# Receive and print an uplink message; return a downlink message
# Usage: TTN_REGION=eu TTN_APP_ID=test TTN_ACCESS_KEY=ttn-account-v2.XXXXXXX ttn_up_down.rb

require 'rubygems'
require 'mqtt'
require 'json'
require 'base64'

ttn_app_id=ENV['TTN_APP_ID']
ttn_app_access_key=ENV['TTN_APP_ACCESS_KEY']
ttn_region=ENV['TTN_REGION']

ttn_dev_id="test"

# connect:
MQTT::Client.connect(
  :host     => "#{ttn_region}.thethings.network",
  :port     => 1883,
  :username => ttn_app_id,
  :password => ttn_app_access_key
) do |c|

  # subscribe to uplink:
  c.get("#{ttn_app_id}/devices/#{ttn_dev_id}/up") do |topic, message|

    # do stuff with the uplink:
    data = JSON.parse message
    payload_up = Base64.decode64(data["payload_raw"]).unpack("C*")
    puts "#{topic}: #{payload_up}"

    # send downlink:
    payload_down = [0x01, 0x02, 0x03, 0x04]
    downlink = {
      :payload_raw => Base64.encode64(payload_down.pack("C*")).strip,
      :port        => 1
    }
    c.publish("#{ttn_app_id}/devices/#{ttn_dev_id}/down", downlink.to_json)

  end
end