// WaitForEnviron waits for an valid environment to arrive from the given
// watcher. It terminates with ErrWaitAborted if it receives a value on abort.
//
// In practice, it shouldn't wait at all: juju *should* never deliver invalid
// environ configs. Regardless, it should be considered deprecated; clients
// should prefer to access an Environ via a shared Tracker.
//
// It never takes responsibility for the supplied watcher; the client remains
// responsible for detecting and handling any watcher errors that may occur,
// whether this func succeeds or fails.
func WaitForEnviron(
	// TODO(wallyworld) - pass in credential watcher
	w watcher.NotifyWatcher,
	getter environs.EnvironConfigGetter,
	newEnviron environs.NewEnvironFunc,
	abort <-chan struct{},
) (environs.Environ, error) {
	for {
		select {
		case <-abort:
			return nil, ErrWaitAborted
		case _, ok := <-w.Changes():
			if !ok {
				return nil, errors.New("environ config watch closed")
			}
			// First check the model config is valid as we want to exit with
			// an error if we have received a config but it is not valid.
			// This distinguishes from the case where environ construction fails
			// because no config has been received yet.
			if _, err := getter.ModelConfig(); err != nil {
				return nil, errors.Annotate(err, "cannot read environ config")
			}
			environ, err := environs.GetEnviron(getter, newEnviron)
			if err == nil {
				return environ, nil
			}
			logger.Errorf("loaded invalid environment configuration: %v", err)
		}
	}
}

// watchStorageAttachment starts watching the storage attachment with
// the specified storage tag, waits for its first event, and records
// the information in the current snapshot.
func (w *RemoteStateWatcher) watchStorageAttachment(
	tag names.StorageTag,
	life params.Life,
	saw watcher.NotifyWatcher,
) error {
	var storageSnapshot StorageSnapshot
	select {
	case <-w.catacomb.Dying():
		return w.catacomb.ErrDying()
	case _, ok := <-saw.Changes():
		if !ok {
			return errors.New("storage attachment watcher closed")
		}
		var err error
		storageSnapshot, err = getStorageSnapshot(w.st, tag, w.unit.Tag())
		if params.IsCodeNotProvisioned(err) {
			// If the storage is unprovisioned, we still want to
			// record the attachment, but we'll mark it as
			// unattached. This allows the uniter to wait for
			// pending storage attachments to be provisioned.
			storageSnapshot = StorageSnapshot{Life: life}
		} else if err != nil {
			return errors.Annotatef(err, "processing initial storage attachment change")
		}
	}
	innerSAW, err := newStorageAttachmentWatcher(
		w.st, saw, w.unit.Tag(), tag, w.storageAttachmentChanges,
	)
	if err != nil {
		return errors.Trace(err)
	}
	w.current.Storage[tag] = storageSnapshot
	w.storageAttachmentWatchers[tag] = innerSAW
	return nil
}

// WaitForEnviron waits for an valid environment to arrive from the given
// watcher. It terminates with ErrWaitAborted if it receives a value on abort.
//
// In practice, it shouldn't wait at all: juju *should* never deliver invalid
// environ configs. Regardless, it should be considered deprecated; clients
// should prefer to access an Environ via a shared Tracker.
//
// It never takes responsibility for the supplied watcher; the client remains
// responsible for detecting and handling any watcher errors that may occur,
// whether this func succeeds or fails.
func WaitForEnviron(
	w watcher.NotifyWatcher,
	getter ConfigGetter,
	newEnviron NewEnvironFunc,
	abort <-chan struct{},
) (environs.Environ, error) {
	for {
		select {
		case <-abort:
			return nil, ErrWaitAborted
		case _, ok := <-w.Changes():
			if !ok {
				return nil, errors.New("environ config watch closed")
			}
			config, err := getter.ModelConfig()
			if err != nil {
				return nil, errors.Annotate(err, "cannot read environ config")
			}
			environ, err := newEnviron(config)
			if err == nil {
				return environ, nil
			}
			logger.Errorf("loaded invalid environment configuration: %v", err)
		}
	}
}

func NewProvisionerTask(
	controllerUUID string,
	machineTag names.MachineTag,
	harvestMode config.HarvestMode,
	machineGetter MachineGetter,
	toolsFinder ToolsFinder,
	machineWatcher watcher.StringsWatcher,
	retryWatcher watcher.NotifyWatcher,
	broker environs.InstanceBroker,
	auth authentication.AuthenticationProvider,
	imageStream string,
	retryStartInstanceStrategy RetryStrategy,
) (ProvisionerTask, error) {
	machineChanges := machineWatcher.Changes()
	workers := []worker.Worker{machineWatcher}
	var retryChanges watcher.NotifyChannel
	if retryWatcher != nil {
		retryChanges = retryWatcher.Changes()
		workers = append(workers, retryWatcher)
	}
	task := &provisionerTask{
		controllerUUID:             controllerUUID,
		machineTag:                 machineTag,
		machineGetter:              machineGetter,
		toolsFinder:                toolsFinder,
		machineChanges:             machineChanges,
		retryChanges:               retryChanges,
		broker:                     broker,
		auth:                       auth,
		harvestMode:                harvestMode,
		harvestModeChan:            make(chan config.HarvestMode, 1),
		machines:                   make(map[string]*apiprovisioner.Machine),
		imageStream:                imageStream,
		retryStartInstanceStrategy: retryStartInstanceStrategy,
	}
	err := catacomb.Invoke(catacomb.Plan{
		Site: &task.catacomb,
		Work: task.loop,
		Init: workers,
	})
	if err != nil {
		return nil, errors.Trace(err)
	}
	return task, nil
}

// newStorageAttachmentsWatcher creates a new worker that wakes on input from
// the supplied watcher's Changes chan, finds out more about them, and delivers
// them on the supplied out chan.
//
// The caller releases responsibility for stopping the supplied watcher and
// waiting for errors, *whether or not this method succeeds*.
func newStorageAttachmentWatcher(
	st StorageAccessor,
	watcher watcher.NotifyWatcher,
	unitTag names.UnitTag,
	storageTag names.StorageTag,
	out chan<- storageAttachmentChange,
) (*storageAttachmentWatcher, error) {
	s := &storageAttachmentWatcher{
		st:         st,
		changes:    watcher.Changes(),
		out:        out,
		storageTag: storageTag,
		unitTag:    unitTag,
	}
	err := catacomb.Invoke(catacomb.Plan{
		Site: &s.catacomb,
		Work: s.loop,
		Init: []worker.Worker{watcher},
	})
	if err != nil {
		return nil, errors.Trace(err)
	}
	return s, nil
}