class WebAuthn::U2fMigrator

def attestation_trust_path
  @attestation_trust_path ||= [OpenSSL::X509::Certificate.new(Base64.strict_decode64(@certificate))]
end

def attestation_type
  WebAuthn::AttestationStatement::ATTESTATION_TYPE_BASIC_OR_ATTCA
end

def authenticator_data
  @authenticator_data ||= WebAuthn::FakeAuthenticator::AuthenticatorData.new(
    rp_id_hash: OpenSSL::Digest::SHA256.digest(@app_id.to_s),
    credential: {
      id: credential_id,
      public_key: credential_cose_key
    },
    sign_count: @counter,
    user_present: true,
    user_verified: false,
    aaguid: WebAuthn::AuthenticatorData::AttestedCredentialData::ZEROED_AAGUID
  )
end

def credential
  @credential ||=
    begin
      hash = authenticator_data.send(:credential)
      WebAuthn::AuthenticatorData::AttestedCredentialData::Credential.new(
        id: hash[:id],
        public_key: hash[:public_key].serialize
      )
    end
end

def credential_cose_key
  decoded_public_key = Base64.strict_decode64(@public_key)
  if WebAuthn::AttestationStatement::FidoU2f::PublicKey.uncompressed_point?(decoded_public_key)
    COSE::Key::EC2.new(
      alg: COSE::Algorithm.by_name("ES256").id,
      crv: 1,
      x: decoded_public_key[1..32],
      y: decoded_public_key[33..-1]
    )
  else
    raise "expected U2F public key to be in uncompressed point format"
  end
end

def credential_id
  Base64.urlsafe_decode64(@key_handle)
end

def initialize(app_id:, certificate:, key_handle:, public_key:, counter:)
  @app_id = app_id
  @certificate = certificate
  @key_handle = key_handle
  @public_key = public_key
  @counter = counter
end