// 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, 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
}

// 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
}

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)
	return &UserManagerAPI{
			state:       st,
			authorizer:  authorizer,
			getCanWrite: getCanWrite},
		nil
}

// 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
}

// 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
}