Central Computer

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


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


local MODEM_SIDE = "top"


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


os.loadAPI("TrainSignalNetwork")

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

local sensorStateEnum = { -- compatible with bitwise operations
    off = 0,
    leftOn = 1,
    rightOn = 2,
    bothOn = 3,
}


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


function onGetSignalState(id)
    local trainSignalNetwork, thisSubNetwork, otherSubNetwork = TrainSignalNetwork.findFromComputerId(id)
    if trainSignalNetwork then
        local isOn = thisSubNetwork.signalState
        rednet.send(thisSubNetwork.id, isOn, protocolEnum.GET_SIGNAL_STATE)
    end
end


function onSensorChange(id, state)
    local trainSignalNetwork, thisSubNetwork, otherSubNetwork = TrainSignalNetwork.findFromComputerId(id)
    if trainSignalNetwork then
        -- proceed based on state
        if state == sensorStateEnum.rightOn then -- a train in the right lane is entering the single lane; activate the signal on the far side relative to here
            otherSubNetwork.signalState = true
            print(otherSubNetwork.id .. "'s signal set to true")
        elseif state == sensorStateEnum.leftOn then -- a train is moving out of the single lane into the left lane; deactivate the signal on this side
            thisSubNetwork.signalState = false
            print(thisSubNetwork.id .. "'s signal set to false")
        end
    end
end


function receiveSignal() -- waits for commands from central cpu
    while true do
        local id, message, protocol = rednet.receive()
        -- print("Received message from computer " .. id .. "\n\t> Protocol: " .. (protocol or "None"))

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


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


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


receiveSignal()