/* hash.js — streaming SHA-256 of files on disk (never loads a whole video).
 * The hex digest of a validated file is its P2P content id (cid). */
import { createHash } from 'node:crypto';
import { createReadStream } from 'node:fs';

export function sha256File(path) {
  return new Promise((resolve, reject) => {
    const h = createHash('sha256');
    createReadStream(path, { highWaterMark: 1024 * 1024 })
      .on('data', (d) => h.update(d))
      .on('error', reject)
      .on('end', () => resolve(h.digest('hex')));
  });
}

// Hash of bytes [offset, offset+length) — used for holder range challenges.
export function sha256Range(path, offset, length) {
  return new Promise((resolve, reject) => {
    if (!(length > 0)) { resolve(createHash('sha256').digest('hex')); return; }
    const h = createHash('sha256');
    createReadStream(path, { start: offset, end: offset + length - 1 })
      .on('data', (d) => h.update(d))
      .on('error', reject)
      .on('end', () => resolve(h.digest('hex')));
  });
}