///////////////////////////////////////////////////////////////
/* Polyfill for Web Bluetooth                                */
(function(navigator) {
  'use strict';

  let allowedDevices = [
    { id: '1', name: 'Device A', connectGATT: function() { return new Promise((resolve, reject) => { reject(); }) } },
    { id: '2', name: 'Device B', connectGATT: function() { return new Promise((resolve, reject) => { reject(); }) } },
    { id: '3', name: 'Device C', connectGATT: function() { return new Promise((resolve, reject) => { resolve(); }) } },
  ];

  navigator.bluetooth.getAllowedDevices = function() {
    return new Promise((resolve, reject) => {
      resolve(allowedDevices);
    });
  }

  navigator.bluetooth.referringDevice = allowedDevices[0];
})(navigator);
///////////////////////////////////////////////////////////////

var button = document.createElement('button');
var index = 0;
var allowedDevices = null;

// Get all bluetooth allowed devices first.
navigator.bluetooth.getDevices()
.then(devices => {

  // Cache all bluetooth allowed devices.
  allowedDevices = devices;

  if (navigator.bluetooth.referringDevice) {
    // Device is coming from Physical Web... let's connect to it now.
    // This assumes this device is the first one in allowedDevices.
    connect(navigator.bluetooth.referringDevice, true);
  } else if (allowedDevices.length > 0) {
    // If website already interacted with bluetooth devices, let's try to connect to them.
    connect(allowedDevices[index], true);
  } else {
    // Show "Scan for devices" button.
    showScanButton();
  }

})
.catch(error => {
  // Show "Scan for devices" button.
  showScanButton();
});


function connect(bluetoothDevice, toContinue) {
  bluetoothDevice.connectGATT()
  .then(server => {
    // Interact with bluetooth device.
  })
  .catch(error => {
    if (toContinue && ++index < allowedDevices.length) {
      // Try to connect to the next allowed device.
      var nextDevice = allowedDevices[index];
      connect(nextDevice, true);
    } else {
      // Show "scan for devices" button.
      showScanButton();
    }
  })
}

function showScanButton() {
  button.style.display = 'block';
  button.addEventListener('click', () => {
    // Start bluetooth discovery session
    var options = { filters: [ { services: [ 'battery_service' ] } ] };
    navigator.bluetooth.requestDevice(options)
    .then(device => {
      connect(device, false);
    })
    .catch(error => {
      console.log(error);
    });
  });
}