsInit = Record<string, string | number | boolean | undefined> | URLSearchParams;
+
+export function buildBackendUrl(path: string, params?: SearchParamsInit): URL {
+  const base = getBackendBaseUrl();
+  const url = new URL(path, base);
+  if (params) {
+    const search =
+      params instanceof URLSearchParams
+        ? params
+        : new URLSearchParams(
+            Object.entries(params).reduce<Record<string, string>>((acc, [key, value]) => {
+              if (value !== undefined) {
+                acc[key] = String(value);
+              }
+              return acc;
+            }, {}),
+          );
+    search.forEach((value, key) => {
+      if (value !== undefined && value !== null) {
+        url.searchParams.set(key, value);
+      }
+    });
+  }
+  return url;
+}
+
+export async function fetchBackend(path: string, init?: RequestInit, params?: SearchParamsInit) {
+  const url = buildBackendUrl(path, params);
+  return fetch(url, init);
+}