apps/backend/src/services/CognitiveErrorIntelligence.ts

/**
 * ╔═══════════════════════════════════════════════════════════════════════════════╗
 * ║              COGNITIVE ERROR INTELLIGENCE (CEI)                               ║
 * ║═══════════════════════════════════════════════════════════════════════════════║
 * ║  Unik intelligent fejlhåndtering der udnytter WidgeTDC's kapabiliteter:       ║
 * ║                                                                               ║
 * ║  1. GRAPH-BASED ERROR CORRELATION                                             ║
 * ║     - Neo4j til at finde relationer mellem fejl                               ║
 * ║     - "Error A forårsager ofte Error B inden for 5 minutter"                  ║
 * ║                                                                               ║
 * ║  2. PREDICTIVE ERROR DETECTION                                                ║
 * ║     - Lærer mønstre der forudsiger fejl FØR de sker                          ║
 * ║     - "Redis memory usage > 80% → OOM inden 10 min"                          ║
 * ║                                                                               ║
 * ║  3. CONTEXT-AWARE SOLUTIONS                                                   ║
 * ║     - Rangerer løsninger baseret på systemets aktuelle tilstand              ║
 * ║     - "Neo4j er nede → prioriter lokale løsninger"                           ║
 * ║                                                                               ║
 * ║  4. AUTO-REMEDIATION                                                          ║
 * ║     - Udfører automatisk reparation for kendte fejl                          ║
 * ║     - "ECONNREFUSED på Redis → restart Redis container"                      ║
 * ║                                                                               ║
 * ║  5. CAUSAL CHAIN ANALYSIS                                                     ║
 * ║     - Bygger grafer over fejl-årsager                                        ║
 * ║     - "Root cause: DNS failure → cascading to 5 services"                    ║
 * ╚═══════════════════════════════════════════════════════════════════════════════╝
 */

import { EventEmitter } from 'events';
import { errorKnowledgeBase, type ErrorPattern, type Solution } from './ErrorKnowledgeBase.js';
import { selfHealing } from './SelfHealingAdapter.js';
import { logger } from '../utils/logger.js';

const log = logger.child({ module: 'CognitiveErrorIntelligence' });

// Dynamic base URL for self-healing API calls
const getBaseUrl = () => `http://localhost:${process.env.PORT || 7860}`;

// ═══════════════════════════════════════════════════════════════════════════
// TYPES
// ═══════════════════════════════════════════════════════════════════════════

interface ErrorEvent {
  id: string;
  timestamp: Date;
  message: string;
  service: string;
  severity: 'low' | 'medium' | 'high' | 'critical';
  context: Record<string, any>;
  stackTrace?: string;
  resolved: boolean;
  resolvedBy?: string;
  resolvedAt?: Date;
}

interface ErrorCorrelation {
  sourceErrorId: string;
  targetErrorId: string;
  correlationType: 'causes' | 'precedes' | 'cooccurs' | 'masks';
  confidence: number;
  avgTimeDelta: number; // milliseconds
  occurrences: number;
}

interface PredictiveSignal {
  metric: string;
  threshold: number;
  operator: '>' | '<' | '=' | '>=' | '<=';
  predictedError: string;
  leadTime: number; // milliseconds before error typically occurs
  confidence: number;
  lastTriggered?: Date;
}

interface RemediationAction {
  id: string;
  name: string;
  description: string;
  errorPatterns: string[]; // Pattern IDs this action can fix
  command?: string; // Shell command to execute
  apiCall?: { endpoint: string; method: string; body?: any };
  requiresApproval: boolean;
  riskLevel: 'low' | 'medium' | 'high';
  successRate: number;
  avgExecutionTime: number;
  lastExecuted?: Date;
}

interface CausalChain {
  rootCause: ErrorEvent;
  effects: ErrorEvent[];
  totalImpact: number; // Number of affected services/operations
  detectedAt: Date;
  resolvedAt?: Date;
}

interface SystemContext {
  services: Map<string, ServiceHealth>;
  activeErrors: ErrorEvent[];
  recentRemediations: RemediationAction[];
  load: {
    cpu: number;
    memory: number;
    connections: number;
  };
}

interface ServiceHealth {
  name: string;
  status: 'healthy' | 'degraded' | 'unhealthy' | 'unknown';
  lastCheck: Date;
  metrics: Record<string, number>;
}

interface IntelligentSolution extends Solution {
  contextScore: number; // How relevant given current system state
  predictedSuccess: number; // ML-based success prediction
  autoRemediable: boolean;
  remediationAction?: RemediationAction;
  reasoning: string; // Why this solution is recommended
}

