feat(api): add httpJson helper

lib/api/http.ts

@@ -0,0 +1,58 @@
+import { isApiError, type ApiError } from "@/lib/errors"
+
+type JsonRequestInit = Omit<RequestInit, "body" | "headers"> & {
+  headers?: HeadersInit
+  body?: BodyInit | null
+  json?: unknown
+}
+
+async function readJsonBody(res: Response): Promise<unknown | null> {
+  const text = await res.text()
+  if (!text) return null
+
+  try {
+    return JSON.parse(text) as unknown
+  } catch {
+    return null
+  }
+}
+
+export async function httpJson<T>(path: string, init?: JsonRequestInit): Promise<T> {
+  if (/^https?:\/\//.test(path)) {
+    throw new Error("Absolute URLs are not allowed")
+  }
+
+  const { json, headers: headersInit, body: bodyInit, ...rest } = init ?? {}
+
+  const headers = new Headers(headersInit)
+  headers.set("Accept", "application/json")
+
+  const body = json === undefined ? bodyInit : JSON.stringify(json)
+
+  if (json !== undefined && !headers.has("Content-Type")) {
+    headers.set("Content-Type", "application/json")
+  }
+
+  const res = await fetch(path, {
+    ...rest,
+    headers,
+    body,
+  })
+
+  const data = await readJsonBody(res)
+
+  if (res.ok) {
+    return data as T
+  }
+
+  const apiError = isApiError(data) ? data : null
+  if (res.status === 401 || apiError?.code === 401) {
+    throw new Error("UNAUTHORIZED")
+  }
+
+  if (apiError) {
+    throw apiError
+  }
+
+  throw { code: res.status, msg: res.statusText || "Request failed" } satisfies ApiError
+}