import fs from 'fs';
import path from 'path';
import crypto from 'crypto';

export const takeChecksum = (file: string): Promise<string> => {
  const hash = crypto.createHash('sha512');
  return new Promise((resolve, reject) => {
    const readStream = fs.createReadStream(path.resolve(file));
    readStream.on('data', (chunk) => {
      try {
        hash.update(chunk);
      } catch(e: unknown) {
        reject(e);
      }
    });
    readStream.on('close', () => resolve(hash.digest('hex')));
    readStream.on('error', (err) => reject(err));
  });
};

export const checkChecksum = async (file: string, checksum: string): Promise<boolean> => {
  const fileSum = await takeChecksum(file);
  return crypto.timingSafeEqual(Buffer.from(fileSum), Buffer.from(checksum));
};