// ═══════════════════════════════════════════════════════════════════════════
// COGNITIVE ERROR INTELLIGENCE CLASS
// ═══════════════════════════════════════════════════════════════════════════

export class CognitiveErrorIntelligence extends EventEmitter {
  private static instance: CognitiveErrorIntelligence;

  // Error tracking
  private errorHistory: ErrorEvent[] = [];
  private readonly MAX_HISTORY = 10000;

  // Correlation learning
  private correlations: Map<string, ErrorCorrelation> = new Map();
  private correlationWindow = 5 * 60 * 1000; // 5 minutes

  // Predictive signals
  private predictiveSignals: PredictiveSignal[] = [];
  private metricsHistory: Map<string, { timestamp: Date; value: number }[]> = new Map();

  // Auto-remediation
  private remediationActions: Map<string, RemediationAction> = new Map();
  private remediationQueue: { error: ErrorEvent; action: RemediationAction }[] = [];
  private isRemediating = false;

  // System context
  private systemContext: SystemContext = {
    services: new Map(),
    activeErrors: [],
    recentRemediations: [],
    load: { cpu: 0, memory: 0, connections: 0 }
  };

  private constructor() {
    super();
    this.initializeDefaultRemediations();
    this.initializePredictiveSignals();
    this.startBackgroundProcessing();
    log.info('🧠 Cognitive Error Intelligence initialized');
  }

  public static getInstance(): CognitiveErrorIntelligence {
    if (!CognitiveErrorIntelligence.instance) {
      CognitiveErrorIntelligence.instance = new CognitiveErrorIntelligence();
    }
    return CognitiveErrorIntelligence.instance;
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 1. INTELLIGENT ERROR HANDLING
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Process an error with full cognitive analysis
   */
  public async processError(
    message: string,
    service: string,
    context: Record<string, any> = {},
    stackTrace?: string
  ): Promise<{
    errorId: string;
    solutions: IntelligentSolution[];
    correlatedErrors: ErrorEvent[];
    causalChain?: CausalChain;
    autoRemediation?: { action: RemediationAction; queued: boolean };
    prediction?: { nextLikelyError: string; confidence: number; timeframe: string };
  }> {
    const errorId = this.generateErrorId();
    const severity = this.assessSeverity(message, context);

    // Create error event
    const errorEvent: ErrorEvent = {
      id: errorId,
      timestamp: new Date(),
      message,
      service,
      severity,
      context,
      stackTrace,
      resolved: false
    };

    // Store in history
    this.recordError(errorEvent);

    // 1. Find correlated errors (what usually happens with this error?)
    const correlatedErrors = this.findCorrelatedErrors(errorEvent);

    // 2. Analyze causal chain (is this the root cause or an effect?)
    const causalChain = this.analyzeCausalChain(errorEvent);

    // 3. Get context-aware solutions
    const solutions = await this.getIntelligentSolutions(message, errorEvent);

    // 4. Check for auto-remediation
    const autoRemediation = await this.checkAutoRemediation(errorEvent, solutions);

    // 5. Predict next likely error
    const prediction = this.predictNextError(errorEvent);

    // 6. Learn correlations for future
    this.learnCorrelations(errorEvent);

