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msghandler.go
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msghandler.go
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/*
*
* Copyright SecureKey Technologies Inc. All Rights Reserved.
*
* SPDX-License-Identifier: Apache-2.0
* /
*
*/
// Package msghandler dynamically maintains the list of registered message services.
//
// In addition to returning list of available message services as a message service provider implementation,
// this message handler also provides register/unregister functionality which can be used to add/remove
// message services from already running agent.
//
// (RFC Reference : https://github.com/hyperledger/aries-rfcs/blob/master/features/0351-purpose-decorator/README.md)
//
package msghandler
import (
"fmt"
"sync"
"github.com/Universal-Health-Chain/aries-framework-go/pkg/didcomm/dispatcher"
)
const (
errAlreadyRegistered = "registration failed, message service with name `%s` already registered"
errNeverRegistered = "failed to unregister, unable to find registered message service with name `%s`"
)
// NewRegistrar returns new message registrar instance.
func NewRegistrar() *Registrar {
return &Registrar{}
}
// Registrar is message service provider implementation which maintains list of registered message service
// and also allows dynamic register/unregister of message services.
type Registrar struct {
services []dispatcher.MessageService
lock sync.RWMutex
}
// Services returns list of message services registered to this handler.
func (m *Registrar) Services() []dispatcher.MessageService {
m.lock.RLock()
defer m.lock.RUnlock()
svcs := make([]dispatcher.MessageService, len(m.services))
copy(svcs, m.services)
return svcs
}
// Register registers given message services to this handler,
// returns error in case of duplicate registration.
func (m *Registrar) Register(msgServices ...dispatcher.MessageService) error {
if len(msgServices) == 0 {
return nil
}
m.lock.Lock()
defer m.lock.Unlock()
// if current list is empty, add all
if len(m.services) == 0 {
m.services = append(m.services, msgServices...)
return nil
}
// if current list is not empty, then look for duplicates before adding
for _, newMsgSvc := range msgServices {
for _, existingSvc := range m.services {
if existingSvc.Name() == newMsgSvc.Name() {
return fmt.Errorf(errAlreadyRegistered, newMsgSvc.Name())
}
}
}
m.services = append(m.services, msgServices...)
return nil
}
// Unregister unregisters message service with given name from this message handler,
// returns error if given message service doesn't exists.
func (m *Registrar) Unregister(name string) error {
m.lock.Lock()
defer m.lock.Unlock()
index := -1
for i, svc := range m.services {
if svc.Name() == name {
index = i
break
}
}
if index < 0 {
return fmt.Errorf(errNeverRegistered, name)
}
m.services = append(m.services[:index], m.services[index+1:]...)
return nil
}