Raspberry Pi Activation Script

#!/usr/bin/env bash
# the preceding line instructs this script to run using the bash interpreter

# main function definition
perform_install()
{
  # echo: output a message to the screen
  echo 'Starting activation process...'

  # install python3
  install_python3

  # install python3-pip (python3 package installer)
  install_python3_pip

  # install websocket-client python3 library
  install_websocket_client

  # install smbus2 python3 library
  install_smbus2

  # download the limitos.py file
  download_limitos_py

  # add the limitos.py process to systemctl
  install_limitos_py

  # remove previous installations
  remove_limitos_js

  # output the registration information
  echo "Register this device within 5 minutes at https://limitos.com/register"
  echo "Registration code: $registration_auth_token"
}

# function to install python3
function install_python3()
{
  # check if python3 is installed
  # command -v: outputs location of specified program, wc -l: count line numbers
  python3_installed=$(command -v python3 | wc -l)

  # if python3 is not installed (command location line count is zero)
  if [ $python3_installed -eq 0 ]
    # then execute the commands below
    then

      # output activation message
      echo 'python3 not found, installing...'

      # install python3, and log output
      sudo apt-get install -y python3 &> 'limitos_install.log'

  # end the if statement
  fi

}

# function to install python3-pip
function install_python3_pip()
{
  # check if python3-pip is installed
  python3_pip_installed=$(command -v pip3 | wc -l)

  # if python3-pip is not installed
  if [ $python3_pip_installed -eq 0 ]
    # then execute the commands below
    then

      # output activation message
      echo 'python3-pip not found, installing...'

      # install python3-pip, and log output
      sudo apt-get install python3-pip -y &> 'limitos_install.log'

  # end the if statement
  fi

}

# function to install python3 websocket libary (websocket-client)
# checking if a library is installed takes almost as long as installation, so we proceed with installation only
function install_websocket_client()
{
  # output activation message
  echo 'installing websocket-client...'

  # install websocket-client, and log output
  sudo pip3 install websocket-client &> 'limitos_install.log'
}

# function to install python3 bus communication library (smbus2)
function install_smbus2()
{
  # output activation message
  echo 'installing smbus2...'

  # install smbus2, and log output
  sudo pip3 install smbus2 &> 'limitos_install.log'
}

# function to download limitos.py
function download_limitos_py()
{
  # create a new device and save the auth_token as device_json
  # curl: request a remote url, -s: silent, -S: show errors, -L: follow redirects, -X POST: use a HTTP POST request
  device_json=$(curl -sSL -X POST https://limitos.com/api/v1/devices)

  # get the device id from the JSON
  # grep: search, -P: use Perl regular expressions, -o: only output the match, '"id":(\d*)': look for "id":(digits)
  # awk: pattern manipulation, -F':': separate by ':', print $2: print the second match
  device_id=$(echo $device_json | grep -Po '"id":(\d*)' | awk -F':' '{print $2}')

  # get the auth token from the JSON
  # '"auth_token":.*?[^\\]"': look for "auth_token":"xxxxxx", tr -d '"': delete quotes
  device_auth_token=$(echo $device_json | grep -Po '"auth_token":.*?[^\\]"' | awk -F':' '{print $2}' | tr -d '"')

  # get a new registration code (using the device auth_token)
  registration_json=$(curl -sSL --data "auth_token=$device_auth_token" https://limitos.com/api/v1/devices/$device_id/registrations)

  # get the auth token from the JSON
  registration_auth_token=$(echo $registration_json | grep -Po '"auth_token":.*?[^\\]"' | awk -F':' '{print $2}' | tr -d '"')

  # retrieve the python script and save it as limitos.py
  curl -sS --data "auth_token=$device_auth_token" https://limitos.com/api/v1/devices/$device_id/python_script > limitos_unverified.py

  # if the file is valid
  if python3 -c "import ast; ast.parse(open('limitos_unverified.py').read())"
    # then execute the commands below
    then

      # move the file
      mv limitos_unverified.py limitos.py

    # else the script is invalid
    else

      # exit
      exit 0

  # end the if statement
  fi
}

# function to remove previous node.js installations of the limitos.py process
function remove_limitos_js()
{
  # check if pm2 is installed
  pm2_installed=$(command -v pm2 | wc -l)

  # if pm2 is installed
  if [ $pm2_installed -eq 1 ]
    # then execute the commands below
    then

      # remove node.js script
      sudo pm2 -s stop limitos
      sudo pm2 -s delete limitos
      sudo pm2 -s save
      rm limitos*.js 2> /dev/null

  # end the if statement
  fi
}

# function to install the limitos.py process
function install_limitos_py()
{
  # output message
  echo 'starting limitos.py process...'

  # get the python3 directory
  python3_directory=$(which python3)

  # get the current directory
  current_directory=$(pwd)

  # retrieve the systemd script
  curl -sS "https://limitos.com/api/v1/devices/systemd_script?python3_directory=$python3_directory¤t_directory=$current_directory" > limitos.service

  # move the service file to /lib/systemd/system/
  sudo mv limitos.service /lib/systemd/system/

  # reload systemd
  sudo systemctl daemon-reload

  # enable the script
  sudo systemctl enable limitos

  # start (or restart) the systemd service
  sudo systemctl restart limitos
}

# run the main function
perform_install