import { reportRequestOutcome } from "../offline/connectivity";

export const DEFAULT_TIMEOUT_MS = 4_000; // GET and writes with Idempotency-Key
export const NON_IDEMPOTENT_WRITE_TIMEOUT_MS = 15_000;
/** A bulk POST writes up to 100 records in one server transaction (15 s allowed there). */
export const BULK_WRITE_TIMEOUT_MS = 15_000;
export const UPLOAD_TIMEOUT_MS = 30_000;
export const DOWNLOAD_TIMEOUT_MS = 60_000;

export function timeoutFor(method: string, headers: HeadersInit | undefined): number {
  if (method.toUpperCase() === "GET" || new Headers(headers).has("Idempotency-Key")) {
    return DEFAULT_TIMEOUT_MS;
  }
  return NON_IDEMPOTENT_WRITE_TIMEOUT_MS;
}

function isBulkPost(input: RequestInfo | URL, method: string | undefined): boolean {
  if ((method ?? "GET").toUpperCase() !== "POST") return false;
  const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
  return /\/bulk(?:[?#]|$)/.test(url);
}

// Statuses that must not carry a body when a Response is rebuilt.
const NULL_BODY_STATUSES = new Set([101, 204, 205, 304]);

// Rejects as soon as the signal aborts, so a stalled stream (which ignores the
// abort on its own) still ends in the abort reason.
function rejectOnAbort<T>(promise: Promise<T>, signal: AbortSignal): Promise<T> {
  return new Promise<T>((resolve, reject) => {
    const onAbort = () => reject(signal.reason);
    if (signal.aborted) {
      onAbort();
      return;
    }
    signal.addEventListener("abort", onAbort, { once: true });
    promise.then(resolve, reject).finally(() => signal.removeEventListener("abort", onAbort));
  });
}

// The timeout is a TOTAL deadline: it also covers receiving the body. The body
// is buffered inside the deadline and handed back as a fresh Response, so every
// caller can keep using json()/text()/blob() without re-arming anything.
export async function fetchWithTimeout(
  input: RequestInfo | URL,
  init: RequestInit & { timeoutMs: number },
): Promise<Response> {
  const { timeoutMs, signal: callerSignal, ...rest } = init;
  const controller = new AbortController();
  const timer = setTimeout(
    () => controller.abort(new DOMException("Zeitüberschreitung der Anfrage", "TimeoutError")),
    timeoutMs,
  );
  const forwardAbort = () => controller.abort(callerSignal?.reason);
  if (callerSignal?.aborted) {
    forwardAbort();
  } else {
    callerSignal?.addEventListener("abort", forwardAbort, { once: true });
  }
  try {
    const response = await rejectOnAbort(
      fetch(input, { ...rest, signal: controller.signal }),
      controller.signal,
    );
    const body = NULL_BODY_STATUSES.has(response.status)
      ? null
      : await rejectOnAbort(response.arrayBuffer(), controller.signal);
    return new Response(body, {
      status: response.status,
      statusText: response.statusText,
      headers: response.headers,
    });
  } finally {
    clearTimeout(timer);
    callerSignal?.removeEventListener("abort", forwardAbort);
  }
}

// TypeError = fetch failed at network level; TimeoutError / AbortError = the
// request was cut off. Never an ApiError (that means the server answered).
export function isNetworkError(error: unknown): boolean {
  if (error instanceof TypeError) {
    return true;
  }
  return (
    error instanceof DOMException && (error.name === "TimeoutError" || error.name === "AbortError")
  );
}

// fetchWithTimeout plus the connectivity signal: ANY HTTP answer (including
// 502/503/504 from a proxy) counts as "reached-server"; a timeout or network
// TypeError counts as "network-error". A caller-initiated AbortError
// (unmount/cancel) says nothing about the network and is not reported.
export async function fetchReportingOutcome(
  input: RequestInfo | URL,
  init: RequestInit & { timeoutMs: number },
): Promise<Response> {
  const timeoutMs = isBulkPost(input, init.method)
    ? Math.max(init.timeoutMs, BULK_WRITE_TIMEOUT_MS)
    : init.timeoutMs;
  try {
    const response = await fetchWithTimeout(input, { ...init, timeoutMs });
    reportRequestOutcome("reached-server");
    return response;
  } catch (error) {
    if (isNetworkError(error) && !(error instanceof DOMException && error.name === "AbortError")) {
      reportRequestOutcome("network-error");
    }
    throw error;
  }
}