// NewAddresserAPI creates a new server-side Addresser API facade.
func NewAddresserAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*AddresserAPI, error) {
	isEnvironManager := authorizer.AuthEnvironManager()
	if !isEnvironManager {
		// Addresser must run as environment manager.
		return nil, common.ErrPerm
	}
	getAuthFunc := func() (common.AuthFunc, error) {
		return func(tag names.Tag) bool {
			return isEnvironManager
		}, nil
	}
	sti := getState(st)
	return &AddresserAPI{
		EnvironWatcher: common.NewEnvironWatcher(sti, resources, authorizer),
		LifeGetter:     common.NewLifeGetter(sti, getAuthFunc),
		Remover:        common.NewRemover(sti, false, getAuthFunc),
		st:             sti,
		resources:      resources,
		authorizer:     authorizer,
	}, nil
}

func (*lifeSuite) TestLife(c *gc.C) {
	st := &fakeState{
		entities: map[names.Tag]entityWithError{
			u("x/0"): &fakeLifer{life: state.Alive},
			u("x/1"): &fakeLifer{life: state.Dying},
			u("x/2"): &fakeLifer{life: state.Dead},
			u("x/3"): &fakeLifer{fetchError: "x3 error"},
		},
	}
	getCanRead := func() (common.AuthFunc, error) {
		x0 := u("x/0")
		x2 := u("x/2")
		x3 := u("x/3")
		return func(tag names.Tag) bool {
			return tag == x0 || tag == x2 || tag == x3
		}, nil
	}
	lg := common.NewLifeGetter(st, getCanRead)
	entities := params.Entities{[]params.Entity{
		{"unit-x-0"}, {"unit-x-1"}, {"unit-x-2"}, {"unit-x-3"}, {"unit-x-4"},
	}}
	results, err := lg.Life(entities)
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(results, gc.DeepEquals, params.LifeResults{
		Results: []params.LifeResult{
			{Life: params.Alive},
			{Error: apiservertesting.ErrUnauthorized},
			{Life: params.Dead},
			{Error: &params.Error{Message: "x3 error"}},
			{Error: apiservertesting.ErrUnauthorized},
		},
	})
}

func (*lifeSuite) TestLifeError(c *gc.C) {
	getCanRead := func() (common.AuthFunc, error) {
		return nil, fmt.Errorf("pow")
	}
	lg := common.NewLifeGetter(&fakeState{}, getCanRead)
	_, err := lg.Life(params.Entities{[]params.Entity{{"x0"}}})
	c.Assert(err, gc.ErrorMatches, "pow")
}

func (*lifeSuite) TestLifeNoArgsNoError(c *gc.C) {
	getCanRead := func() (common.AuthFunc, error) {
		return nil, fmt.Errorf("pow")
	}
	lg := common.NewLifeGetter(&fakeState{}, getCanRead)
	result, err := lg.Life(params.Entities{})
	c.Assert(err, jc.ErrorIsNil)
	c.Assert(result.Results, gc.HasLen, 0)
}

// NewProvisionerAPI creates a new server-side ProvisionerAPI facade.
func NewProvisionerAPI(st *state.State, resources *common.Resources, authorizer common.Authorizer) (*ProvisionerAPI, error) {
	if !authorizer.AuthMachineAgent() && !authorizer.AuthEnvironManager() {
		return nil, common.ErrPerm
	}
	getAuthFunc := func() (common.AuthFunc, error) {
		isEnvironManager := authorizer.AuthEnvironManager()
		isMachineAgent := authorizer.AuthMachineAgent()
		authEntityTag := authorizer.GetAuthTag()

