/**
 * @file openInPreview.ts — the ONE rule every link in the dashboard follows
 * (a chat's markdown link or bare URL, a terminal's link): a page served by
 * THIS machine (`localhost`, `127.0.0.1`, `0.0.0.0`, `[::1]`) opens in the
 * session view's Preview tab, everything else in a browser tab as before.
 * The request travels as a window event (like `openInChanges.ts`); the
 * Workspace page answers it only while it shows a session panel, so with no
 * listener — another page, or a remote dashboard where "localhost" is the
 * viewer's own machine — the link falls back to a browser tab. Also holds the
 * URL checks the Preview tab itself uses.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

export const OPEN_IN_PREVIEW_EVENT = "agenthub:open-in-preview";

/** The event's detail. `handled` is set by the listener, read by the sender. */
export type OpenInPreview = { url: string; handled: boolean };

const LOOPBACK = new Set(["localhost", "127.0.0.1", "0.0.0.0", "[::1]", "::1"]);

/** A URL the Preview may show: http(s) only, `0.0.0.0` read as `localhost`
 *  (a dev server prints it, a browser cannot open it), never the dashboard's
 *  own origin (the frame would then BE the dashboard, cookies and API
 *  included). A bare `localhost:3000` gets `http://`. Null when refused. */
export function normalizePreviewUrl(raw: string, self = window.location.origin): string | null {
  let text = raw.trim();
  if (!text) return null;
  if (!/^[a-z][a-z0-9+.-]*:\/\//i.test(text)) text = `http://${text}`;
  let u: URL;
  try {
    u = new URL(text);
  } catch {
    return null;
  }
  if (u.protocol !== "http:" && u.protocol !== "https:") return null;
  if (u.username || u.password) return null;
  if (u.hostname === "0.0.0.0") u.hostname = "localhost";
  if (u.origin === self) return null;
  return u.toString();
}

/** True for a page served by the machine the BROWSER runs on. */
export function isLoopbackUrl(url: string): boolean {
  try {
    const u = new URL(url);
    return (u.protocol === "http:" || u.protocol === "https:") && LOOPBACK.has(u.hostname);
  } catch {
    return false;
  }
}

/** The dashboard itself is opened from this machine: only then does a
 *  `localhost` link name the same machine the agents run on. */
export function dashboardIsLocal(hostname = window.location.hostname): boolean {
  return LOOPBACK.has(hostname);
}

/** Asks the open session panel to show `url`. False when nothing took it
 *  (not a local page, a remote dashboard, no session panel). */
export function openInPreview(url: string): boolean {
  if (!isLoopbackUrl(url) || !dashboardIsLocal()) return false;
  const target = normalizePreviewUrl(url);
  if (!target) return false;
  const detail: OpenInPreview = { url: target, handled: false };
  window.dispatchEvent(new CustomEvent(OPEN_IN_PREVIEW_EVENT, { detail }));
  return detail.handled;
}

/** A link click: Preview when the rule says so, else a browser tab. A
 *  Ctrl/Cmd/Shift/middle click always keeps the browser's own behaviour. */
export function onLinkClick(
  e: {
    ctrlKey: boolean;
    metaKey: boolean;
    shiftKey: boolean;
    button: number;
    preventDefault: () => void;
  },
  url: string
): void {
  if (e.ctrlKey || e.metaKey || e.shiftKey || e.button !== 0) return;
  if (openInPreview(url)) e.preventDefault();
}