class Module

# File lib/safe_monkeypatch.rb, line 18
def safe_monkeypatch(meth, options={})
  options = options.dup
  info = options.delete(:error)

  if meth.is_a? UnboundMethod
    method = meth
    meth = method.name
  else
    begin
      method = instance_method(meth)
    rescue NameError => e
      raise SafeMonkeypatch::InvalidMethod, "#{inspect} has no method #{meth} anymore"
    end
  end

  source = method.source

  if options.empty?
    raise SafeMonkeypatch::ConfigurationError, "Provide at least one cypher name like: md5: '...'"
  end

  found_match = false
  error_parts = ["#{inspect}##{meth} expected to have"]

  options.each do |cypher_name, expected|
    cypher = Digest.const_get(cypher_name.upcase)
    actual = cypher.hexdigest(source)
    found_match = if expected.is_a? Array
                    expected.any? { |e| e == actual }
                  else
                    actual == expected
                  end

    unless found_match
      error_parts << "#{cypher_name} expected: #{expected.inspect}, but has: #{actual.inspect}"
    end
  end

  error_parts << info.to_s if info

  if block_given? && found_match
    yield
  elsif block_given?
    nil # pass
  elsif not found_match
    raise SafeMonkeypatch::UpstreamChanged, error_parts.join(" ")
  end
end