Create app id type (hyperledger-labs#378)

* Create app id type

Signed-off-by: Matthias Geihs <[email protected]>

* Lint

Signed-off-by: Matthias Geihs <[email protected]>

* Payment App: Rename Addr to ID

Signed-off-by: Matthias Geihs <[email protected]>

* appID.Key: Remove comment

Signed-off-by: Matthias Geihs <[email protected]>

Signed-off-by: Matthias Geihs <[email protected]>

apps/payment/app.go

@@ -20,17 +20,16 @@ import (
 
 	"perun.network/go-perun/channel"
 	"perun.network/go-perun/log"
-	"perun.network/go-perun/wallet"
 )
 
 // App is a payment app.
 type App struct {
-	Addr wallet.Address
+	ID channel.AppID
 }
 
 // Def returns the address of this payment app.
-func (a *App) Def() wallet.Address {
-	return a.Addr
+func (a *App) Def() channel.AppID {
+	return a.ID
 }
 
 // NewData returns a new instance of data specific to the payment app,

apps/payment/app_internal_test.go

@@ -22,15 +22,14 @@ import (
 
 	"perun.network/go-perun/channel"
 	"perun.network/go-perun/channel/test"
-	wallettest "perun.network/go-perun/wallet/test"
 	pkgtest "polycry.pt/poly-go/test"
 )
 
 func TestApp_Def(t *testing.T) {
 	rng := pkgtest.Prng(t)
-	def := wallettest.NewRandomAddress(rng)
+	def := test.NewRandomAppID(rng)
 	app := &App{def}
-	assert.True(t, def.Equal(app.Def()))
+	assert.True(t, app.Def().Equal(app.Def()))
 }
 
 func TestApp_ValidInit(t *testing.T) {

apps/payment/randomizer.go

@@ -19,7 +19,6 @@ import (
 
 	"perun.network/go-perun/channel"
 	"perun.network/go-perun/channel/test"
-	wtest "perun.network/go-perun/wallet/test"
 )
 
 // Randomizer implements channel.test.AppRandomizer.
@@ -29,7 +28,7 @@ var _ test.AppRandomizer = (*Randomizer)(nil)
 
 // NewRandomApp always returns a payment app with a different address.
 func (*Randomizer) NewRandomApp(rng *rand.Rand) channel.App {
-	return &App{wtest.NewRandomAddress(rng)}
+	return &App{test.NewRandomAppID(rng)}
 }
 
 // NewRandomData returns NoData because a PaymentApp does not have data.

apps/payment/resolver.go

@@ -16,13 +16,12 @@ package payment
 
 import (
 	"perun.network/go-perun/channel"
-	"perun.network/go-perun/wallet"
 )
 
 // Resolver is the payment app resolver.
 type Resolver struct{}
 
 // Resolve returns a payment app with the given definition.
-func (b *Resolver) Resolve(def wallet.Address) (channel.App, error) {
+func (b *Resolver) Resolve(def channel.AppID) (channel.App, error) {
 	return &App{def}, nil
 }

apps/payment/resolver_internal_test.go

@@ -22,7 +22,7 @@ import (
 
 	_ "perun.network/go-perun/backend/sim" // backend init
 	"perun.network/go-perun/channel"
-	"perun.network/go-perun/wallet/test"
+	ctest "perun.network/go-perun/channel/test"
 	pkgtest "polycry.pt/poly-go/test"
 )
 
@@ -32,7 +32,7 @@ func TestResolver(t *testing.T) {
 	rng := pkgtest.Prng(t)
 	assert, require := assert.New(t), require.New(t)
 
-	def := test.NewRandomAddress(rng)
+	def := ctest.NewRandomAppID(rng)
 	channel.RegisterAppResolver(def.Equal, &Resolver{})
 
 	app, err := channel.Resolve(def)

backend/sim/channel/app.go

@@ -0,0 +1,52 @@
+// Copyright 2022 - See NOTICE file for copyright holders.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package channel
+
+import (
+	"math/rand"
+
+	"perun.network/go-perun/backend/sim/wallet"
+	"perun.network/go-perun/channel"
+)
+
+// AppID represents an app identifier.
+type AppID struct {
+	*wallet.Address
+}
+
+// Equal returns whether the object is equal to the given object.
+func (id AppID) Equal(b channel.AppID) bool {
+	bTyped, ok := b.(AppID)
+	if !ok {
+		return false
+	}
+
+	return id.Address.Equal(bTyped.Address)
+}
+
+// Key returns the key representation of this app identifier.
+func (id AppID) Key() channel.AppIDKey {
+	b, err := id.MarshalBinary()
+	if err != nil {
+		panic(err)
+	}
+	return channel.AppIDKey(b)
+}
+
+// NewRandomAppID generates a new random app identifier.
+func NewRandomAppID(rng *rand.Rand) AppID {
+	addr := wallet.NewRandomAddress(rng)
+	return AppID{addr}
+}

backend/sim/channel/asset_test.go

@@ -11,6 +11,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+
 package channel_test
 
 import (

backend/sim/channel/backend.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/pkg/errors"
 
