let chart = null;
window.onload = init;

async function init() {
  let start = new Date();
  start.setDate(start.getDate() - 7);
  const end = new Date();

  document.getElementById("date-start").valueAsDate = start;
  document.getElementById("date-end").valueAsDate = end;
  document.getElementById("btn-refresh").addEventListener("click", loadData);

  await loadDevices();
  await loadData();
}

async function loadData() {
  const start = document.getElementById("date-start").value;
  const end = document.getElementById("date-end").value;
  const granularity = document.getElementById("granularity").value;
  const device_eui = document.getElementById("device").value;

  const points = await fetchConsumption({
    device_eui: device_eui,
    start: start,
    end: end,
    granularity: granularity,
  });

  if (chart) {
    chart.destroy();
  }
  chart = renderChart(points, granularity);
  updateKPIs(points);
}

function updateKPIs(points) {
  const totalDisplay = document.getElementById("kpi-total");
  const avgDisplay = document.getElementById("kpi-avg");
  const countDisplay = document.getElementById("kpi-count");

  if (!points || points.length === 0) {
    total.textContent = "-";
    avg.textContent = "-";
    count.textContent = "-";
    return;
  }

  const totalValue = points.reduce((acc, p) => acc + p.delta_m3, 0);
  const avgValue = totalValue / points.length;

  totalDisplay.textContent = totalValue.toFixed(3);
  avgDisplay.textContent = avgValue.toFixed(3);
  countDisplay.textContent = points.length;
}

async function loadDevices() {
  const selectDeviceElmt = document.getElementById("device");

  const devices = await fetchDevices();

  devices.forEach((device) => {
    selectDeviceElmt.add(new Option(device.device_eui))
  });

  selectDeviceElmt.value = devices[0]?.device_eui ?? "";
}