		return func(tag names.Tag) bool {
			if isMachineAgent && tag == authEntityTag {
				// A machine agent can always access its own machine.
				return true
			}
			switch tag := tag.(type) {
			case names.MachineTag:
				parentId := state.ParentId(tag.Id())
				if parentId == "" {
					// All top-level machines are accessible by the
					// environment manager.
					return isEnvironManager
				}
				// All containers with the authenticated machine as a
				// parent are accessible by it.
				// TODO(dfc) sometimes authEntity tag is nil, which is fine because nil is
				// only equal to nil, but it suggests someone is passing an authorizer
				// with a nil tag.
				return isMachineAgent && names.NewMachineTag(parentId) == authEntityTag
			default:
				return false
			}
		}, nil
	}
	env, err := st.Environment()
	if err != nil {
		return nil, err
	}
	urlGetter := common.NewToolsURLGetter(env.UUID(), st)
	return &ProvisionerAPI{
		Remover:                common.NewRemover(st, false, getAuthFunc),
		StatusSetter:           common.NewStatusSetter(st, getAuthFunc),
		StatusGetter:           common.NewStatusGetter(st, getAuthFunc),
		DeadEnsurer:            common.NewDeadEnsurer(st, getAuthFunc),
		PasswordChanger:        common.NewPasswordChanger(st, getAuthFunc),
		LifeGetter:             common.NewLifeGetter(st, getAuthFunc),
		StateAddresser:         common.NewStateAddresser(st),
		APIAddresser:           common.NewAPIAddresser(st, resources),
		EnvironWatcher:         common.NewEnvironWatcher(st, resources, authorizer),
		EnvironMachinesWatcher: common.NewEnvironMachinesWatcher(st, resources, authorizer),
		InstanceIdGetter:       common.NewInstanceIdGetter(st, getAuthFunc),
		ToolsFinder:            common.NewToolsFinder(st, st, urlGetter),
		st:                     st,
		resources:              resources,
		authorizer:             authorizer,
		getAuthFunc:            getAuthFunc,
	}, nil
}

// NewInstancePollerAPI creates a new server-side InstancePoller API
// facade.
func NewInstancePollerAPI(
	st *state.State,
	resources facade.Resources,
	authorizer facade.Authorizer,
	clock clock.Clock,
) (*InstancePollerAPI, error) {

	if !authorizer.AuthModelManager() {
		// InstancePoller must run as environment manager.
		return nil, common.ErrPerm
	}
	accessMachine := common.AuthFuncForTagKind(names.MachineTagKind)
	sti := getState(st)

	// Life() is supported for machines.
	lifeGetter := common.NewLifeGetter(
		sti,
		accessMachine,
	)
	// ModelConfig() and WatchForModelConfigChanges() are allowed
	// with unrestriced access.
	modelWatcher := common.NewModelWatcher(
		sti,
		resources,
		authorizer,
	)
	// WatchModelMachines() is allowed with unrestricted access.
	machinesWatcher := common.NewModelMachinesWatcher(
		sti,
		resources,
		authorizer,
	)
	// InstanceId() is supported for machines.
	instanceIdGetter := common.NewInstanceIdGetter(
		sti,
		accessMachine,
	)
	// Status() is supported for machines.
	statusGetter := common.NewStatusGetter(
		sti,
		accessMachine,
	)

	return &InstancePollerAPI{
		LifeGetter:           lifeGetter,
		ModelWatcher:         modelWatcher,
		ModelMachinesWatcher: machinesWatcher,
		InstanceIdGetter:     instanceIdGetter,
		StatusGetter:         statusGetter,
		st:                   sti,
		resources:            resources,
		authorizer:           authorizer,
		accessMachine:        accessMachine,
		clock:                clock,
	}, nil
}

func NewFacade(backend Backend, resources *common.Resources, authorizer common.Authorizer) (*Facade, error) {
	if !authorizer.AuthModelManager() {
		return nil, common.ErrPerm
	}
	expect := names.NewModelTag(backend.ModelUUID())
	getCanAccess := func() (common.AuthFunc, error) {
		return func(tag names.Tag) bool {
			return tag == expect
		}, nil
	}
	life := common.NewLifeGetter(backend, getCanAccess)
	watch := common.NewAgentEntityWatcher(backend, resources, getCanAccess)
	return &Facade{
		LifeGetter:         life,
		AgentEntityWatcher: watch,
	}, nil
}

// NewDeployerAPI creates a new server-side DeployerAPI facade.
func NewDeployerAPI(
	st *state.State,
	resources facade.Resources,
	authorizer facade.Authorizer,
) (*DeployerAPI, error) {
	if !authorizer.AuthMachineAgent() {
		return nil, common.ErrPerm
	}
	getAuthFunc := func() (common.AuthFunc, error) {
		// Get all units of the machine and cache them.
		thisMachineTag := authorizer.GetAuthTag()
		units, err := getAllUnits(st, thisMachineTag)
		if err != nil {
			return nil, err
		}
		// Then we just check if the unit is already known.
		return func(tag names.Tag) bool {
			for _, unit := range units {
				// TODO (thumper): remove the names.Tag conversion when gccgo
				// implements concrete-type-to-interface comparison correctly.
				if names.Tag(names.NewUnitTag(unit)) == tag {
					return true
				}
			}
			return false
		}, nil
	}
	getCanWatch := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	return &DeployerAPI{
		Remover:         common.NewRemover(st, true, getAuthFunc),
		PasswordChanger: common.NewPasswordChanger(st, getAuthFunc),
		LifeGetter:      common.NewLifeGetter(st, getAuthFunc),
		StateAddresser:  common.NewStateAddresser(st),
		APIAddresser:    common.NewAPIAddresser(st, resources),
		UnitsWatcher:    common.NewUnitsWatcher(st, resources, getCanWatch),
		StatusSetter:    common.NewStatusSetter(st, getAuthFunc),
		st:              st,
		resources:       resources,
		authorizer:      authorizer,
	}, nil
}

