feat(kernel): add system requirements validation and service criticality definitions

Author: hotlong

packages/core/src/kernel.ts

@@ -1,6 +1,7 @@
 import { Plugin, PluginContext } from './types.js';
 import { createLogger, ObjectLogger } from './logger.js';
 import type { LoggerConfig } from '@objectstack/spec/system';
+import { ServiceRequirementDef } from '@objectstack/spec/system';
 import { PluginLoader, PluginMetadata, ServiceLifecycle, ServiceFactory, PluginStartupResult } from './plugin-loader.js';
 
 /**
@@ -185,6 +186,44 @@ export class ObjectKernel {
         return this;
     }
 
+    /**
+     * Validate Critical System Requirements
+     */
+    private validateSystemRequirements() {
+        this.logger.debug('Validating system service requirements...');
+        const missingServices: string[] = [];
+        const missingCoreServices: string[] = [];
+        
+        // Iterate through all defined requirements
+        for (const [serviceName, criticality] of Object.entries(ServiceRequirementDef)) {
+            const hasService = this.services.has(serviceName) || this.pluginLoader.hasService(serviceName);
+            
+            if (!hasService) {
+                if (criticality === 'required') {
+                    this.logger.error(`CRITICAL: Required service missing: ${serviceName}`);
+                    missingServices.push(serviceName);
+                } else if (criticality === 'core') {
+                    this.logger.warn(`CORE: Core service missing, functionality may be degraded: ${serviceName}`);
+                    missingCoreServices.push(serviceName);
+                } else {
+                    this.logger.info(`Info: Optional service not present: ${serviceName}`);
+                }
+            }
+        }
+
+        if (missingServices.length > 0) {
+            const errorMsg = `System failed to start. Missing critical services: ${missingServices.join(', ')}`;
+            this.logger.error(errorMsg);
+            throw new Error(errorMsg);
+        }
+
+        if (missingCoreServices.length > 0) {
+            this.logger.warn(`System started with degraded capabilities. Missing core services: ${missingCoreServices.join(', ')}`);
+        }
+        
+        this.logger.info('System requirement check passed');
+    }
+
     /**
      * Bootstrap the kernel with enhanced features
      */
@@ -231,6 +270,7 @@ export class ObjectKernel {
             }
 
             // Phase 3: Trigger kernel:ready hook
+            this.validateSystemRequirements(); // Final check before ready
             this.logger.debug('Triggering kernel:ready hook');
             await this.context.trigger('kernel:ready');
 

packages/core/src/plugin-loader.ts

@@ -246,6 +246,13 @@ export class PluginLoader {
         this.serviceInstances.set(name, service);
     }
 
+    /**
+     * Check if a service is registered (either as instance or factory)
+     */
+    hasService(name: string): boolean {
+        return this.serviceInstances.has(name) || this.serviceFactories.has(name);
+    }
+
     /**
      * Detect circular dependencies in service factories
      * Note: This only detects cycles in service dependencies, not plugin dependencies.

packages/spec/src/system/service-registry.zod.ts

@@ -38,6 +38,41 @@ export const CoreServiceName = z.enum([
 
 export type CoreServiceName = z.infer<typeof CoreServiceName>;
 
+/**
+ * Service Criticality Level
+ * Defines the startup behavior when a service is missing.
+ */
+export const ServiceCriticalitySchema = z.enum([
+  'required', // System fails to start if missing (Exit Code 1)
+  'core',     // System warns if missing, functionality degraded (Warn)
+  'optional', // System ignores if missing, feature disabled (Info)
+]);
+
+/**
+ * Service Requirement Definition
+ */
+export const ServiceRequirementDef = {
+  // Required: The kernel cannot function without these
+  metadata: 'required',
+  data: 'required',
+  auth: 'required',
+
+  // Core: Highly recommended, defaults to in-memory if missing
+  cache: 'core',
+  queue: 'core',
+  job: 'core',
+
+  // Optional: Add-on capabilities
+  'file-storage': 'optional',
+  search: 'optional',
+  automation: 'optional',
+  graphql: 'optional',
+  analytics: 'optional',
+  hub: 'optional',
+  realtime: 'optional',
+  notification: 'optional',
+} as const;
+
 // ==========================================
 // Service Capabilities
 // ==========================================