class Google::Auth::GCECredentials

def add_universe_domain_to hash
  return if @universe_domain_overridden
  universe_domain =
    if disable_universe_domain_check
      # TODO: Remove when universe domain metadata endpoint is stable (see b/349488459).
      "googleapis.com"
    else
      Google::Cloud.env.lookup_metadata "universe", "universe-domain"
    end
  universe_domain = "googleapis.com" if !universe_domain || universe_domain.empty?
  hash["universe_domain"] = universe_domain.strip
end

def adjust_for_stale_expires_in hash, retrieval_time
  return unless hash["expires_in"].is_a? Numeric
  offset = 1 + (Process.clock_gettime(Process::CLOCK_MONOTONIC) - retrieval_time).round
  hash["expires_in"] -= offset if offset.positive?
  hash["expires_in"] = 0 if hash["expires_in"].negative?
end

def build_token_hash body, content_type, retrieval_time
  hash =
    if ["text/html", "application/text"].include? content_type
      parse_encoded_token body
    else
      Signet::OAuth2.parse_credentials body, content_type
    end
  add_universe_domain_to hash
  adjust_for_stale_expires_in hash, retrieval_time
  hash
end

def compute_auth_token_uri
  "#{compute_check_uri}/computeMetadata/v1/instance/service-accounts/default/token".freeze
end

def compute_check_uri
  "http://#{metadata_host}".freeze
end

def compute_id_token_uri
  "#{compute_check_uri}/computeMetadata/v1/instance/service-accounts/default/identity".freeze
end

def fetch_access_token _options = {}
  query, entry =
    if token_type == :id_token
      [{ "audience" => target_audience, "format" => "full" }, "service-accounts/default/identity"]
    else
      [{}, "service-accounts/default/token"]
    end
  query[:scopes] = Array(scope).join "," if scope
  begin
    log_fetch_query
    resp = Google::Cloud.env.lookup_metadata_response "instance", entry, query: query
    log_fetch_resp resp
    case resp.status
    when 200
      build_token_hash resp.body, resp.headers["content-type"], resp.retrieval_monotonic_time
    when 403, 500
      raise Signet::UnexpectedStatusError, "Unexpected error code #{resp.status} #{UNEXPECTED_ERROR_SUFFIX}"
    when 404
      raise Signet::AuthorizationError, NO_METADATA_SERVER_ERROR
    else
      raise Signet::AuthorizationError, "Unexpected error code #{resp.status} #{UNEXPECTED_ERROR_SUFFIX}"
    end
  rescue Google::Cloud::Env::MetadataServerNotResponding => e
    log_fetch_err e
    raise Signet::AuthorizationError, e.message
  end
end

def initialize options = {}
  # Override the constructor to remember whether the universe domain was
  # overridden by a constructor argument.
  @universe_domain_overridden = options["universe_domain"] || options[:universe_domain] ? true : false
  # TODO: Remove when universe domain metadata endpoint is stable (see b/349488459).
  @disable_universe_domain_check = true
  super options
end

def log_fetch_err _err
  logger&.info do
    Google::Logging::Message.from(
      message: "MDS did not respond to token request",
      "credentialsId" => object_id
    )
  end
end

def log_fetch_query
  if token_type == :id_token
    logger&.info do
      Google::Logging::Message.from(
        message: "Requesting id token from MDS with aud=#{target_audience}",
        "credentialsId" => object_id
      )
    end
  else
    logger&.info do
      Google::Logging::Message.from(
        message: "Requesting access token from MDS",
        "credentialsId" => object_id
      )
    end
  end
end

def log_fetch_resp resp
  logger&.info do
    Google::Logging::Message.from(
      message: "Received #{resp.status} from MDS",
      "credentialsId" => object_id
    )
  end
end

def metadata_host
  ENV.fetch "GCE_METADATA_HOST", DEFAULT_METADATA_HOST
end

def on_gce? _options = {}, _reload = false # rubocop:disable Style/OptionalBooleanParameter
  Google::Cloud.env.metadata?
end

def parse_encoded_token body
  hash = { token_type.to_s => body }
  if token_type == :id_token
    expires_at = expires_at_from_id_token body
    hash["expires_at"] = expires_at if expires_at
  end
  hash
end

def reset_cache
  Google::Cloud.env.compute_metadata.reset_existence!
  Google::Cloud.env.compute_metadata.cache.expire_all!
end

def universe_domain
  value = super
  return value unless value.nil?
  fetch_access_token!
  super
end