/**
 * Performance Metrics Service
 *
 * Tracks app startup time, API response times, and BLE operation durations
 * to ensure performance targets are met:
 * - App startup: < 3 seconds
 * - BLE operations: < 10 seconds
 */

export interface PerformanceMetric {
  name: string;
  duration: number;
  timestamp: number;
  success: boolean;
  metadata?: Record<string, unknown>;
}

export interface PerformanceThresholds {
  appStartup: number; // Target: 3000ms
  bleOperation: number; // Target: 10000ms
  apiCall: number; // Target: 2000ms
}

export const PERFORMANCE_THRESHOLDS: PerformanceThresholds = {
  appStartup: 3000, // 3 seconds
  bleOperation: 10000, // 10 seconds
  apiCall: 2000, // 2 seconds
};

class PerformanceService {
  private metrics: PerformanceMetric[] = [];
  private timers = new Map<string, number>();
  private appStartTime: number | null = null;
  private appReadyTime: number | null = null;

  /**
   * Mark app startup begin (should be called as early as possible)
   */
  markAppStart(): void {
    this.appStartTime = Date.now();
  }

  /**
   * Mark app ready (should be called when first screen is interactive)
   * Returns duration in milliseconds
   */
  markAppReady(): number {
    this.appReadyTime = Date.now();
    const duration = this.appStartTime ? this.appReadyTime - this.appStartTime : 0;

    this.addMetric({
      name: 'app_startup',
      duration,
      timestamp: this.appReadyTime,
      success: duration <= PERFORMANCE_THRESHOLDS.appStartup,
      metadata: {
        threshold: PERFORMANCE_THRESHOLDS.appStartup,
        withinTarget: duration <= PERFORMANCE_THRESHOLDS.appStartup,
      },
    });

    if (duration > PERFORMANCE_THRESHOLDS.appStartup) {
      console.warn(`[Performance] App startup exceeded threshold: ${duration}ms (target: ${PERFORMANCE_THRESHOLDS.appStartup}ms)`);
    }

    return duration;
  }

  /**
   * Get app startup duration (if app is ready)
   */
  getAppStartupDuration(): number | null {
    if (!this.appStartTime || !this.appReadyTime) return null;
    return this.appReadyTime - this.appStartTime;
  }

  /**
   * Start a timer for an operation
   */
  startTimer(name: string): void {
    this.timers.set(name, Date.now());
  }

  /**
   * End a timer and record the metric
   * Returns duration in milliseconds
   */
  endTimer(name: string, success = true, metadata?: Record<string, unknown>): number {
    const startTime = this.timers.get(name);
    if (!startTime) {
      console.warn(`[Performance] Timer "${name}" was not started`);
      return 0;
    }

    const endTime = Date.now();
    const duration = endTime - startTime;
    this.timers.delete(name);

    this.addMetric({
      name,
      duration,
      timestamp: endTime,
      success,
      metadata,
    });

    return duration;
  }

  /**
   * Track a BLE operation
   */
  trackBleOperation(
    operation: 'scan' | 'connect' | 'command' | 'wifi_config' | 'bulk_wifi',
    duration: number,
    success: boolean,
    metadata?: Record<string, unknown>
  ): void {
    const withinTarget = duration <= PERFORMANCE_THRESHOLDS.bleOperation;

    this.addMetric({
      name: `ble_${operation}`,
      duration,
      timestamp: Date.now(),
      success,
      metadata: {
        ...metadata,
        threshold: PERFORMANCE_THRESHOLDS.bleOperation,
        withinTarget,
      },
    });

    if (!withinTarget) {
      console.warn(`[Performance] BLE ${operation} exceeded threshold: ${duration}ms (target: ${PERFORMANCE_THRESHOLDS.bleOperation}ms)`);
    }
  }

  /**
   * Track an API call
   */
  trackApiCall(
    endpoint: string,
    duration: number,
    success: boolean,
    metadata?: Record<string, unknown>
  ): void {
    const withinTarget = duration <= PERFORMANCE_THRESHOLDS.apiCall;

    this.addMetric({
      name: `api_${endpoint}`,
      duration,
      timestamp: Date.now(),
      success,
      metadata: {
        ...metadata,
        threshold: PERFORMANCE_THRESHOLDS.apiCall,
        withinTarget,
      },
    });

    if (!withinTarget && success) {
      console.warn(`[Performance] API ${endpoint} exceeded threshold: ${duration}ms (target: ${PERFORMANCE_THRESHOLDS.apiCall}ms)`);
    }
  }

  /**
   * Add a metric to the collection
   */
  private addMetric(metric: PerformanceMetric): void {
    this.metrics.push(metric);

    // Keep only last 100 metrics to avoid memory issues
    if (this.metrics.length > 100) {
      this.metrics = this.metrics.slice(-100);
    }
  }

  /**
   * Get all metrics
   */
  getMetrics(): PerformanceMetric[] {
    return [...this.metrics];
  }

  /**
   * Get metrics by name pattern
   */
  getMetricsByName(pattern: string | RegExp): PerformanceMetric[] {
    return this.metrics.filter((m) =>
      typeof pattern === 'string' ? m.name.includes(pattern) : pattern.test(m.name)
    );
  }

  /**
   * Get average duration for a metric type
   */
  getAverageDuration(pattern: string | RegExp): number | null {
    const matching = this.getMetricsByName(pattern);
    if (matching.length === 0) return null;

    const total = matching.reduce((sum, m) => sum + m.duration, 0);
    return total / matching.length;
  }

  /**
   * Get performance summary
   */
  getSummary(): {
    appStartup: { duration: number | null; withinTarget: boolean };
    bleOperations: { count: number; avgDuration: number | null; successRate: number };
    apiCalls: { count: number; avgDuration: number | null; successRate: number };
  } {
    const bleMetrics = this.getMetricsByName(/^ble_/);
    const apiMetrics = this.getMetricsByName(/^api_/);

    const bleSuccessCount = bleMetrics.filter((m) => m.success).length;
    const apiSuccessCount = apiMetrics.filter((m) => m.success).length;

    const appDuration = this.getAppStartupDuration();

    return {
      appStartup: {
        duration: appDuration,
        withinTarget: appDuration !== null && appDuration <= PERFORMANCE_THRESHOLDS.appStartup,
      },
      bleOperations: {
        count: bleMetrics.length,
        avgDuration: this.getAverageDuration(/^ble_/),
        successRate: bleMetrics.length > 0 ? bleSuccessCount / bleMetrics.length : 1,
      },
      apiCalls: {
        count: apiMetrics.length,
        avgDuration: this.getAverageDuration(/^api_/),
        successRate: apiMetrics.length > 0 ? apiSuccessCount / apiMetrics.length : 1,
      },
    };
  }

  /**
   * Clear all metrics
   */
  clear(): void {
    this.metrics = [];
    this.timers.clear();
    this.appStartTime = null;
    this.appReadyTime = null;
  }
}

// Singleton instance
export const performanceService = new PerformanceService();