import { join } from "node:path";
import { run } from "./util/exec";

export interface DeckRender { pages: number; title: string }

const TOOL = join(import.meta.dir, "..", "py", "pdf_tool.py");

/**
 * Renders page images (p-001.jpg ...) and text.json into `outDir` with PyMuPDF in a subprocess,
 * so the server process never holds a PDF engine. `python` is STC_PYTHON (default python3).
 */
export async function renderPdf(python: string, pdf: string, outDir: string, opts: { onPage?: (page: number, total: number) => void; signal?: AbortSignal } = {}): Promise<DeckRender> {
  let last = "";
  await run([python, "-I", TOOL, "render", pdf, outDir], {
    signal: opts.signal,
    onLine(l) {
      const m = /^page (\d+)\/(\d+)$/.exec(l);
      if (m) opts.onPage?.(Number(m[1]), Number(m[2]));
      else if (l.trim()) last = l;
    },
  });
  return JSON.parse(last) as DeckRender;
}