// NewMetricsManager creates a runner that will run the metricsmanagement workers.
func newMetricsManager(client metricsmanager.MetricsManagerClient, notify chan string) (worker.Runner, error) {
	// TODO(fwereade): break this out into separate manifolds (with their own facades).

	// Periodic workers automatically retry so none should return an error. If they do
	// it's ok to restart them individually.
	isFatal := func(error) bool {
		return false
	}
	// All errors are equal
	moreImportant := func(error, error) bool {
		return false
	}

	runner := worker.NewRunner(isFatal, moreImportant, worker.RestartDelay)
	err := runner.StartWorker("sender", func() (worker.Worker, error) {
		return newSender(client, notify), nil
	})

	if err != nil {
		return nil, errors.Trace(err)
	}

	err = runner.StartWorker("cleanup", func() (worker.Worker, error) {
		return newCleanup(client, notify), nil
	})
	if err != nil {
		return nil, errors.Trace(err)
	}
	return runner, nil
}

// Init initializes the command for running.
func (a *UnitAgent) Init(args []string) error {
	if a.UnitName == "" {
		return cmdutil.RequiredError("unit-name")
	}
	if !names.IsValidUnit(a.UnitName) {
		return fmt.Errorf(`--unit-name option expects "<service>/<n>" argument`)
	}
	if err := a.AgentConf.CheckArgs(args); err != nil {
		return err
	}
	a.runner = worker.NewRunner(cmdutil.IsFatal, cmdutil.MoreImportant, worker.RestartDelay)

	if !a.logToStdErr {
		if err := a.ReadConfig(a.Tag().String()); err != nil {
			return err
		}
		agentConfig := a.CurrentConfig()

		// the writer in ctx.stderr gets set as the loggo writer in github.com/juju/cmd/logging.go
		a.ctx.Stderr = &lumberjack.Logger{
			Filename:   agent.LogFilename(agentConfig),
			MaxSize:    300, // megabytes
			MaxBackups: 2,
		}

	}

	return nil
}

func (*RunnerSuite) TestOneWorkerStartWhenStopping(c *gc.C) {
	runner := worker.NewRunner(allFatal, noImportance, 3*time.Second)
	starter := newTestWorkerStarter()
	starter.stopWait = make(chan struct{})

	// Start a worker, and wait for it.
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)

	// XXX the above does not imply the *runner* knows it's started.
	// voodoo sleep ahoy!
	time.Sleep(testing.ShortWait)

	// Stop the worker, which will block...
	err = runner.StopWorker("id")
	c.Assert(err, jc.ErrorIsNil)

	// While it's still blocked, try to start another.
	err = runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)

	// Unblock the stopping worker, and check that the task is
	// restarted immediately without the usual restart timeout
	// delay.
	t0 := time.Now()
	close(starter.stopWait)
	starter.assertStarted(c, false) // stop notification
	starter.assertStarted(c, true)  // start notification
	restartDuration := time.Since(t0)
	if restartDuration > 1*time.Second {
		c.Fatalf("task did not restart immediately")
	}
	c.Assert(worker.Stop(runner), gc.IsNil)
}

// NewMetricsManager creates a runner that will run the metricsmanagement workers.
func NewMetricsManager(client metricsmanager.MetricsManagerClient) (worker.Runner, error) {
	// Periodic workers automatically retry so none should return an error. If they do
	// it's ok to restart them individually.
	isFatal := func(error) bool {
		return false
	}
	// All errors are equal
	moreImportant := func(error, error) bool {
		return false
	}
	runner := worker.NewRunner(isFatal, moreImportant, worker.RestartDelay)
	err := runner.StartWorker("sender", func() (worker.Worker, error) {
		return NewSender(client), nil
	})

	if err != nil {
		return nil, errors.Trace(err)
	}
	err = runner.StartWorker("cleanup", func() (worker.Worker, error) {
		return NewCleanup(client), nil
	})
	if err != nil {
		return nil, errors.Trace(err)
	}
	return runner, nil
}

func (a *agent) mongoWorker() (worker.Worker, error) {
	dialInfo := gitjujutesting.MgoDialInfo(coretesting.Certs, a.hostPort)
	session, err := mgo.DialWithInfo(dialInfo)
	if err != nil {
		return nil, err
	}
	mc := &mongoConn{
		localHostPort: a.hostPort,
		session:       session,
	}

