// NewLoggerAPI creates a new server-side logger API end point.
func NewLoggerAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*LoggerAPI, error) {
	if !authorizer.AuthMachineAgent() && !authorizer.AuthUnitAgent() {
		return nil, common.ErrPerm
	}
	return &LoggerAPI{state: st, resources: resources, authorizer: authorizer}, nil
}

// NewCharmRevisionUpdaterAPI creates a new server-side charmrevisionupdater API end point.
func NewCharmRevisionUpdaterAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*CharmRevisionUpdaterAPI, error) {
	if !authorizer.AuthMachineAgent() && !authorizer.AuthEnvironManager() {
		return nil, common.ErrPerm
	}
	return &CharmRevisionUpdaterAPI{
		state: st, resources: resources, authorizer: authorizer}, nil
}

// NewAPI returns an object implementing an agent API
// with the given authorizer representing the currently logged in client.
func NewAPI(st *state.State, resources *common.Resources, auth common.Authorizer) (*API, error) {
	// Agents are defined to be any user that's not a client user.
	if !auth.AuthMachineAgent() && !auth.AuthUnitAgent() {
		return nil, common.ErrPerm
	}
	getCanChange := func() (common.AuthFunc, error) {
		return auth.AuthOwner, nil
	}
	return &API{
		PasswordChanger: common.NewPasswordChanger(st, getCanChange),
		st:              st,
		auth:            auth,
	}, nil
}

func newClientAllWatcher(st *state.State, resources *common.Resources, auth common.Authorizer, id string) (interface{}, error) {
	if !auth.AuthClient() {
		return nil, common.ErrPerm
	}
	watcher, ok := resources.Get(id).(*multiwatcher.Watcher)
	if !ok {
		return nil, common.ErrUnknownWatcher
	}
	return &srvClientAllWatcher{
		watcher:   watcher,
		id:        id,
		resources: resources,
	}, nil
}

// NewKeyUpdaterAPI creates a new server-side keyupdater API end point.
func NewKeyUpdaterAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*KeyUpdaterAPI, error) {
	// Only machine agents have access to the keyupdater service.
	if !authorizer.AuthMachineAgent() {
		return nil, common.ErrPerm
	}
	// No-one else except the machine itself can only read a machine's own credentials.
	getCanRead := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	return &KeyUpdaterAPI{state: st, resources: resources, authorizer: authorizer, getCanRead: getCanRead}, nil
}

// NewNetworkerAPI creates a new client-side Networker API facade.
func NewNetworkerAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*NetworkerAPI, error) {
	if !authorizer.AuthMachineAgent() {
		return nil, common.ErrPerm
	}
	getAuthFunc := func() (common.AuthFunc, error) {
		authEntityTag := authorizer.GetAuthTag().String()

		return func(tag string) bool {
			if tag == authEntityTag {
				// A machine agent can always access its own machine.
				return true
			}
			t, err := names.ParseMachineTag(tag)
			if err != nil {
				// Only machine tags are allowed.
				return false
			}
			id := t.Id()
			for parentId := state.ParentId(id); parentId != ""; parentId = state.ParentId(parentId) {
				// Until a top-level machine is reached.
				// TODO(dfc) comparing the two interfaces caused a compiler crash with
				// gcc version 4.9.0 (Ubuntu 4.9.0-7ubuntu1). Work around the issue
				// by comparing by string value.
				if names.NewMachineTag(parentId).String() == authEntityTag {
					// All containers with the authenticated machine as a
					// parent are accessible by it.
					return true
				}
			}
			// Not found authorized machine agent among ancestors of the current one.
			return false
		}, nil
	}

	return &NetworkerAPI{
		st:          st,
		resources:   resources,
		authorizer:  authorizer,
		getAuthFunc: getAuthFunc,
	}, nil
}

// upgraderFacade is a bit unique vs the other API Facades, as it has two
// implementations that actually expose the same API and which one gets
// returned depends on who is calling.
// Both of them conform to the exact Upgrader API, so the actual calls that are
// available do not depend on who is currently connected.
func upgraderFacade(st *state.State, resources *common.Resources, auth common.Authorizer) (Upgrader, error) {
	// The type of upgrader we return depends on who is asking.
	// Machines get an UpgraderAPI, units get a UnitUpgraderAPI.
	// This is tested in the state/api/upgrader package since there
	// are currently no direct srvRoot tests.
	// TODO(dfc) this is redundant
	tag, err := names.ParseTag(auth.GetAuthTag().String())
	if err != nil {
		return nil, common.ErrPerm
	}
	switch tag.(type) {
	case names.MachineTag:
		return NewUpgraderAPI(st, resources, auth)
	case names.UnitTag:
		return NewUnitUpgraderAPI(st, resources, auth)
	}
	// Not a machine or unit.
	return nil, common.ErrPerm
}

