import { ensureNavId, peekNavId } from "./history";
import { anyBlockingLayer } from "./layerStack";
import { createStore } from "./store";

// Downloading a link is an action you start anywhere: the Files page's link box, a link pasted onto
// any page, the command palette. They all hand the link to ONE app-wide download dialog
// (features/downloads/DownloadIntake), so none of them mounts a dialog of its own.

const pending = createStore<string | null>(null);

/** An http(s) link, alone — what a paste or the link box may download; anything else is not one. */
export function asDownloadLink(text: string | null | undefined): string | null {
  const s = text?.trim() ?? "";
  return /^https?:\/\/\S+$/i.test(s) ? s : null;
}

/** Whether a paste here is the page's to take: not typed into a field, and nothing on top that owns
 *  the keyboard — a dialog, a player, an open menu (the reader is busy with that, and a link pasted
 *  at it is not a request to download). The layer stack knows them all; a player marks no
 *  `aria-modal`, so the markup alone would miss it. */
export function pasteIsForThePage(target: EventTarget | null): boolean {
  const el = target instanceof Element ? target : null;
  if (el?.closest("input, textarea, select, [contenteditable]:not([contenteditable='false'])"))
    return false;
  return !anyBlockingLayer() && !document.querySelector("[aria-modal='true']");
}

/** Ask to download `url`: the app's download dialog opens on it. */
export const requestDownload = (url: string): void => pending.set(url);

/** The link the dialog is open on (null = closed). DownloadIntake only. */
export const usePendingDownload = (): string | null => pending.useValue();

/** The dialog closed, downloading or not. */
export const clearPendingDownload = (): void => pending.set(null);

// The palette's "Download from link…" takes the reader to the Files page's link box. A token for the
// history entry the navigation made (as lib/homeIntent's): Files is a lazy module, often not mounted
// when it is asked, and a request that outlived its entry must not grab the focus on a later visit.
const linkBox = createStore<number | null>(null);

/** Ask the Files page to focus its link box on THIS entry — `setPage("files", requestLinkBox)`. */
export const requestLinkBox = (): void => linkBox.set(ensureNavId());

/** The pending request (null = none) — the render subscription that wakes the link box. */
export const useLinkBoxRequest = (): number | null => linkBox.useValue();

/** Take the request, clearing it; true only on the entry it was made for. */
export const takeLinkBox = (): boolean => {
  const entry = linkBox.get();
  if (entry === null) return false;
  linkBox.set(null);
  return entry === peekNavId();
};