const authChannelName = "makers3d-auth";
const authTabIdKey = "makers3d-auth-tab";

export type AuthEventType = "login" | "logout";

function getTabId() {
  let tabId = window.sessionStorage.getItem(authTabIdKey);
  if (!tabId) {
    tabId = crypto.randomUUID();
    window.sessionStorage.setItem(authTabIdKey, tabId);
  }
  return tabId;
}

export function notifyAuthChanged(type: AuthEventType) {
  if (typeof window === "undefined") {
    return;
  }

  const payload = JSON.stringify({ type, source: getTabId(), at: Date.now() });

  if ("BroadcastChannel" in window) {
    const channel = new BroadcastChannel(authChannelName);
    channel.postMessage(payload);
    channel.close();
  }

  window.localStorage.setItem(authChannelName, payload);
}

export function listenAuthChanged(callback: (type: AuthEventType) => void) {
  if (typeof window === "undefined") {
    return () => {};
  }

  function handlePayload(payload: unknown) {
    if (typeof payload !== "string") {
      return;
    }

    try {
      const event = JSON.parse(payload) as { type?: AuthEventType; source?: string };
      if (event.source === getTabId()) {
        return;
      }
      if (event.type === "login" || event.type === "logout") {
        callback(event.type);
      }
    } catch {
      // Ignore malformed cross-tab payloads.
    }
  }

  const channel = "BroadcastChannel" in window ? new BroadcastChannel(authChannelName) : null;
  channel?.addEventListener("message", (event) => handlePayload(event.data));

  const storageListener = (event: StorageEvent) => {
    if (event.key === authChannelName) {
      handlePayload(event.newValue);
    }
  };

  window.addEventListener("storage", storageListener);

  return () => {
    channel?.close();
    window.removeEventListener("storage", storageListener);
  };
}