Railcraft Station

--Station Program:
--  Keeps track of trains at each track
--  Can choose which train to dispatch
--Constants:
local ticketMachine = peripheral.wrap("back")
local mon
local mon_x, mon_y
local note_block
local stationDisplayOffset = 0
local RedstoneSide = "bottom"
rednet.open("front")
--Station Name:
local STATION_NAME
--Station Dest:
local STATION_DEST
--Server Computer ID:
local SERVER_ID
--File to hold station data:
local STATION_FILE = "stations"
--Protocols:
local METADATA_PROT = "md"
local METADATA_RQ = "rq"
local UPDATE_PROT = "ud"
local UPDATE_RQ = "rq"
local DISPATCH_PROT = "dp"
local REQUEST_PROT = "rq"
local STATION_LIST_PROT = "sl"
local STATION_LIST_RQ = "rq"
local REBOOT_PROT = "rb"
local REBOOT_RQ = "rb"
--Data on each track available for control.
local tracks
--Data for every station in the network, for dispatch choices.
local stations
--Returns the number of items in a table.
function tableSize(tbl)
    local count = 0
    for i in pairs(tbl) do count = count + 1 end
    return count
end

--Gets the information of a train at a specific track.
function scanTrainAtTrack(trackNumber)
    local trainData = {}
    local ids = tracks[trackNumber].sensor.getMinecartIds()
    for i in pairs(ids) do
        local success, rawdata = pcall(tracks[trackNumber].sensor.getMinecartData, ids[i])
        if (success) then
            local data = rawdata.all()
            --Test if the locomotive is numbered, and check that it is above this sensor.
            if ((string.len(data.name) < 4) and (data.position.x < 1) and (data.position.z < 1) and (data.position.x > -1) and (data.position.z > -1)) then
                tracks[trackNumber].train = tonumber(data.name)
                return
            end
        end
    end
    tracks[trackNumber].train = -1
end

--Scans all tracks and saves the data to the trains table.
function scanAllTracks()
    for i in pairs(tracks) do
        scanTrainAtTrack(i)
    end
end

--Handles ticket creation failure.
function onTicketMachineFailure()
    print("Unable to create ticket.")
end

--Creates a ticket for a destination and sends it to a train, the train departs.
function dispatchTrack(dest, trackNumber)
    local success = ticketMachine.createTicket(dest, 1)
    if (not success) then
        onTicketMachineFailure()
        return
    end
    rs.setBundledOutput(RedstoneSide, tracks[trackNumber].ticketColor)
    os.sleep(1)
    rs.setBundledOutput(RedstoneSide, 0)
    print("Train "..tracks[trackNumber].train.." dispatched to "..dest..".")
end

--Dispatches the given train by ID
function dispatchTrain(dest, trainId)
    for i in pairs(tracks) do
        if (tracks[i].train == trainId) then
            dispatchTrack(dest, i)
        end
    end
end

--Dispatches the first train available to leave.
function dispatchFirstAvailableTrain(dest)
    for i in pairs(tracks) do
        if (tracks[i].train ~= -1) then
            dispatchTrack(dest, i)
            return
        end
    end
    print("No train available to dispatch.")
end

--Sends station name, dest, ID, and track number to the server, upon request.
function sendMetadata()
    rednet.send(SERVER_ID, {name = STATION_NAME, dest = STATION_DEST, id = os.getComputerID(), trackCount = tableSize(tracks)}, METADATA_PROT)
    print("Metadata sent to the server.")
end

--Sends an updated list of trains at this station to the server.
function sendUpdate()
    local trains = {}
    for i in pairs(tracks) do
        if (tracks[i].train ~= -1) then
            table.insert(trains, tracks[i].train)
        end
    end
    rednet.send(SERVER_ID, trains, UPDATE_PROT)
    print("Update sent to server.")
end

--Sends a request to the server to send a train to a new destination.
function sendRequest(dest)
    rednet.send(SERVER_ID, dest, REQUEST_PROT)
    print("Sent request for a train to "..dest)
end

--Initializes the station.
function init()
    term.clear()
    term.setCursorPos(1,1)
    print("Initializing station...")
    local f = fs.open("station_config", "r")
    local config = textutils.unserialize(f.readAll())
    f.close()
    STATION_NAME = config.name
    STATION_DEST = config.dest
    SERVER_ID = config.server_id
    mon = peripheral.wrap(config.monitor_id)
    note_block = peripheral.wrap(config.note_block_id)
    mon_x, mon_y = mon.getSize()
    tracks = config.tracks
    for i in pairs(tracks) do
        tracks[i].sensor = peripheral.wrap(tracks[i].sensor_id)
    end
    sendMetadata()
    scanAllTracks()
    printTrains()
    sendUpdate()
end

--Sets up the monitor display.
function initMonitor()
    mon.setBackgroundColor(colors.white)
    mon.clear()
    mon.setCursorPos(1,1)
    mon.setTextColor(colors.lightGray)
    mon.setBackgroundColor(colors.black)
    for i = 1, mon_x do
        mon.setCursorPos(i,1)
        mon.write(" ")
    end
    mon.setCursorPos(1,1)
    mon.write(STATION_NAME)
    mon.setCursorPos(mon_x-1,2)
    mon.setTextColor(colors.white)
    mon.setBackgroundColor(colors.lime)
    mon.write("/\\")
    mon.setBackgroundColor(colors.red)
    mon.setCursorPos(mon_x-1,3)
    mon.write("\\/")
    mon.setTextColor(colors.gray)
    mon.setBackgroundColor(colors.white)
    mon.setCursorPos(1,2)
    mon.write("Click a station to depart.")
    mon.setCursorPos(1,3)
    mon.write("Departing Track: ")
    loadStationList()
    displayStations()
end