// NewMachinerAPI creates a new instance of the Machiner API.
func NewMachinerAPI(st *state.State, resources *common.Resources, authorizer common.Authorizer) (*MachinerAPI, error) {
	if !authorizer.AuthMachineAgent() {
		return nil, common.ErrPerm
	}
	getCanModify := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	getCanRead := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	return &MachinerAPI{
		LifeGetter:         common.NewLifeGetter(st, getCanRead),
		StatusSetter:       common.NewStatusSetter(st, getCanModify),
		DeadEnsurer:        common.NewDeadEnsurer(st, getCanModify),
		AgentEntityWatcher: common.NewAgentEntityWatcher(st, resources, getCanRead),
		APIAddresser:       common.NewAPIAddresser(st, resources),
		st:                 st,
		auth:               authorizer,
		getCanModify:       getCanModify,
	}, nil
}

// NewUniterAPI creates a new instance of the Uniter API.
func NewUniterAPI(st *state.State, resources *common.Resources, authorizer common.Authorizer) (*UniterAPI, error) {
	if !authorizer.AuthUnitAgent() {
		return nil, common.ErrPerm
	}
	accessUnit := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	accessService := func() (common.AuthFunc, error) {
		switch tag := authorizer.GetAuthTag().(type) {
		case names.UnitTag:
			entity, err := st.Unit(tag.Id())
			if err != nil {
				return nil, errors.Trace(err)
			}
			serviceName := entity.ServiceName()
			serviceTag := names.NewServiceTag(serviceName)
			return func(tag names.Tag) bool {
				return tag == serviceTag
			}, nil
		default:
			return nil, errors.Errorf("expected names.UnitTag, got %T", tag)
		}
	}
	accessUnitOrService := common.AuthEither(accessUnit, accessService)

	return &UniterAPI{
		LifeGetter:         common.NewLifeGetter(st, accessUnitOrService),
		StatusSetter:       common.NewStatusSetter(st, accessUnit),
		DeadEnsurer:        common.NewDeadEnsurer(st, accessUnit),
		AgentEntityWatcher: common.NewAgentEntityWatcher(st, resources, accessUnitOrService),
		APIAddresser:       common.NewAPIAddresser(st, resources),
		EnvironWatcher:     common.NewEnvironWatcher(st, resources, authorizer),

		st:            st,
		auth:          authorizer,
		resources:     resources,
		accessUnit:    accessUnit,
		accessService: accessService,
	}, nil
}

