import { EventEmitter } from 'events';
import { ErrorHandlingManager } from './errorHandlingManager.js';

/**
 * Advanced System Resilience Orchestrator for ZAI Platform
 * Coordinates all resilience mechanisms for maximum system stability
 */
export class ResilienceOrchestrator extends EventEmitter {
  constructor() {
    super();
    
    this.errorHandler = new ErrorHandlingManager();
    this.resilienceComponents = new Map();
    this.systemHealth = new Map();
    this.resilienceMetrics = new Map();
    this.adaptiveStrategies = new Map();
    
    // Resilience configuration
    this.resilienceConfig = {
      healthCheckInterval: 30000, // 30 seconds
      adaptiveThreshold: 0.8,
      cascadeFailureDetection: true,
      proactiveRecovery: true,
      resilienceScore: 0.95,
      maxConcurrentFailures: 3,
      systemStabilityThreshold: 0.9
    };
    
    // Resilience components
    this.resilienceComponents = new Map([
      ['error_handling', this.errorHandler],
      ['circuit_breakers', new CircuitBreakerManager()],
      ['bulkhead_isolation', new BulkheadManager()],
      ['timeout_management', new TimeoutManager()],
      ['retry_policies', new RetryPolicyManager()],
      ['fallback_mechanisms', new FallbackManager()],
      ['health_monitoring', new HealthMonitoringManager()],
      ['chaos_engineering', new ChaosEngineeringManager()]
    ]);
    
    this.initializeResilience();
    this.startResilienceOrchestration();
    
    console.log('🛡️ Advanced System Resilience Orchestrator initialized');
  }

  /**
   * Initialize resilience orchestration
   */
  initializeResilience() {
    // Initialize all resilience components
    for (const [componentName, component] of this.resilienceComponents.entries()) {
      try {
        if (typeof component.initialize === 'function') {
          component.initialize();
        }
        
        // Set up event listeners for component events
        if (component instanceof EventEmitter) {
          component.on('failure', (event) => this.handleComponentFailure(componentName, event));
          component.on('recovery', (event) => this.handleComponentRecovery(componentName, event));
          component.on('degradation', (event) => this.handleComponentDegradation(componentName, event));
        }
        
        console.log(`✅ Resilience component initialized: ${componentName}`);
      } catch (error) {
        console.error(`❌ Failed to initialize resilience component ${componentName}:`, error.message);
      }
    }
    
    // Initialize adaptive strategies
    this.initializeAdaptiveStrategies();
    
    console.log('🛡️ Resilience orchestration initialized');
  }

  /**
   * Initialize adaptive resilience strategies
   */
  initializeAdaptiveStrategies() {
    const strategies = [
      {
        name: 'load_based_adaptation',
        trigger: 'high_load',
        threshold: 0.8,
        actions: ['enable_circuit_breakers', 'reduce_timeouts', 'activate_bulkheads']
      },
      {
        name: 'error_rate_adaptation',
        trigger: 'high_error_rate',
        threshold: 0.1,
        actions: ['aggressive_retries', 'fallback_activation', 'service_isolation']
      },
      {
        name: 'latency_adaptation',
        trigger: 'high_latency',
        threshold: 1000, // ms
        actions: ['timeout_reduction', 'parallel_requests', 'cache_warming']
      },
      {
        name: 'cascade_prevention',
        trigger: 'cascade_failure_risk',
        threshold: 0.7,
        actions: ['emergency_isolation', 'load_shedding', 'graceful_degradation']
      }
    ];
    
    for (const strategy of strategies) {
      this.adaptiveStrategies.set(strategy.name, {
        ...strategy,
        active: false,
        lastTriggered: null,
        effectiveness: 0.8
      });
    }
    
    console.log(`🧠 ${strategies.length} adaptive strategies initialized`);
  }

  /**
   * Orchestrate resilience response to system events
   */
  async orchestrateResilience(event) {
    const orchestrationId = this.generateOrchestrationId();
    
    const orchestration = {
      id: orchestrationId,
      timestamp: Date.now(),
      event,
      resilienceActions: [],
      adaptiveStrategies: [],
      systemImpact: 'LOW',
      recoveryTime: null,
      success: false
    };
    
    try {
      console.log(`🛡️ Orchestrating resilience response for: ${event.type}`);
      
      // Assess system impact
      orchestration.systemImpact = await this.assessSystemImpact(event);
      
      // Determine required resilience actions
      const requiredActions = await this.determineResilienceActions(event, orchestration.systemImpact);
      
      // Execute resilience actions in priority order
      for (const action of requiredActions) {
        const actionResult = await this.executeResilienceAction(action, event);
        orchestration.resilienceActions.push(actionResult);
        
        if (!actionResult.success) {
          console.warn(`⚠️ Resilience action failed: ${action.type}`);
        }
      }
      
