Auto office joiner

app.rb

#!/usr/bin/env ruby
# encoding: utf-8

require 'net/http'
require 'socket'

LAST_SEEN_TIME_OUT = 60 * 60 * 2 # 2 hours
ACCESS_TOKEN = "YOUR_ACCESS_TOKEN"
CHANNEL_ID = "YOUR_CHANNEL_ID"
CHANNEL_NAME="YOUR_CHANNEL_NAME"
TOKEN_OWNER = "SLACK_ID_OF_USER_THAT_OWNS_THE_TOKEN"

def current_ips
  ips = []
  raw_data = `nmap -sn #{ip_address}/24 | grep "scan report for" | awk '{print $5}'`
  raw_data.each_line do |line|
    ips << line.chomp
  end
  ips
end

def ip_address
  ip = Socket.ip_address_list.detect{|intf| intf.ipv4_private?}
  return if ip.nil?
  ip.ip_address
end

def find_mac_for_ip(ip)
  `arp -a | grep "(#{ip})" | awk '{print $4}'`.chomp.downcase
end

def known_devices
  {
    "e1:e5:c0:97:3d:0c" => "Jeroen",
    "5d:2c:b1:62:d9:45" => "Bob",
    "8f:70:a9:32:01:49" => "Michiel",
  }
end

def users
  {
    "jeroen" => "xxx",
    "bob" => "yyy",
    "michiel" => "zzz",
  }
end

def still_in_office?(last_seen)
  return false if last_seen.nil?

  # Is last seen within 4 hours
  last_seen.to_i + (LAST_SEEN_TIME_OUT) > Time.now.to_i
end

def device_to_name(device_mac)
  known_devices[device_mac] || "Unknown device: #{device_mac}"
end

def join_channel(user_token)
  if user_token == TOKEN_OWNER
    Net::HTTP.get(URI("https://slack.com/api/channels.join?token=#{ACCESS_TOKEN}&name=#{CHANNEL_NAME}"))
  else
    Net::HTTP.get(URI("https://slack.com/api/channels.invite?token=#{ACCESS_TOKEN}&channel=#{CHANNEL_ID}&user=#{user_token}"))
  end
end

def leave_channel(user_token)
  if user_token == TOKEN_OWNER
    Net::HTTP.get(URI("https://slack.com/api/channels.leave?token=#{ACCESS_TOKEN}&channel=#{CHANNEL_ID}"))
  else
    Net::HTTP.get(URI("https://slack.com/api/channels.kick?token=#{ACCESS_TOKEN}&channel=#{CHANNEL_ID}&user=#{user_token}"))
  end
end

@first_run ||= true
loop do
  puts "=" * 20
  @last_devices ||= {}

  current_ips.each do |ip|
    @last_devices[find_mac_for_ip(ip)] = Time.now
  end

  begin
    if @first_run
      p "Running on IP: #{ip_address}"
      offline_devices = known_devices.reject { |device| @last_devices.include?(device) }
      offline_devices.each do |device, name|
        user_token = users[name.downcase]
        leave_channel(user_token)
        puts "#{name} was not in the office when the script started"
      end
      @first_run = false
    end

    @last_devices.each do |device, time|
      unless known_devices.include?(device)
        puts "Unknown device: #{device}"
        next
      end

      user_token = users[device_to_name(device).downcase]

      if user_token.nil?
        puts "Unknown user: #{device_to_name(device).downcase} with device #{device}"
        next
      end

      if still_in_office?(@last_devices[device])
        join_channel(user_token)
        puts "#{device_to_name(device)} is in the office"
      else
        @last_devices.delete(device)
        leave_channel(user_token)
        puts "#{device_to_name(device)} is not in the office"
      end
    end
  rescue SocketError
    puts "No network connection, retrying in 10 seconds"
  end
end