Add ToProto() and FromProto().

CHANGELOG.md

@@ -10,6 +10,13 @@ The format is based on [Keep a Changelog], and this project adheres to
 [keep a changelog]: https://keepachangelog.com/en/1.0.0/
 [semantic versioning]: https://semver.org/spec/v2.0.0.html
 
+## [Unreleased]
+
+### Added
+
+- Added `ToProto()` and `FromProto()` to convert application configurations to
+  and from their protocol buffers representations.
+
 ## [0.13.2] - 2024-08-12
 
 ### Fixed

api/client.go

@@ -35,7 +35,7 @@ func (c *Client) ListApplications(
 
 	var configs []configkit.Application
 	for _, in := range res.GetApplications() {
-		out, err := unmarshalApplication(in)
+		out, err := configkit.FromProto(in)
 		if err != nil {
 			return nil, err
 		}

api/server.go

@@ -20,7 +20,7 @@ func NewServer(apps ...configkit.Application) *Server {
 	s := &Server{}
 
 	for _, in := range apps {
-		out, err := marshalApplication(in)
+		out, err := configkit.ToProto(in)
 		if err != nil {
 			panic(err)
 		}

api/server_test.go

@@ -1,6 +1,7 @@
-package api
+package api_test
 
 import (
+	. "github.com/dogmatiq/configkit/api"
 	"github.com/dogmatiq/configkit/internal/entity"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"

internal/entity/doc.go

@@ -0,0 +1,5 @@
+// Package entity provides internal implementations of the entities defined in
+// the configkit package.
+//
+// deprecated: Packages should define their own implementations instead.
+package entity

api/marshaling.go → marshal.go

@@ -1,18 +1,17 @@
-package api
+package configkit
 
 import (
+	"context"
 	"errors"
 	"fmt"
 
-	"github.com/dogmatiq/configkit"
-	"github.com/dogmatiq/configkit/internal/entity"
 	"github.com/dogmatiq/configkit/message"
 	"github.com/dogmatiq/interopspec/configspec"
 )
 
-// marshalApplication marshals an application config to its protobuf
+// ToProto converts an application configuration to its protocol buffers
 // representation.
-func marshalApplication(in configkit.Application) (*configspec.Application, error) {
+func ToProto(in Application) (*configspec.Application, error) {
 	out := &configspec.Application{}
 
 	var err error
@@ -38,25 +37,19 @@ func marshalApplication(in configkit.Application) (*configspec.Application, erro
 	return out, nil
 }
 
-// unmarshalApplication unmarshals an application config from its protobuf
+// FromProto converts an application configuration from its protocol buffers
 // representation.
-func unmarshalApplication(in *configspec.Application) (configkit.Application, error) {
-	out := &entity.Application{
-		MessageNamesValue: configkit.EntityMessageNames{
-			Produced: message.NameRoles{},
-			Consumed: message.NameRoles{},
-		},
-		HandlersValue: configkit.HandlerSet{},
-	}
+func FromProto(in *configspec.Application) (Application, error) {
+	out := &unmarshaledApplication{}
 
 	var err error
-	out.IdentityValue, err = unmarshalIdentity(in.GetIdentity())
+	out.ident, err = unmarshalIdentity(in.GetIdentity())
 	if err != nil {
 		return nil, err
 	}
 
-	out.TypeNameValue = in.GetGoType()
-	if out.TypeNameValue == "" {
+	out.typeName = in.GetGoType()
+	if out.typeName == "" {
 		return nil, errors.New("application type name is empty")
 	}
 
@@ -66,22 +59,31 @@ func unmarshalApplication(in *configspec.Application) (configkit.Application, er
 			return nil, err
 		}
 
-		out.HandlersValue.Add(hOut)
+		if out.handlers == nil {
+			out.handlers = HandlerSet{}
+		}
+		out.handlers.Add(hOut)
 
 		for n, r := range hOut.MessageNames().Produced {
-			out.MessageNamesValue.Produced[n] = r
+			if out.names.Produced == nil {
+				out.names.Produced = message.NameRoles{}
+			}
+			out.names.Produced[n] = r
 		}
 
 		for n, r := range hOut.MessageNames().Consumed {
-			out.MessageNamesValue.Consumed[n] = r
+			if out.names.Consumed == nil {
+				out.names.Consumed = message.NameRoles{}
+			}
+			out.names.Consumed[n] = r
 		}
 	}
 
 	return out, nil
 }
 
 // marshalHandler marshals a handler config to its protobuf representation.
-func marshalHandler(in configkit.Handler) (*configspec.Handler, error) {
+func marshalHandler(in Handler) (*configspec.Handler, error) {
 	out := &configspec.Handler{
 		IsDisabled: in.IsDisabled(),
 	}
@@ -118,37 +120,33 @@ func marshalHandler(in configkit.Handler) (*configspec.Handler, error) {
 