      // Trigger adaptive strategies if needed
      const adaptiveStrategies = await this.triggerAdaptiveStrategies(event, orchestration);
      orchestration.adaptiveStrategies = adaptiveStrategies;
      
      // Verify system stability
      const stabilityCheck = await this.verifySystemStability();
      orchestration.success = stabilityCheck.stable;
      orchestration.recoveryTime = Date.now() - orchestration.timestamp;
      
      if (orchestration.success) {
        console.log(`✅ Resilience orchestration successful: ${orchestrationId} (${orchestration.recoveryTime}ms)`);
      } else {
        console.error(`❌ Resilience orchestration failed: ${orchestrationId}`);
      }
      
      this.emit('resilienceOrchestrated', orchestration);
      
      return orchestration;
      
    } catch (error) {
      orchestration.error = error.message;
      console.error('❌ Resilience orchestration error:', error.message);
      
      return orchestration;
    }
  }

  /**
   * Assess system impact of an event
   */
  async assessSystemImpact(event) {
    const impact = {
      level: 'LOW',
      affectedServices: [],
      cascadeRisk: 0,
      userImpact: 'MINIMAL',
      businessImpact: 'LOW'
    };
    
    // Analyze event severity
    switch (event.type) {
      case 'service_failure':
        impact.level = 'HIGH';
        impact.affectedServices = [event.service];
        impact.cascadeRisk = 0.7;
        impact.userImpact = 'MODERATE';
        impact.businessImpact = 'MEDIUM';
        break;
        
      case 'database_error':
        impact.level = 'CRITICAL';
        impact.affectedServices = ['all_data_dependent'];
        impact.cascadeRisk = 0.9;
        impact.userImpact = 'HIGH';
        impact.businessImpact = 'HIGH';
        break;
        
      case 'network_partition':
        impact.level = 'CRITICAL';
        impact.affectedServices = ['all_distributed'];
        impact.cascadeRisk = 0.95;
        impact.userImpact = 'HIGH';
        impact.businessImpact = 'CRITICAL';
        break;
        
      case 'high_load':
        impact.level = 'MEDIUM';
        impact.affectedServices = ['performance_sensitive'];
        impact.cascadeRisk = 0.4;
        impact.userImpact = 'MODERATE';
        impact.businessImpact = 'LOW';
        break;
        
      default:
        impact.level = 'LOW';
        impact.cascadeRisk = 0.1;
    }
    
    // Calculate cascade failure risk
    if (impact.cascadeRisk > 0.8) {
      impact.level = 'CRITICAL';
      impact.userImpact = 'HIGH';
      impact.businessImpact = 'CRITICAL';
    }
    
    return impact;
  }

  /**
   * Determine required resilience actions
   */
  async determineResilienceActions(event, systemImpact) {
    const actions = [];
    
    // Base actions for all events
    actions.push({
      type: 'health_check',
      priority: 1,
      component: 'health_monitoring',
      params: { event }
    });
    
    // Impact-specific actions
    switch (systemImpact.level) {
      case 'CRITICAL':
        actions.push(
          {
            type: 'emergency_isolation',
            priority: 2,
            component: 'bulkhead_isolation',
            params: { services: systemImpact.affectedServices }
          },
          {
            type: 'activate_all_circuit_breakers',
            priority: 3,
            component: 'circuit_breakers',
            params: { aggressive: true }
          },
          {
            type: 'enable_fallbacks',
            priority: 4,
            component: 'fallback_mechanisms',
            params: { mode: 'emergency' }
          }
        );
        break;
        
      case 'HIGH':
        actions.push(
          {
            type: 'selective_isolation',
            priority: 2,
            component: 'bulkhead_isolation',
            params: { services: systemImpact.affectedServices }
          },
          {
            type: 'activate_circuit_breakers',
            priority: 3,
            component: 'circuit_breakers',
            params: { services: systemImpact.affectedServices }
          }
        );
        break;
        
      case 'MEDIUM':
        actions.push(
          {
            type: 'adjust_timeouts',
            priority: 2,
            component: 'timeout_management',
            params: { reduction: 0.5 }
          },
          {
            type: 'enable_retries',
            priority: 3,
            component: 'retry_policies',
            params: { aggressive: false }
          }
        );
        break;
    }
    
    // Event-specific actions
    if (event.type === 'database_error') {
      actions.push({
        type: 'database_fallback',
        priority: 2,
        component: 'fallback_mechanisms',
        params: { fallbackType: 'read_replica' }
      });
    }
    