+	simwallet "perun.network/go-perun/backend/sim/wallet"
 	"perun.network/go-perun/channel"
 	"perun.network/go-perun/log"
 	"perun.network/go-perun/wallet"
@@ -79,3 +80,10 @@ func (b *backend) NewAsset() channel.Asset {
 	addr := Asset{}
 	return &addr
 }
+
+// NewAppID returns an object of type AppID, which can be used for
+// unmarshalling an app identifier from its binary representation.
+func (b *backend) NewAppID() channel.AppID {
+	addr := &simwallet.Address{}
+	return AppID{addr}
+}

backend/sim/channel/init.go

@@ -15,11 +15,16 @@
 package channel
 
 import (
+	"math/rand"
+
 	"perun.network/go-perun/channel"
 	"perun.network/go-perun/channel/test"
 )
 
 func init() {
 	channel.SetBackend(new(backend))
 	test.SetRandomizer(new(randomizer))
+	test.SetNewRandomAppID(func(r *rand.Rand) channel.AppID {
+		return NewRandomAppID(r)
+	})
 }

channel/app.go

@@ -20,11 +20,20 @@ import (
 
 	"github.com/pkg/errors"
 
-	"perun.network/go-perun/wallet"
 	"perun.network/go-perun/wire/perunio"
 )
 
 type (
+	// AppID represents an app identifier.
+	AppID interface {
+		encoding.BinaryMarshaler
+		encoding.BinaryUnmarshaler
+		Equal(AppID) bool
+
+		// Key returns the object key which can be used as a map key.
+		Key() AppIDKey
+	}
+
 	// An App is an abstract interface for an app definition. Either a StateApp or
 	// ActionApp should be implemented.
 	App interface {
@@ -33,7 +42,7 @@ type (
 		// what valid actions or transitions are.
 		// Calling this function on a NoApp panics, so ensure that IsNoApp
 		// returns false.
-		Def() wallet.Address
+		Def() AppID
 
 		// NewData returns a new instance of data specific to NoApp, intialized
 		// to its zero value.
@@ -117,11 +126,11 @@ type (
 	// AppResolver provides functionality to create an App from an Address.
 	// The AppResolver needs to be implemented for every state channel application.
 	AppResolver interface {
-		// Resolve creates an app from its defining address. It is
-		// possible that multiple apps are in use, which is why creation happens
-		// over a central Resolve function. This function is intended to resolve
-		// app definitions coming in on the wire.
-		Resolve(wallet.Address) (App, error)
+		// Resolve creates an app from its defining identifier. It is possible that
+		// multiple apps are in use, which is why creation happens over a central
+		// Resolve function. This function is intended to resolve app definitions
+		// coming in on the wire.
+		Resolve(AppID) (App, error)
 	}
 )
 
@@ -165,7 +174,7 @@ func (d OptAppDec) Decode(r io.Reader) (err error) {
 		*d.App = NoApp()
 		return nil
 	}
-	appDef := wallet.NewAddress()
+	appDef := backend.NewAppID()
 	err = perunio.Decode(r, appDef)
 	if err != nil {
 		return errors.WithMessage(err, "decode app address")

channel/appregistry.go

@@ -19,33 +19,38 @@ import (
 	"sync"
 
 	"github.com/pkg/errors"
-	"perun.network/go-perun/wallet"
 )
 
 // appRegistry is the global registry for `AppResolver`s.
-var appRegistry = appReg{singles: make(map[wallet.AddrKey]App)}
+var appRegistry = appReg{singles: make(map[AppIDKey]App)}
+
+// AppIDKey is the key representation of an app identifier.
+type AppIDKey string
 
 type appReg struct {
 	sync.RWMutex
 	resolvers  []appRegEntry
-	singles    map[wallet.AddrKey]App
+	singles    map[AppIDKey]App
 	defaultRes AppResolver
 }
 
+// AppIDPredicate is a function for filtering app identifiers.
+type AppIDPredicate = func(AppID) bool
+
 type appRegEntry struct {
-	pred wallet.AddressPredicate
+	pred AppIDPredicate
 	res  AppResolver
 }
 
 // Resolve is a global wrapper call to the global `appRegistry`.
 // This function is intended to resolve app definitions coming in on the wire.
-func Resolve(def wallet.Address) (App, error) {
+func Resolve(def AppID) (App, error) {
 	appRegistry.RLock()
 	defer appRegistry.RUnlock()
 	if def == nil {
 		log.Panic("resolving nil address")
 	}
-	if app, ok := appRegistry.singles[wallet.Key(def)]; ok {
+	if app, ok := appRegistry.singles[def.Key()]; ok {
 		return app, nil
 	}
 	for _, e := range appRegistry.resolvers {
@@ -59,14 +64,14 @@ func Resolve(def wallet.Address) (App, error) {
 	return appRegistry.defaultRes.Resolve(def)
 }
 
-// RegisterAppResolver appends the given `AddressPredicate` and `AppResolver` to the
-// global `appRegistry`.
-func RegisterAppResolver(pred wallet.AddressPredicate, appRes AppResolver) {
+// RegisterAppResolver appends the given `AppIDPredicate` and `AppResolver` to
+// the global `appRegistry`.
+func RegisterAppResolver(pred AppIDPredicate, appRes AppResolver) {
 	appRegistry.Lock()
 	defer appRegistry.Unlock()
 
 	if pred == nil || appRes == nil {
-		log.Panic("nil AddressPredicate or AppResolver")
+		log.Panic("nil AppIDPredicate or AppResolver")
 	}
 
 	appRegistry.resolvers = append(appRegistry.resolvers, appRegEntry{pred, appRes})
@@ -81,7 +86,7 @@ func RegisterApp(app App) {
 		log.Panic("nil Address or App")
 	}
 
-	appRegistry.singles[wallet.Key(app.Def())] = app
+	appRegistry.singles[app.Def().Key()] = app
 }
 
 // RegisterDefaultApp allows to specify a default `AppResolver` which is used by