refactor: replace concrete type assertions with capability interfaces (closes #59) (#120)

Replace two concrete type assertions in cmd/server/main.go with interface checks:

1. svc.(*module.OpenAPIGenerator) → svc.(interfaces.SchemaRegistrar)
   - Define SchemaRegistrar in interfaces/ with Name(), RegisterAdminSchemas(),
     ApplySchemas() methods
   - Add RegisterAdminSchemas() method to *OpenAPIGenerator that delegates to
     the package-level RegisterAdminSchemas function
   - Add compile-time check: var _ interfaces.SchemaRegistrar = (*OpenAPIGenerator)(nil)

2. svc.(*module.WorkflowRegistry) → svc.(interfaces.WorkflowStoreProvider)
   - Define WorkflowStoreProvider in interfaces/ with Name() and WorkflowStore() any
   - Add WorkflowStore() any method to *WorkflowRegistry returning the store opaquely
     (avoids interfaces→module circular import)
   - Add compile-time check: var _ interfaces.WorkflowStoreProvider = (*WorkflowRegistry)(nil)

No behaviour is changed; only the mechanism for identifying capable services is updated.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: intel352

cmd/server/main.go

@@ -29,6 +29,7 @@ import (
 	"github.com/GoCodeAlone/workflow/dynamic"
 	"github.com/GoCodeAlone/workflow/environment"
 	"github.com/GoCodeAlone/workflow/handlers"
+	"github.com/GoCodeAlone/workflow/interfaces"
 	"github.com/GoCodeAlone/workflow/module"
 	"github.com/GoCodeAlone/workflow/observability"
 	"github.com/GoCodeAlone/workflow/observability/tracing"
@@ -479,8 +480,8 @@ func registerManagementServices(logger *slog.Logger, app *serverApp) {
 
 	// Enrich OpenAPI spec via the service registry
 	for _, svc := range engine.GetApp().SvcRegistry() {
-		if gen, ok := svc.(*module.OpenAPIGenerator); ok {
-			module.RegisterAdminSchemas(gen)
+		if gen, ok := svc.(interfaces.SchemaRegistrar); ok {
+			gen.RegisterAdminSchemas()
 			gen.ApplySchemas()
 			logger.Info("Registered typed OpenAPI schemas", "module", gen.Name())
 		}
@@ -506,10 +507,12 @@ func (app *serverApp) initStores(logger *slog.Logger) error {
 	// Discover the WorkflowRegistry from the service registry
 	var store *module.V1Store
 	for _, svc := range engine.GetApp().SvcRegistry() {
-		if reg, ok := svc.(*module.WorkflowRegistry); ok {
-			store = reg.Store()
-			logger.Info("Using WorkflowRegistry store", "module", reg.Name())
-			break
+		if provider, ok := svc.(interfaces.WorkflowStoreProvider); ok {
+			if s, ok := provider.WorkflowStore().(*module.V1Store); ok {
+				store = s
+				logger.Info("Using WorkflowRegistry store", "module", provider.Name())
+				break
+			}
 		}
 	}
 

interfaces/registry.go

@@ -0,0 +1,35 @@
+package interfaces
+
+// SchemaRegistrar is implemented by any service that can register admin
+// schemas into an OpenAPI specification and apply them. Using this interface
+// in cmd/server allows the server to enrich the OpenAPI spec without holding
+// a concrete *module.OpenAPIGenerator pointer.
+//
+// *module.OpenAPIGenerator satisfies this interface.
+type SchemaRegistrar interface {
+	// Name returns the module name (used for logging).
+	Name() string
+
+	// RegisterAdminSchemas registers all admin API request/response schemas
+	// onto this generator. Equivalent to calling module.RegisterAdminSchemas(gen).
+	RegisterAdminSchemas()
+
+	// ApplySchemas applies all previously registered component schemas and
+	// operation schema overrides to the current OpenAPI spec.
+	ApplySchemas()
+}
+
+// WorkflowStoreProvider is implemented by any service that exposes a workflow
+// data store. Using this interface in cmd/server decouples the server startup
+// code from the concrete *module.WorkflowRegistry type.
+//
+// *module.WorkflowRegistry satisfies this interface.
+type WorkflowStoreProvider interface {
+	// Name returns the module name (used for logging).
+	Name() string
+
+	// WorkflowStore returns the underlying workflow data store as an opaque
+	// value. The caller is responsible for asserting the concrete type
+	// (typically *module.V1Store) when further operations are required.
+	WorkflowStore() any
+}

module/openapi_generator.go

@@ -10,9 +10,13 @@ import (
 	"sync"
 
 	"github.com/CrisisTextLine/modular"
+	"github.com/GoCodeAlone/workflow/interfaces"
 	"gopkg.in/yaml.v3"
 )
 
+// Compile-time assertion: *OpenAPIGenerator must satisfy interfaces.SchemaRegistrar.
+var _ interfaces.SchemaRegistrar = (*OpenAPIGenerator)(nil)
+
 // --- OpenAPI 3.0 spec structs (minimal inline definitions) ---
 
 // OpenAPISpec represents a minimal OpenAPI 3.0 specification document.
@@ -681,3 +685,10 @@ func (g *OpenAPIGenerator) ApplySchemas() {
 		}
 	}
 }
+
+// RegisterAdminSchemas satisfies the interfaces.SchemaRegistrar interface.
+// It delegates to the package-level RegisterAdminSchemas function, registering
+// all admin API request/response schemas onto this generator.
+func (g *OpenAPIGenerator) RegisterAdminSchemas() {
+	RegisterAdminSchemas(g)
+}

module/workflow_registry.go

@@ -5,8 +5,12 @@ import (
 	"fmt"
 
 	"github.com/CrisisTextLine/modular"
+	"github.com/GoCodeAlone/workflow/interfaces"
 )
 
+// Compile-time assertion: *WorkflowRegistry must satisfy interfaces.WorkflowStoreProvider.
+var _ interfaces.WorkflowStoreProvider = (*WorkflowRegistry)(nil)
+
 // WorkflowRegistry is a module that provides the V1Store as a service,
 // making the workflow data store (companies, projects, workflows) available
 // to other modules via the service registry. It can either use a shared
@@ -84,6 +88,13 @@ func (w *WorkflowRegistry) Store() *V1Store {
 	return w.store
 }
 
+// WorkflowStore satisfies the interfaces.WorkflowStoreProvider interface.
+// It returns the underlying V1Store as an opaque any value so that the
+// interfaces package does not need to import the module package.
+func (w *WorkflowRegistry) WorkflowStore() any {
+	return w.store
+}
+
 func (w *WorkflowRegistry) ProvidesServices() []modular.ServiceProvider {
 	return []modular.ServiceProvider{
 		{Name: w.name, Description: "Workflow data registry (companies, projects, workflows)", Instance: w},