Implement power supply and disk

[andraantariksa]

PR for #19

[j8r]

Thanks for your contribution @andraantariksa, very appreciated! I left several comments.

[j8r]

I would use abstract struct because:

• this objects are immutable
• we usually want to use Hardware::Battery instead of Hardware::PowerSupply if we have a battery.

[j8r]

Also, a dedicated error type can be created inside like:

class Error < Exception
end

[andraantariksa]

I would use abstract struct because:

• this objects are immutable
• we usually want to use Hardware::Battery instead of Hardware::PowerSupply if we have a battery.

I'm using class because it allows me to use inheritance and to define Hardware::PowerSupply as non abstract so it may be used

[j8r]

I don't know why one would use PowerSupply directly, because it is either a UPS, Battery, Main or USB.

[andraantariksa]

After I think it again, PowerSupply is not necessary to be used directly. I have made it into an abstract struct..

[j8r]

Again, using an intermediate arrray is not efficient: use PowerSupply.each, and break if an entry match Battery

[j8r]

Why did you resolve some of this un-resolved comments like this one?

[andraantariksa]

Ah, that's because I have solve it locally 😅. I have changed this into

def self.new : Hardware::Battery
    battery_power_device : Battery | Nil = nil
    PowerSupply.each.each do |device_name|
      temp_device : PowerSupply = PowerSupply.new_with_type(device_name)
      if temp_device.is_a?(Battery)
        battery_power_device = temp_device
        break
      end
    end
    if battery_power_device
      battery_power_device
    else
      raise InvalidDevice.new "No battery device found"
    end
  end

Where PowerSupply.each is

def self.each : Iterator(String)
  Dir.new(device_directory).each_child
end
``

[j8r]

This methods must return String. Use getter model_name : String do ... end, it is a convenient wrapper for memoization.

(Same with other methods below)

[andraantariksa]

Okay, so it will be something like this right?

@serial_number : String | Nil = nil
# Reports the serial number of the device
getter serial_number : String do
  unless @serial_number
    @serial_number = File.read(@current_device_path / "serial_number").rstrip
  end
  @serial_number
end

[j8r]

Use self.new, and return the found, already allocated Battery.

[j8r]

If you don't see what I mean in the comments, I can push a commit which implements my proposals (after you are done of course). Then, you can review it too.

[j8r]

I propose to merge this when the test are executed (somehow) in the CI. Then, I can open a PR to do minor improvements here and there.