	fn := func(err0, err1 error) bool { return true }
	runner := worker.NewRunner(connectionIsFatal(mc), fn, worker.RestartDelay)
	singularRunner, err := singular.New(runner, mc)
	if err != nil {
		return nil, fmt.Errorf("cannot start singular runner: %v", err)
	}
	a.notify.workerConnected()
	singularRunner.StartWorker(fmt.Sprint("worker-", a.notify.id), func() (worker.Worker, error) {
		return worker.NewSimpleWorker(func(stop <-chan struct{}) error {
			return a.worker(session, stop)
		}), nil
	})
	return runner, nil
}

func (m *modelWorkerManager) loop() error {
	m.runner = worker.NewRunner(
		neverFatal, neverImportant, m.config.ErrorDelay,
	)
	if err := m.catacomb.Add(m.runner); err != nil {
		return errors.Trace(err)
	}
	watcher := m.config.Backend.WatchModels()
	if err := m.catacomb.Add(watcher); err != nil {
		return errors.Trace(err)
	}

	for {
		select {
		case <-m.catacomb.Dying():
			return m.catacomb.ErrDying()
		case uuids, ok := <-watcher.Changes():
			if !ok {
				return errors.New("changes stopped")
			}
			for _, modelUUID := range uuids {
				if err := m.ensure(m.config.ControllerUUID, modelUUID); err != nil {
					return errors.Trace(err)
				}
			}
		}
	}
}

func (s *ContainerSetupSuite) setupContainerWorker(c *gc.C, tag names.MachineTag) (worker.StringsWatchHandler, worker.Runner) {
	testing.PatchExecutable(c, s, "ubuntu-cloudimg-query", containertesting.FakeLxcURLScript)
	runner := worker.NewRunner(allFatal, noImportance)
	pr := s.st.Provisioner()
	machine, err := pr.Machine(tag)
	c.Assert(err, jc.ErrorIsNil)
	err = machine.SetSupportedContainers(instance.ContainerTypes...)
	c.Assert(err, jc.ErrorIsNil)
	cfg := s.AgentConfigForTag(c, tag)

	watcherName := fmt.Sprintf("%s-container-watcher", machine.Id())
	params := provisioner.ContainerSetupParams{
		Runner:              runner,
		WorkerName:          watcherName,
		SupportedContainers: instance.ContainerTypes,
		ImageURLGetter:      &containertesting.MockURLGetter{},
		Machine:             machine,
		Provisioner:         pr,
		Config:              cfg,
		InitLock:            s.initLock,
	}
	handler := provisioner.NewContainerSetupHandler(params)
	runner.StartWorker(watcherName, func() (worker.Worker, error) {
		return worker.NewStringsWorker(handler), nil
	})
	return handler, runner
}

func (*runnerSuite) TestOneWorkerStartWhenStopping(c *gc.C) {
	worker.RestartDelay = 3 * time.Second
	runner := worker.NewRunner(allFatal, noImportance)
	starter := newTestWorkerStarter()
	starter.stopWait = make(chan struct{})

	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)
	err = runner.StopWorker("id")
	c.Assert(err, jc.ErrorIsNil)
	err = runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)

	close(starter.stopWait)
	starter.assertStarted(c, false)
	// Check that the task is restarted immediately without
	// the usual restart timeout delay.
	t0 := time.Now()
	starter.assertStarted(c, true)
	restartDuration := time.Since(t0)
	if restartDuration > 1*time.Second {
		c.Fatalf("task did not restart immediately")
	}
	c.Assert(worker.Stop(runner), gc.IsNil)
}

func newRunner() worker.Runner {
	return worker.NewRunner(
		func(err error) bool {
			return err == errFatal
		},
		func(err0, err1 error) bool { return true },
	)
}

func (*runnerSuite) TestOneWorkerStartFatalError(c *gc.C) {
	runner := worker.NewRunner(allFatal, noImportance)
	starter := newTestWorkerStarter()
	starter.startErr = errors.New("cannot start test task")
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	err = runner.Wait()
	c.Assert(err, gc.Equals, starter.startErr)
}

func (*runnerSuite) TestOneWorkerStart(c *gc.C) {
	runner := worker.NewRunner(noneFatal, noImportance)
	starter := newTestWorkerStarter()
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)

	c.Assert(worker.Stop(runner), gc.IsNil)
	starter.assertStarted(c, false)
}

func (*runnerSuite) TestOneWorkerStartStop(c *gc.C) {
	runner := worker.NewRunner(allFatal, noImportance, time.Millisecond)
	starter := newTestWorkerStarter()
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)
	err = runner.StopWorker("id")
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, false)
	c.Assert(worker.Stop(runner), gc.IsNil)
}

func (*runnerSuite) TestOneWorkerStopFatalError(c *gc.C) {
	runner := worker.NewRunner(allFatal, noImportance)
	starter := newTestWorkerStarter()
	starter.stopErr = errors.New("stop error")
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)
	err = runner.StopWorker("id")
	c.Assert(err, jc.ErrorIsNil)
	err = runner.Wait()
	c.Assert(err, gc.Equals, starter.stopErr)
}

