build-index.ts

import { MultiZipReader } from '@fparchive/multi-zip-reader';
import * as path from 'path';
import * as fs from 'fs';

async function run() {
  const folderPath = process.argv[2];
  const indexFilePath = path.join(folderPath, 'fp-index.dat');
  if (fs.existsSync(indexFilePath)) {
    fs.unlinkSync(indexFilePath);
  }
  
  if (!folderPath) {
    console.error('Please provide a folder path as the first argument');
    process.exit(1);
  }

  const reader = new MultiZipReader();
  await reader.loadDirectory(folderPath);
  const indexFileContent: IndexFileContent = {};
  for (const source of reader.sources) {
    const relPath = path.relative(folderPath, source.path);
    indexFileContent[relPath] = {};
    for (const file in source.data) {
      const zipOffset = await reader.getZipDataOffset(file);
      if (zipOffset) {
        indexFileContent[relPath][file] = [zipOffset.compressedLength, zipOffset.offset];
      }
    }
  }

  // Save index to file
  await fs.promises.writeFile(indexFilePath, JSON.stringify(indexFileContent));
}

type IndexFileContent = {
  [k: string]: Record<string, FilePosition>
}

type FilePosition = [number, number]; // [length, offset]

run();