// 附件：SHA-256 内容寻址去重存储
import crypto from 'node:crypto';
import fs from 'node:fs';
import path from 'node:path';
import { getDb, BLOB_DIR } from './db.mjs';

export function upload(user_id, { sha256, size, mime, file_name, data_b64 }) {
  const d = getDb();
  if (!/^[a-f0-9]{64}$/.test(sha256 || '')) throw new Error('sha256 格式不合法');
  const buf = Buffer.from(data_b64 || '', 'base64');
  const actual = crypto.createHash('sha256').update(buf).digest('hex');
  if (actual !== sha256) throw new Error('内容哈希与声明不符');
  if (size != null && buf.length !== Number(size)) throw new Error('大小与声明不符');
  if (buf.length > 100 * 1024 * 1024) throw new Error('单文件不得超过 100MB');

  const dir = path.join(BLOB_DIR, user_id);
  fs.mkdirSync(dir, { recursive: true });
  const file = path.join(dir, sha256);
  if (!fs.existsSync(file)) fs.writeFileSync(file, buf);

  const existing = d.prepare('SELECT 1 FROM attachments WHERE user_id=? AND sha256=?').get(user_id, sha256);
  if (!existing) {
    d.prepare('INSERT INTO attachments (user_id, sha256, size, mime, file_name) VALUES (?,?,?,?,?)')
      .run(user_id, sha256, buf.length, mime ?? null, (file_name || '').slice(0, 255));
    return { dedup: false, size: buf.length };
  }
  return { dedup: true, size: buf.length };
}

export function download(user_id, sha256) {
  const d = getDb();
  const row = d.prepare('SELECT * FROM attachments WHERE user_id=? AND sha256=?').get(user_id, sha256);
  if (!row) return null;
  const file = path.join(BLOB_DIR, user_id, sha256);
  if (!fs.existsSync(file)) return null;
  return { buf: fs.readFileSync(file), mime: row.mime, file_name: row.file_name, size: row.size };
}