OC DNS/File server

local comp = require("component")
local fs = require("filesystem")
local modem = comp.modem
local term = require("term")
local event = require("event")
local serial = require("serialization")

local debug = ...

local dn = "c/" -- Change this if you didn't label your drive c. (Like a real man.)
local timeout = 150 -- Maximum number of times the server will listen for an incoming file before bailing out.

function initTables()
    if not fs.isDirectory(dn.."DNS") then fs.makeDirectory(dn.."DNS") end
    if fs.exists(dn.."DNS/DNSList") then
        fileData = io.open(dn.."DNS/DNSList")
        dnsList = serial.unserialize(fileData:read())
        fileData:close()
        dnsCount = #dnsList
    end
end

function addMsg(msg)
    if msgTab == nil then
        msgTab = {}
        msgCount = 0
    end
    msgCount = msgCount + 1
    msgTab[msgCount] = msg
    if debug ~= nil then
        drawScreen()
    end
end

function saveDNS()
    file = io.open(dn.."DNS/DNSList", "w")
    file:write(serial.serialize(dnsList))
    file:close()
end

function addClient(name, add, portId)
    if dnsList == nil then
        dnsList = {}
        dnsCount = 0
    end
    for i = 1, #dnsList do
        if dnsList[i]["label"] == name then
            if dnsList[i]["address"] == add then
                for i = 1, 5 do
                    modem.send(add, tonumber(portId), name.." online.")
                end
                addMsg(name.." online.")
                return false
            else
                modem.send(add, tonumber(portId), "ERROR: Hostname exists")
                return false
            end
        end
    end
    dnsCount = dnsCount + 1
    dnsList[dnsCount] = {
        label = name,
        address = add,
        port = portId,
        }
    modem.send(add, tonumber(portId), "DNS registered as "..name)
    addMsg("registry confirmation sent to "..name)
    saveDNS()
    drawScreen()
    return true
end

function nameLookup(address)
    for i = 1, #dnsList do
        if dnsList[i]["address"] == address then
            return dnsList[i]["label"]
        end
    end
end

function clientLookup(name)
    for i = 1, #dnsList do
        if dnsList[i]["label"] == name then
          return dnsList[i]["address"], dnsList[i]["port"]
         end
    end
end

function listen()
    if not modem.isOpen(1) then modem.open(1) end
    ev, la, sa, port, dist, protocol, opt1, opt2, opt3 = event.pull(.4, _, ev, la, sa, port, dist, protocol, opt1, opt2, opt3)
    if ev == "modem_message" then
        addMsg(protocol.." protocol activated.")
        if protocol == "register" then
            if addClient(opt1, sa, tonumber(opt2)) then
                addMsg("Client '"..opt1.."' registered on port "..opt2..".")
            end
            return
        elseif protocol == "send" then
            dest, dPort = clientLookup(opt1)
            addMsg("Sending data to "..dest.." on port "..dPort)
            modem.send(dest, dPort, opt2, opt3)
            return
        elseif protocol == "file_request" then
            addMsg("File transfer requested by "..nameLookup(sa))
            addMsg("Checking for file "..opt2)
            dest, dPort = clientLookup(opt1)
            if fileGet(dest, dPort, opt2) then
                addMsg("File sent.")
            else
                modem.send(dest, dPort, "file not found.")
                addMsg("File not found.")
            end
            return
        elseif protocol == "file_transfer" then
            clName = nameLookup(sa)
            dest, dPort = clientLookup(clName)
            fileReceive(dest, dPort, opt1)
        elseif protocol == "directory_request" then
            dest, dPort = clientLookup(opt1)
            addMsg("Directory request from "..opt1)
            sendList(dest, dPort)
            addMsg("Directory list sent.")
            return
        end
    elseif ev == "key_down" then
        running = false
    end
end

function fileGet(reciever, portId, filename)
    addMsg("File requested... "..filename)
    if fs.isDirectory(dn.."REPO/"..filename.."/") then
        addMsg("File found at "..dn.."REPO/"..filename.." checking versions.")
        verCheck = io.open(dn.."REPO/"..filename.."/latest.txt", "r")
        latestVersion = tonumber(verCheck:read("*line"))
        installDir = verCheck:read("*line")
        verCheck:close()
        addMsg("File version: "..latestVersion.." checking filesize.")
        filesize = fs.size(dn.."REPO/"..filename.."/"..latestVersion)
        addMsg(filesize)
        if filesize > 8000 then
            addMsg("File too large, breaking it down.")
            transferTab = {}
            tCount = 0
            data = assert(io.open(dn.."REPO/"..filename.."/"..latestVersion, "r"))
            while filesize > 0 do
                tCount = tCount + 1
                transferTab[tCount] = data:read(8000)
                filesize = filesize - 8000
            end
            data:close()
            addMsg("Data broken into "..tCount.." packets.")
            for i = 1, 5 do
                modem.send(reciever, portId, "init_transfer", installDir, tCount)
            end
            for i = 1, #transferTab do
                addMsg("Sending data packet "..i..".")
                packetId = "packet_transfer_"..i
                for j = 1, 5 do
                    modem.send(reciever, portId, packetId, installDir, transferTab[i])
                end
            end
            return true
        else
            addMsg("Sending data.")
            data = assert(io.open(dn.."REPO/"..filename.."/"..latestVersion, "r"))
            filedata = data:read("*all")
            data:close()
            for i = 1, 5 do
                modem.send(reciever, portId, "file_transfer", installDir, filedata)
            end
            addMsg("Data sent.")
            return true
        end
    else
        return false
    end
end

