/**
 * Observability & Health Monitoring Implementation
 * Provides structured logging, event codes, and health monitoring
 * 
 * @author Matthew Raymer
 * @version 1.1.0
 */

export interface HealthStatus {
  nextRuns: number[];
  lastOutcomes: string[];
  cacheAgeMs: number | null;
  staleArmed: boolean;
  queueDepth: number;
  circuitBreakers: {
    total: number;
    open: number;
    failures: number;
  };
  performance: {
    avgFetchTime: number;
    avgNotifyTime: number;
    successRate: number;
  };
}

export interface EventLog {
  id: string;
  timestamp: number;
  level: 'INFO' | 'WARN' | 'ERROR';
  eventCode: string;
  message: string;
  data?: Record<string, unknown>;
  duration?: number;
}

export interface PerformanceMetrics {
  fetchTimes: number[];
  notifyTimes: number[];
  callbackTimes: number[];
  successCount: number;
  failureCount: number;
  lastReset: number;
}

/**
 * Observability Manager
 * Handles structured logging, health monitoring, and performance tracking
 */
export class ObservabilityManager {
  private eventLogs: EventLog[] = [];
  private performanceMetrics: PerformanceMetrics = {
    fetchTimes: [],
    notifyTimes: [],
    callbackTimes: [],
    successCount: 0,
    failureCount: 0,
    lastReset: Date.now()
  };
  private maxLogs = 1000;
  private maxMetrics = 100;

  /**
   * Log structured event with event code
   */
  logEvent(
    level: 'INFO' | 'WARN' | 'ERROR',
    eventCode: string,
    message: string,
    data?: Record<string, unknown>,
    duration?: number
  ): void {
    const event: EventLog = {
      id: this.generateEventId(),
      timestamp: Date.now(),
      level,
      eventCode,
      message,
      data,
      duration
    };

    this.eventLogs.unshift(event);
    
    // Keep only recent logs
    if (this.eventLogs.length > this.maxLogs) {
      this.eventLogs = this.eventLogs.slice(0, this.maxLogs);
    }

    // Console output with structured format
    const logMessage = `[${eventCode}] ${message}`;
    const logData = data ? ` | Data: ${JSON.stringify(data)}` : '';
    const logDuration = duration ? ` | Duration: ${duration}ms` : '';
    
    switch (level) {
      case 'INFO':
        // console.log(logMessage + logData + logDuration);
        break;
      case 'WARN':
        // console.warn(logMessage + logData + logDuration);
        break;
      case 'ERROR':
        // console.error(logMessage + logData + logDuration);
        break;
    }
  }

  /**
   * Record performance metrics
   */
  recordMetric(type: 'fetch' | 'notify' | 'callback', duration: number, success: boolean): void {
    switch (type) {
      case 'fetch':
        this.performanceMetrics.fetchTimes.push(duration);
        break;
      case 'notify':
        this.performanceMetrics.notifyTimes.push(duration);
        break;
      case 'callback':
        this.performanceMetrics.callbackTimes.push(duration);
        break;
    }

    if (success) {
      this.performanceMetrics.successCount++;
    } else {
      this.performanceMetrics.failureCount++;
    }

    // Keep only recent metrics
    this.trimMetrics();
  }

  /**
   * Get health status
   */
  async getHealthStatus(): Promise<HealthStatus> {
    const now = Date.now();
    const recentLogs = this.eventLogs.filter(log => now - log.timestamp < 24 * 60 * 60 * 1000); // Last 24 hours
    
    // Calculate next runs (mock implementation)
    const nextRuns = this.calculateNextRuns();
    
    // Get last outcomes from recent logs
    const lastOutcomes = recentLogs
      .filter(log => log.eventCode.startsWith('DNP-FETCH-') || log.eventCode.startsWith('DNP-NOTIFY-'))
      .slice(0, 10)
      .map(log => log.eventCode);
    
    // Calculate cache age (mock implementation)
    const cacheAgeMs = this.calculateCacheAge();
    
    // Check if stale armed
    const staleArmed = cacheAgeMs ? cacheAgeMs > 3600000 : true; // 1 hour
    
    // Calculate queue depth
    const queueDepth = recentLogs.filter(log => 
      log.eventCode.includes('QUEUE') || log.eventCode.includes('RETRY')
    ).length;
    
    // Circuit breaker status
    const circuitBreakers = this.getCircuitBreakerStatus();
    
    // Performance metrics
    const performance = this.calculatePerformanceMetrics();
    
    return {
      nextRuns,
      lastOutcomes,
      cacheAgeMs,
      staleArmed,
      queueDepth,
      circuitBreakers,
      performance
    };
  }

  /**
   * Get recent event logs
   */
  getRecentLogs(limit = 50): EventLog[] {
    return this.eventLogs.slice(0, limit);
  }

  /**
   * Get performance metrics
   */
  getPerformanceMetrics(): PerformanceMetrics {
    return { ...this.performanceMetrics };
  }

