Get a breakdown of 2.4GHz channel utilization. Assumes wireless interface accessible at "wlan0".

PLAYDOUGH_CHANNEL_STRENGTHS.rb

#!/usr/bin/env ruby
require 'json'

ALLOWED_CHANNELS = ['Ch 1', 'Ch 6', 'Ch 11']
Infinity = Float::INFINITY

wifi = `iwlist wlan0 scan`
pieces2ghz = wifi.split("Cell ")[1..-1].select{|x| x.include?('Frequency:2') && x.include?('Channel ') }

data = pieces2ghz.map{ |x| [ x.split('Channel ')[1].split(')')[0].to_i, (x.split('Signal level=')[1].split('/')[0] rescue '0').to_i, (x.split('Protocol:')[1].split("\n")[0] rescue '[UNKNOWN]') ] }

channels = {}
channels = data.reduce(channels) do |channels, x|
   k = "Ch #{x[0]}"
   channels[k] = [channels[k] || -100, x[1] || -100].max
   channels
end

if channels.empty?
   puts "Unable to get Wi-Fi information. Is Wi-Fi on?"
   exit 1
end

interferers = channels.keys - ALLOWED_CHANNELS

if !interferers.empty?
   interference =  interferers.reduce(-Infinity) { |max, ch| [channels[ch].to_f, max.to_f].max }
end

channels[:interference] = (interference == -Infinity) ? null : interference.to_i

# Some scans produce negative dBMs (correct), but some (raspi) produce positive (wrong)
if channels.first[1] > 0
   channels[:interference_state] = interference > 40 ? 3 : (interference > 0 ? 2 : 1 )
else
   channels[:interference_state] = interference > -60 ? 3 : (interference > -100 ? 2 : 1 )
end

puts channels.to_json.gsub(/"/, "'")