// startMachine creates a new data value for tracking details of the
// machine and starts watching the machine for units added or removed.
func (fw *Firewaller) startMachine(tag names.MachineTag) error {
	machined := &machineData{
		fw:           fw,
		tag:          tag,
		unitds:       make(map[names.UnitTag]*unitData),
		openedPorts:  make([]network.PortRange, 0),
		definedPorts: make(map[network.PortRange]names.UnitTag),
	}
	m, err := machined.machine()
	if params.IsCodeNotFound(err) {
		return nil
	} else if err != nil {
		return errors.Annotate(err, "cannot watch machine units")
	}
	unitw, err := m.WatchUnits()
	if err != nil {
		return err
	}
	select {
	case <-fw.tomb.Dying():
		return tomb.ErrDying
	case change, ok := <-unitw.Changes():
		if !ok {
			return watcher.EnsureErr(unitw)
		}
		fw.machineds[tag] = machined
		err = fw.unitsChanged(&unitsChange{machined, change})
		if err != nil {
			delete(fw.machineds, tag)
			return errors.Annotatef(err, "cannot respond to units changes for %q", tag)
		}
	}
	go machined.watchLoop(unitw)
	return nil
}

func opClientAddRelation(c *gc.C, st api.Connection, mst *state.State) (func(), error) {
	_, err := st.Client().AddRelation("nosuch1", "nosuch2")
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func opClientDestroyRelation(c *gc.C, st *api.State, mst *state.State) (func(), error) {
	err := st.Client().DestroyRelation("nosuch1", "nosuch2")
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func opClientServiceSetCharm(c *gc.C, st api.Connection, mst *state.State) (func(), error) {
	err := service.NewClient(st).ServiceSetCharm("nosuch", "local:quantal/wordpress", false, false)
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func (p *updater) startMachines(tags []names.MachineTag) error {
	for _, tag := range tags {
		if c := p.machines[tag]; c == nil {
			// We don't know about the machine - start
			// a goroutine to deal with it.
			m, err := p.context.getMachine(tag)
			if params.IsCodeNotFound(err) {
				logger.Warningf("watcher gave notification of non-existent machine %q", tag.Id())
				continue
			}
			if err != nil {
				return err
			}
			// We don't poll manual machines.
			isManual, err := m.IsManual()
			if err != nil {
				return err
			}
			if isManual {
				continue
			}
			c = make(chan struct{})
			p.machines[tag] = c
			go runMachine(p.context.newMachineContext(), m, c, p.machineDead)
		} else {
			select {
			case <-p.context.dying():
				return p.context.errDying()
			case c <- struct{}{}:
			}
		}
	}
	return nil
}

// Life returns the entity's life value; or ErrNotFound; or some
// other error.
func (facade *Facade) Life(entity names.Tag) (life.Value, error) {
	args := params.Entities{
		Entities: []params.Entity{{Tag: entity.String()}},
	}
	var results params.LifeResults
	err := facade.caller.FacadeCall("Life", args, &results)
	if err != nil {
		return "", errors.Trace(err)
	}
	if count := len(results.Results); count != 1 {
		return "", errors.Errorf("expected 1 Life result, got %d", count)
	}
	result := results.Results[0]
	if err := result.Error; err != nil {
		if params.IsCodeNotFound(err) {
			return "", ErrNotFound
		}
		return "", errors.Trace(result.Error)
	}
	life := life.Value(result.Life)
	if err := life.Validate(); err != nil {
		return "", errors.Trace(err)
	}
	return life, nil
}

// UpdateStorage responds to changes in the lifecycle states of the
// storage attachments corresponding to the supplied storage tags,
// sending storage hooks on the channel returned by Hooks().
func (a *Attachments) UpdateStorage(tags []names.StorageTag) error {
	ids := make([]params.StorageAttachmentId, len(tags))
	for i, storageTag := range tags {
		ids[i] = params.StorageAttachmentId{
			StorageTag: storageTag.String(),
			UnitTag:    a.unitTag.String(),
		}
	}
	results, err := a.st.StorageAttachmentLife(ids)
	if err != nil {
		return errors.Trace(err)
	}
	for i, result := range results {
		if result.Error == nil {
			continue
		} else if params.IsCodeNotFound(result.Error) {
			a.pending.Remove(tags[i])
			continue
		}
		return errors.Annotatef(
			result.Error, "getting life of storage %s attachment", tags[i].Id(),
		)
	}
	for i, result := range results {
		if result.Error != nil {
			continue
		}
		if err := a.updateOneStorage(tags[i], result.Life); err != nil {
			return errors.Trace(err)
		}
	}
	return nil
}

