Central CPU

-- this is the startup script for the central cpu at spawn


----| config |----------------------------


local MODEM_SIDE = "top"


----| setup |----------------------------


os.loadAPI("TrainSignalSystem")

local actionEnum = {
    GET_SIGNAL_STATE = "GET_SIGNAL_STATE",
    SENSOR_CHANGE = "SENSOR_CHANGE",
}


----| functions |----------------------------


function onGetSignalState(id)
    local trainSignalSystem = TrainSignalSystem.findFromComputerId(id)
    if trainSignalSystem then
        local isOn = trainSignalSystem.isOn
        rednet.send(trainSignalSystem.signalId, isOn)
    end
end


function onSensorChange(id)
    local trainSignalSystem = TrainSignalSystem.findFromComputerId(id)
    if trainSignalSystem then
        if id == trainSignalSystem.onSensorId and trainSignalSystem.isOn == false then -- activate the signal
            print("Activating signal...")
            trainSignalSystem.isOn = true
            rednet.send(trainSignalSystem.signalId, true) -- send a message to the computer that handles the signal light
        elseif id == trainSignalSystem.offSensorId and trainSignalSystem.isOn == true then -- deactivate the signal
            print("Deactivating signal...")
            trainSignalSystem.isOn = false
            rednet.send(trainSignalSystem.signalId, false) -- send a message to the computer that handles the signal light
        end
    end
end


function receiveSignal() -- waits for commands from central cpu
    while true do
        print("Waiting for a message...")
        local id, message = rednet.receive()
        print("Received message from computer " .. id)

        -- proceed based on the action given in the message
        if message == actionEnum.SENSOR_CHANGE then
            onSensorChange(id)
        elseif message == actionEnum.GET_SIGNAL_STATE then
            onGetSignalState(id)
        end
    end
end


----| main |----------------------------


rednet.open(MODEM_SIDE)
print("Rednet opened.")


receiveSignal()