document.addEventListener("DOMContentLoaded", () => {
  let table = null;
  const allPackets = [];
  const protoCounts = { TCP: 0, UDP: 0, DNS: 0, Other: 0 };
  const srcCounts = {};
  let protocolChart = null;
  
  // --- New variables for smoother, dynamic updates ---
  let uiUpdateScheduled = false;
  const UI_UPDATE_INTERVAL = 1000; // Update heavy visuals once per second

  function initChart() {
    const ctx = document.getElementById('protocolChart')?.getContext('2d');
    if (!ctx) return;
    protocolChart = new Chart(ctx, {
      type: 'doughnut',
      data: {
        labels: ['TCP', 'UDP', 'DNS', 'Other'],
        datasets: [{ data: [0, 0, 0, 0], backgroundColor: ['#0d6efd', '#ffc107', '#dc3545', '#6f42c1'] }]
      },
      options: { responsive: true, maintainAspectRatio: false, plugins: { legend: { position: 'bottom' } } }
    });
  }

  function initDataTable() {
    const cols = ["Time", "Source", "Destination", "Protocol", "Length"];
    let headerRow = '<tr>';
    cols.forEach(txt => headerRow += `<th>${txt}</th>`);
    headerRow += '</tr>';
    $("#table-header").html(headerRow);

    table = $('#packet-table').DataTable({
      deferRender:    true,
      scroller:       true,
      scrollY:        "60vh",
      scrollCollapse: true,
      paging:         true, 
      lengthChange:   false,
      info:           true,
      order:          [[0, 'desc']],
      language:       { search: "", searchPlaceholder: "Search..." },
      createdRow: function(row, data, dataIndex) {
        if (allPackets[dataIndex]) {
            $(row).data('packet', allPackets[dataIndex]);
        }
      }
    });
  }

  function getProtocol(pkt) {
    if (pkt.proto === "DNS") return "DNS";
    if (pkt.proto === 6) return "TCP";
    if (pkt.proto === 17) return "UDP";
    return "Other";
  }

  // --- Main Update Logic ---
  // This function updates all the heavy visual elements
  function updateHeavyVisuals() {
    // Update KPI cards (except total, which is updated instantly)
    $('#count-TCP').text(protoCounts.TCP);
    $('#count-UDP').text(protoCounts.UDP);
    $('#count-DNS').text(protoCounts.DNS);

    if (protocolChart) {
      protocolChart.data.datasets[0].data = [protoCounts.TCP, protoCounts.UDP, protoCounts.DNS, protoCounts.Other];
      protocolChart.update('none'); // 'none' for smooth animation
    }

    const topSources = Object.entries(srcCounts).sort(([, a], [, b]) => b - a).slice(0, 5);
    const ul = $("#top-sources").empty();
    topSources.forEach(([ip, count]) => {
      $("<li>").addClass("list-group-item d-flex justify-content-between align-items-center").html(`${ip} <span class="badge bg-primary rounded-pill">${count}</span>`).appendTo(ul);
    });
  }
  
  // This function processes all historical data once on load
  function processHistoricalData(historicalPackets) {
      historicalPackets.forEach(pkt => {
        allPackets.push(pkt);
        const proto = getProtocol(pkt);
        if (protoCounts.hasOwnProperty(proto)) protoCounts[proto]++;
        srcCounts[pkt.src] = (srcCounts[pkt.src] || 0) + 1;
      });
      
      const rowsToAdd = allPackets.map(p => {
        const time = new Date(p.timestamp * 1000).toLocaleTimeString();
        return [time, p.src, p.dst, getProtocol(p), p.length || '-'];
      });

      table.rows.add(rowsToAdd).draw();
      $('#count-All').text(allPackets.length);
      updateHeavyVisuals(); // Update heavy visuals once after history is loaded
  }

  // --- INITIALIZATION AND DATA LOADING ---
  initChart();
  initDataTable();

  fetch("/api/packets")
    .then(r => r.ok ? r.json() : [])
    .then(processHistoricalData)
    .catch(err => console.error("Error loading history:", err));

  // --- LIVE SOCKET.IO UPDATES ---
  const socket = io();
  socket.on('new_packet', pkt => {
    // 1. Instantly update the in-memory data
    allPackets.push(pkt);
    const proto = getProtocol(pkt);
    if (protoCounts.hasOwnProperty(proto)) protoCounts[proto]++;
    srcCounts[pkt.src] = (srcCounts[pkt.src] || 0) + 1;

    // 2. Instantly update the total count and add the row to the table
    $('#count-All').text(allPackets.length);
    const time = new Date(pkt.timestamp * 1000).toLocaleTimeString();
    
    // ** THIS IS THE BUG FIX **
    // It was `p.length` before, which is undefined. It is now `pkt.length`.
    const rowData = [time, pkt.src, pkt.dst, getProtocol(pkt), pkt.length || '-'];
    table.row.add(rowData).draw(false);

    // 3. Schedule a throttled update for the heavy visuals
    if (!uiUpdateScheduled) {
      uiUpdateScheduled = true;
      setTimeout(() => {
        updateHeavyVisuals();
        uiUpdateScheduled = false;
      }, UI_UPDATE_INTERVAL);
    }
  });

  // --- EVENT HANDLERS ---
  $("#packet-table tbody").on("click", "tr", function(){
    const pkt = $(this).data('packet');
    if (!pkt) return;
    let html = '<ul class="list-group">';
    Object.entries(pkt).forEach(([k,v])=> {
      html += `<li class="list-group-item"><strong>${k}:</strong> ${v}</li>`;
    });
    html += '</ul>';
    $("#packet-detail-body").html(html);
    new bootstrap.Modal($("#packetDetailModal")).show();
  });

  $("#download-btn").on("click", () => {
    if (!allPackets.length) {
      return alert("No packet data to download.");
    }
    const ws = XLSX.utils.json_to_sheet(allPackets);
    const wb = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, "NetworkData");
    const ts = new Date().toISOString().replace(/[:.]/g,"-");
    const name = `network_data_${ts}.xlsx`;
    XLSX.writeFile(wb, name);
  });
});