func (*runnerSuite) TestOneWorkerDieFatalError(c *gc.C) {
	runner := worker.NewRunner(allFatal, noImportance)
	starter := newTestWorkerStarter()
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)
	dieErr := errors.New("error when running")
	starter.die <- dieErr
	err = runner.Wait()
	c.Assert(err, gc.Equals, dieErr)
	starter.assertStarted(c, false)
}

func (*runnerSuite) TestOneWorkerFinish(c *gc.C) {
	runner := worker.NewRunner(noneFatal, noImportance, time.Millisecond)
	starter := newTestWorkerStarter()
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)

	starter.die <- nil
	starter.assertStarted(c, false)
	starter.assertNeverStarted(c)

	c.Assert(worker.Stop(runner), gc.IsNil)
}

// NewEnvWorkerManager returns a Worker which manages a worker which
// needs to run on a per environment basis. It takes a function which will
// be called to start a worker for a new environment. This worker
// will be killed when an environment goes away.
func NewEnvWorkerManager(
	st InitialState,
	startEnvWorker func(InitialState, *state.State) (worker.Worker, error),
) worker.Worker {
	m := &envWorkerManager{
		st:             st,
		startEnvWorker: startEnvWorker,
	}
	m.runner = worker.NewRunner(cmdutil.IsFatal, cmdutil.MoreImportant)
	go func() {
		defer m.tomb.Done()
		m.tomb.Kill(m.loop())
	}()
	return m
}

func (*runnerSuite) TestOneWorkerRestartDelay(c *gc.C) {
	worker.RestartDelay = 100 * time.Millisecond
	runner := worker.NewRunner(noneFatal, noImportance)
	starter := newTestWorkerStarter()
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, gc.IsNil)
	starter.assertStarted(c, true)
	starter.die <- fmt.Errorf("non-fatal error")
	starter.assertStarted(c, false)
	t0 := time.Now()
	starter.assertStarted(c, true)
	restartDuration := time.Since(t0)
	if restartDuration < worker.RestartDelay {
		c.Fatalf("restart delay was not respected; got %v want %v", restartDuration, worker.RestartDelay)
	}
}

func (s *ContainerSetupSuite) setupContainerWorker(c *gc.C, tag names.MachineTag) (worker.StringsWatchHandler, worker.Runner) {
	runner := worker.NewRunner(allFatal, noImportance)
	pr := s.st.Provisioner()
	machine, err := pr.Machine(tag)
	c.Assert(err, gc.IsNil)
	err = machine.SetSupportedContainers(instance.ContainerTypes...)
	c.Assert(err, gc.IsNil)
	cfg := s.AgentConfigForTag(c, tag)

	watcherName := fmt.Sprintf("%s-container-watcher", machine.Id())
	handler := provisioner.NewContainerSetupHandler(runner, watcherName, instance.ContainerTypes, machine, pr, cfg, s.initLock)
	runner.StartWorker(watcherName, func() (worker.Worker, error) {
		return worker.NewStringsWorker(handler), nil
	})
	return handler, runner
}

func (*runnerSuite) TestErrorImportance(c *gc.C) {
	moreImportant := func(err0, err1 error) bool {
		return err0.(errorLevel) > err1.(errorLevel)
	}
	id := func(i int) string { return fmt.Sprint(i) }
	runner := worker.NewRunner(allFatal, moreImportant)
	for i := 0; i < 10; i++ {
		starter := newTestWorkerStarter()
		starter.stopErr = errorLevel(i)
		err := runner.StartWorker(id(i), testWorkerStart(starter))
		c.Assert(err, jc.ErrorIsNil)
	}
	err := runner.StopWorker(id(4))
	c.Assert(err, jc.ErrorIsNil)
	err = runner.Wait()
	c.Assert(err, gc.Equals, errorLevel(9))
}

func (*runnerSuite) TestOneWorkerRestart(c *gc.C) {
	runner := worker.NewRunner(noneFatal, noImportance)
	starter := newTestWorkerStarter()
	err := runner.StartWorker("id", testWorkerStart(starter))
	c.Assert(err, jc.ErrorIsNil)
	starter.assertStarted(c, true)

	// Check it restarts a few times time.
	for i := 0; i < 3; i++ {
		starter.die <- fmt.Errorf("an error")
		starter.assertStarted(c, false)
		starter.assertStarted(c, true)
	}

	c.Assert(worker.Stop(runner), gc.IsNil)
	starter.assertStarted(c, false)
}