// NewUpgraderAPI creates a new client-side UpgraderAPI facade.
func NewUpgraderAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*UpgraderAPI, error) {
	if !authorizer.AuthMachineAgent() {
		return nil, common.ErrPerm
	}
	getCanReadWrite := func() (common.AuthFunc, error) {
		return authorizer.AuthOwner, nil
	}
	return &UpgraderAPI{
		ToolsGetter: common.NewToolsGetter(st, getCanReadWrite),
		ToolsSetter: common.NewToolsSetter(st, getCanReadWrite),
		st:          st,
		resources:   resources,
		authorizer:  authorizer,
	}, nil
}

func NewUserManagerAPI(
	st *state.State,
	authorizer common.Authorizer,
) (*UserManagerAPI, error) {
	if !authorizer.AuthClient() {
		return nil, common.ErrPerm
	}

	// TODO(mattyw) - replace stub with real canWrite function
	getCanWrite := common.AuthAlways(true)

	// TODO(waigani) - replace stub with real canRead function
	getCanRead := common.AuthAlways(true)
	return &UserManagerAPI{
			state:       st,
			authorizer:  authorizer,
			getCanWrite: getCanWrite,
			getCanRead:  getCanRead},
		nil
}

// NewNetworkerAPI creates a new client-side Networker API facade.
func NewNetworkerAPI(
	st *state.State,
	_ *common.Resources,
	authorizer common.Authorizer,
) (*NetworkerAPI, error) {
	if !authorizer.AuthMachineAgent() {
		return nil, common.ErrPerm
	}
	getAuthFunc := func() (common.AuthFunc, error) {
		authEntityTag := authorizer.GetAuthTag()

		return func(tag string) bool {
			if tag == authEntityTag {
				// A machine agent can always access its own machine.
				return true
			}
			t, err := names.ParseTag(tag, names.MachineTagKind)
			if err != nil {
				// Only machine tags are allowed.
				return false
			}
			id := t.Id()
			for parentId := state.ParentId(id); parentId != ""; parentId = state.ParentId(parentId) {
				// Until a top-level machine is reached.
				if names.NewMachineTag(parentId).String() == authEntityTag {
					// All containers with the authenticated machine as a
					// parent are accessible by it.
					return true
				}
			}
			// Not found authorized machine agent among ancestors of the current one.
			return false
		}, nil
	}

	return &NetworkerAPI{
		st:          st,
		authorizer:  authorizer,
		getAuthFunc: getAuthFunc,
	}, 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
}

// NewDeployerAPI creates a new server-side DeployerAPI facade.
func NewDeployerAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.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 string) bool {
			for _, unit := range units {
				if names.NewUnitTag(unit).String() == 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),
		st:              st,
		resources:       resources,
		authorizer:      authorizer,
	}, nil
}

// NewKeyManagerAPI creates a new server-side keyupdater API end point.
func NewKeyManagerAPI(
	st *state.State,
	resources *common.Resources,
	authorizer common.Authorizer,
) (*KeyManagerAPI, error) {
	// Only clients and environment managers can access the key manager service.
	if !authorizer.AuthClient() && !authorizer.AuthEnvironManager() {
		return nil, common.ErrPerm
	}
	// TODO(wallyworld) - replace stub with real canRead function
	// For now, only admins can read authorised ssh keys.
	getCanRead := func() (common.AuthFunc, error) {
		return func(_ string) bool {
			return authorizer.GetAuthTag() == adminUser
		}, nil
	}
	// TODO(wallyworld) - replace stub with real canWrite function
	// For now, only admins can write authorised ssh keys for users.
	// Machine agents can write the juju-system-key.
	getCanWrite := func() (common.AuthFunc, error) {
		return func(tag string) bool {
			// Are we a machine agent writing the Juju system key.
			if tag == config.JujuSystemKey {
				// TODO(dfc) this can never be false
				_, err := names.ParseMachineTag(authorizer.GetAuthTag().String())
				return err == nil
			}
			// Are we writing the auth key for a user.
			if _, err := st.User(tag); err != nil {
				return false
			}
			return authorizer.GetAuthTag() == adminUser
		}, nil
	}
	return &KeyManagerAPI{
		state: st, resources: resources, authorizer: authorizer, getCanRead: getCanRead, getCanWrite: getCanWrite}, 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) {
		unit, ok := authorizer.GetAuthEntity().(*state.Unit)
		if !ok {
			panic("authenticated entity is not a unit")
		}
		return func(tag string) bool {
			return tag == names.NewServiceTag(unit.ServiceName()).String()
		}, nil
	}
	accessUnitOrService := common.AuthEither(accessUnit, accessService)
	// Uniter can always watch for environ changes.
	getCanWatch := common.AuthAlways(true)
	// Uniter can not get the secrets.
	getCanReadSecrets := common.AuthAlways(false)
	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, getCanWatch, getCanReadSecrets),

