class RSpec::Mocks::ConstantMutator::DefinedConstantReplacer

def mutate
  @context = recursive_const_get(@context_parts.join('::'))
  @original_value = get_const_defined_on(@context, @const_name)
  constants_to_transfer = verify_constants_to_transfer!
  @context.send(:remove_const, @const_name)
  @context.const_set(@const_name, @mutated_value)
  transfer_nested_constants(constants_to_transfer)
end

def rspec_reset
  @context.send(:remove_const, @const_name)
  @context.const_set(@const_name, @original_value)
end

def to_constant
  const = super
  const.stubbed = true
  const.previously_defined = true
  const
end

def transfer_nested_constants(constants)
  constants.each do |const|
    @mutated_value.const_set(const, get_const_defined_on(original_value, const))
  end
end

def verify_constants_to_transfer!
  return [] unless @transfer_nested_constants
  { @original_value => "the original value", @mutated_value => "the stubbed value" }.each do |value, description|
    unless value.respond_to?(:constants)
      raise ArgumentError,
        "Cannot transfer nested constants for #{@full_constant_name} " +
        "since #{description} is not a class or module and only classes " +
        "and modules support nested constants."
    end
  end
  if @transfer_nested_constants.is_a?(Array)
    @transfer_nested_constants = @transfer_nested_constants.map(&:to_s) if RUBY_VERSION == '1.8.7'
    undefined_constants = @transfer_nested_constants - constants_defined_on(@original_value)
    if undefined_constants.any?
      available_constants = constants_defined_on(@original_value) - @transfer_nested_constants
      raise ArgumentError,
        "Cannot transfer nested constant(s) #{undefined_constants.join(' and ')} " +
        "for #{@full_constant_name} since they are not defined. Did you mean " +
        "#{available_constants.join(' or ')}?"
    end
    @transfer_nested_constants
  else
    constants_defined_on(@original_value)
  end
end