 // unmarshalHandler unmarshals a handler configuration from its protocol buffers
 // representation.
-func unmarshalHandler(in *configspec.Handler) (configkit.Handler, error) {
-	out := &entity.Handler{
-		MessageNamesValue: configkit.EntityMessageNames{
-			Produced: message.NameRoles{},
-			Consumed: message.NameRoles{},
-		},
-		IsDisabledValue: in.GetIsDisabled(),
+func unmarshalHandler(in *configspec.Handler) (Handler, error) {
+	out := &unmarshaledHandler{
+		isDisabled: in.GetIsDisabled(),
 	}
 
 	var err error
-	out.IdentityValue, err = unmarshalIdentity(in.GetIdentity())
+	out.ident, err = unmarshalIdentity(in.GetIdentity())
 	if err != nil {
 		return nil, err
 	}
 
-	out.TypeNameValue = in.GetGoType()
-	if out.TypeNameValue == "" {
+	out.typeName = in.GetGoType()
+	if out.typeName == "" {
 		return nil, errors.New("handler type name is empty")
 	}
 
-	out.HandlerTypeValue, err = unmarshalHandlerType(in.GetType())
+	out.handlerType, err = unmarshalHandlerType(in.GetType())
 	if err != nil {
 		return nil, err
 	}
 
-	out.MessageNamesValue.Produced, err = unmarshalNameRoles(in.GetProducedMessages())
+	out.names.Produced, err = unmarshalNameRoles(in.GetProducedMessages())
 	if err != nil {
 		return nil, err
 	}
 
-	out.MessageNamesValue.Consumed, err = unmarshalNameRoles(in.GetConsumedMessages())
+	out.names.Consumed, err = unmarshalNameRoles(in.GetConsumedMessages())
 	if err != nil {
 		return nil, err
 	}
@@ -178,7 +176,7 @@ func marshalNameRoles(in message.NameRoles) (map[string]configspec.MessageRole,
 	return out, nil
 }
 
-// marshalNameRoles unmarshals a message.NameRoles collection from
+// unmarshalNameRoles unmarshals a message.NameRoles collection from
 // its protocol buffers representation.
 func unmarshalNameRoles(in map[string]configspec.MessageRole) (message.NameRoles, error) {
 	out := message.NameRoles{}
@@ -201,9 +199,9 @@ func unmarshalNameRoles(in map[string]configspec.MessageRole) (message.NameRoles
 	return out, nil
 }
 
-// marshalIdentity marshals a configkit.Identity to its protocol buffers
+// marshalIdentity marshals a Identity to its protocol buffers
 // representation.
-func marshalIdentity(in configkit.Identity) (*configspec.Identity, error) {
+func marshalIdentity(in Identity) (*configspec.Identity, error) {
 	if err := in.Validate(); err != nil {
 		return nil, err
 	}
@@ -214,46 +212,46 @@ func marshalIdentity(in configkit.Identity) (*configspec.Identity, error) {
 	}, nil
 }
 
-// unmarshalIdentity unmarshals a configkit.Identity from its protocol buffers
+// unmarshalIdentity unmarshals a Identity from its protocol buffers
 // representation.
-func unmarshalIdentity(in *configspec.Identity) (configkit.Identity, error) {
-	return configkit.NewIdentity(
+func unmarshalIdentity(in *configspec.Identity) (Identity, error) {
+	return NewIdentity(
 		in.GetName(),
 		in.GetKey(),
 	)
 }
 