    // Sort by priority
    actions.sort((a, b) => a.priority - b.priority);
    
    return actions;
  }

  /**
   * Execute resilience action
   */
  async executeResilienceAction(action, event) {
    const startTime = Date.now();
    
    const actionResult = {
      type: action.type,
      component: action.component,
      startTime,
      endTime: null,
      duration: 0,
      success: false,
      result: null,
      error: null
    };
    
    try {
      const component = this.resilienceComponents.get(action.component);
      
      if (!component) {
        throw new Error(`Resilience component not found: ${action.component}`);
      }
      
      // Execute action based on type
      let result;
      switch (action.type) {
        case 'health_check':
          result = await component.performHealthCheck(action.params);
          break;
        case 'emergency_isolation':
          result = await component.emergencyIsolation(action.params);
          break;
        case 'activate_circuit_breakers':
          result = await component.activateCircuitBreakers(action.params);
          break;
        case 'enable_fallbacks':
          result = await component.enableFallbacks(action.params);
          break;
        case 'adjust_timeouts':
          result = await component.adjustTimeouts(action.params);
          break;
        case 'enable_retries':
          result = await component.enableRetries(action.params);
          break;
        default:
          result = await component.executeAction(action.type, action.params);
      }
      
      actionResult.success = true;
      actionResult.result = result;
      
    } catch (error) {
      actionResult.error = error.message;
      console.error(`❌ Resilience action failed: ${action.type} - ${error.message}`);
    }
    
    actionResult.endTime = Date.now();
    actionResult.duration = actionResult.endTime - startTime;
    
    return actionResult;
  }

  /**
   * Trigger adaptive strategies
   */
  async triggerAdaptiveStrategies(event, orchestration) {
    const triggeredStrategies = [];
    
    for (const [strategyName, strategy] of this.adaptiveStrategies.entries()) {
      const shouldTrigger = await this.shouldTriggerStrategy(strategy, event, orchestration);
      
      if (shouldTrigger) {
        const strategyResult = await this.executeAdaptiveStrategy(strategy, event);
        triggeredStrategies.push(strategyResult);
        
        strategy.active = true;
        strategy.lastTriggered = Date.now();
      }
    }
    
    return triggeredStrategies;
  }

  /**
   * Verify system stability after resilience actions
   */
  async verifySystemStability() {
    const stability = {
      stable: true,
      score: 0,
      issues: [],
      recommendations: []
    };
    
    // Check all resilience components
    let totalScore = 0;
    let componentCount = 0;
    
    for (const [componentName, component] of this.resilienceComponents.entries()) {
      try {
        const componentHealth = await this.checkComponentHealth(component);
        
        if (componentHealth.healthy) {
          totalScore += componentHealth.score;
        } else {
          stability.issues.push(`${componentName}: ${componentHealth.issue}`);
        }
        
        componentCount++;
      } catch (error) {
        stability.issues.push(`${componentName}: Health check failed`);
      }
    }
    
    stability.score = componentCount > 0 ? totalScore / componentCount : 0;
    stability.stable = stability.score >= this.resilienceConfig.systemStabilityThreshold;
    
    if (!stability.stable) {
      stability.recommendations.push('Consider additional resilience measures');
      stability.recommendations.push('Monitor system closely for cascade failures');
    }
    
    return stability;
  }

  /**
   * Start resilience orchestration monitoring
   */
  startResilienceOrchestration() {
    // Monitor system health every 30 seconds
    setInterval(() => {
      this.performSystemHealthCheck();
    }, this.resilienceConfig.healthCheckInterval);
    
    // Evaluate adaptive strategies every minute
    setInterval(() => {
      this.evaluateAdaptiveStrategies();
    }, 60000);
    
    // Chaos engineering tests every hour
    setInterval(() => {
      this.performChaosEngineering();
    }, 3600000);
    
    console.log('🛡️ Resilience orchestration monitoring started');
  }

  /**
   * Utility methods
   */
  generateOrchestrationId() {
    return 'ORCH_' + Date.now() + '_' + Math.random().toString(36).substr(2, 9);
  }
  
  async shouldTriggerStrategy(strategy, event, orchestration) {
    // Simplified strategy triggering logic
    switch (strategy.trigger) {
      case 'high_load':
        return orchestration.systemImpact === 'HIGH' || orchestration.systemImpact === 'CRITICAL';
      case 'high_error_rate':
        return event.type.includes('error') || event.type.includes('failure');
      case 'high_latency':
        return event.type.includes('timeout') || event.type.includes('slow');
      case 'cascade_failure_risk':
        return orchestration.systemImpact === 'CRITICAL';
      default:
        return false;
    }
  }
  
  async executeAdaptiveStrategy(strategy, event) {
    console.log(`🧠 Executing adaptive strategy: ${strategy.name}`);
    
    const result = {
      strategy: strategy.name,
      actions: strategy.actions,
      success: true,
      effectiveness: strategy.effectiveness
    };
    
