let socket = null;
let characteristic = null;
let prevRes = null;

let btn = document.querySelector("#ble-connect");

function delay(ms) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

async function connect(props) {
  const device = await navigator.bluetooth.requestDevice({
    filters: [{ services: ["cycling_speed_and_cadence"] }],
    acceptAllDevices: false,
  });
  console.log(`%c\n👩🏼‍⚕️`, "font-size: 82px;", "Starting CSC...\n\n");
  const server = await device.gatt.connect();
  await delay(500);
  console.log("Getting Service...");
  const service = await server.getPrimaryService("cycling_speed_and_cadence");
  console.log("Getting Characteristic...");
  characteristic = await service.getCharacteristic("csc_measurement");
  await characteristic.startNotifications();
  console.log("> Notifications started");
  characteristic.addEventListener("characteristicvaluechanged", props.onChange);
  console.log("> Characteristic value changed event listener added");
  socket = io({
    reconnection: true,
    reconnectionDelay: 1000,
    reconnectionAttempts: 20,
    forceNew: true,
  });

  socket.on("connect", () => {
    btn.classList.remove("bg-red-600");
    btn.classList.add("bg-green-600");
  });

  socket.on("disconnect", (reason) => {
    if (reason === "io server disconnect") {
      // the disconnection was initiated by the server, you need to reconnect manually
      socket.connect();
    }
    // else the socket will automatically try to reconnect
  });
}

async function disconnect() {
  if (characteristic) {
    try {
      await characteristic.stopNotifications();
      log("> Notifications stopped");
      characteristic.removeEventListener(
        "characteristicvaluechanged",
        handleNotifications
      );
    } catch (error) {
      log("Argh! " + error);
    }
  }
}

function parseCSC(e) {
  const value = e.target.value;
  const flags = value.getUint8(0, true);
  const hasWheel = !!(flags & 0x01);
  const hasCrank = !!(flags & 0x02);
  let index = 1;
  const res = {
    wheelRevs: null,
    wheelTime: null,
    crankRevs: null,
    crankTime: null,
  };
  if (hasWheel) {
    res.wheelRevs = value.getUint32(index, true);
    index += 4;
    res.wheelTime = value.getUint16(index, true);
    index += 2;
  }
  if (hasCrank) {
    res.crankRevs = value.getUint16(index, true);
    index += 2;
    res.crankTime = value.getUint16(index, true);
    index += 2;
  }
  console.log("CSC", res);
  if (prevRes) {
    let rpm = revsToRPM(prevRes, res);
    //if (rpm > 0)
    socket.emit("message", { rpm: parseFloat(rpm.toFixed(2)), id: 1 });
  }
  prevRes = res;
  return res;
}

function revsToRPM(prevRes, res) {
  const deltaRevs = res.crankRevs - prevRes.crankRevs;
  if (deltaRevs === 0) {
    // no rotation
    return 0;
  }

  let deltaTime = (res.crankTime - prevRes.crankTime) / 1024;
  if (deltaTime < 0) {
    // time counter wraparound
    deltaTime += Math.pow(2, 16) / 1024;
  }
  deltaTime /= 60; // seconds to minutes

  const rpm = deltaRevs / deltaTime;
  return rpm;
}

btn.addEventListener("click", () =>
  connect({
    onChange: parseCSC,
  }).catch((err) => {
    swal("Oops", err, "error");
  })
);