    // Emit event for real-time monitoring
    this.emit('error:processed', {
      errorId,
      severity,
      solutions: solutions.length,
      autoRemediation: autoRemediation?.queued
    });

    log.info(`🧠 Processed error ${errorId}: ${solutions.length} solutions, ${correlatedErrors.length} correlations`);

    return {
      errorId,
      solutions,
      correlatedErrors,
      causalChain,
      autoRemediation,
      prediction
    };
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 2. GRAPH-BASED ERROR CORRELATION
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Find errors that are correlated with this error
   */
  private findCorrelatedErrors(error: ErrorEvent): ErrorEvent[] {
    const correlated: ErrorEvent[] = [];
    const recentErrors = this.errorHistory.filter(
      e => e.timestamp.getTime() > Date.now() - this.correlationWindow && e.id !== error.id
    );

    for (const recent of recentErrors) {
      const correlationKey = this.getCorrelationKey(recent.message, error.message);
      const correlation = this.correlations.get(correlationKey);

      if (correlation && correlation.confidence > 0.5) {
        correlated.push(recent);
      }
    }

    return correlated;
  }

  /**
   * Learn correlations from error patterns
   */
  private learnCorrelations(error: ErrorEvent): void {
    const recentErrors = this.errorHistory.filter(
      e => e.timestamp.getTime() > error.timestamp.getTime() - this.correlationWindow && e.id !== error.id
    );

    for (const recent of recentErrors) {
      const timeDelta = error.timestamp.getTime() - recent.timestamp.getTime();
      const correlationKey = this.getCorrelationKey(recent.message, error.message);

      if (!this.correlations.has(correlationKey)) {
        this.correlations.set(correlationKey, {
          sourceErrorId: recent.id,
          targetErrorId: error.id,
          correlationType: timeDelta < 1000 ? 'cooccurs' : 'precedes',
          confidence: 0.1,
          avgTimeDelta: timeDelta,
          occurrences: 1
        });
      } else {
        const existing = this.correlations.get(correlationKey)!;
        existing.occurrences++;
        existing.avgTimeDelta = (existing.avgTimeDelta + timeDelta) / 2;
        // Increase confidence with more observations (Bayesian update)
        existing.confidence = Math.min(0.95, existing.confidence + (1 - existing.confidence) * 0.1);
      }
    }
  }

  /**
   * Persist correlations to Neo4j for graph analysis
   */
  public async persistCorrelationsToNeo4j(): Promise<number> {
    try {
      const { neo4jService } = await import('../database/Neo4jService.js');
      let persisted = 0;

      for (const [key, correlation] of this.correlations) {
        if (correlation.occurrences >= 3 && correlation.confidence > 0.5) {
          await neo4jService.runQuery(`
            MERGE (source:ErrorPattern {signature: $sourceSignature})
            MERGE (target:ErrorPattern {signature: $targetSignature})
            MERGE (source)-[r:${correlation.correlationType.toUpperCase()}]->(target)
            SET r.confidence = $confidence,
                r.avgTimeDelta = $avgTimeDelta,
                r.occurrences = $occurrences,
                r.updatedAt = datetime()
          `, {
            sourceSignature: key.split('→')[0],
            targetSignature: key.split('→')[1],
            confidence: correlation.confidence,
            avgTimeDelta: correlation.avgTimeDelta,
            occurrences: correlation.occurrences
          });
          persisted++;
        }
      }

      log.info(`📊 Persisted ${persisted} error correlations to Neo4j`);
      return persisted;
    } catch (e) {
      log.warn('Neo4j not available for correlation persistence');
      return 0;
    }
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 3. CAUSAL CHAIN ANALYSIS
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Analyze if this error is root cause or effect
   */
  private analyzeCausalChain(error: ErrorEvent): CausalChain | undefined {
    const recentErrors = this.errorHistory.filter(
      e => Math.abs(e.timestamp.getTime() - error.timestamp.getTime()) < this.correlationWindow
    );

    if (recentErrors.length < 2) return undefined;

    // Find the earliest error in the chain (likely root cause)
    const sortedByTime = [...recentErrors].sort(
      (a, b) => a.timestamp.getTime() - b.timestamp.getTime()
    );

    const rootCause = sortedByTime[0];
    const effects = sortedByTime.slice(1);

    // Calculate impact
    const affectedServices = new Set(effects.map(e => e.service));

    return {
      rootCause,
      effects,
      totalImpact: affectedServices.size,
      detectedAt: new Date()
    };
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 4. CONTEXT-AWARE INTELLIGENT SOLUTIONS
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Get solutions ranked by current system context
   */
  private async getIntelligentSolutions(
    errorMessage: string,
    errorEvent: ErrorEvent
  ): Promise<IntelligentSolution[]> {
    // Get base solutions from knowledge base
    const baseSolutions = errorKnowledgeBase.getSolutions(errorMessage);

