/**
 * Telemetry management with cardinality budgets
 */

import { TelemetryMetrics, TelemetryLogs } from './types';
import { hashDid, redactPii } from './validation';

export class TelemetryManager {
  private metrics: Map<string, any> = new Map();
  private logLevel: 'DEBUG' | 'INFO' | 'WARN' | 'ERROR';
  
  constructor(logLevel: 'DEBUG' | 'INFO' | 'WARN' | 'ERROR' = 'INFO') {
    this.logLevel = logLevel;
    this.registerMetrics();
  }
  
  private registerMetrics(): void {
    // Counter metrics (low cardinality)
    this.metrics.set('starred_projects_poll_attempts_total', 
      this.createCounter('starred_projects_poll_attempts_total', 'Total number of polling attempts'));
    
    this.metrics.set('starred_projects_poll_success_total',
      this.createCounter('starred_projects_poll_success_total', 'Total number of successful polls'));
    
    this.metrics.set('starred_projects_poll_failure_total',
      this.createCounter('starred_projects_poll_failure_total', 'Total number of failed polls'));
    
    this.metrics.set('starred_projects_changes_found_total',
      this.createCounter('starred_projects_changes_found_total', 'Total number of changes found'));
    
    this.metrics.set('starred_projects_notifications_generated_total',
      this.createCounter('starred_projects_notifications_generated_total', 'Total notifications generated'));
    
    this.metrics.set('starred_projects_error_total',
      this.createCounter('starred_projects_error_total', 'Total number of errors'));
    
    this.metrics.set('starred_projects_rate_limit_total',
      this.createCounter('starred_projects_rate_limit_total', 'Total number of rate limit hits'));
    
    // Histogram metrics (low cardinality)
    this.metrics.set('starred_projects_poll_duration_seconds',
      this.createHistogram('starred_projects_poll_duration_seconds', 'Polling duration in seconds', 
        [0.1, 0.5, 1, 2, 5, 10, 30]));
    
    this.metrics.set('starred_projects_api_latency_seconds',
      this.createHistogram('starred_projects_api_latency_seconds', 'API latency in seconds',
        [0.05, 0.1, 0.25, 0.5, 1, 2, 5]));
    
    // Gauge metrics (low cardinality)
    this.metrics.set('starred_projects_outbox_size',
      this.createGauge('starred_projects_outbox_size', 'Current number of undelivered notifications'));
    
    this.metrics.set('starred_projects_outbox_backpressure_active',
      this.createGauge('starred_projects_outbox_backpressure_active', 'Backpressure active (0/1)'));
    
    this.metrics.set('starred_projects_api_throughput_rps',
      this.createGauge('starred_projects_api_throughput_rps', 'API throughput in requests per second'));
  }
  
  private createCounter(name: string, help: string): Record<string, unknown> {
    // Mock counter implementation
    return {
      name,
      help,
      type: 'counter',
      value: 0,
      inc: () => { this.metrics.get(name)!.value++; }
    };
  }
  
  private createHistogram(name: string, help: string, buckets: number[]): Record<string, unknown> {
    // Mock histogram implementation
    return {
      name,
      help,
      type: 'histogram',
      buckets,
      values: new Array(buckets.length + 1).fill(0),
      observe: (value: number) => {
        const metric = this.metrics.get(name)!;
        // Find bucket and increment
        for (let i = 0; i < buckets.length; i++) {
          if (value <= buckets[i]) {
            metric.values[i]++;
            return;
          }
        }
        metric.values[buckets.length]++; // +Inf bucket
      }
    };
  }
  
  private createGauge(name: string, help: string): Record<string, unknown> {
    // Mock gauge implementation
    return {
      name,
      help,
      type: 'gauge',
      value: 0,
      set: (value: number) => { this.metrics.get(name)!.value = value; }
    };
  }
  
  // Low-cardinality metric recording
  recordPollAttempt(): void {
    this.metrics.get('starred_projects_poll_attempts_total')?.inc();
  }
  
  recordPollSuccess(durationSeconds: number): void {
    this.metrics.get('starred_projects_poll_success_total')?.inc();
    this.metrics.get('starred_projects_poll_duration_seconds')?.observe(durationSeconds);
  }
  
  recordPollFailure(): void {
    this.metrics.get('starred_projects_poll_failure_total')?.inc();
  }
  
  recordChangesFound(count: number): void {
    for (let i = 0; i < count; i++) {
      this.metrics.get('starred_projects_changes_found_total')?.inc();
    }
  }
  
  recordNotificationsGenerated(count: number): void {
    for (let i = 0; i < count; i++) {
      this.metrics.get('starred_projects_notifications_generated_total')?.inc();
    }
  }
  
  recordError(): void {
    this.metrics.get('starred_projects_error_total')?.inc();
  }
  
  recordRateLimit(): void {
    this.metrics.get('starred_projects_rate_limit_total')?.inc();
  }
  
  recordApiLatency(latencySeconds: number): void {
    this.metrics.get('starred_projects_api_latency_seconds')?.observe(latencySeconds);
  }
  
  recordOutboxSize(size: number): void {
    this.metrics.get('starred_projects_outbox_size')?.set(size);
  }
  
  recordBackpressureActive(active: boolean): void {
    this.metrics.get('starred_projects_outbox_backpressure_active')?.set(active ? 1 : 0);
  }
  
  recordApiThroughput(rps: number): void {
    this.metrics.get('starred_projects_api_throughput_rps')?.set(rps);
  }
  
