class Ammeter::OutputCapturer

def self.capture(io, &block)
  case io
  when :stdout
    capture_stdout(&block)
  when :stderr
    capture_stderr(&block)
  else
    raise "Unknown IO #{io}"
  end
end

def self.capture_stderr(&block)
  captured_stream = StringIO.new
  orginal_io, $stderr = $stderr, captured_stream
  block.call
  captured_stream.string
ensure
  $stderr = orginal_io
end

def self.capture_stdout(&block)
  captured_stream = StringIO.new
  orginal_io, $stdout = $stdout, captured_stream
  block.call
  captured_stream.string
ensure
  $stdout = orginal_io
end