(function () {
  'use strict';

  var config = window.WPGearedCWVMonitor || {};
  var endpoint = config.endpoint;
  var siteId = config.siteId;
  var siteKey = config.siteKey;
  var sampleRate = Math.max(0, Math.min(1, Number(config.sampleRate || 1)));
  var queue = [];
  var flushTimer = null;

  if (!endpoint || !siteId || !siteKey || sampleRate <= 0) {
    debug('Tracker disabled: missing endpoint/site credentials or sample rate is zero.');
    return;
  }

  if (!isSampled()) {
    debug('Visitor skipped by sample rate.');
    return;
  }

  loadWebVitals()
    .then(function (webVitals) {
      if (!webVitals || !webVitals.onLCP || !webVitals.onINP || !webVitals.onCLS) {
        throw new Error('web-vitals attribution build did not expose onLCP/onINP/onCLS.');
      }

      var options = { reportAllChanges: false };
      webVitals.onLCP(handleMetric, options);
      webVitals.onINP(handleMetric, options);
      webVitals.onCLS(handleMetric, options);
      debug('Core Web Vitals observers registered.');
    })
    .catch(function (error) {
      debug('Unable to load web-vitals.', error);
    });

  document.addEventListener('visibilitychange', function () {
    if (document.visibilityState === 'hidden') {
      flush(true);
    }
  });
  window.addEventListener('pagehide', function () {
    flush(true);
  });

  function handleMetric(metric) {
    var event = {
      metric: metric.name,
      value: round(metric.value),
      delta: round(metric.delta || 0),
      rating: metric.rating,
      webVitalsId: metric.id,
      navigationType: metric.navigationType || '',
      debugTarget: extractDebugTarget(metric),
      attribution: config.includeAttribution ? sanitizeAttribution(metric.attribution || {}) : {},
      url: getPageUrl(),
      pageTitle: config.pageTitle || document.title || '',
      sessionId: getSessionId(),
      visitorId: getVisitorId(),
      device: getDevice(),
      viewport: getViewport(),
      connection: getConnection(),
      referrerHost: getReferrerHost(),
      visibilityState: document.visibilityState,
      occurredAt: new Date().toISOString(),
    };

    queue.push(event);
    if (metric.rating === 'poor') {
      flush(false);
      return;
    }

    clearTimeout(flushTimer);
    flushTimer = setTimeout(function () {
      flush(false);
    }, 2500);
  }

  function flush(useBeacon) {
    if (!queue.length) {
      return;
    }

    var events = queue.splice(0, queue.length);
    var body = JSON.stringify({
      siteId: siteId,
      siteKey: siteKey,
      events: events,
    });

    if (useBeacon && navigator.sendBeacon) {
      var blob = new Blob([body], { type: 'application/json' });
      if (navigator.sendBeacon(endpoint, blob)) {
        debug('Events sent with beacon.', events.length);
        return;
      }
    }

    fetch(endpoint, {
      method: 'POST',
      mode: 'cors',
      keepalive: body.length < 60000,
      headers: { 'Content-Type': 'application/json' },
      body: body,
    }).catch(function (error) {
      debug('Event send failed.', error);
    });
  }

  function loadWebVitals() {
    if (window.webVitals) {
      return Promise.resolve(window.webVitals);
    }

    return new Promise(function (resolve, reject) {
      var script = document.createElement('script');
      script.src = config.webVitalsUrl || 'https://unpkg.com/web-vitals@5.3.0/dist/web-vitals.attribution.iife.js';
      script.async = true;
      script.crossOrigin = 'anonymous';
      script.onload = function () {
        resolve(window.webVitals);
      };
      script.onerror = function () {
        reject(new Error('Failed to load ' + script.src));
      };
      document.head.appendChild(script);
    });
  }

