import fs from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";
import type { Page } from "playwright";

/**
 * Raw DOM candidates scanned in-page (§13–§15). Generic: relies on links, landmarks, ARIA roles,
 * media elements and text density — never on generated class names. Adapters refine these later.
 *
 * The in-page code lives in `snapshot.page.js` (plain JS) because TypeScript transpilers inject
 * helpers such as `__name` into function bodies, which do not exist inside the page.
 */
export interface DomCandidate {
  kind: "link" | "article" | "video" | "image" | "heading" | "search" | "button";
  href?: string;
  text: string; // visible text (trimmed)
  aria_label?: string;
  role?: string;
  region: string; // main / feed / sidebar / dialog / header / navigation / comments / unknown
  index: number; // document order among candidates
  visible: boolean; // within viewport
  top: number; // bounding rect top (for feed position)
  meta?: Record<string, string>; // duration, views, author text found in the same card
  locator_hint: string; // a stable-ish CSS selector path we can use to click (prefers href / aria-label)
}

export interface DomSnapshot {
  url: string;
  title: string;
  lang?: string;
  h1?: string;
  landmarks: string[];
  candidates: DomCandidate[];
  video_elements: { src?: string; current_src?: string; duration?: number; width: number; height: number; playing: boolean; poster?: string }[];
  text_excerpt: string; // first ~600 chars of main text
  scroll: { y: number; height: number; viewport: number };
  has_login_form: boolean;
  dialog_open: boolean;
}

const here = path.dirname(fileURLToPath(import.meta.url));
const SNAPSHOT_SOURCE = fs
  .readFileSync(path.join(here, "snapshot.page.js"), "utf8")
  .replace(/^\s*\/\/.*$/gm, "") // strip comment lines so the string is a bare function expression
  .trim();

export async function snapshotDom(page: Page, opts: { maxCandidates?: number } = {}): Promise<DomSnapshot> {
  const max = opts.maxCandidates ?? 250;
  return (await page.evaluate(`(${SNAPSHOT_SOURCE})(${max})`)) as DomSnapshot;
}