module JSON::JWK::JWKizable::EC

def coordinates
  unless @coordinates
    hex = public_key.to_bn.to_s(16)
    data_len = hex.length - 2
    hex_x = hex[2, data_len / 2]
    hex_y = hex[2 + data_len / 2, data_len / 2]
    @coordinates = {
      x: hex_x,
      y: hex_y
    }
    @coordinates[:d] = private_key.to_s(16) if private_key?
  end
  @coordinates
end

def curve_name
  case group.curve_name
  when 'prime256v1'
    :'P-256'
  when 'secp384r1'
    :'P-384'
  when 'secp521r1'
    :'P-521'
  when 'secp256k1'
    :secp256k1
  else
    raise UnknownAlgorithm.new('Unknown EC Curve')
  end
end

def to_jwk(ex_params = {})
  params = {
    kty: :EC,
    crv: curve_name,
    x: Base64.urlsafe_encode64([coordinates[:x]].pack('H*'), padding: false),
    y: Base64.urlsafe_encode64([coordinates[:y]].pack('H*'), padding: false)
  }.merge ex_params
  params[:d] = Base64.urlsafe_encode64([coordinates[:d]].pack('H*'), padding: false) if private_key?
  JWK.new params
end