  function isSampled() {
    var key = 'wpgeared_cwv_sampled';
    var existing = sessionStorage.getItem(key);
    if (existing !== null) {
      return existing === '1';
    }
    var sampled = Math.random() <= sampleRate;
    sessionStorage.setItem(key, sampled ? '1' : '0');
    return sampled;
  }

  function extractDebugTarget(metric) {
    var attribution = metric.attribution || {};
    return clean(
      attribution.element ||
      attribution.eventTarget ||
      attribution.interactionTarget ||
      attribution.largestShiftTarget ||
      attribution.largestShiftSource ||
      attribution.url ||
      ''
    );
  }

  function sanitizeAttribution(input) {
    var output = {};
    Object.keys(input || {}).slice(0, 35).forEach(function (key) {
      var value = input[key];
      if (value && value.nodeType === 1) {
        output[key] = selector(value);
      } else if (Array.isArray(value)) {
        output[key] = value.slice(0, 8).map(function (item) {
          return item && item.nodeType === 1 ? selector(item) : clean(item);
        });
      } else if (value && typeof value === 'object') {
        output[key] = sanitizeAttribution(value);
      } else if (typeof value === 'number') {
        output[key] = round(value);
      } else if (typeof value === 'boolean') {
        output[key] = value;
      } else {
        output[key] = clean(value);
      }
    });
    return output;
  }

  function selector(element) {
    if (!element || element.nodeType !== 1) {
      return '';
    }
    var tag = element.tagName.toLowerCase();
    if (element.id) {
      return tag + '#' + element.id;
    }
    var className = String(element.className || '')
      .split(/\s+/)
      .filter(Boolean)
      .slice(0, 3)
      .join('.');
    return clean(tag + (className ? '.' + className : ''));
  }

  function getPageUrl() {
    var url = new URL(window.location.href);
    url.hash = '';
    if (!config.includeQueryString) {
      url.search = '';
    }
    return url.toString();
  }

  function getViewport() {
    return {
      width: window.innerWidth,
      height: window.innerHeight,
      dpr: window.devicePixelRatio || 1,
    };
  }

  function getDevice() {
    var width = window.innerWidth || 0;
    if (width < 768) {
      return 'mobile';
    }
    if (width < 1100) {
      return 'tablet';
    }
    return 'desktop';
  }

  function getConnection() {
    var connection = navigator.connection || navigator.mozConnection || navigator.webkitConnection;
    if (!connection) {
      return {};
    }
    return {
      effectiveType: clean(connection.effectiveType),
      rtt: round(connection.rtt || 0),
      downlink: round(connection.downlink || 0),
      saveData: Boolean(connection.saveData),
    };
  }

  function getReferrerHost() {
    if (!document.referrer) {
      return '';
    }
    try {
      return new URL(document.referrer).host;
    } catch (error) {
      return '';
    }
  }

  function getVisitorId() {
    return getStoredId(localStorage, 'wpgeared_cwv_visitor_id');
  }

  function getSessionId() {
    return getStoredId(sessionStorage, 'wpgeared_cwv_session_id');
  }

  function getStoredId(storage, key) {
    try {
      var existing = storage.getItem(key);
      if (existing) {
        return existing;
      }
      var id = 'wpg_' + Math.random().toString(36).slice(2) + Date.now().toString(36);
      storage.setItem(key, id);
      return id;
    } catch (error) {
      return 'wpg_' + Math.random().toString(36).slice(2);
    }
  }

  function clean(value) {
    return String(value == null ? '' : value)
      .replace(/[\u0000-\u001f\u007f]/g, ' ')
      .replace(/\s+/g, ' ')
      .trim()
      .slice(0, 500);
  }

  function round(value) {
    var number = Number(value);
    if (!Number.isFinite(number)) {
      return 0;
    }
    return Math.round(number * 1000) / 1000;
  }

  function debug() {
    if (config.debug && window.console) {
      console.log.apply(console, ['[WPGeared CWV]'].concat(Array.prototype.slice.call(arguments)));
    }
  }
})();