detect_tablet_mode

#!/usr/bin/env ruby

trap('INT'){}

def magnitude(v)
  Math.sqrt v.map{|x| x*x}.reduce(:+)
end

def vector_product(v1,v2)
  v1.zip(v2).map{|i1,i2| i1*i2}.reduce(:+)
end

def vector_angle(v1, v2)
  Math.acos(vector_product(v1,v2) / (magnitude(v1)*magnitude(v2)))
end

def scale_vector(v, c)
  v.map{|i| i*c}
end

def sign((y1,z1),(y2,z2))
  val = z1*y2 - y1*z2
  if val == 0 then 1 else val / val.abs end
end

def read_in(dev, in_name)
  File.read("#{dev}/in_#{in_name}")
end

def read_float_in(dev, property_name, in_name)
  read_in(dev, "#{property_name}_#{in_name}").to_f
end

def device(device_id)
  "/sys/bus/iio/devices/iio:device#{device_id}"
end

def read_3d_sensor(device_id, property_name)
  dev = device device_id
  offset = read_float_in(dev, property_name, "offset")
  scale  = read_float_in(dev, property_name, "scale")
  %w(x y z).map{|axis| (read_float_in(dev, property_name, "#{axis}_raw") + offset) * scale}
end

def read_angle(display_accel_id, keyboard_accel_id)
  accel_3d_display  = read_3d_sensor(display_accel_id,  "accel")
  accel_3d_keyboard = read_3d_sensor(keyboard_accel_id, "accel")
  accel_2d_display  = accel_3d_display[1..2]
  accel_2d_keyboard = accel_3d_keyboard[1..2]

  return    sign(accel_2d_keyboard, accel_2d_display) *
    vector_angle(accel_2d_keyboard, accel_2d_display)
end

def read_mode(display_accel_id, keyboard_accel_id)
  angle = read_angle(display_accel_id, keyboard_accel_id)
  if angle.abs > 2.8 or angle < -0.5
    :tablet
  else
    :laptop
  end
end

if ARGV.count != 2
  puts "Usage: #{File.basename($0)} <display-accelerometer-id> <keyboard-accelerometer-id>"
  puts "Example: #{File.basename($0)} 1 6"
else
  puts read_mode(ARGV[0],ARGV[1])
end