class RSpec::Matchers::BuiltIn::Output

def actual_output_description
  return "nothing" unless captured?
  actual_formatted
end

def captured?
  @actual.length > 0
end

def description
  if @expected
    "output #{description_of @expected} to #{@stream_capturer.name}"
  else
    "output to #{@stream_capturer.name}"
  end
end

def diffable?
  true
end

def does_not_match?(block)
  !matches?(block) && Proc === block
end

def failure_message
  "expected block to #{description}, but #{positive_failure_reason}"
end

def failure_message_when_negated
  "expected block to not #{description}, but #{negative_failure_reason}"
end

def initialize(expected)
  @expected        = expected
  @actual          = ""
  @block           = nil
  @stream_capturer = NullCapture
end

def matches?(block)
  @block = block
  return false unless Proc === block
  @actual = @stream_capturer.capture(block)
  @expected ? values_match?(@expected, @actual) : captured?
end

def negative_failure_reason
  return "was not a block" unless Proc === @block
  "output #{actual_output_description}"
end

def positive_failure_reason
  return "was not a block" unless Proc === @block
  return "output #{actual_output_description}" if @expected
  "did not"
end

def supports_block_expectations?
  true
end

def supports_value_expectations?
  false
end

def to_stderr
  @stream_capturer = CaptureStderr
  self
end

def to_stderr_from_any_process
  @stream_capturer = CaptureStreamToTempfile.new("stderr", $stderr)
  self
end

def to_stdout
  @stream_capturer = CaptureStdout
  self
end

def to_stdout_from_any_process
  @stream_capturer = CaptureStreamToTempfile.new("stdout", $stdout)
  self
end