// storageChanged responds to unit storage changes.
func (w *RemoteStateWatcher) storageChanged(keys []string) error {
	tags := make([]names.StorageTag, len(keys))
	for i, key := range keys {
		tags[i] = names.NewStorageTag(key)
	}
	ids := make([]params.StorageAttachmentId, len(keys))
	for i, tag := range tags {
		ids[i] = params.StorageAttachmentId{
			StorageTag: tag.String(),
			UnitTag:    w.unit.Tag().String(),
		}
	}
	results, err := w.st.StorageAttachmentLife(ids)
	if err != nil {
		return errors.Trace(err)
	}

	w.mu.Lock()
	defer w.mu.Unlock()

	for i, result := range results {
		tag := tags[i]
		if result.Error == nil {
			if storageSnapshot, ok := w.current.Storage[tag]; ok {
				// We've previously started a watcher for this storage
				// attachment, so all we needed to do was update the
				// lifecycle state.
				storageSnapshot.Life = result.Life
				w.current.Storage[tag] = storageSnapshot
				continue
			}
			// We haven't seen this storage attachment before, so start
			// a watcher now; add it to our catacomb in case of mishap;
			// and wait for the initial event.
			saw, err := w.st.WatchStorageAttachment(tag, w.unit.Tag())
			if err != nil {
				return errors.Annotate(err, "watching storage attachment")
			}
			if err := w.catacomb.Add(saw); err != nil {
				return errors.Trace(err)
			}
			if err := w.watchStorageAttachment(tag, result.Life, saw); err != nil {
				return errors.Trace(err)
			}
		} else if params.IsCodeNotFound(result.Error) {
			if watcher, ok := w.storageAttachmentWatchers[tag]; ok {
				// already under catacomb management, any error tracked already
				worker.Stop(watcher)
				delete(w.storageAttachmentWatchers, tag)
			}
			delete(w.current.Storage, tag)
		} else {
			return errors.Annotatef(
				result.Error, "getting life of %s attachment",
				names.ReadableString(tag),
			)
		}
	}
	return nil
}

func opClientDestroyRelation(c *gc.C, st api.Connection, mst *state.State) (func(), error) {
	err := application.NewClient(st).DestroyRelation("nosuch1", "nosuch2")
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func opClientAddServiceUnits(c *gc.C, st api.Connection, mst *state.State) (func(), error) {
	_, err := application.NewClient(st).AddUnits("nosuch", 1, nil)
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

// refreshMachine refreshes the specified machine's instance ID. If it is set,
// then the machine watcher is stopped and pending entities' parameters are
// updated. If the machine is not provisioned yet, this method is a no-op.
func refreshMachine(ctx *context, tag names.MachineTag) error {
	w, ok := ctx.machines[tag]
	if !ok {
		return errors.Errorf("machine %s is not being watched", tag.Id())
	}
	stopAndRemove := func() error {
		worker.Stop(w)
		delete(ctx.machines, tag)
		return nil
	}
	results, err := ctx.config.Machines.InstanceIds([]names.MachineTag{tag})
	if err != nil {
		return errors.Annotate(err, "getting machine instance ID")
	}
	if err := results[0].Error; err != nil {
		if params.IsCodeNotProvisioned(err) {
			return nil
		} else if params.IsCodeNotFound(err) {
			// Machine is gone, so stop watching.
			return stopAndRemove()
		}
		return errors.Annotate(err, "getting machine instance ID")
	}
	machineProvisioned(ctx, tag, instance.Id(results[0].Result))
	// machine provisioning is the only thing we care about;
	// stop the watcher.
	return stopAndRemove()
}

// RestoreError makes a best effort at converting the given error
// back into an error originally converted by ServerError(). If the
// error could not be converted then false is returned.
func RestoreError(err error) (error, bool) {
	err = errors.Cause(err)

	if apiErr, ok := err.(*params.Error); !ok {
		return err, false
	} else if apiErr == nil {
		return nil, true
	}
	if params.ErrCode(err) == "" {
		return err, false
	}
	msg := err.Error()

