simplify runtime registry

- removed the ability to register the crypto driver along with the engine runtime
- refactored FetchEngineRuntime to FetchRuntime for consistency

engine.go

@@ -79,3 +79,24 @@ type EngineRuntime interface {
 	// ErrorResult that is used by the engine runtime
 	DecodeErrorResult([]byte) (ErrorResult, error)
 }
+
+// registry is an in-memory registry of supported EngineRuntime instances.
+// Support for different engine runtimes is only available if they are first registered with this package.
+var registry = map[EngineKind]EngineRuntime{}
+
+// RegisterRuntime registers an EngineRuntime with the package.
+// If a runtime instance already exists for the EngineKind, it is overwritten.
+func RegisterRuntime(runtime EngineRuntime) {
+	registry[runtime.Kind()] = runtime
+}
+
+// FetchRuntime retrieves an EngineRuntime for a given EngineKind.
+// If the runtime for the engine kind is not registered, returns false.
+func FetchRuntime(kind EngineKind) (EngineRuntime, bool) {
+	runtime, exists := registry[kind]
+	if !exists {
+		return nil, false
+	}
+
+	return runtime, true
+}

registry_test.go → engine_test.go

@@ -9,19 +9,19 @@ import (
 func TestRegisterEngineRuntime(t *testing.T) {
 	// register a mock engine runtime
 	mock := &mockEngineRuntime{kind: PISA}
-	RegisterRuntime(mock, nil)
+	RegisterRuntime(mock)
 
 	// verify that the engine runtime was registered correctly
-	r, ok := FetchEngineRuntime(PISA)
+	r, ok := FetchRuntime(PISA)
 	require.True(t, ok, "Expected engine runtime to be registered")
 	require.Equal(t, r.Kind(), PISA, "Expected registered engine runtime to have kind %s, but got %s", PISA, r.Kind())
 
 	// overwrite the mock engine runtime with a new one
 	mock2 := &mockEngineRuntime{kind: PISA}
-	RegisterRuntime(mock2, nil)
+	RegisterRuntime(mock2)
 
 	// verify that the new engine runtime was registered correctly
-	r, ok = FetchEngineRuntime(PISA)
+	r, ok = FetchRuntime(PISA)
 	require.True(t, ok, "Expected engine runtime to be registered")
 	require.Equal(t, r.Kind(), PISA, "Expected registered engine runtime to have kind %s, but got %s", PISA, r.Kind())
 
@@ -30,15 +30,15 @@ func TestRegisterEngineRuntime(t *testing.T) {
 
 func TestFetchEngineRuntime(t *testing.T) {
 	// fetch an unregistered engine runtime
-	_, ok := FetchEngineRuntime(MERU)
+	_, ok := FetchRuntime(MERU)
 	require.False(t, ok, "Expected engine runtime not to be registered")
 
 	// register a mock engine runtime
 	mock := &mockEngineRuntime{kind: MERU}
-	RegisterRuntime(mock, nil)
+	RegisterRuntime(mock)
 
 	// fetch the registered engine runtime
-	r, ok := FetchEngineRuntime(MERU)
+	r, ok := FetchRuntime(MERU)
 	require.True(t, ok, "Expected engine runtime to be registered")
 	require.Equal(t, r.Kind(), MERU, "Expected registered engine runtime to have kind %s, but got %s", MERU, r.Kind())
 }

manifest.go

@@ -178,7 +178,7 @@ func (header ManifestHeader) validate() error {
 		return errors.New("unsupported manifest syntax")
 	}
 
-	if _, ok := FetchEngineRuntime(header.LogicEngine()); !ok {
+	if _, ok := FetchRuntime(header.LogicEngine()); !ok {
 		return errors.New("unsupported manifest engine: element registry not found")
 	}
 
@@ -209,7 +209,7 @@ func (manifest *Manifest) Depolorize(depolorizer *polo.Depolorizer) (err error)
 		return err
 	}
 
-	runtime, _ := FetchEngineRuntime(manifest.Header().LogicEngine())
+	runtime, _ := FetchRuntime(manifest.Header().LogicEngine())
 
 	manifest.Elements = make([]ManifestElement, 0, len(raw.Elements))
 
@@ -264,7 +264,7 @@ func (manifest *Manifest) UnmarshalJSON(data []byte) (err error) {
 		return err
 	}
 
-	runtime, _ := FetchEngineRuntime(manifest.Header().LogicEngine())
+	runtime, _ := FetchRuntime(manifest.Header().LogicEngine())
 
 	manifest.Elements = make([]ManifestElement, 0, len(raw.Elements))
 
@@ -314,7 +314,7 @@ func (manifest *Manifest) UnmarshalYAML(node *yaml.Node) error {
 		return err
 	}
 
-	runtime, _ := FetchEngineRuntime(manifest.Header().LogicEngine())
+	runtime, _ := FetchRuntime(manifest.Header().LogicEngine())
 
 	manifest.Elements = make([]ManifestElement, 0, len(raw.Elements))