Sharing Files

// Direct Arweave link
https://arweave.net/abc123xyz...

// Or through Helix for tracking
https://helix.storage/share/clx1234...
  → Redirects to arweave.net/abc123xyz...
  → Increments download counter

// Generate a secure share link for an encrypted file
async function createEncryptedShare(
  fileId: string,
  encryptionKey: CryptoKey,
  options: ShareOptions
) {
  // Generate random password for URL
  const password = generateSecurePassword(32);

  // Derive key from password
  const salt = crypto.getRandomValues(new Uint8Array(16));
  const shareKey = await deriveKey(password, salt);

  // Encrypt the file's encryption key
  const exportedKey = await crypto.subtle.exportKey('raw', encryptionKey);
  const { encrypted, iv } = await encrypt(exportedKey, shareKey);

  // Create share in database
  const share = await fetch('/api/share', {
    method: 'POST',
    body: JSON.stringify({
      fileId,
      encryptedKey: packKeyData(encrypted, iv, salt),
      expiresAt: options.expiresAt,
      maxDownloads: options.maxDownloads,
    }),
  });

  const { id } = await share.json();

  // Return URL with password in fragment
  return `https://helix.storage/share/${id}#${password}`;
}

function generateSecurePassword(length: number): string {
  const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  const array = crypto.getRandomValues(new Uint8Array(length));
  return Array.from(array, b => chars[b % chars.length]).join('');
}

interface ShareOptions {
  // Expiration (optional)
  expiresAt?: Date;

  // Download limit (optional)
  maxDownloads?: number;
}

// Examples
const shareOptions = {
  // Expires in 7 days
  expiresAt: new Date(Date.now() + 7 * 24 * 60 * 60 * 1000),

  // Allow only 5 downloads
  maxDownloads: 5,
};

async function verifyShareAccess(shareId: string) {
  const share = await prisma.shareLink.findUnique({
    where: { id: shareId },
    include: { file: true },
  });

  if (!share) {
    throw new Error('Share link not found');
  }

  // Check expiration
  if (share.expiresAt && share.expiresAt < new Date()) {
    throw new Error('Share link has expired');
  }

  // Check download limit
  if (share.maxDownloads && share.downloadCount >= share.maxDownloads) {
    throw new Error('Download limit reached');
  }

  // Increment download count
  await prisma.shareLink.update({
    where: { id: shareId },
    data: { downloadCount: { increment: 1 } },
  });

  return share;
}

// Delete the share link
await fetch(`/api/share/${shareId}`, {
  method: 'DELETE',
  headers: {
    Authorization: `Bearer ${token}`,
  },
});

// The file remains on Arweave, but the share link
// no longer resolves. Recipients who saved the
// encrypted key locally may still access the file.