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

// NewRsyslogAPI creates a new instance of the Rsyslog API.
func NewRsyslogAPI(st *state.State, resources *common.Resources, authorizer common.Authorizer) (*RsyslogAPI, error) {
	if !authorizer.AuthMachineAgent() && !authorizer.AuthUnitAgent() {
		return nil, common.ErrPerm
	}
	// Can always watch for environ changes.
	getCanWatch := common.AuthAlways(true)
	// Does not get the secrets.
	getCanReadSecrets := common.AuthAlways(false)
	return &RsyslogAPI{
		EnvironWatcher: common.NewEnvironWatcher(st, resources, getCanWatch, getCanReadSecrets),
		st:             st,
		authorizer:     authorizer,
		resources:      resources,
		canModify:      authorizer.AuthEnvironManager(),
		StateAddresser: common.NewStateAddresser(st),
	}, nil
}

func isAgent(auth common.Authorizer) bool {
	return auth.AuthMachineAgent() || auth.AuthUnitAgent()
}

// 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.
	accessUnit := getAuthFuncForTagKind(names.UnitTagKind)
	accessService := getAuthFuncForTagKind(names.ServiceTagKind)
	accessMachine := getAuthFuncForTagKind(names.MachineTagKind)
	accessEnviron := getAuthFuncForTagKind("")
	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,
		accessEnviron,
		accessEnviron,
	)
	// Watch() is supported for units or services.
	entityWatcher := common.NewAgentEntityWatcher(
		st,
		resources,
		accessUnitOrService,
	)
	// WatchUnits() is supported for machines.
	unitsWatcher := common.NewUnitsWatcher(st,
		resources,
		accessMachine,
	)
	// WatchEnvironMachines() is allowed with unrestricted access.
	machinesWatcher := common.NewEnvironMachinesWatcher(
		st,
		resources,
		accessEnviron,
	)
	// 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,
	}, nil
}

// 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 string) bool {
			if isMachineAgent && tag == authEntityTag {
				// A machine agent can always access its own machine.
				return true
			}
			t, err := names.ParseTag(tag, names.MachineTagKind)
			if err != nil {
				return false
			}
			parentId := state.ParentId(t.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.
			return isMachineAgent && names.NewMachineTag(parentId).String() == authEntityTag
		}, nil
	}
	// Both provisioner types can watch the environment.
	getCanWatch := common.AuthAlways(true)
	// Only the environment provisioner can read secrets.
	getCanReadSecrets := common.AuthAlways(authorizer.AuthEnvironManager())
	return &ProvisionerAPI{
		Remover:                common.NewRemover(st, false, getAuthFunc),
		StatusSetter:           common.NewStatusSetter(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),
		ToolsGetter:            common.NewToolsGetter(st, getAuthFunc),
		EnvironWatcher:         common.NewEnvironWatcher(st, resources, getCanWatch, getCanReadSecrets),
		EnvironMachinesWatcher: common.NewEnvironMachinesWatcher(st, resources, getCanReadSecrets),
		InstanceIdGetter:       common.NewInstanceIdGetter(st, getAuthFunc),
		st:                     st,
		resources:              resources,
		authorizer:             authorizer,
		getAuthFunc:            getAuthFunc,
		getCanWatchMachines:    getCanReadSecrets,
	}, nil
}