'use client';

import { useEffect } from 'react';
import { trackWebVitals, trackPerformance } from './analytics';

// Web Vitals types
interface Metric {
  name: string;
  value: number;
  delta: number;
  id: string;
}

// Simple Web Vitals implementation (since we don't want to add external dependencies)
const getCLS = (onPerfEntry: (metric: Metric) => void) => {
  let clsValue = 0;
  let sessionValue = 0;
  let sessionEntries: PerformanceEntry[] = [];

  const observer = new PerformanceObserver((list) => {
    for (const entry of list.getEntries()) {
      if (!(entry as PerformanceEntry & { hadRecentInput?: boolean }).hadRecentInput) {
        const firstSessionEntry = sessionEntries[0];
        const lastSessionEntry = sessionEntries[sessionEntries.length - 1];

        if (sessionValue && entry.startTime - lastSessionEntry.startTime < 1000 && entry.startTime - firstSessionEntry.startTime < 5000) {
          sessionValue += (entry as PerformanceEntry & { value?: number }).value || 0;
          sessionEntries.push(entry);
        } else {
          sessionValue = (entry as PerformanceEntry & { value?: number }).value || 0;
          sessionEntries = [entry];
        }

        if (sessionValue > clsValue) {
          clsValue = sessionValue;
          onPerfEntry({
            name: 'CLS',
            value: clsValue,
            delta: clsValue,
            id: `cls-${Date.now()}`,
          });
        }
      }
    }
  });

  observer.observe({ type: 'layout-shift', buffered: true });
};

const getFID = (onPerfEntry: (metric: Metric) => void) => {
  const observer = new PerformanceObserver((list) => {
    for (const entry of list.getEntries()) {
      onPerfEntry({
        name: 'FID',
        value: (entry as PerformanceEntry & { processingStart?: number }).processingStart! - entry.startTime,
        delta: (entry as PerformanceEntry & { processingStart?: number }).processingStart! - entry.startTime,
        id: `fid-${Date.now()}`,
      });
    }
  });

  observer.observe({ type: 'first-input', buffered: true });
};

const getFCP = (onPerfEntry: (metric: Metric) => void) => {
  const observer = new PerformanceObserver((list) => {
    for (const entry of list.getEntries()) {
      if (entry.name === 'first-contentful-paint') {
        onPerfEntry({
          name: 'FCP',
          value: entry.startTime,
          delta: entry.startTime,
          id: `fcp-${Date.now()}`,
        });
      }
    }
  });

  observer.observe({ type: 'paint', buffered: true });
};

const getLCP = (onPerfEntry: (metric: Metric) => void) => {
  const observer = new PerformanceObserver((list) => {
    const entries = list.getEntries();
    const lastEntry = entries[entries.length - 1];
    
    onPerfEntry({
      name: 'LCP',
      value: lastEntry.startTime,
      delta: lastEntry.startTime,
      id: `lcp-${Date.now()}`,
    });
  });

  observer.observe({ type: 'largest-contentful-paint', buffered: true });
};

const getTTFB = (onPerfEntry: (metric: Metric) => void) => {
  const observer = new PerformanceObserver((list) => {
    for (const entry of list.getEntries()) {
      if (entry.entryType === 'navigation') {
        const navEntry = entry as PerformanceNavigationTiming;
        onPerfEntry({
          name: 'TTFB',
          value: navEntry.responseStart - navEntry.fetchStart,
          delta: navEntry.responseStart - navEntry.fetchStart,
          id: `ttfb-${Date.now()}`,
        });
      }
    }
  });

  observer.observe({ type: 'navigation', buffered: true });
};

// Custom hook for Web Vitals tracking
export const useWebVitals = () => {
  useEffect(() => {
    if (typeof window === 'undefined') return;

    // Track Core Web Vitals
    getCLS((metric) => {
      trackWebVitals({
        ...metric,
        name: metric.name as 'CLS' | 'FID' | 'FCP' | 'LCP' | 'TTFB',
        url: window.location.pathname,
      });
    });

    getFID((metric) => {
      trackWebVitals({
        ...metric,
        name: metric.name as 'CLS' | 'FID' | 'FCP' | 'LCP' | 'TTFB',
        url: window.location.pathname,
      });
    });

    getFCP((metric) => {
      trackWebVitals({
        ...metric,
        name: metric.name as 'CLS' | 'FID' | 'FCP' | 'LCP' | 'TTFB',
        url: window.location.pathname,
      });
    });

    getLCP((metric) => {
      trackWebVitals({
        ...metric,
        name: metric.name as 'CLS' | 'FID' | 'FCP' | 'LCP' | 'TTFB',
        url: window.location.pathname,
      });
    });

    getTTFB((metric) => {
      trackWebVitals({
        ...metric,
        name: metric.name as 'CLS' | 'FID' | 'FCP' | 'LCP' | 'TTFB',
        url: window.location.pathname,
      });
    });

    // Track page load performance
    const handleLoad = () => {
      setTimeout(() => {
        trackPerformance({
          name: 'page-load-complete',
          value: performance.now(),
          url: window.location.pathname,
          timestamp: Date.now(),
          userAgent: navigator.userAgent,
        });
      }, 0);
    };

    if (document.readyState === 'complete') {
      handleLoad();
    } else {
      window.addEventListener('load', handleLoad);
    }

    return () => {
      window.removeEventListener('load', handleLoad);
    };
  }, []);
};