	if singleton, ok := singletonError(err); ok {
		return singleton, true
	}

	// TODO(ericsnow) Support the other error types handled by ServerError().
	switch {
	case params.IsCodeUnauthorized(err):
		return errors.NewUnauthorized(nil, msg), true
	case params.IsCodeNotFound(err):
		// TODO(ericsnow) UnknownModelError should be handled here too.
		// ...by parsing msg?
		return errors.NewNotFound(nil, msg), true
	case params.IsCodeAlreadyExists(err):
		return errors.NewAlreadyExists(nil, msg), true
	case params.IsCodeNotAssigned(err):
		return errors.NewNotAssigned(nil, msg), true
	case params.IsCodeHasAssignedUnits(err):
		// TODO(ericsnow) Handle state.HasAssignedUnitsError here.
		// ...by parsing msg?
		return err, false
	case params.IsCodeNoAddressSet(err):
		// TODO(ericsnow) Handle isNoAddressSetError here.
		// ...by parsing msg?
		return err, false
	case params.IsCodeNotProvisioned(err):
		return errors.NewNotProvisioned(nil, msg), true
	case params.IsCodeUpgradeInProgress(err):
		// TODO(ericsnow) Handle state.UpgradeInProgressError here.
		// ...by parsing msg?
		return err, false
	case params.IsCodeMachineHasAttachedStorage(err):
		// TODO(ericsnow) Handle state.HasAttachmentsError here.
		// ...by parsing msg?
		return err, false
	case params.IsCodeNotSupported(err):
		return errors.NewNotSupported(nil, msg), true
	case params.IsBadRequest(err):
		return errors.NewBadRequest(nil, msg), true
	case params.IsMethodNotAllowed(err):
		return errors.NewMethodNotAllowed(nil, msg), true
	case params.ErrCode(err) == params.CodeDischargeRequired:
		// TODO(ericsnow) Handle DischargeRequiredError here.
		return err, false
	default:
		return err, false
	}
}

func opClientServiceDestroy(c *gc.C, st *api.State, mst *state.State) (func(), error) {
	err := st.Client().ServiceDestroy("non-existent")
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func opClientServiceDestroy(c *gc.C, st api.Connection, mst *state.State) (func(), error) {
	err := application.NewClient(st).Destroy("non-existent")
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func opClientAddServiceUnits(c *gc.C, st api.Connection, mst *state.State) (func(), error) {
	_, err := st.Client().AddServiceUnits("nosuch", 1, "")
	if params.IsCodeNotFound(err) {
		err = nil
	}
	return func() {}, err
}

func (s *storageAttachmentWatcher) loop() error {
	for {
		select {
		case <-s.catacomb.Dying():
			return s.catacomb.ErrDying()
		case _, ok := <-s.changes:
			if !ok {
				return errors.New("storage attachment watcher closed")
			}
			snapshot, err := getStorageSnapshot(
				s.st, s.storageTag, s.unitTag,
			)
			if params.IsCodeNotFound(err) {
				// The storage attachment was removed
				// from state, so we can stop watching.
				return nil
			} else if params.IsCodeNotProvisioned(err) {
				// We do not care about unattached
				// storage here.
				continue
			} else if err != nil {
				return err
			}
			change := storageAttachmentChange{
				s.storageTag,
				snapshot,
			}
			select {
			case <-s.catacomb.Dying():
				return s.catacomb.ErrDying()
			case s.out <- change:
			}
		}
	}
}

// startMachine creates a new data value for tracking details of the
// machine and starts watching the machine for units added or removed.
func (fw *Firewaller) startMachine(tag names.MachineTag) error {
	machined := &machineData{
		fw:           fw,
		tag:          tag,
		unitds:       make(map[names.UnitTag]*unitData),
		openedPorts:  make([]network.PortRange, 0),
		definedPorts: make(map[network.PortRange]names.UnitTag),
	}
	m, err := machined.machine()
	if params.IsCodeNotFound(err) {
		return nil
	} else if err != nil {
		return errors.Annotate(err, "cannot watch machine units")
	}
	unitw, err := m.WatchUnits()
	if err != nil {
		return errors.Trace(err)
	}
	// XXX(fwereade): this is the best of a bunch of bad options. We've started
	// the watch, so we're responsible for it; but we (probably?) need to do this
	// little dance below to update the machined data on the fw loop goroutine,
	// whence it's usually accessed, before we start the machined watchLoop
	// below. That catacomb *should* be the only one responsible -- and it *is*
	// responsible -- but having it in the main fw catacomb as well does no harm,
	// and greatly simplifies the code below (which would otherwise have to
	// manage unitw lifetime and errors manually).
	if err := fw.catacomb.Add(unitw); err != nil {
		return errors.Trace(err)
	}
	select {
	case <-fw.catacomb.Dying():
		return fw.catacomb.ErrDying()
	case change, ok := <-unitw.Changes():
		if !ok {
			return errors.New("machine units watcher closed")
		}
		fw.machineds[tag] = machined
		err = fw.unitsChanged(&unitsChange{machined, change})
		if err != nil {
			delete(fw.machineds, tag)
			return errors.Annotatef(err, "cannot respond to units changes for %q", tag)
		}
	}

	err = catacomb.Invoke(catacomb.Plan{
		Site: &machined.catacomb,
		Work: func() error {
			return machined.watchLoop(unitw)
		},
	})
	if err != nil {
		delete(fw.machineds, tag)
		return errors.Trace(err)
	}

