/**
 * @file Shows a browser notification — the single `notify()` both
 * `useNotifications` (live events) and Settings' "Send Test Notification"
 * button call, so the test proves the real delivery path and can report
 * where it actually landed instead of a bare fire-and-forget.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

export type NotifyVia = "native" | "push" | "local" | "blocked" | "none";

export interface NotifyError {
  statusCode?: number;
  message?: string;
}

export interface NotifyResult {
  via: NotifyVia;
  errors: NotifyError[];
}

/**
 * Prefers a server-relayed push (so it can arrive even if this tab isn't the
 * active one, or the browser is backgrounded) and falls back to a local
 * service-worker/`Notification` call when the server didn't deliver.
 * @param title Notification title.
 * @param body Notification body text.
 * @param url Same-origin path to focus/navigate to on click (e.g. the lane
 *   that raised this notification). Omit for notifications with no target.
 */
export async function notify(title: string, body: string, url?: string): Promise<NotifyResult> {
  if (!("Notification" in window) || Notification.permission !== "granted") {
    return { via: "blocked", errors: [] };
  }

  const errors: NotifyError[] = [];

  // A 200 from /api/push/send means the request was ACCEPTED, not that anything
  // reached the user: with no push subscription (no service worker, a
  // non-secure origin, a browser that never subscribed) or a push service the
  // server cannot reach, it answers `{ok:true, native:false, pushed:0}` and
  // nobody is notified. Only `native` or `pushed > 0` is actual delivery —
  // anything else falls through to the local notification below, which is why
  // the fallback is keyed on the RESULT rather than on fetch throwing.
  try {
    const res = await fetch("/api/push/send", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify({ title, body, url }),
    });
    const result = res.ok ? await res.json().catch(() => null) : null;
    if (result?.native) return { via: "native", errors };
    if (result && result.pushed > 0) return { via: "push", errors };
    if (!res.ok) errors.push({ statusCode: res.status });
  } catch (e) {
    errors.push({ message: e instanceof Error ? e.message : String(e) });
  }

  try {
    // Vector, not `/favicon.ico` (32x32 raster) — crisp at whatever size the
    // OS renders it, matching the icon server/lib/push.js already sends.
    const data = url ? { url } : undefined;
    if ("serviceWorker" in navigator) {
      const registration = await navigator.serviceWorker.ready;
      await registration.showNotification(title, {
        body,
        icon: "/favicon.svg",
        silent: false,
        data,
      });
    } else {
      const n = new Notification(title, { body, icon: "/favicon.svg", data });
      if (url) {
        // No service worker to catch the click here — navigate this tab directly.
        n.onclick = () => {
          window.focus();
          window.location.assign(url);
        };
      }
    }
    return { via: "local", errors };
  } catch (e) {
    errors.push({ message: e instanceof Error ? e.message : String(e) });
    return { via: "none", errors };
  }
}