module Spec
  module Matchers
    # :call-seq:
    #   should be_close(expected, delta)
    #   should_not be_close(expected, delta)
    #
    # Passes if actual == expected +/- delta
    #
    # == Example
    #
    #   result.should be_close(3.0, 0.5)
    def be_close(expected, delta)
      Matcher.new :be_close, expected, delta do |_expected_, _delta_|
        match do |actual|
          (actual - _expected_).abs < _delta_
        end

        failure_message_for_should do |actual|
          "expected #{_expected_} +/- (< #{_delta_}), got #{actual}"
        end

        failure_message_for_should_not do |actual|
          "expected #{_expected_} +/- (< #{_delta_}), got #{actual}"
        end

        description do
          "be close to #{_expected_} (within +- #{_delta_})"
        end
      end
    end
  end
end