	// register the machined with the firewaller's catacomb.
	return fw.catacomb.Add(machined)
}

// reconcileInstances compares the initially started watcher for machines,
// units and services with the opened and closed ports of the instances and
// opens and closes the appropriate ports for each instance.
func (fw *Firewaller) reconcileInstances() error {
	for _, machined := range fw.machineds {
		m, err := machined.machine()
		if params.IsCodeNotFound(err) {
			if err := fw.forgetMachine(machined); err != nil {
				return err
			}
			continue
		}
		if err != nil {
			return err
		}
		instanceId, err := m.InstanceId()
		if errors.IsNotProvisioned(err) {
			logger.Errorf("Machine not yet provisioned: %v", err)
			continue
		}
		if err != nil {
			return err
		}
		instances, err := fw.environ.Instances([]instance.Id{instanceId})
		if err == environs.ErrNoInstances {
			return nil
		}
		if err != nil {
			return err
		}
		machineId := machined.tag.Id()
		initialPortRanges, err := instances[0].Ports(machineId)
		if err != nil {
			return err
		}

		// Check which ports to open or to close.
		toOpen := diffRanges(machined.openedPorts, initialPortRanges)
		toClose := diffRanges(initialPortRanges, machined.openedPorts)
		if len(toOpen) > 0 {
			logger.Infof("opening instance port ranges %v for %q",
				toOpen, machined.tag)
			if err := instances[0].OpenPorts(machineId, toOpen); err != nil {
				// TODO(mue) Add local retry logic.
				return err
			}
			network.SortPortRanges(toOpen)
		}
		if len(toClose) > 0 {
			logger.Infof("closing instance port ranges %v for %q",
				toClose, machined.tag)
			if err := instances[0].ClosePorts(machineId, toClose); err != nil {
				// TODO(mue) Add local retry logic.
				return err
			}
			network.SortPortRanges(toClose)
		}
	}
	return nil
}

// commonLoop implements the loop structure common to the client
// watchers. It should be started in a separate goroutine by any
// watcher that embeds commonWatcher. It kills the commonWatcher's
// tomb when an error occurs.
func (w *commonWatcher) commonLoop() {
	defer close(w.in)
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		// When the watcher has been stopped, we send a Stop request
		// to the server, which will remove the watcher and return a
		// CodeStopped error to any currently outstanding call to
		// Next. If a call to Next happens just after the watcher has
		// been stopped, we'll get a CodeNotFound error; Either way
		// we'll return, wait for the stop request to complete, and
		// the watcher will die with all resources cleaned up.
		defer wg.Done()
		<-w.tomb.Dying()
		if err := w.call("Stop", nil); err != nil {
			logger.Errorf("error trying to stop watcher: %v", err)
		}
	}()
	wg.Add(1)
	go func() {
		// Because Next blocks until there are changes, we need to
		// call it in a separate goroutine, so the watcher can be
		// stopped normally.
		defer wg.Done()
		for {
			result := w.newResult()
			err := w.call("Next", &result)
			if err != nil {
				if params.IsCodeStopped(err) || params.IsCodeNotFound(err) {
					if w.tomb.Err() != tomb.ErrStillAlive {
						// The watcher has been stopped at the client end, so we're
						// expecting one of the above two kinds of error.
						// We might see the same errors if the server itself
						// has been shut down, in which case we leave them
						// untouched.
						err = tomb.ErrDying
					}
				}
				// Something went wrong, just report the error and bail out.
				w.tomb.Kill(err)
				return
			}
			select {
			case <-w.tomb.Dying():
				return
			case w.in <- result:
				// Report back the result we just got.
			}
		}
	}()
	wg.Wait()
}

func (s syncToolsAPIAdapter) FindTools(majorVersion int, stream string) (coretools.List, error) {
	result, err := s.syncToolsAPI.FindTools(majorVersion, -1, "", "")
	if err != nil {
		return nil, err
	}
	if result.Error != nil {
		if params.IsCodeNotFound(result.Error) {
			return nil, coretools.ErrNoMatches
		}
		return nil, result.Error
	}
	return result.List, nil
}