-// marshalHandlerType marshals a configkit.HandlerType to its protocol buffers
+// marshalHandlerType marshals a HandlerType to its protocol buffers
 // representation.
-func marshalHandlerType(t configkit.HandlerType) (configspec.HandlerType, error) {
+func marshalHandlerType(t HandlerType) (configspec.HandlerType, error) {
 	if err := t.Validate(); err != nil {
 		return configspec.HandlerType_UNKNOWN_HANDLER_TYPE, err
 	}
 
 	switch t {
-	case configkit.AggregateHandlerType:
+	case AggregateHandlerType:
 		return configspec.HandlerType_AGGREGATE, nil
-	case configkit.ProcessHandlerType:
+	case ProcessHandlerType:
 		return configspec.HandlerType_PROCESS, nil
-	case configkit.IntegrationHandlerType:
+	case IntegrationHandlerType:
 		return configspec.HandlerType_INTEGRATION, nil
-	default: // configkit.ProjectionHandlerType
+	default: // ProjectionHandlerType
 		return configspec.HandlerType_PROJECTION, nil
 	}
 }
 
-// unmarshalHandlerType unmarshals a configkit.HandlerType from its protocol
+// unmarshalHandlerType unmarshals a HandlerType from its protocol
 // buffers representation.
-func unmarshalHandlerType(t configspec.HandlerType) (configkit.HandlerType, error) {
+func unmarshalHandlerType(t configspec.HandlerType) (HandlerType, error) {
 	switch t {
 	case configspec.HandlerType_AGGREGATE:
-		return configkit.AggregateHandlerType, nil
+		return AggregateHandlerType, nil
 	case configspec.HandlerType_PROCESS:
-		return configkit.ProcessHandlerType, nil
+		return ProcessHandlerType, nil
 	case configspec.HandlerType_INTEGRATION:
-		return configkit.IntegrationHandlerType, nil
+		return IntegrationHandlerType, nil
 	case configspec.HandlerType_PROJECTION:
-		return configkit.ProjectionHandlerType, nil
+		return ProjectionHandlerType, nil
 	default:
 		return "", fmt.Errorf("unknown handler type: %#v", t)
 	}
@@ -290,3 +288,83 @@ func unmarshalMessageRole(r configspec.MessageRole) (message.Role, error) {
 		return "", fmt.Errorf("unknown message role: %#v", r)
 	}
 }
+
+// unmarshaledApplication is an implementation of [Application] that has been
+// produced by unmarshaling a configuration.
+type unmarshaledApplication struct {
+	ident    Identity
+	names    EntityMessageNames
+	typeName string
+	handlers HandlerSet
+}
+
+func (a *unmarshaledApplication) Identity() Identity {
+	return a.ident
+}
+
+func (a *unmarshaledApplication) MessageNames() EntityMessageNames {
+	return a.names
+}
+
+func (a *unmarshaledApplication) TypeName() string {
+	return a.typeName
+}
+
+func (a *unmarshaledApplication) AcceptVisitor(ctx context.Context, v Visitor) error {
+	return v.VisitApplication(ctx, a)
+}
+
+func (a *unmarshaledApplication) Handlers() HandlerSet {
+	return a.handlers
+}
+
+// unmarshaledHandler is an implementation of [Handler] that has been produced
+// by unmarshaling a configuration.
+type unmarshaledHandler struct {
+	ident       Identity
+	names       EntityMessageNames
+	typeName    string
+	handlerType HandlerType
+	isDisabled  bool
+}
+
+// Identity returns the identity of the entity.
+func (h *unmarshaledHandler) Identity() Identity {
+	return h.ident
+}
+
+// MessageNames returns information about the messages used by the entity.
+func (h *unmarshaledHandler) MessageNames() EntityMessageNames {
+	return h.names
+}
+
+// TypeName returns the fully-qualified type name of the entity.
+func (h *unmarshaledHandler) TypeName() string {
+	return h.typeName
+}
+
+// HandlerType returns the type of handler.
+func (h *unmarshaledHandler) HandlerType() HandlerType {
+	return h.handlerType
+}
+
+// IsDisabled returns true if the handler is disabled.
+func (h *unmarshaledHandler) IsDisabled() bool {
+	return h.isDisabled
+}
+
+// AcceptVisitor calls the appropriate method on v for this entity type.
+func (h *unmarshaledHandler) AcceptVisitor(ctx context.Context, v Visitor) error {
+	h.handlerType.MustValidate()
+
+	switch h.handlerType {
+	case AggregateHandlerType:
+		return v.VisitAggregate(ctx, h)
+	case ProcessHandlerType:
+		return v.VisitProcess(ctx, h)
+	case IntegrationHandlerType:
+		return v.VisitIntegration(ctx, h)
+	default: // ProjectionHandlerType
+		return v.VisitProjection(ctx, h)
+	}
+}