class RSpec::Mocks::MethodDouble

def add_default_stub(*args, &implementation)
  return if stubs.any?
  add_stub(*args, &implementation)
end

def add_expectation(error_generator, expectation_ordering, expected_from, opts, &implementation)
  configure_method
  expectation = message_expectation_class.new(error_generator, expectation_ordering,
                                              expected_from, self, :expectation, opts, &implementation)
  expectations << expectation
  expectation
end

def add_simple_expectation(method_name, response, error_generator, backtrace_line)
  setup_simple_method_double method_name, response, expectations, error_generator, backtrace_line
end

def add_simple_stub(method_name, response)
  setup_simple_method_double method_name, response, stubs
end

def add_stub(error_generator, expectation_ordering, expected_from, opts={}, &implementation)
  configure_method
  stub = message_expectation_class.new(error_generator, expectation_ordering, expected_from,
                                       self, :stub, opts, &implementation)
  stubs.unshift stub
  stub
end

def build_expectation(error_generator, expectation_ordering)
  expected_from = IGNORED_BACKTRACE_LINE
  message_expectation_class.new(error_generator, expectation_ordering, expected_from, self)
end

def clear
  expectations.clear
  stubs.clear
end

def configure_method
  @original_visibility = visibility
  @method_stasher.stash unless @method_is_proxied
  define_proxy_method
end

def define_proxy_method
  return if @method_is_proxied
  save_original_implementation_callable!
  definition_target.class_exec(self, method_name, @original_visibility || visibility) do |method_double, method_name, visibility|
    define_method(method_name) do |*args, &block|
      method_double.proxy_method_invoked(self, *args, &block)
    end
    # This can't be `if respond_to?(:ruby2_keywords, true)`,
    # see https://github.com/rspec/rspec-mocks/pull/1385#issuecomment-755340298
    ruby2_keywords(method_name) if Module.private_method_defined?(:ruby2_keywords)
    __send__(visibility, method_name)
  end
  @method_is_proxied = true
rescue RuntimeError, TypeError => e
  # TODO: drop in favor of FrozenError in ruby 2.5+
  #  RuntimeError (and FrozenError) for ruby 2.x
  #  TypeError for ruby 1.x
  if (defined?(FrozenError) && e.is_a?(FrozenError)) || FROZEN_ERROR_MSG === e.message
    raise ArgumentError, "Cannot proxy frozen objects, rspec-mocks relies on proxies for method stubbing and expectations."
  end
  raise
end

def definition_target
  @definition_target ||= usable_rspec_prepended_module || object_singleton_class
end

def definition_target
  object_singleton_class
end

def initialize(object, method_name, proxy)
  @method_name = method_name
  @object = object
  @proxy = proxy
  @original_visibility = nil
  @method_stasher = InstanceMethodStasher.new(object, method_name)
  @method_is_proxied = false
  @expectations = []
  @stubs = []
end

def message_expectation_class
  MessageExpectation
end

def new_rspec_prepended_module
  RSpecPrependedModule.new.tap do |mod|
    object_singleton_class.__send__ :prepend, mod
  end
end

def object_singleton_class
  class << @object; self; end
end

def original_implementation_callable
  # If original method is not present, uses the `method_missing`
  # handler of the object. This accounts for cases where the user has not
  # correctly defined `respond_to?`, and also 1.8 which does not provide
  # method handles for missing methods even if `respond_to?` is correct.
  @original_implementation_callable ||= original_method ||
    Proc.new do |*args, &block|
      @object.__send__(:method_missing, @method_name, *args, &block)
    end
end

def original_method
  @original_method ||=
    @method_stasher.original_method ||
    @proxy.original_method_handle_for(method_name)
end

def proxy_method_invoked(_obj, *args, &block)
  @proxy.message_received method_name, *args, &block
end

def raise_method_not_stubbed_error
  RSpec::Mocks.error_generator.raise_method_not_stubbed_error(method_name)
end

def remove_method_from_definition_target
  definition_target.__send__(:remove_method, @method_name)
rescue NameError
  # This can happen when the method has been monkeyed with by
  # something outside RSpec. This happens, for example, when
  # `file.write` has been stubbed, and then `file.reopen(other_io)`
  # is later called, as `File#reopen` appears to redefine `write`.
  #
  # Note: we could avoid rescuing this by checking
  # `definition_target.instance_method(@method_name).owner == definition_target`,
  # saving us from the cost of the expensive exception, but this error is
  # extremely rare (it was discovered on 2014-12-30, only happens on
  # RUBY_VERSION < 2.0 and our spec suite only hits this condition once),
  # so we'd rather avoid the cost of that check for every method double,
  # and risk the rare situation where this exception will get raised.
  RSpec.warn_with(
    "WARNING: RSpec could not fully restore #{@object.inspect}." \
    "#{@method_name}, possibly because the method has been redefined " \
    "by something outside of RSpec."
  )
end

def remove_stub
  raise_method_not_stubbed_error if stubs.empty?
  remove_stub_if_present
end

def remove_stub_if_present
  expectations.empty? ? reset : stubs.clear
end

def reset
  restore_original_method
  clear
end

def restore_original_method
  return unless @method_is_proxied
  remove_method_from_definition_target
  @method_stasher.restore if @method_stasher.method_is_stashed?
  restore_original_visibility
  @method_is_proxied = false
rescue RuntimeError, TypeError => e
  # TODO: drop in favor of FrozenError in ruby 2.5+
  #  RuntimeError (and FrozenError) for ruby 2.x
  #  TypeError for ruby 1.x
  if (defined?(FrozenError) && e.is_a?(FrozenError)) || FROZEN_ERROR_MSG === e.message
    return show_frozen_warning
  end
  raise
end

def restore_original_visibility
  return unless @original_visibility &&
    MethodReference.method_defined_at_any_visibility?(object_singleton_class, @method_name)
  object_singleton_class.__send__(@original_visibility, method_name)
end

def setup_simple_method_double(method_name, response, collection, error_generator=nil, backtrace_line=nil)
  define_proxy_method
  me = SimpleMessageExpectation.new(method_name, response, error_generator, backtrace_line)
  collection.unshift me
  me
end

def show_frozen_warning
  RSpec.warn_with(
    "WARNING: rspec-mocks was unable to restore the original `#{@method_name}` " \
    "method on #{@object.inspect} because it has been frozen.  If you reuse this " \
    "object, `#{@method_name}` will continue to respond with its stub implementation.",
    :call_site                      => nil,
    :use_spec_location_as_call_site => true
  )
end

def usable_rspec_prepended_module
  @proxy.prepended_modules_of_singleton_class.each do |mod|
    # If we have one of our modules prepended before one of the user's
    # modules that defines the method, use that, since our module's
    # definition will take precedence.
    return mod if RSpecPrependedModule === mod
    # If we hit a user module with the method defined first,
    # we must create a new prepend module, even if one exists later,
    # because ours will only take precedence if it comes first.
    return new_rspec_prepended_module if mod.method_defined?(method_name)
  end
  nil
end

def verify
  expectations.each { |e| e.verify_messages_received }
end

def visibility
  @proxy.visibility_for(@method_name)
end