--Displays the destinations on the screen.
function displayStations()
    mon.setBackgroundColor(colors.white)
    for i=4,mon_y do
        for k=1,mon_x do
            mon.setCursorPos(k,i)
            mon.write(" ")
        end
    end
    for i=1,mon_y-4 do
        mon.setCursorPos(1,i+3)
        if (i % 2 == 0) then
            mon.setTextColor(colors.lightBlue)
            mon.setBackgroundColor(colors.gray)
        else
            mon.setTextColor(colors.blue)
            mon.setBackgroundColor(colors.lightGray)
        end
        if (i+stationDisplayOffset <= tableSize(stations)) then
            for i=1,mon_x do mon.write(" ") end
            mon.setCursorPos(1,i+3)
            if (stations[i+stationDisplayOffset].dest == STATION_DEST) then
                mon.setTextColor(colors.magenta)
            end
            mon.write(stations[i+stationDisplayOffset].name)
        end
    end
end

--Displays the list of trains at this station.
function printTrains()
    print("Trains:")
    for i in pairs(tracks) do
        if (tracks[i].train ~= -1) then
            print("  Track: "..i.." Train: "..tracks[i].train)
        end
    end
end

--Saves the list of stations to a file.
function saveStationList()
    local f = fs.open(STATION_FILE, "w")
    f.write(textutils.serialize(stations))
    f.close()
end

--Reads the stations list from a file.
function loadStationList()
    if (not fs.exists(STATION_FILE)) then
        local f = fs.open(STATION_FILE, "w")
        f.write("{}")
        f.close()
        stations = {}
        requestStationList()
    else
        local f = fs.open(STATION_FILE, "r")
        stations = textutils.unserialize(f.readAll())
        f.close()
    end
end

--What to do if the server updates the stations list:
function onStationListReceived(newStationList)
    stations = newStationList
    saveStationList()
    displayStations()
    print("  Received updated stations list.")
end

--Ask the server for a copy of the stations list.
function requestStationList()
    rednet.send(SERVER_ID, STATION_LIST_RQ, STATION_LIST_PROT)
    print("Requested stations list.")
end

--Handles monitor touch events and what to do.
function onMonitorTouch(x,y)
    --Check if the user clicked one of the arrows.
    if ((y < 4) and (x > mon_x-2)) then
        if (y == 2 and stationDisplayOffset > 0) then
        --Clicked up
            stationDisplayOffset = stationDisplayOffset - 1
        elseif (y == 3 and stationDisplayOffset < tableSize(stations)-1) then
        --Clicked down.
            stationDisplayOffset = stationDisplayOffset + 1
        end
        displayStations()
    elseif (y > 3) then
    --Clicked on a station.
        if (stations[y-3+stationDisplayOffset].dest ~= STATION_DEST) then
            sendRequest(stations[y-3+stationDisplayOffset].dest)
        end
    end
end

--Handles dispatch requests.
function onDispatchRequestReceived(msg)
    mon.setCursorPos(19,3)
    mon.setTextColor(colors.lime)
    mon.setBackgroundColor(colors.white)
    for i in pairs(tracks) do
        if (tracks[i].train == msg[2]) then
            mon.write(tonumber(string.format("%." .. (0) .. "f", i)))
            note_block.setPitch(20)
            for k=1,i do
                note_block.triggerNote()
                os.sleep(0.4)
            end
            os.sleep(1)
        end
    end
    dispatchTrain(msg[1],msg[2])
end

--What to do after a train has been detected leaving.
function onTrainDeparture(trackNumber)
    mon.setBackgroundColor(colors.white)
    mon.setCursorPos(19,3)
    mon.write("   ")
    tracks[trackNumber].train = -1
end

--Listens for events. Main event handler.
function eventHandler()
    local event,p1,p2,p3,p4,p5 = os.pullEvent()
    if (event == "rednet_message") then
        if (p3 == METADATA_PROT and p2 == METADATA_RQ) then
            sendMetadata()
            sendUpdate()
        elseif (p3 == UPDATE_PROT and p2 == UPDATE_RQ) then
            sendUpdate()
        elseif (p3 == DISPATCH_PROT) then
            --Dispatch message: destination and train id
            onDispatchRequestReceived(p2)
        elseif (p3 == STATION_LIST_PROT) then
            --Update list of stations.
            onStationListReceived(p2)
        elseif (p3 == REBOOT_PROT and p2 == REBOOT_RQ) then
            os.reboot()
        end
    elseif (event == "redstone") then
        for i in pairs(tracks) do
            --Test if a train arrived.
            if (tracks[i].train == -1 and rs.testBundledInput(RedstoneSide, tracks[i].detectorColor)) then
                scanTrainAtTrack(i)
                sendUpdate()
            --Test if a train left.
            elseif (tracks[i].train ~= -1 and rs.testBundledInput(RedstoneSide, tracks[i].detectorColor) == false) then
                onTrainDeparture(i)
            end
        end
    elseif (event == "monitor_touch") then
        onMonitorTouch(p2,p3)
    end
end

--Main Loop:
init()
initMonitor()
while (true) do
    eventHandler()
end