    // Enhance with context awareness
    const intelligentSolutions: IntelligentSolution[] = [];

    for (const solution of baseSolutions) {
      const contextScore = this.calculateContextScore(solution, errorEvent);
      const predictedSuccess = this.predictSolutionSuccess(solution, errorEvent);
      const remediation = this.findRemediationAction(solution);

      intelligentSolutions.push({
        ...solution,
        contextScore,
        predictedSuccess,
        autoRemediable: remediation !== undefined && !remediation.requiresApproval,
        remediationAction: remediation,
        reasoning: this.generateReasoning(solution, contextScore, predictedSuccess)
      });
    }

    // Sort by combined intelligence score
    return intelligentSolutions.sort((a, b) => {
      const scoreA = a.contextScore * 0.3 + a.predictedSuccess * 0.4 + a.confidence * 0.3;
      const scoreB = b.contextScore * 0.3 + b.predictedSuccess * 0.4 + b.confidence * 0.3;
      return scoreB - scoreA;
    });
  }

  /**
   * Calculate how relevant a solution is given current system state
   */
  private calculateContextScore(solution: Solution, error: ErrorEvent): number {
    let score = 0.5; // Base score

    // Check if solution's source is a service that's currently healthy
    const serviceHealth = this.systemContext.services.get(error.service);
    if (serviceHealth?.status === 'healthy') {
      score += 0.1;
    }

    // Prefer solutions that don't require unavailable services
    if (solution.description.toLowerCase().includes('redis')) {
      const redisHealth = this.systemContext.services.get('redis');
      if (redisHealth?.status !== 'healthy') {
        score -= 0.2; // Penalize if Redis is down
      }
    }

    // Boost solutions that have worked recently
    if (solution.successCount && solution.successCount > 0) {
      const successRate = solution.successCount / ((solution.successCount || 0) + (solution.failureCount || 0));
      score += successRate * 0.2;
    }

    // Consider system load
    if (this.systemContext.load.cpu > 80 && solution.description.toLowerCase().includes('intensive')) {
      score -= 0.1; // Don't suggest CPU-intensive solutions when load is high
    }

    return Math.max(0, Math.min(1, score));
  }

  /**
   * Predict success based on historical data
   */
  private predictSolutionSuccess(solution: Solution, error: ErrorEvent): number {
    // Use feedback data if available
    if (solution.successCount !== undefined && solution.failureCount !== undefined) {
      const total = solution.successCount + solution.failureCount;
      if (total >= 3) {
        return solution.successCount / total;
      }
    }

    // Fall back to confidence score with context adjustment
    return solution.confidence * this.calculateContextScore(solution, error);
  }

  /**
   * Generate human-readable reasoning for recommendation
   */
  private generateReasoning(solution: Solution, contextScore: number, predictedSuccess: number): string {
    const reasons: string[] = [];

    if (solution.verified) {
      reasons.push('verified solution');
    }

    if (contextScore > 0.7) {
      reasons.push('matches current system state');
    }

    if (predictedSuccess > 0.8) {
      reasons.push(`${Math.round(predictedSuccess * 100)}% predicted success`);
    }

    if (solution.successCount && solution.successCount > 5) {
      reasons.push(`worked ${solution.successCount} times before`);
    }

    return reasons.length > 0 ? `Recommended: ${reasons.join(', ')}` : 'Standard recommendation';
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 5. AUTO-REMEDIATION ENGINE
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Check if error can be auto-remediated
   */
  private async checkAutoRemediation(
    error: ErrorEvent,
    solutions: IntelligentSolution[]
  ): Promise<{ action: RemediationAction; queued: boolean } | undefined> {
    // Find auto-remediable solutions
    const autoRemediable = solutions.find(s => s.autoRemediable && s.remediationAction);

    if (!autoRemediable?.remediationAction) return undefined;

    const action = autoRemediable.remediationAction;

    // Safety checks
    if (action.riskLevel === 'high') {
      log.warn(`⚠️ High-risk remediation requires approval: ${action.name}`);
      this.emit('remediation:approval-required', { error, action });
      return { action, queued: false };
    }

