import koffi, { KoffiFunction } from "koffi";import { join } from "path";import { stat } from "fs/promises";import { platform } from "os";import { PDF_PARSER_PATH } from "../natives"; // TODO: add a timeout to the Rust parser export type PDFMetadata = {  numPages: number;  title?: string;}; class RustPDFParser {  private static instance: RustPDFParser;  private _getPDFMetadata: KoffiFunction;   private constructor() {    const lib = koffi.load(PDF_PARSER_PATH);    this._getPDFMetadata = lib.func("get_pdf_metadata", "string", ["string"]);  }   public static async isParserAvailable(): Promise<boolean> {    if (RustPDFParser.instance) {      return true;    }     try {      await stat(PDF_PARSER_PATH);      RustPDFParser.instance = new RustPDFParser();      return true;    } catch (_) {      return false;    }  }   public static async getInstance(): Promise<RustPDFParser> {    if (!RustPDFParser.instance) {      try {        await stat(PDF_PARSER_PATH);      } catch (_) {        throw Error("Rust pdf-parser shared library not found");      }      RustPDFParser.instance = new RustPDFParser();    }    return RustPDFParser.instance;  }   public async getPDFMetadata(path: string): Promise<PDFMetadata> {    return new Promise<PDFMetadata>((resolve, reject) => {      this._getPDFMetadata.async(path, (err: Error, res: string) => {        if (err) {          reject(err);        } else {          if (res.startsWith("RUSTFC:ERROR:")) {            reject(new Error(res.replace("RUSTFC:ERROR:", "")));          } else {            try {              const metadata = JSON.parse(res) as PDFMetadata;              resolve(metadata);            } catch (e) {              reject(new Error("Failed to parse PDF metadata."));            }          }        }      });    });  }} export async function getPDFMetadata(path: string): Promise<PDFMetadata> {  const converter = await RustPDFParser.getInstance();  return await converter.getPDFMetadata(path);}