File Download Service

[dmitrytrager]

GET /api/v1/files/{id} with resume support

• Create FileDownloader service:

class FileDownloader
  def download(file_id, expected_checksum:, resume_from: 0)
    # Downloads to temp file
    # Supports Range header for resume
    # Returns path to downloaded file
  end
end

• Download to temp directory (tmp/downloads/)
• Track partial download progress for resume capability
• Return downloaded file path for attachment

Verify downloaded files match manifest checksums

• Create ChecksumVerifier service:

class ChecksumVerifier
  def verify!(file_path, expected_sha256)
    actual = Digest::SHA256.file(file_path).hexdigest
    expected = expected_sha256.delete_prefix("sha256:")
    raise ChecksumMismatchError unless actual == expected
  end
end

• Consider using MD5 since active storage uses MD5 for checksums
• Integrate verification before ActiveStorage attachment
• On mismatch: delete file, retry download (up to 3 attempts)

Ensure proper ActiveStorage setup for offline operation

• Verify config/storage.yml uses local disk:
  local:
  service: Disk
  root: <%= Rails.root.join("storage") %>
• Set in config/environments/production.rb:
  config.active_storage.service = :local
• Configure blob cleanup: old blobs purged when TopicFile destroyed
• Add storage/ to backup strategy