    // Check if we've tried this recently (prevent loops)
    const recentTry = this.systemContext.recentRemediations.find(
      r => r.id === action.id && r.lastExecuted &&
      Date.now() - r.lastExecuted.getTime() < 60000 // 1 minute cooldown
    );

    if (recentTry) {
      log.info(`⏳ Skipping remediation ${action.name} - cooldown active`);
      return { action, queued: false };
    }

    // Queue for execution
    this.remediationQueue.push({ error, action });
    this.processRemediationQueue();

    return { action, queued: true };
  }

  /**
   * Process remediation queue
   */
  private async processRemediationQueue(): Promise<void> {
    if (this.isRemediating || this.remediationQueue.length === 0) return;

    this.isRemediating = true;

    while (this.remediationQueue.length > 0) {
      const { error, action } = this.remediationQueue.shift()!;

      try {
        log.info(`🔧 Executing auto-remediation: ${action.name}`);
        this.emit('remediation:started', { error, action });

        const startTime = Date.now();
        let success = false;

        if (action.command) {
          // Execute shell command
          const { exec } = await import('child_process');
          await new Promise<void>((resolve, reject) => {
            exec(action.command!, { timeout: 30000 }, (err, stdout, stderr) => {
              if (err) {
                log.error(`Remediation command failed: ${stderr}`);
                reject(err);
              } else {
                log.info(`Remediation output: ${stdout}`);
                success = true;
                resolve();
              }
            });
          });
        } else if (action.apiCall) {
          // Execute API call - prepend base URL to relative paths
          const endpoint = action.apiCall.endpoint.startsWith('/')
            ? `${getBaseUrl()}${action.apiCall.endpoint}`
            : action.apiCall.endpoint;
          const response = await fetch(endpoint, {
            method: action.apiCall.method,
            headers: { 'Content-Type': 'application/json' },
            body: action.apiCall.body ? JSON.stringify(action.apiCall.body) : undefined
          });
          success = response.ok;
        }

        // Update action stats
        action.lastExecuted = new Date();
        action.avgExecutionTime = (action.avgExecutionTime + (Date.now() - startTime)) / 2;
        if (success) {
          action.successRate = (action.successRate * 0.9) + 0.1; // Exponential moving average
        } else {
          action.successRate = action.successRate * 0.9;
        }

        // Mark error as resolved if successful
        if (success) {
          error.resolved = true;
          error.resolvedBy = `auto:${action.id}`;
          error.resolvedAt = new Date();
        }

        this.systemContext.recentRemediations.push(action);
        this.emit('remediation:completed', { error, action, success });

      } catch (e) {
        log.error(`Remediation failed: ${e}`);
        this.emit('remediation:failed', { error, action, reason: String(e) });
      }
    }

    this.isRemediating = false;
  }

  /**
   * Find remediation action for a solution
   */
  private findRemediationAction(solution: Solution): RemediationAction | undefined {
    for (const action of this.remediationActions.values()) {
      // Check if solution description matches any remediation pattern
      if (action.errorPatterns.some(pattern =>
        solution.description.toLowerCase().includes(pattern.toLowerCase())
      )) {
        return action;
      }
    }
    return undefined;
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 6. PREDICTIVE ERROR DETECTION
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Update metrics for predictive analysis
   */
  public recordMetric(metric: string, value: number): void {
    if (!this.metricsHistory.has(metric)) {
      this.metricsHistory.set(metric, []);
    }

    const history = this.metricsHistory.get(metric)!;
    history.push({ timestamp: new Date(), value });

    // Keep only last hour
    const oneHourAgo = Date.now() - 3600000;
    const filtered = history.filter(h => h.timestamp.getTime() > oneHourAgo);
    this.metricsHistory.set(metric, filtered);

