refactor: split container executor validation states

internal/backendexecutor/executor.go

@@ -158,44 +158,53 @@ func (e *Executor) run(ctx context.Context, transactionID string, request Reques
 		if err != nil {
 			return err
 		}
-		switch record.State {
-		case transaction.StateCreated:
-			if _, err := e.store.Transition(ctx, transactionID, transaction.StateValidating, "backend container validation started"); err != nil {
+		done, err := e.advanceState(ctx, transactionID, record.State, request)
+		if err != nil {
 			return err
 		}
+		if done {
+			return nil
+		}
+	}
+}
+
+func (e *Executor) advanceState(ctx context.Context, transactionID string, state transaction.State, request Request) (bool, error) {
+	switch state {
+	case transaction.StateCreated:
+		_, err := e.store.Transition(ctx, transactionID, transaction.StateValidating, "backend container validation started")
+		return false, err
 	case transaction.StateValidating:
+		return false, e.validateAndPrepare(ctx, transactionID, request)
+	case transaction.StatePrepared:
+		if err := e.prepare(ctx, transactionID, request); err != nil {
+			return false, e.failUnlessRecoverable(ctx, transactionID, err)
+		}
+		_, err := e.store.Transition(ctx, transactionID, transaction.StateStarting, "backend container prepared")
+		return false, err
+	case transaction.StateStarting:
+		if err := e.prepare(ctx, transactionID, request); err != nil {
+			return false, err
+		}
+		if err := e.startAndCheck(ctx, transactionID, request); err != nil {
+			return false, err
+		}
+		_, err := e.store.Transition(ctx, transactionID, transaction.StateSwitching, "backend container is healthy")
+		return false, err
+	case transaction.StateSwitching:
+		return true, nil
+	default:
+		return false, fmt.Errorf("backend container executor cannot run transaction %s in state %s", transactionID, state)
+	}
+}
+
+func (e *Executor) validateAndPrepare(ctx context.Context, transactionID string, request Request) error {
 	if err := e.validate(ctx, request); err != nil {
 		_, transitionErr := e.store.Transition(ctx, transactionID, transaction.StateFailed, err.Error())
 		return errors.Join(err, transitionErr)
 	}
-			if _, err := e.store.Transition(ctx, transactionID, transaction.StatePrepared, "backend container inputs validated"); err != nil {
+	_, err := e.store.Transition(ctx, transactionID, transaction.StatePrepared, "backend container inputs validated")
 	return err
 }
-		case transaction.StatePrepared:
-			if err := e.prepare(ctx, transactionID, request); err != nil {
-				return e.failUnlessRecoverable(ctx, transactionID, err)
-			}
-			if _, err := e.store.Transition(ctx, transactionID, transaction.StateStarting, "backend container prepared"); err != nil {
-				return err
-			}
-		case transaction.StateStarting:
-			// 重放 PREPARED 步骤会核对持久化意图，阻止恢复时换入另一组请求参数。
-			if err := e.prepare(ctx, transactionID, request); err != nil {
-				return err
-			}
-			if err := e.startAndCheck(ctx, transactionID, request); err != nil {
-				return err
-			}
-			if _, err := e.store.Transition(ctx, transactionID, transaction.StateSwitching, "backend container is healthy"); err != nil {
-				return err
-			}
-		case transaction.StateSwitching:
-			return nil
-		default:
-			return fmt.Errorf("backend container executor cannot run transaction %s in state %s", transactionID, record.State)
-		}
-	}
-}
 
 // failUnlessRecoverable 判断 prepare 阶段的错误是否可恢复。
 // 若 cause 是 UncertainStepError 或 ErrStepConflict，则直接原样返回（保留不确定性以便重放恢复）；
@@ -321,6 +330,19 @@ func (e *Executor) streamContainerLogs(ctx context.Context, name string, report
 // validateRequest 对请求字段做静态校验，确保所有取值精确且自洽。
 // 任一字段不符合要求时返回描述性错误。
 func validateRequest(request Request) error {
+	if err := validateImageAcquisition(request); err != nil {
+		return err
+	}
+	if err := validateImageIdentity(request); err != nil {
+		return err
+	}
+	if err := validateContainerRuntime(request); err != nil {
+		return err
+	}
+	return validateHealthEndpoint(request)
+}
+
+func validateImageAcquisition(request Request) error {
 	switch request.ImageAcquisition {
 	case ImageAcquisitionLoad:
 		if !filepath.IsAbs(request.ArchivePath) {
@@ -337,6 +359,10 @@ func validateRequest(request Request) error {
 	default:
 		return fmt.Errorf("unsupported image acquisition: %q", request.ImageAcquisition)
 	}
+	return nil
+}
+
+func validateImageIdentity(request Request) error {
 	if request.ImageReference == "" || strings.TrimSpace(request.ImageReference) != request.ImageReference {
 		return errors.New("exact image reference is required")
 	}
@@ -349,6 +375,10 @@ func validateRequest(request Request) error {
 	if request.ContainerName == "" || strings.TrimSpace(request.ContainerName) != request.ContainerName {
 		return errors.New("exact container name is required")
 	}
+	return nil
+}
+
+func validateContainerRuntime(request Request) error {
 	if request.Port != 8080 && request.Port != 8081 && request.Port != 18910 && request.Port != 28910 {
 		return fmt.Errorf("container port must be 8080, 8081, 18910, or 28910: %d", request.Port)
 	}
@@ -372,6 +402,10 @@ func validateRequest(request Request) error {
 	if err := validateRestartPolicy(request.RestartPolicy); err != nil {
 		return err
 	}
+	return nil
+}
+
+func validateHealthEndpoint(request Request) error {
 	path := request.HealthPath
 	if path == "" {
 		path = healthPath