feat: add operation and resource validation with intelligent suggestions

- Added OperationSimilarityService for validating operations with "Did you mean...?" suggestions
- Added ResourceSimilarityService for validating resources with plural/singular detection
- Implements Levenshtein distance algorithm for typo detection
- Pattern matching for common operation/resource mistakes
- 5-minute cache with automatic cleanup to prevent memory leaks
- Confidence scoring (30% minimum threshold) for suggestion quality
- Resource-aware operation filtering for contextual suggestions
- Safe JSON parsing with ValidationServiceError for proper error handling
- Type guards for safe property access
- Performance optimizations with early termination
- Comprehensive test coverage (37 new tests)
- Integration tested with n8n-mcp-tester agent

Example use cases:
- "listFiles" → suggests "search" for Google Drive
- "files" → suggests singular "file"
- "flie" → suggests "file" (typo correction)
- "downlod" → suggests "download"

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

src/services/enhanced-config-validator.ts

@@ -8,6 +8,10 @@
 import { ConfigValidator, ValidationResult, ValidationError, ValidationWarning } from './config-validator';
 import { NodeSpecificValidators, NodeValidationContext } from './node-specific-validators';
 import { FixedCollectionValidator } from '../utils/fixed-collection-validator';
+import { OperationSimilarityService } from './operation-similarity-service';
+import { ResourceSimilarityService } from './resource-similarity-service';
+import { NodeRepository } from '../database/node-repository';
+import { DatabaseAdapter } from '../database/database-adapter';
 
 export type ValidationMode = 'full' | 'operation' | 'minimal';
 export type ValidationProfile = 'strict' | 'runtime' | 'ai-friendly' | 'minimal';
@@ -35,6 +39,18 @@ export interface OperationContext {
 }
 
 export class EnhancedConfigValidator extends ConfigValidator {
+  private static operationSimilarityService: OperationSimilarityService | null = null;
+  private static resourceSimilarityService: ResourceSimilarityService | null = null;
+  private static nodeRepository: NodeRepository | null = null;
+
+  /**
+   * Initialize similarity services (called once at startup)
+   */
+  static initializeSimilarityServices(repository: NodeRepository): void {
+    this.nodeRepository = repository;
+    this.operationSimilarityService = new OperationSimilarityService(repository);
+    this.resourceSimilarityService = new ResourceSimilarityService(repository);
+  }
   /**
    * Validate with operation awareness
    */
@@ -213,7 +229,10 @@ export class EnhancedConfigValidator extends ConfigValidator {
       });
       return;
     }
-    
+
+    // Validate resource and operation using similarity services
+    this.validateResourceAndOperation(nodeType, config, result);
+
     // First, validate fixedCollection properties for known problematic nodes
     this.validateFixedCollectionStructures(nodeType, config, result);
     
@@ -642,4 +661,127 @@ export class EnhancedConfigValidator extends ConfigValidator {
     
     // Add any Filter-node-specific validation here in the future
   }
+
+  /**
+   * Validate resource and operation values using similarity services
+   */
+  private static validateResourceAndOperation(
+    nodeType: string,
+    config: Record<string, any>,
+    result: EnhancedValidationResult
+  ): void {
+    // Skip if similarity services not initialized
+    if (!this.operationSimilarityService || !this.resourceSimilarityService || !this.nodeRepository) {
+      return;
+    }
+
+    // Validate resource field if present
+    if (config.resource !== undefined) {
+      // Remove any existing resource error from base validator to replace with our enhanced version
+      result.errors = result.errors.filter(e => e.property !== 'resource');
+      const validResources = this.nodeRepository.getNodeResources(nodeType);
+      const resourceIsValid = validResources.some(r => {
+        const resourceValue = typeof r === 'string' ? r : r.value;
+        return resourceValue === config.resource;
+      });
+
+      if (!resourceIsValid && config.resource !== '') {
+        // Find similar resources
+        const suggestions = this.resourceSimilarityService.findSimilarResources(
+          nodeType,
+          config.resource,
+          3
+        );
+
+        // Build error message with suggestions
+        let errorMessage = `Invalid resource "${config.resource}" for node ${nodeType}.`;
+        let fix = '';
+
+        if (suggestions.length > 0) {
+          const topSuggestion = suggestions[0];
+          // Always use "Did you mean" for the top suggestion
+          errorMessage += ` Did you mean "${topSuggestion.value}"?`;
+          if (topSuggestion.confidence >= 0.8) {
+            fix = `Change resource to "${topSuggestion.value}". ${topSuggestion.reason}`;
+          } else {
+            // For lower confidence, still show valid resources in the fix
+            fix = `Valid resources: ${validResources.slice(0, 5).map(r => {
+              const val = typeof r === 'string' ? r : r.value;
+              return `"${val}"`;
+            }).join(', ')}${validResources.length > 5 ? '...' : ''}`;
+          }
+        } else {
+          // No similar resources found, list valid ones
+          fix = `Valid resources: ${validResources.slice(0, 5).map(r => {
+            const val = typeof r === 'string' ? r : r.value;
+            return `"${val}"`;
+          }).join(', ')}${validResources.length > 5 ? '...' : ''}`;
+        }
+
+        result.errors.push({
+          type: 'invalid_value',
+          property: 'resource',
+          message: errorMessage,
+          fix
+        });
+      }
+    }
+
+    // Validate operation field if present
+    if (config.operation !== undefined) {
+      // Remove any existing operation error from base validator to replace with our enhanced version
+      result.errors = result.errors.filter(e => e.property !== 'operation');
+      const validOperations = this.nodeRepository.getNodeOperations(nodeType, config.resource);
+      const operationIsValid = validOperations.some(op => {
+        const opValue = op.operation || op.value || op;
+        return opValue === config.operation;
+      });
+
+      if (!operationIsValid && config.operation !== '') {
+        // Find similar operations
+        const suggestions = this.operationSimilarityService.findSimilarOperations(
+          nodeType,
+          config.operation,
+          config.resource,
+          3
+        );
+
+        // Build error message with suggestions
+        let errorMessage = `Invalid operation "${config.operation}" for node ${nodeType}`;
+        if (config.resource) {
+          errorMessage += ` with resource "${config.resource}"`;
+        }
+        errorMessage += '.';
+
+        let fix = '';
+
+        if (suggestions.length > 0) {
+          const topSuggestion = suggestions[0];
+          if (topSuggestion.confidence >= 0.8) {
+            errorMessage += ` Did you mean "${topSuggestion.value}"?`;
+            fix = `Change operation to "${topSuggestion.value}". ${topSuggestion.reason}`;
+          } else {
+            errorMessage += ` Similar operations: ${suggestions.map(s => `"${s.value}"`).join(', ')}`;
+            fix = `Valid operations${config.resource ? ` for resource "${config.resource}"` : ''}: ${validOperations.slice(0, 5).map(op => {
+              const val = op.operation || op.value || op;
+              return `"${val}"`;
+            }).join(', ')}${validOperations.length > 5 ? '...' : ''}`;
+          }
+        } else {
+          // No similar operations found, list valid ones
+          fix = `Valid operations${config.resource ? ` for resource "${config.resource}"` : ''}: ${validOperations.slice(0, 5).map(op => {
+            const val = op.operation || op.value || op;
+            return `"${val}"`;
+          }).join(', ')}${validOperations.length > 5 ? '...' : ''}`;
+        }
+
+        result.errors.push({
+          type: 'invalid_value',
+          property: 'operation',
+          message: errorMessage,
+          fix
+        });
+      }
+    }
+  }
 }