const axios = require('axios');
const { headers, body } = event;
const { authorization } = params;

if (authorization && authorization !== headers.authorization) {
  await $respond({
    immediate: true,
    status: 401,
    body: 'Missing or incorrect Authorization header in request'
  });
  $end('Missing or incorrect Authorization header in request');
}

console.log('Got body', body);

// See https://www.thethingsnetwork.org/docs/applications/http/
// When using a Decoder in the application's Payload Formats in
// TTN Console, then body.payload_fields will be available too.
const bytes = Buffer.from(body.payload_raw, 'base64');

// Assuming a Kickstarter The Things Node, with the default sketch;
// see https://www.thethingsnetwork.org/docs/devices/node/
const events = {
  1: 'setup',
  2: 'interval',
  3: 'motion',
  4: 'button'
};

const decoded = {
  event: events[body.port] || 'unknown',
  battery: (bytes[0] << 8 | bytes[1]) / 1000,
  light: bytes[2] << 8 | bytes[3],
  // Sign-extend to 32 bits to support negative values, by shifting
  // 24 bits to the left (16 too far), followed by a sign-propagating
  // right shift of 16 bits, to effectively shift 8 bits:
  temperature: (bytes[4] << 24 >> 16 | bytes[5]) / 100
};

console.log('Decoded', decoded);

const rgb = {
  setup: 0b101, // magenta
  interval: 0b100, // red
  motion: null,
  button: 0b010 // green
}[decoded.event];

if (!rgb) {
  $end('No downlink needed');
}

const downlink = {
  dev_id: body.dev_id,
  port: 1,
  confirmed: false,
  schedule: 'replace',
  payload_raw: Buffer.from([rgb]).toString('base64')
};

const options = {
  url: body.downlink_url,
  method: 'POST',
  headers: {
    'Accept': 'application/json',
    'Content-Type': 'application/json'
  },
  data: downlink
};

console.log('Will POST', options);

// As we want to schedule the downlink as soon as possible, we cannot use
// $send.http (which would send fully asynchronously, after the workflow
// runs, but would not count against workflow quota)
const response = await axios(options);

const result = `Sent downlink to ${options.url}, ${response.status} ${response.statusText}`;
console.log(result);

// The HTTP Integration doesn't really care about the response
await $respond({
  immediate: true,
  status: 202,
  body: result
});