A LUA script for Domoticz that controls an MPD server volume (via `mpc` client) under the orders of a dummy Domoticz dimmer

script_device_MPD_Radio.lua

--
-- LUA script for Domoticz that controls an MPD server (via `mpc` client) under
-- the orders of a dummy Domoticz dimmer device.
--
-- No configuration required on the device, the LUA script listen to order such
-- as "Set Level: 42 %" and sends adequate `mpc volume` commands.
--
commandArray = {}

-- Name of the dummy Domoticz dimmer:
DomDevice = 'MPD radio'

if devicechanged[DomDevice] then
    --print(DomDevice..' received order: '..devicechanged[DomDevice]) -- DEBUG:
    if devicechanged[DomDevice] == 'On' then
        --print(DomDevice..' should be set to: On') -- DEBUG:
        os.execute('mpc play')
    elseif string.match(devicechanged[DomDevice], 'Set Level: ') then -- "Set Level: 42 %" type of order
        --print(DomDevice..' level changed ('..otherdevices_svalues[DomDevice]..')') -- DEBUG:

        -- Compute the volume: Use the "Set Level: 42 %" order and strip anything that's not a digit
        volume = devicechanged[DomDevice]:gsub('%D', '')
        volume = tonumber(volume)

        -- Supports level=0 (even though Domoticz seems to handle it: Setting device's level/slider to "0", sets device to "Off")
        if volume == 0 then
            --print('Asked level for '..DomDevice..' is 0') -- DEBUG:
            commandArray[1]={[DomDevice]='Off'}
        else
            --print('Setting MPD volume to '..volume) -- DEBUG:
            os.execute('mpc volume '..volume)

            -- Conveniently make sure mpd plays after setting volume
            --print('Forcing MPD to play') -- DEBUG:
            os.execute('mpc play')
        end
    elseif devicechanged[DomDevice] == 'Off' then
        --print(DomDevice..' should be set to: Off') -- DEBUG:
        os.execute('mpc pause')
    end
end

return commandArray