// NewUniterAPIV4 creates a new instance of the Uniter API, version 3.
func NewUniterAPIV4(st *state.State, resources facade.Resources, authorizer facade.Authorizer) (*UniterAPIV3, error) {
	if !authorizer.AuthUnitAgent() {
		return nil, common.ErrPerm
	}
	var unit *state.Unit
	var err error
	switch tag := authorizer.GetAuthTag().(type) {
	case names.UnitTag:
		unit, err = st.Unit(tag.Id())
		if err != nil {
			return nil, errors.Trace(err)
		}
	default:
		return nil, errors.Errorf("expected names.UnitTag, got %T", tag)
	}
	accessUnit := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	accessService := func() (common.AuthFunc, error) {
		switch tag := authorizer.GetAuthTag().(type) {
		case names.UnitTag:
			entity, err := st.Unit(tag.Id())
			if err != nil {
				return nil, errors.Trace(err)
			}
			applicationName := entity.ApplicationName()
			applicationTag := names.NewApplicationTag(applicationName)
			return func(tag names.Tag) bool {
				return tag == applicationTag
			}, nil
		default:
			return nil, errors.Errorf("expected names.UnitTag, got %T", tag)
		}
	}
	accessMachine := func() (common.AuthFunc, error) {
		switch tag := authorizer.GetAuthTag().(type) {
		case names.UnitTag:
			entity, err := st.Unit(tag.Id())
			if err != nil {
				return nil, errors.Trace(err)
			}
			machineId, err := entity.AssignedMachineId()
			if err != nil {
				return nil, errors.Trace(err)
			}
			machineTag := names.NewMachineTag(machineId)
			return func(tag names.Tag) bool {
				return tag == machineTag
			}, nil
		default:
			return nil, errors.Errorf("expected names.UnitTag, got %T", tag)
		}
	}
	storageAPI, err := newStorageAPI(getStorageState(st), resources, accessUnit)
	if err != nil {
		return nil, err
	}
	msAPI, err := meterstatus.NewMeterStatusAPI(st, resources, authorizer)
	if err != nil {
		return nil, errors.Annotate(err, "could not create meter status API handler")
	}
	accessUnitOrService := common.AuthEither(accessUnit, accessService)
	return &UniterAPIV3{
		LifeGetter:                 common.NewLifeGetter(st, accessUnitOrService),
		DeadEnsurer:                common.NewDeadEnsurer(st, accessUnit),
		AgentEntityWatcher:         common.NewAgentEntityWatcher(st, resources, accessUnitOrService),
		APIAddresser:               common.NewAPIAddresser(st, resources),
		ModelWatcher:               common.NewModelWatcher(st, resources, authorizer),
		RebootRequester:            common.NewRebootRequester(st, accessMachine),
		LeadershipSettingsAccessor: leadershipSettingsAccessorFactory(st, resources, authorizer),
		MeterStatus:                msAPI,
		// TODO(fwereade): so *every* unit should be allowed to get/set its
		// own status *and* its service's? This is not a pleasing arrangement.
		StatusAPI: NewStatusAPI(st, accessUnitOrService),

		st:            st,
		auth:          authorizer,
		resources:     resources,
		accessUnit:    accessUnit,
		accessService: accessService,
		accessMachine: accessMachine,
		unit:          unit,
		StorageAPI:    *storageAPI,
	}, nil
}

// NewFirewallerAPI creates a new server-side FirewallerAPI facade.
func NewFirewallerAPI(
	st *state.State,
	resources facade.Resources,
	authorizer facade.Authorizer,
) (*FirewallerAPI, error) {
	if !authorizer.AuthModelManager() {
		// Firewaller must run as environment manager.
		return nil, common.ErrPerm
	}
	// Set up the various authorization checkers.
	accessEnviron := common.AuthFuncForTagKind(names.ModelTagKind)
	accessUnit := common.AuthFuncForTagKind(names.UnitTagKind)
	accessService := common.AuthFuncForTagKind(names.ApplicationTagKind)
	accessMachine := common.AuthFuncForTagKind(names.MachineTagKind)
	accessUnitOrService := common.AuthEither(accessUnit, accessService)
	accessUnitServiceOrMachine := common.AuthEither(accessUnitOrService, accessMachine)

	// Life() is supported for units, services or machines.
	lifeGetter := common.NewLifeGetter(
		st,
		accessUnitServiceOrMachine,
	)
	// ModelConfig() and WatchForModelConfigChanges() are allowed
	// with unrestriced access.
	modelWatcher := common.NewModelWatcher(
		st,
		resources,
		authorizer,
	)
	// Watch() is supported for applications only.
	entityWatcher := common.NewAgentEntityWatcher(
		st,
		resources,
		accessService,
	)
	// WatchUnits() is supported for machines.
	unitsWatcher := common.NewUnitsWatcher(st,
		resources,
		accessMachine,
	)
	// WatchModelMachines() is allowed with unrestricted access.
	machinesWatcher := common.NewModelMachinesWatcher(
		st,
		resources,
		authorizer,
	)
	// InstanceId() is supported for machines.
	instanceIdGetter := common.NewInstanceIdGetter(
		st,
		accessMachine,
	)

	environConfigGetter := stateenvirons.EnvironConfigGetter{st}
	cloudSpecAPI := cloudspec.NewCloudSpec(environConfigGetter.CloudSpec, common.AuthFuncForTag(st.ModelTag()))

	return &FirewallerAPI{
		LifeGetter:           lifeGetter,
		ModelWatcher:         modelWatcher,
		AgentEntityWatcher:   entityWatcher,
		UnitsWatcher:         unitsWatcher,
		ModelMachinesWatcher: machinesWatcher,
		InstanceIdGetter:     instanceIdGetter,
		CloudSpecAPI:         cloudSpecAPI,
		st:                   st,
		resources:            resources,
		authorizer:           authorizer,
		accessUnit:           accessUnit,
		accessService:        accessService,
		accessMachine:        accessMachine,
		accessEnviron:        accessEnviron,
	}, nil
}