  // High-cardinality data (logs only, not metrics)
  logPollingEvent(event: TelemetryLogs): void {
    if (this.shouldLog('INFO')) {
      const redactedEvent = redactPii({
        ...event,
        activeDid: hashDid(event.activeDid) // Hash for privacy
      });
      
      console.log('Polling event:', redactedEvent);
    }
  }
  
  logError(error: Error, context?: Record<string, any>): void {
    if (this.shouldLog('ERROR')) {
      const redactedContext = context ? redactPii(context) : undefined;
      console.error('Polling error:', {
        message: error.message,
        stack: error.stack,
        context: redactedContext
      });
    }
  }
  
  logWarning(message: string, context?: Record<string, any>): void {
    if (this.shouldLog('WARN')) {
      const redactedContext = context ? redactPii(context) : undefined;
      console.warn('Polling warning:', { message, context: redactedContext });
    }
  }
  
  logDebug(message: string, context?: Record<string, any>): void {
    if (this.shouldLog('DEBUG')) {
      const redactedContext = context ? redactPii(context) : undefined;
      console.debug('Polling debug:', { message, context: redactedContext });
    }
  }
  
  private shouldLog(level: 'DEBUG' | 'INFO' | 'WARN' | 'ERROR'): boolean {
    const levels = { DEBUG: 0, INFO: 1, WARN: 2, ERROR: 3 };
    return levels[level] >= levels[this.logLevel];
  }
  
  // Get all metrics for export
  getMetrics(): TelemetryMetrics {
    const metrics: Record<string, unknown> = {};
    for (const [name, metric] of this.metrics) {
      metrics[name] = metric.value;
    }
    return metrics as TelemetryMetrics;
  }
  
  // Get metrics in Prometheus format
  getPrometheusMetrics(): string {
    let output = '';
    for (const [name, metric] of this.metrics) {
      output += `# HELP ${name} ${metric.help}\n`;
      output += `# TYPE ${name} ${metric.type}\n`;
      
      if (metric.type === 'histogram') {
        // Export histogram buckets
        for (let i = 0; i < metric.buckets.length; i++) {
          output += `${name}_bucket{le="${metric.buckets[i]}"} ${metric.values[i]}\n`;
        }
        output += `${name}_bucket{le="+Inf"} ${metric.values[metric.buckets.length]}\n`;
        output += `${name}_count ${metric.values.reduce((a: number, b: number) => a + b, 0)}\n`;
      } else {
        output += `${name} ${metric.value}\n`;
      }
    }
    return output;
  }
}

/**
 * Lint rule to prevent high-cardinality labels in metrics
 */
export function validateMetricLabels(labels: Record<string, string>): void {
  const highCardinalityPatterns = [
    /requestId/i,
    /activeDid/i,
    /jwtId/i,
    /userId/i,
    /sessionId/i,
    /traceId/i,
    /spanId/i
  ];
  
  for (const [key, value] of Object.entries(labels)) {
    for (const pattern of highCardinalityPatterns) {
      if (pattern.test(key)) {
        throw new Error(
          `High-cardinality label detected: ${key}. ` +
          `Use logs for request-level data, not metrics. ` +
          `Consider using a hash or removing the label.`
        );
      }
    }
    
    // Check for high-cardinality values
    if (value.length > 50 || /^[a-f0-9]{32,}$/.test(value)) {
      throw new Error(
        `High-cardinality value detected for label ${key}: ${value}. ` +
        `Consider using a hash or removing the label.`
      );
    }
  }
}

/**
 * Safe metric recording with validation
 */
export function recordMetricWithValidation(
  telemetry: TelemetryManager,
  metricName: string,
  value: number,
  labels?: Record<string, string>
): void {
  if (labels) {
    validateMetricLabels(labels);
  }
  
  // Record metric based on type
  switch (metricName) {
    case 'starred_projects_poll_attempts_total':
      telemetry.recordPollAttempt();
      break;
    case 'starred_projects_poll_success_total':
      telemetry.recordPollSuccess(value);
      break;
    case 'starred_projects_poll_failure_total':
      telemetry.recordPollFailure();
      break;
    case 'starred_projects_changes_found_total':
      telemetry.recordChangesFound(value);
      break;
    case 'starred_projects_notifications_generated_total':
      telemetry.recordNotificationsGenerated(value);
      break;
    case 'starred_projects_error_total':
      telemetry.recordError();
      break;
    case 'starred_projects_rate_limit_total':
      telemetry.recordRateLimit();
      break;
    case 'starred_projects_api_latency_seconds':
      telemetry.recordApiLatency(value);
      break;
    case 'starred_projects_outbox_size':
      telemetry.recordOutboxSize(value);
      break;
    case 'starred_projects_outbox_backpressure_active':
      telemetry.recordBackpressureActive(value > 0);
      break;
    case 'starred_projects_api_throughput_rps':
      telemetry.recordApiThroughput(value);
      break;
    default:
      throw new Error(`Unknown metric: ${metricName}`);
  }
}