  /**
   * Reset performance metrics
   */
  resetMetrics(): void {
    this.performanceMetrics = {
      fetchTimes: [],
      notifyTimes: [],
      callbackTimes: [],
      successCount: 0,
      failureCount: 0,
      lastReset: Date.now()
    };
    
    this.logEvent('INFO', 'DNP-METRICS-RESET', 'Performance metrics reset');
  }

  /**
   * Compact old logs (called by cleanup job)
   */
  compactLogs(olderThanMs: number = 30 * 24 * 60 * 60 * 1000): number { // 30 days
    const cutoff = Date.now() - olderThanMs;
    const initialCount = this.eventLogs.length;
    
    this.eventLogs = this.eventLogs.filter(log => log.timestamp >= cutoff);
    
    const removedCount = initialCount - this.eventLogs.length;
    if (removedCount > 0) {
      this.logEvent('INFO', 'DNP-LOGS-COMPACTED', `Removed ${removedCount} old logs`);
    }
    
    return removedCount;
  }

  // Private helper methods
  private generateEventId(): string {
    return `evt_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
  }

  private trimMetrics(): void {
    if (this.performanceMetrics.fetchTimes.length > this.maxMetrics) {
      this.performanceMetrics.fetchTimes = this.performanceMetrics.fetchTimes.slice(-this.maxMetrics);
    }
    if (this.performanceMetrics.notifyTimes.length > this.maxMetrics) {
      this.performanceMetrics.notifyTimes = this.performanceMetrics.notifyTimes.slice(-this.maxMetrics);
    }
    if (this.performanceMetrics.callbackTimes.length > this.maxMetrics) {
      this.performanceMetrics.callbackTimes = this.performanceMetrics.callbackTimes.slice(-this.maxMetrics);
    }
  }

  private calculateNextRuns(): number[] {
    // Mock implementation - would calculate from actual schedules
    const now = Date.now();
    return [
      now + (60 * 60 * 1000), // 1 hour from now
      now + (24 * 60 * 60 * 1000) // 24 hours from now
    ];
  }

  private calculateCacheAge(): number | null {
    // Mock implementation - would get from actual cache
    return 1800000; // 30 minutes
  }

  private getCircuitBreakerStatus(): { total: number; open: number; failures: number } {
    // Mock implementation - would get from actual circuit breakers
    return {
      total: 3,
      open: 1,
      failures: 5
    };
  }

  private calculatePerformanceMetrics(): {
    avgFetchTime: number;
    avgNotifyTime: number;
    successRate: number;
  } {
    const fetchTimes = this.performanceMetrics.fetchTimes;
    const notifyTimes = this.performanceMetrics.notifyTimes;
    const totalOperations = this.performanceMetrics.successCount + this.performanceMetrics.failureCount;
    
    return {
      avgFetchTime: fetchTimes.length > 0 ? 
        fetchTimes.reduce((a, b) => a + b, 0) / fetchTimes.length : 0,
      avgNotifyTime: notifyTimes.length > 0 ? 
        notifyTimes.reduce((a, b) => a + b, 0) / notifyTimes.length : 0,
      successRate: totalOperations > 0 ? 
        this.performanceMetrics.successCount / totalOperations : 0
    };
  }
}

// Singleton instance
export const observability = new ObservabilityManager();

// Event code constants
export const EVENT_CODES = {
  FETCH_START: 'DNP-FETCH-START',
  FETCH_SUCCESS: 'DNP-FETCH-SUCCESS',
  FETCH_FAILURE: 'DNP-FETCH-FAILURE',
  FETCH_RETRY: 'DNP-FETCH-RETRY',
  NOTIFY_START: 'DNP-NOTIFY-START',
  NOTIFY_SUCCESS: 'DNP-NOTIFY-SUCCESS',
  NOTIFY_FAILURE: 'DNP-NOTIFY-FAILURE',
  NOTIFY_SKIPPED_TTL: 'DNP-NOTIFY-SKIPPED-TTL',
  CALLBACK_START: 'DNP-CB-START',
  CALLBACK_SUCCESS: 'DNP-CB-SUCCESS',
  CALLBACK_FAILURE: 'DNP-CB-FAILURE',
  CALLBACK_RETRY: 'DNP-CB-RETRY',
  CALLBACK_CIRCUIT_OPEN: 'DNP-CB-CIRCUIT-OPEN',
  CALLBACK_CIRCUIT_CLOSE: 'DNP-CB-CIRCUIT-CLOSE',
  BOOT_RECOVERY: 'DNP-BOOT-RECOVERY',
  SCHEDULE_UPDATE: 'DNP-SCHEDULE-UPDATE',
  CACHE_HIT: 'DNP-CACHE-HIT',
  CACHE_MISS: 'DNP-CACHE-MISS',
  TTL_EXPIRED: 'DNP-TTL-EXPIRED',
  METRICS_RESET: 'DNP-METRICS-RESET',
  LOGS_COMPACTED: 'DNP-LOGS-COMPACTED'
} as const;