//.........这里部分代码省略.........
				return canAccessStorageMachine(tag, false)
			default:
				return false
			}
		}, nil
	}
	canAccessStorageEntity := func(tag names.Tag, allowMachines bool) bool {
		switch tag := tag.(type) {
		case names.VolumeTag:
			machineTag, ok := names.VolumeMachine(tag)
			if ok {
				return canAccessStorageMachine(machineTag, false)
			}
			return authorizer.AuthEnvironManager()
		case names.FilesystemTag:
			machineTag, ok := names.FilesystemMachine(tag)
			if ok {
				return canAccessStorageMachine(machineTag, false)
			}
			return authorizer.AuthEnvironManager()
		case names.MachineTag:
			return allowMachines && canAccessStorageMachine(tag, true)
		default:
			return false
		}
	}
	getStorageEntityAuthFunc := func() (common.AuthFunc, error) {
		return func(tag names.Tag) bool {
			return canAccessStorageEntity(tag, false)
		}, nil
	}
	getLifeAuthFunc := func() (common.AuthFunc, error) {
		return func(tag names.Tag) bool {
			return canAccessStorageEntity(tag, true)
		}, nil
	}
	getAttachmentAuthFunc := func() (func(names.MachineTag, names.Tag) bool, error) {
		// getAttachmentAuthFunc returns a function that validates
		// access by the authenticated user to an attachment.
		return func(machineTag names.MachineTag, attachmentTag names.Tag) bool {
			// Machine agents can access their own machine, and
			// machines contained. Environment managers can access
			// top-level machines.
			if !canAccessStorageMachine(machineTag, true) {
				return false
			}
			// Environment managers can access environment-scoped
			// volumes and volumes scoped to their own machines.
			// Other machine agents can access volumes regardless
			// of their scope.
			if !authorizer.AuthEnvironManager() {
				return true
			}
			var machineScope names.MachineTag
			var hasMachineScope bool
			switch attachmentTag := attachmentTag.(type) {
			case names.VolumeTag:
				machineScope, hasMachineScope = names.VolumeMachine(attachmentTag)
			case names.FilesystemTag:
				machineScope, hasMachineScope = names.FilesystemMachine(attachmentTag)
			}
			return !hasMachineScope || machineScope == authorizer.GetAuthTag()
		}, nil
	}
	getMachineAuthFunc := func() (common.AuthFunc, error) {
		return func(tag names.Tag) bool {
			if tag, ok := tag.(names.MachineTag); ok {
				return canAccessStorageMachine(tag, true)
			}
			return false
		}, nil
	}
	getBlockDevicesAuthFunc := func() (common.AuthFunc, error) {
		return func(tag names.Tag) bool {
			if tag, ok := tag.(names.MachineTag); ok {
				return canAccessStorageMachine(tag, false)
			}
			return false
		}, nil
	}
	stateInterface := getState(st)
	settings := getSettingsManager(st)
	return &StorageProvisionerAPI{
		LifeGetter:       common.NewLifeGetter(stateInterface, getLifeAuthFunc),
		DeadEnsurer:      common.NewDeadEnsurer(stateInterface, getStorageEntityAuthFunc),
		EnvironWatcher:   common.NewEnvironWatcher(stateInterface, resources, authorizer),
		InstanceIdGetter: common.NewInstanceIdGetter(st, getMachineAuthFunc),
		StatusSetter:     common.NewStatusSetter(st, getStorageEntityAuthFunc),

		st:                       stateInterface,
		settings:                 settings,
		resources:                resources,
		authorizer:               authorizer,
		getScopeAuthFunc:         getScopeAuthFunc,
		getStorageEntityAuthFunc: getStorageEntityAuthFunc,
		getAttachmentAuthFunc:    getAttachmentAuthFunc,
		getMachineAuthFunc:       getMachineAuthFunc,
		getBlockDevicesAuthFunc:  getBlockDevicesAuthFunc,
	}, nil
}