function fileReceive(sender, portId, filename)
    addMsg("Checking for directory "..dn.."REPO/"..filename)
    if not fs.isDirectory(dn.."REPO/"..filename) then
        addMsg("Directory not found, creating.")
        fs.makeDirectory(dn.."REPO/"..filename)
    end
    addMsg("Sending file detail request.")
    for i = 1, 5 do
        modem.send(sender, portId, "transfer_details")
    end
    loopCount = 0
    while true do
        ev, la, sa, po, di, msg, version, installDir, packetCount = event.pull(.1, "modem_message", ev, la, sa, po, di, msg, version, installDir, packetCount)
        if msg ~= nil then
            addMsg(msg)
            if string.sub(msg, 1, 5) == "multi" then
                packetCount = string.sub(msg, 7, #msg)
                addMsg("Reviewing file details.")
                addMsg("Install directory: "..installDir)
                addMsg("File version: "..version)
                addMsg("Packets: "..packetCount)
                packetCount = tonumber(packetCount)
                break
            elseif string.sub(msg, 1, 6) == "single" then
                addMsg("Reviewing file details.")
                addMsg("Install directory: "..installDir)
                addMsg("File version: "..version)
                packetCount = 1
                break
            end
        end
        if loopCount == timeout then
            return false
        else
            loopCount = loopCount + 1
        end
    end
    if packetCount > 1 then
        for i = 1, packetCount do
            while true do
                ev, la, sa, po, di, msg, filePacket = event.pull(.1, "modem_message", ev, la, sa, po, di, msg, filePacket)
                if msg == "data_packet_"..i then
                    if i == 1 then
                        fileData = filePacket
                    else
                        fileData = fileData..filePacket
                    end
                    addMsg("Data packet "..i.." received.")
                    break
                end
            end
        end
    else
        while true do
            ev, la, sa, po, di, msg, filePacket = event.pull(.1, "modem_message", ev, la, sa, po, di, msg, filePacket)
            if msg == "data_packet" then
                fileData = filePacket
                addMsg("Data packet received.")
                break
            end
        end
    end
    addMsg("Writing files.")
    data = io.open(dn.."REPO/"..filename.."/"..version, "w")
    data:write(fileData)
    data:close()
    data = io.open(dn.."REPO/"..filename.."/latest.txt", "w")
    data:write(version, "\n")
    data:write(installDir)
    data:close()
    addMsg("Files written.")
end

function sendList(reciever, portId)
    path = dn.."REPO/"
    filedata = fs.list(path)
    dataTab = {}
    i = 0
    for k in filedata do
        i = i + 1
        dataTab[i] = k
    end
    dataTab = serial.serialize(dataTab)
    modem.send(reciever, portId, "directory_transfer", dataTab)
end

function drawScreen(reciever, portId)
    term.clear()
    print("DNS Server running.")
    print("DNS lookup table:-")
    print(" ")
    if dnsList ~= nil then
        for i = 1, #dnsList do
            print(i..". "..dnsList[i]["label"]..", Address: "..dnsList[i]["address"].." Port: "..dnsList[i]["port"]..".")
        end
    end
    print(" ")
    if debug ~= nil then
        if msgTab ~= nil then
            for i = 1, #msgTab do
                print(msgTab[i])
            end
        end
    end
end

function listenUp(target)
    local msg = nil
    local opt1 = nil
    local opt2 = nil
    local opt3 = nil
    local loopCount = 0
    if not modem.isOpen(1) then modem.open(1) end
    while true do
        local ev, la, sa, po, di, msg, opt1, opt2, opt3 = event.pull(.3, "modem_message", ev, la, sa, po, di, msg, opt1, opt2, opt3)
        if msg ~= nil then addMsg(msg) end
        if target ~= nil then
            if msg == target then
                if opt3 ~= nil then
                    return msg, opt1, opt2, opt3
                elseif opt2 ~= nil then
                    return msg, opt1, opt2
                elseif opt1 ~= nil then
                    return msg, opt1
                elseif msg ~= nil then
                    return msg
                end
            end
        else
            if msg ~= nil then
                if opt3 ~= nil then
                    return msg, opt1, opt2, opt3
                elseif opt2 ~= nil then
                    return msg, opt1, opt2
                elseif opt1 ~= nil then
                    return msg, opt1
                elseif msg ~= nil then
                    return msg
                end
            end
        end
    end
end

initTables()
running = true
drawScreen()
while running do
    listen()
end