class Aws::Plugins::Retries::ClockSkew

def clock_correction(endpoint)
  @mutex.synchronize { @endpoint_clock_corrections[endpoint.to_s] }
end

def clock_skewed?(context)
  server_time = server_time(context.http_response)
  !!server_time &&
    (Time.now.utc - server_time).abs > CLOCK_SKEW_THRESHOLD
end

def estimated_skew(endpoint)
  @mutex.synchronize { @endpoint_estimated_skews[endpoint.to_s] }
end

def initialize
  @mutex = Mutex.new
  # clock_corrections are recorded only on errors
  # and only when time difference is greater than the
  # CLOCK_SKEW_THRESHOLD
  @endpoint_clock_corrections = Hash.new(0)
  # estimated_skew is calculated on every request
  # and is used to estimate a TTL for requests
  @endpoint_estimated_skews = Hash.new(nil)
end

def server_time(response)
  begin
    Time.parse(response.headers['date']).utc
  rescue
    nil
  end
end

def set_clock_correction(endpoint, correction)
  @mutex.synchronize do
    @endpoint_clock_corrections[endpoint.to_s] = correction
  end
end

def update_clock_correction(context)
  endpoint = context.http_request.endpoint
  now_utc = Time.now.utc
  server_time = server_time(context.http_response)
  if server_time && (now_utc - server_time).abs > CLOCK_SKEW_THRESHOLD
    set_clock_correction(endpoint, server_time - now_utc)
  end
end

def update_estimated_skew(context)
  endpoint = context.http_request.endpoint
  now_utc = Time.now.utc
  server_time = server_time(context.http_response)
  return unless server_time
  @mutex.synchronize do
    @endpoint_estimated_skews[endpoint.to_s] = server_time - now_utc
  end
end