declare global {
  interface Window {
    gtag: (...args: unknown[]) => void;
    dataLayer: unknown[];
  }
}

const GA_MEASUREMENT_ID = process.env.NEXT_PUBLIC_GA_MEASUREMENT_ID || '';

export interface CookiePreferences {
  necessary: boolean;
  analytics: boolean;
  marketing: boolean;
  functionality: boolean;
  timestamp?: number;
}

const DEFAULT_PREFERENCES: CookiePreferences = {
  necessary: true,
  analytics: true,
  marketing: false,
  functionality: true,
};

export function getDefaultPreferences(): CookiePreferences {
  return { ...DEFAULT_PREFERENCES };
}

export function getStoredPreferences(): CookiePreferences | null {
  if (typeof window === 'undefined') return null;

  try {
    const stored = localStorage.getItem('novalon-cookie-preferences');
    if (stored) {
      return JSON.parse(stored) as CookiePreferences;
    }
  } catch (e) {
    console.warn('[Analytics] Failed to read cookie preferences:', e);
  }

  return null;
}

export function storePreferences(preferences: CookiePreferences): void {
  if (typeof window === 'undefined') return;

  try {
    localStorage.setItem(
      'novalon-cookie-preferences',
      JSON.stringify(preferences)
    );
  } catch (e) {
    console.warn('[Analytics] Failed to store cookie preferences:', e);
  }
}

export function updateConsentDetailed(preferences: CookiePreferences): void {
  if (typeof window === 'undefined' || !window.gtag) return;

  window.gtag('consent', 'update', {
    analytics_storage: preferences.analytics ? 'granted' : 'denied',
    ad_storage: preferences.marketing ? 'granted' : 'denied',
    functionality_storage: preferences.functionality ? 'granted' : 'denied',
  });
}

export function trackEvent(
  action: string,
  category: string,
  label?: string,
  value?: number
): void {
  if (typeof window === 'undefined' || !window.gtag || !GA_MEASUREMENT_ID) {
    return;
  }

  window.gtag('event', action, {
    event_category: category,
    event_label: label,
    event_value: value,
    send_to: GA_MEASUREMENT_ID,
  });
}

export function trackButtonClick(
  buttonName: string,
  _pageLocation?: string
): void {
  trackEvent('button_click', 'engagement', buttonName, undefined);
}

export function trackError(
  errorType: string,
  message: string,
  fatal: boolean = false,
  additionalContext?: Record<string, string | number | boolean>
): void {
  if (typeof window === 'undefined' || !window.gtag || !GA_MEASUREMENT_ID) {
    console.warn('[GA4] Error tracking not available:', { errorType, message });
    return;
  }

  const errorData: Record<string, string | number | boolean> = {
    description: `[${errorType}] ${message}`,
    fatal: fatal ? 'true' : 'false',
    url: typeof window !== 'undefined' ? window.location.href : '',
    timestamp: new Date().toISOString(),
    ...additionalContext,
  };

  window.gtag('event', 'exception', {
    ...errorData,
    send_to: GA_MEASUREMENT_ID,
  });

  if (process.env.NODE_ENV === 'development') {
    console.log('[GA4] Error tracked:', errorData);
  }
}

export function trackPageView(url: string, title: string): void {
  if (typeof window === 'undefined' || !window.gtag || !GA_MEASUREMENT_ID) {
    return;
  }

  window.gtag('config', GA_MEASUREMENT_ID, {
    page_path: url,
    page_title: title,
  });
}

export function trackPerformance(
  metricName: string,
  value: number,
  category: string = 'web_vitals'
): void {
  if (typeof window === 'undefined' || !window.gtag || !GA_MEASUREMENT_ID) {
    return;
  }

  window.gtag('event', metricName, {
    event_category: category,
    event_value: Math.round(value),
    value: Math.round(value),
    send_to: GA_MEASUREMENT_ID,
  });
}

export function trackContactForm(
  formData: { name: string; email: string; company: string } | string,
  success?: boolean
): void {
  if (typeof formData === 'string') {
    trackEvent('form_submit', 'contact', formData, success ? 1 : 0);
  } else {
    trackEvent('form_submit', 'contact', formData.company, success !== false ? 1 : 0);
  }

  if (success !== false) {
    trackConversion('contact_form_submit', 1);
  }
}

export function trackConversion(conversionLabel: string, value?: number): void {
  if (typeof window === 'undefined' || !window.gtag || !GA_MEASUREMENT_ID) {
    return;
  }

  window.gtag('event', 'conversion', {
    send_to: GA_MEASUREMENT_ID,
    transaction_id: `${Date.now()}_${Math.random().toString(36).slice(2, 8)}`,
    value: value || 1,
    currency: 'CNY',
    conversion_label: conversionLabel,
  });
}

export function trackOutboundLink(url: string, _linkText?: string): void {
  trackEvent('outbound_click', 'engagement', url);

  if (typeof window !== 'undefined' && window.gtag && GA_MEASUREMENT_ID) {
    window.gtag('event', 'click', {
      event_category: 'outbound',
      event_label: url,
      transport_type: 'beacon',
      send_to: GA_MEASUREMENT_ID,
    });
  }
}

export function trackScrollDepth(percentage: number, _maxScroll?: number): void {
  trackEvent(`scroll_${percentage}`, 'engagement', `${percentage}%`);
}