// newUniterBaseAPI creates a new instance of the uniter base API.
func newUniterBaseAPI(st *state.State, resources *common.Resources, authorizer common.Authorizer) (*uniterBaseAPI, error) {
	if !authorizer.AuthUnitAgent() {
		return nil, common.ErrPerm
	}
	var unit *state.Unit
	var err error
	switch tag := authorizer.GetAuthTag().(type) {
	case names.UnitTag:
		unit, err = st.Unit(tag.Id())
		if err != nil {
			return nil, errors.Trace(err)
		}
	default:
		return nil, errors.Errorf("expected names.UnitTag, got %T", tag)
	}
	accessUnit := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	accessService := func() (common.AuthFunc, error) {
		switch tag := authorizer.GetAuthTag().(type) {
		case names.UnitTag:
			entity, err := st.Unit(tag.Id())
			if err != nil {
				return nil, errors.Trace(err)
			}
			serviceName := entity.ServiceName()
			serviceTag := names.NewServiceTag(serviceName)
			return func(tag names.Tag) bool {
				return tag == serviceTag
			}, nil
		default:
			return nil, errors.Errorf("expected names.UnitTag, got %T", tag)
		}
	}
	accessMachine := func() (common.AuthFunc, error) {
		machineId, err := unit.AssignedMachineId()
		if err != nil {
			return nil, errors.Trace(err)
		}
		machine, err := st.Machine(machineId)
		if err != nil {
			return nil, errors.Trace(err)
		}
		return func(tag names.Tag) bool {
			return tag == machine.Tag()
		}, nil
	}

	accessUnitOrService := common.AuthEither(accessUnit, accessService)
	return &uniterBaseAPI{
		LifeGetter:                 common.NewLifeGetter(st, accessUnitOrService),
		DeadEnsurer:                common.NewDeadEnsurer(st, accessUnit),
		AgentEntityWatcher:         common.NewAgentEntityWatcher(st, resources, accessUnitOrService),
		APIAddresser:               common.NewAPIAddresser(st, resources),
		EnvironWatcher:             common.NewEnvironWatcher(st, resources, authorizer),
		RebootRequester:            common.NewRebootRequester(st, accessMachine),
		LeadershipSettingsAccessor: leadershipSettingsAccessorFactory(st, resources, authorizer),

		// TODO(fwereade): so *every* unit should be allowed to get/set its
		// own status *and* its service's? This is not a pleasing arrangement.
		StatusAPI: NewStatusAPI(st, accessUnitOrService),

		st:            st,
		auth:          authorizer,
		resources:     resources,
		accessUnit:    accessUnit,
		accessService: accessService,
		unit:          unit,
	}, nil
}

// NewFirewallerAPI creates a new server-side FirewallerAPI facade.
func NewFirewallerAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*FirewallerAPI, error) {
	if !authorizer.AuthEnvironManager() {
		// Firewaller must run as environment manager.
		return nil, common.ErrPerm
	}
	// Set up the various authorization checkers.
	accessEnviron := common.AuthFuncForTagKind(names.EnvironTagKind)
	accessUnit := common.AuthFuncForTagKind(names.UnitTagKind)
	accessService := common.AuthFuncForTagKind(names.ServiceTagKind)
	accessMachine := common.AuthFuncForTagKind(names.MachineTagKind)
	accessUnitOrService := common.AuthEither(accessUnit, accessService)
	accessUnitServiceOrMachine := common.AuthEither(accessUnitOrService, accessMachine)

	// Life() is supported for units, services or machines.
	lifeGetter := common.NewLifeGetter(
		st,
		accessUnitServiceOrMachine,
	)
	// EnvironConfig() and WatchForEnvironConfigChanges() are allowed
	// with unrestriced access.
	environWatcher := common.NewEnvironWatcher(
		st,
		resources,
		authorizer,
	)
	// Watch() is supported for services only.
	entityWatcher := common.NewAgentEntityWatcher(
		st,
		resources,
		accessService,
	)
	// WatchUnits() is supported for machines.
	unitsWatcher := common.NewUnitsWatcher(st,
		resources,
		accessMachine,
	)
	// WatchEnvironMachines() is allowed with unrestricted access.
	machinesWatcher := common.NewEnvironMachinesWatcher(
		st,
		resources,
		authorizer,
	)
	// InstanceId() is supported for machines.
	instanceIdGetter := common.NewInstanceIdGetter(
		st,
		accessMachine,
	)

	return &FirewallerAPI{
		LifeGetter:             lifeGetter,
		EnvironWatcher:         environWatcher,
		AgentEntityWatcher:     entityWatcher,
		UnitsWatcher:           unitsWatcher,
		EnvironMachinesWatcher: machinesWatcher,
		InstanceIdGetter:       instanceIdGetter,
		st:                     st,
		resources:              resources,
		authorizer:             authorizer,
		accessUnit:             accessUnit,
		accessService:          accessService,
		accessMachine:          accessMachine,
		accessEnviron:          accessEnviron,
	}, nil
}