    // Check predictive signals
    this.checkPredictiveSignals(metric, value);
  }

  /**
   * Check if metric triggers a predictive signal
   */
  private checkPredictiveSignals(metric: string, value: number): void {
    for (const signal of this.predictiveSignals) {
      if (signal.metric !== metric) continue;

      let triggered = false;
      switch (signal.operator) {
        case '>': triggered = value > signal.threshold; break;
        case '<': triggered = value < signal.threshold; break;
        case '>=': triggered = value >= signal.threshold; break;
        case '<=': triggered = value <= signal.threshold; break;
        case '=': triggered = value === signal.threshold; break;
      }

      if (triggered) {
        signal.lastTriggered = new Date();
        log.warn(`⚠️ PREDICTIVE ALERT: ${metric} = ${value} → ${signal.predictedError} likely in ${signal.leadTime / 1000}s`);

        this.emit('prediction:triggered', {
          signal,
          currentValue: value,
          expectedError: signal.predictedError,
          expectedIn: signal.leadTime
        });
      }
    }
  }

  /**
   * Predict next likely error based on current error
   */
  private predictNextError(error: ErrorEvent): { nextLikelyError: string; confidence: number; timeframe: string } | undefined {
    // Find correlations where this error is the source
    const errorSignature = this.normalizeSignature(error.message);
    let bestPrediction: { error: string; confidence: number; timeDelta: number } | undefined;

    for (const [key, correlation] of this.correlations) {
      if (key.startsWith(errorSignature) && correlation.correlationType === 'precedes') {
        if (!bestPrediction || correlation.confidence > bestPrediction.confidence) {
          bestPrediction = {
            error: key.split('→')[1],
            confidence: correlation.confidence,
            timeDelta: correlation.avgTimeDelta
          };
        }
      }
    }

    if (bestPrediction && bestPrediction.confidence > 0.5) {
      return {
        nextLikelyError: bestPrediction.error,
        confidence: bestPrediction.confidence,
        timeframe: this.formatTimeDelta(bestPrediction.timeDelta)
      };
    }

    return undefined;
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // 7. INITIALIZATION & BACKGROUND PROCESSING
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Initialize default auto-remediation actions
   */
  private initializeDefaultRemediations(): void {
    const defaultActions: RemediationAction[] = [
      {
        id: 'restart-redis',
        name: 'Restart Redis Connection',
        description: 'Reconnect to Redis when connection is lost',
        errorPatterns: ['ECONNREFUSED', 'redis', 'connection refused'],
        apiCall: { endpoint: '/api/healing/service/redis', method: 'POST' },
        requiresApproval: false,
        riskLevel: 'low',
        successRate: 0.85,
        avgExecutionTime: 1000
      },
      {
        id: 'clear-memory-cache',
        name: 'Clear Memory Cache',
        description: 'Clear in-memory caches when memory is low',
        errorPatterns: ['heap', 'memory', 'OOM'],
        apiCall: { endpoint: '/api/system/clear-cache', method: 'POST' },
        requiresApproval: false,
        riskLevel: 'low',
        successRate: 0.9,
        avgExecutionTime: 500
      },
      {
        id: 'retry-database',
        name: 'Retry Database Connection',
        description: 'Attempt to reconnect to database',
        errorPatterns: ['database', 'postgres', 'neo4j', 'SQLSTATE'],
        apiCall: { endpoint: '/api/healing/service/database', method: 'POST' },
        requiresApproval: false,
        riskLevel: 'medium',
        successRate: 0.75,
        avgExecutionTime: 3000
      },
      {
        id: 'restart-service',
        name: 'Restart Service',
        description: 'Full service restart - requires approval',
        errorPatterns: ['fatal', 'crash', 'unrecoverable'],
        command: 'npm run restart:backend',
        requiresApproval: true,
        riskLevel: 'high',
        successRate: 0.95,
        avgExecutionTime: 15000
      }
    ];

    for (const action of defaultActions) {
      this.remediationActions.set(action.id, action);
    }
  }

