server.lua

-- for kind of a documentation go to https://pastebin.com/DBP8CBMd




function requestPayment(player, amount, text) -- sends the specified player a request with the specified text to pay the computer the specified amount of money. If the player confirms the payment the server will send back a rednet message in this form: {["action"] = "receivedPayment", ["amount"] = amount, ["player"] = player}
rednet.send(systemId,createMessageString({["action"]="requestPayment",["player"]=player,["amount"]=amount,["text"]=text}),"server")
end



function pay(player, amount, text) -- pays the specified player the specified amount of money and sends them the specified message (if the message is specified). If the payment is succesfull then the server helper will send back a rednet message in this form: {["action"] = "paymentConfirmation", ["player"] = playerName, ["amount"] = amount}
rednet.send(systemId,createMessageString({["action"]="pay",["player"]=player,["amount"]=amount,["text"]=text}),"server")
end



function getBalance() -- requests the balance of the computer, if it is succesfull, the server helper will send back a rednet message in this form: {["action"] = "sendingBalance", ["balance"] = registeredComputers[id]["balance"]}
rednet.send(systemId,createMessageString({["action"]="getBalance"}),"server")
end



function getOwner() -- requests the name of the owner from the server helper, if it is succesfull, the server helper will send back a rednet message in this form: {["action"] = "sendingOwner", ["owner"] = registeredComputers[id]["owner"]}
rednet.send(systemId,createMessageString({["action"]="getOwner"}),"server")
end



function encrypt(text)
local result = ""
local keyLength = #key

    for i = 1, #text do
    local textByte = text:byte(i)
    local keyByte = key:byte((i - 1) % keyLength + 1)
    result = result .. string.char(bit.bxor(textByte, keyByte))
    end

return result
end



function decrypt(encryptedText)
return encrypt(encryptedText)
end



function createMessageString(messageTable)
local outTable = {}
local returnString = "@@"
local i = 1
    for k,v in pairs(messageTable) do
    outTable[i] = {["key"] = k, ["value"] = v}
    i=i+1
    end

    for i = 1, #outTable do
    local i = math.random(1,#outTable)
    returnString = returnString .. outTable[i]["key"] .. "=" .. outTable[i]["value"] .. ","
    table.remove(outTable,i)
    end


returnString = encrypt(returnString)

return returnString
end



function getMessageTable(messageString) -- returns the decoded and processed message as a table (example: diwjaifwifhwoifhaiwdj --> action=test,value=hello there, --> {["action"]="test",["value"]="hello there"}) be carefull tough, cause every value and key will be strings
local messageString = decrypt(messageString)

    if string.sub(messageString,1,2) == "@@" then
    messageString = string.sub(messageString,3,-1)
    else
    return {}
    end


local returnTable = {}

local curPos = 1
    while true do
    local equalPos = string.find(messageString,"=",curPos)
        if not equalPos then
        break
        end
    local curKey = string.sub(messageString,curPos,equalPos-1)
    curPos = equalPos+1
    local commaPos = string.find(messageString,",",curPos)
        if not commaPos then
        break
        end
    local curValue = string.sub(messageString,curPos,commaPos-1)
    curPos = commaPos+1
    returnTable[curKey] = curValue
    end

return returnTable
end







    for k,name in pairs(peripheral.getNames()) do
        if peripheral.getType(name) == "modem" then
            if peripheral.wrap(name).isWireless() then
            rednet.open(name)
            end
        end
    end

    if not fs.exists("key") then
    term.setTextColor(colors.red)
    print("Please enter the key:")
    key = read()
    local file = fs.open("key","w")
    file.write(key)
    file.flush()
    file.close()
    else
    local file = fs.open("key","r")
    key = file.readAll()
    file.close()
    end

    if not fs.exists("systemId") then
    term.setTextColor(colors.white)
    print("Connecting to the system...")
        while true do
        rednet.broadcast(createMessageString({["action"]="register",["key"]=key}),"server")
        id, message, protocol = rednet.receive("serverResponse",5)
            if message and protocol == "serverResponse" then
                local response = getMessageTable(message)
                if response["action"] == "registrationResponse" then
                term.setTextColor(colors.green)
                print("Succesfully connected to the system.")
                systemId = id
                local file = fs.open("systemId","w")
                file.write(id)
                file.flush()
                file.close()
                break
                end
            end
        print("Registration failed, trying again.")
        end
    else
    local file = fs.open("systemId","r")
    systemId = tonumber(file.readAll())
    file.close()
    end