(function() {
  'use strict';

  var ENDPOINT = 'https://analytics.perceptum.nl/api/ingest';
  var API_KEY = 'lv_live_g4BPVde7QJwg_kAvPZD1ab7XKV3FCCX0';
  var HEARTBEAT_INTERVAL = 5000;

  // Persistent visitor ID (localStorage - NOT a cookie, GDPR-friendly)
  var visitorId = localStorage.getItem('lv_vid');
  var isNewVisitor = !visitorId;
  if (!visitorId) {
    visitorId = crypto.randomUUID ? crypto.randomUUID() :
      Math.random().toString(36).substr(2) + Date.now().toString(36) + Math.random().toString(36).substr(2);
    localStorage.setItem('lv_vid', visitorId);
  }

  // Session management with page sequence tracking
  var storedSession = sessionStorage.getItem('lv_session');
  var sessionData = storedSession ? JSON.parse(storedSession) : null;

  // Check if session is still valid (within 30 min)
  var isValidSession = sessionData && (Date.now() - sessionData.lastActivity < 1800000);

  var sessionId = isValidSession ? sessionData.id :
    (crypto.randomUUID ? crypto.randomUUID() : Math.random().toString(36).substr(2) + Date.now().toString(36));
  var pageSeq = isValidSession ? sessionData.pageSeq + 1 : 1;
  // Track if this is a new session (for new visitor detection)
  var isFirstPageOfSession = !isValidSession || pageSeq === 1;

  // Save session state
  sessionStorage.setItem('lv_session', JSON.stringify({
    id: sessionId,
    pageSeq: pageSeq,
    lastActivity: Date.now()
  }));

  var pageEnteredAt = Date.now();
  var activeTime = 0;
  var lastActiveTimestamp = Date.now();
  var isVisible = !document.hidden;
  var maxScrollDepth = 0;

  function getScrollDepth() {
    var scrollTop = window.scrollY || document.documentElement.scrollTop;
    var docHeight = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight);
    var winHeight = window.innerHeight;
    if (docHeight <= winHeight) return 100;
    return Math.min(100, Math.round((scrollTop + winHeight) / docHeight * 100));
  }

  document.addEventListener('visibilitychange', function() {
    if (document.hidden) {
      activeTime += Date.now() - lastActiveTimestamp;
      isVisible = false;
    } else {
      lastActiveTimestamp = Date.now();
      isVisible = true;
    }
  });

  var scrollThrottle = null;
  window.addEventListener('scroll', function() {
    if (scrollThrottle) return;
    scrollThrottle = setTimeout(function() {
      scrollThrottle = null;
      var depth = getScrollDepth();
      if (depth > maxScrollDepth) maxScrollDepth = depth;
    }, 200);
  }, { passive: true });

  function buildPayload(eventType) {
    var currentActive = isVisible ? activeTime + (Date.now() - lastActiveTimestamp) : activeTime;
    // Update session activity timestamp
    var sess = JSON.parse(sessionStorage.getItem('lv_session') || '{}');
    sess.lastActivity = Date.now();
    sessionStorage.setItem('lv_session', JSON.stringify(sess));

    return {
      sid: sessionId,
      vid: visitorId,
      url: window.location.pathname + window.location.search,
      title: document.title,
      ref: document.referrer || null,
      active_ms: currentActive,
      scroll_depth: maxScrollDepth,
      is_visible: isVisible,
      screen: screen.width + 'x' + screen.height,
      viewport: window.innerWidth + 'x' + window.innerHeight,
      lang: navigator.language,
      event: eventType,
      ts: Date.now(),
      page_seq: pageSeq,
      is_new: isNewVisitor && isFirstPageOfSession
    };
  }

  function send(payload) {
    var data = JSON.stringify(payload);
    if (payload.event === 'leave' && navigator.sendBeacon) {
      navigator.sendBeacon(ENDPOINT + '?key=' + API_KEY, data);
    } else {
      fetch(ENDPOINT, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': 'Bearer ' + API_KEY
        },
        body: data,
        keepalive: true
      }).catch(function() {});
    }
  }

  function startHeartbeat() {
    setInterval(function() {
      if (isVisible) send(buildPayload('heartbeat'));
    }, HEARTBEAT_INTERVAL);
  }

  send(buildPayload('pageview'));
  maxScrollDepth = getScrollDepth();
  startHeartbeat();

  window.addEventListener('beforeunload', function() {
    send(buildPayload('leave'));
  });

  document.addEventListener('visibilitychange', function() {
    if (document.hidden) send(buildPayload('leave'));
  });

  // Expose public API for custom event tracking
  window.liveview = {
    track: function(eventName, properties) {
      if (!eventName || typeof eventName !== 'string') return;
      var payload = {
        sid: sessionId,
        vid: visitorId,
        url: window.location.pathname + window.location.search,
        event: 'custom',
        event_name: eventName,
        properties: properties || {},
        ts: Date.now()
      };
      fetch(ENDPOINT, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': 'Bearer ' + API_KEY
        },
        body: JSON.stringify(payload),
        keepalive: true
      }).catch(function() {});
    },
    // Get visitor ID (useful for integrations)
    getVisitorId: function() { return visitorId; },
    getSessionId: function() { return sessionId; }
  };
})();