  /**
   * Initialize predictive signals
   */
  private initializePredictiveSignals(): void {
    this.predictiveSignals = [
      {
        metric: 'memory_usage_percent',
        threshold: 85,
        operator: '>',
        predictedError: 'JavaScript heap out of memory',
        leadTime: 300000, // 5 minutes
        confidence: 0.8
      },
      {
        metric: 'redis_connections',
        threshold: 95,
        operator: '>',
        predictedError: 'ECONNREFUSED on Redis',
        leadTime: 60000, // 1 minute
        confidence: 0.7
      },
      {
        metric: 'postgres_connections',
        threshold: 90,
        operator: '>',
        predictedError: 'SQLSTATE 53300 too many connections',
        leadTime: 120000, // 2 minutes
        confidence: 0.75
      },
      {
        metric: 'event_loop_lag_ms',
        threshold: 500,
        operator: '>',
        predictedError: 'Event loop blocked - degraded performance',
        leadTime: 30000, // 30 seconds
        confidence: 0.85
      }
    ];
  }

  /**
   * Start background processing
   */
  private startBackgroundProcessing(): void {
    // Cleanup old history every 5 minutes
    setInterval(() => {
      const cutoff = Date.now() - 3600000; // 1 hour
      this.errorHistory = this.errorHistory.filter(e => e.timestamp.getTime() > cutoff);

      // Cleanup old correlations with low confidence
      for (const [key, correlation] of this.correlations) {
        if (correlation.confidence < 0.3 && correlation.occurrences < 3) {
          this.correlations.delete(key);
        }
      }
    }, 300000);

    // Persist correlations to Neo4j every 10 minutes
    setInterval(() => {
      this.persistCorrelationsToNeo4j();
    }, 600000);
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // HELPER METHODS
  // ═══════════════════════════════════════════════════════════════════════════

  private generateErrorId(): string {
    return `err_${Date.now()}_${Math.random().toString(36).substring(2, 8)}`;
  }

  private assessSeverity(message: string, context: Record<string, any>): ErrorEvent['severity'] {
    const lower = message.toLowerCase();
    if (lower.includes('fatal') || lower.includes('critical') || lower.includes('crash')) return 'critical';
    if (lower.includes('error') || lower.includes('failed') || lower.includes('refused')) return 'high';
    if (lower.includes('warning') || lower.includes('timeout')) return 'medium';
    return 'low';
  }

  private recordError(error: ErrorEvent): void {
    this.errorHistory.push(error);
    this.systemContext.activeErrors.push(error);

    // Trim history if too large
    if (this.errorHistory.length > this.MAX_HISTORY) {
      this.errorHistory = this.errorHistory.slice(-this.MAX_HISTORY / 2);
    }
  }

  private getCorrelationKey(sourceMsg: string, targetMsg: string): string {
    return `${this.normalizeSignature(sourceMsg)}→${this.normalizeSignature(targetMsg)}`;
  }

  private normalizeSignature(msg: string): string {
    return msg
      .toLowerCase()
      .replace(/[0-9]+/g, 'N')
      .replace(/\s+/g, ' ')
      .substring(0, 100);
  }

  private formatTimeDelta(ms: number): string {
    if (ms < 1000) return `${ms}ms`;
    if (ms < 60000) return `${Math.round(ms / 1000)}s`;
    return `${Math.round(ms / 60000)}min`;
  }

  // ═══════════════════════════════════════════════════════════════════════════
  // PUBLIC API
  // ═══════════════════════════════════════════════════════════════════════════

  /**
   * Update system context (called by health checks)
   */
  public updateSystemContext(updates: Partial<SystemContext>): void {
    Object.assign(this.systemContext, updates);
  }

  /**
   * Get current intelligence stats
   */
  public getStats() {
    return {
      errorHistory: this.errorHistory.length,
      correlations: this.correlations.size,
      predictiveSignals: this.predictiveSignals.length,
      remediationActions: this.remediationActions.size,
      activeErrors: this.systemContext.activeErrors.length,
      recentRemediations: this.systemContext.recentRemediations.length
    };
  }

  /**
   * Get correlations for visualization
   */
  public getCorrelations(): ErrorCorrelation[] {
    return Array.from(this.correlations.values())
      .filter(c => c.confidence > 0.5)
      .sort((a, b) => b.confidence - a.confidence);
  }

  /**
   * Manually approve a pending remediation
   */
  public approveRemediation(actionId: string): boolean {
    const action = this.remediationActions.get(actionId);
    if (action) {
      action.requiresApproval = false;
      return true;
    }
    return false;
  }
}

// Singleton export
export const cognitiveErrorIntelligence = CognitiveErrorIntelligence.getInstance();