    // Simulate strategy execution
    for (const action of strategy.actions) {
      console.log(`  🔧 Executing action: ${action}`);
    }
    
    return result;
  }
  
  async checkComponentHealth(component) {
    // Simplified component health check
    return {
      healthy: Math.random() > 0.1, // 90% healthy
      score: 0.8 + Math.random() * 0.2,
      issue: Math.random() > 0.9 ? 'Minor performance degradation' : null
    };
  }
  
  async performSystemHealthCheck() {
    const healthCheck = {
      timestamp: Date.now(),
      overallHealth: 'HEALTHY',
      componentHealth: new Map(),
      resilienceScore: 0
    };
    
    let totalScore = 0;
    let componentCount = 0;
    
    for (const [componentName, component] of this.resilienceComponents.entries()) {
      const health = await this.checkComponentHealth(component);
      healthCheck.componentHealth.set(componentName, health);
      
      if (health.healthy) {
        totalScore += health.score;
      }
      componentCount++;
    }
    
    healthCheck.resilienceScore = componentCount > 0 ? totalScore / componentCount : 0;
    
    if (healthCheck.resilienceScore < 0.7) {
      healthCheck.overallHealth = 'DEGRADED';
    } else if (healthCheck.resilienceScore < 0.5) {
      healthCheck.overallHealth = 'CRITICAL';
    }
    
    this.emit('systemHealthChecked', healthCheck);
  }
  
  async evaluateAdaptiveStrategies() {
    for (const [strategyName, strategy] of this.adaptiveStrategies.entries()) {
      if (strategy.active) {
        // Check if strategy should be deactivated
        const timeSinceTriggered = Date.now() - strategy.lastTriggered;
        
        if (timeSinceTriggered > 300000) { // 5 minutes
          strategy.active = false;
          console.log(`🧠 Deactivating adaptive strategy: ${strategyName}`);
        }
      }
    }
  }
  
  async performChaosEngineering() {
    const chaosComponent = this.resilienceComponents.get('chaos_engineering');
    
    if (chaosComponent) {
      console.log('🔬 Performing chaos engineering test');
      await chaosComponent.performChaosTest();
    }
  }
  
  /**
   * Get resilience statistics
   */
  getResilienceStats() {
    return {
      components: {
        total: this.resilienceComponents.size,
        healthy: Array.from(this.resilienceComponents.keys()).length // Simplified
      },
      adaptiveStrategies: {
        total: this.adaptiveStrategies.size,
        active: Array.from(this.adaptiveStrategies.values()).filter(s => s.active).length
      },
      systemHealth: {
        overallScore: 0.92, // Simplified
        stabilityThreshold: this.resilienceConfig.systemStabilityThreshold
      },
      errorHandling: this.errorHandler.getErrorHandlingStats()
    };
  }
}

// Simplified resilience component classes
class CircuitBreakerManager extends EventEmitter {
  initialize() { console.log('🔌 Circuit Breaker Manager initialized'); }
  async activateCircuitBreakers(params) { return { activated: params.services || ['all'] }; }
  async performHealthCheck() { return { healthy: true, score: 0.9 }; }
}

class BulkheadManager extends EventEmitter {
  initialize() { console.log('🚧 Bulkhead Manager initialized'); }
  async emergencyIsolation(params) { return { isolated: params.services }; }
  async performHealthCheck() { return { healthy: true, score: 0.85 }; }
}

class TimeoutManager extends EventEmitter {
  initialize() { console.log('⏱️ Timeout Manager initialized'); }
  async adjustTimeouts(params) { return { adjusted: true, reduction: params.reduction }; }
  async performHealthCheck() { return { healthy: true, score: 0.88 }; }
}

class RetryPolicyManager extends EventEmitter {
  initialize() { console.log('🔄 Retry Policy Manager initialized'); }
  async enableRetries(params) { return { enabled: true, aggressive: params.aggressive }; }
  async performHealthCheck() { return { healthy: true, score: 0.87 }; }
}

class FallbackManager extends EventEmitter {
  initialize() { console.log('🔀 Fallback Manager initialized'); }
  async enableFallbacks(params) { return { enabled: true, mode: params.mode }; }
  async performHealthCheck() { return { healthy: true, score: 0.91 }; }
}

class HealthMonitoringManager extends EventEmitter {
  initialize() { console.log('🏥 Health Monitoring Manager initialized'); }
  async performHealthCheck() { return { healthy: true, score: 0.95 }; }
}

class ChaosEngineeringManager extends EventEmitter {
  initialize() { console.log('🔬 Chaos Engineering Manager initialized'); }
  async performChaosTest() { return { test: 'network_latency', result: 'passed' }; }
  async performHealthCheck() { return { healthy: true, score: 0.80 }; }
}
