Function fetchWithTimeout

frontend/connection/src/utils.ts:184–256

(
  url: string,
  timeoutMs: number
)

 * Normalizes different error types (timeout, network, HTTP errors) into FetchError.
 */
export async function fetchWithTimeout(
  url: string,
  timeoutMs: number
): Promise<{ data: unknown; url: string }> {
  const controller = new AbortController()
  // eslint-disable-next-line no-restricted-globals -- Network timeout utility runs outside React and cannot use hooks.
  const timeoutId = setTimeout(() => controller.abort(), timeoutMs)

  try {
    const response = await fetch(url, { signal: controller.signal })
    clearTimeout(timeoutId)

    if (!response.ok) {
      // Server responded with error status
      let data: unknown
      try {
        data = await response.json()
      } catch {
        try {
          data = await response.text()
        } catch {
          data = null
        }
      }

      throw new FetchError(
        `Request failed with status ${response.status}`,
        url,
        {
          response: {
            status: response.status,
            statusText: response.statusText,
            data,
          },
        }
      )
    }

    // Try JSON first, fall back to text (healthz returns string, host-config returns JSON)
    // We don't rely on Content-Type since proxies/CDNs may not preserve headers correctly
    const text = await response.text()
    try {
      return { data: JSON.parse(text), url }
    } catch {
      return { data: text, url }
    }
  } catch (error) {
    clearTimeout(timeoutId)

    // Re-throw FetchError as-is
    if (error instanceof FetchError) {
      throw error
    }

    // Handle AbortController timeout
    if (error instanceof DOMException && error.name === "AbortError") {
      throw new FetchError("Connection timed out", url, { isTimeout: true })
    }