Snap - Fixed

local settings={}
settings["debug"]=false
settings["reserveFuelLevel"]=10
settings["nextStep"]=nil
settings["rightNext"]=false
settings["leftNext"]=false


--CONSTANTS
local cNone=0
local cLeft=1
local cYes=2
local cNo=3
local cPowerDown=4
local cPowerUp=5
local cForward=6
local cReadyCharge=7
local cComplete=8
local cGoHome=9
local cRight=10
local cReboot=11
local cShutdown=12
local cClearSettings=13
local cNeedFuel=14
local cPairing=15

function loadSettings()
   local file = fs.open("SnapBoxSettings","r")
   local data = file.readAll()
   file.close()
   settings=textutils.unserialize(data)
end

function saveSettings()
    local file = fs.open("SnapBoxSettings","w")
    file.write(textutils.serialize(settings))
    file.close()
end

function needFuel()
    local level=turtle.getFuelLevel()
    if level=="unlimited" or level>settings["reserveFuelLevel"] then
        sendMessageToPartner(cNo)
    else
        sendMessageToPartner(cYes)
    end
end

function checkStatus()
    if turtle.getItemCount(1)>0 then
        print("Energy Cell OK")
    else
        print("Please insert Locked Energy Tesseract or Redstone Energy Cell into slot 1")
        while turtle.getItemCount(1)==0 do
            turtle.select(1)
            sleep(0.1)
        end
    end
    if turtle.getFuelLevel()~="unlimited" and turtle.getFuelLevel()<settings["reserveFuelLevel"] then
        if turtle.getItemCount(16)>0 then
            print("Fuel Level OK")
        else
            turtle.select(16)
            print("Please insert fuel into slot 16")
            while turtle.getItemCount(16)==0 do
                sleep(0.1)
            end
        end
    end
end

function waitForPartner()
    print("Waiting for Box")
    sendMessageToPartner(cPairing)
    local message=nil
    while message~=cPairing do
        event = os.pullEvent("redstone")
        message=redstone.getAnalogInput("front")
    end
    sendMessageToPartner(cPairing)
    print("Off we go")
end

function sendMessageToPartner(message)
    if debug==true then
        print("Sent "..message)
    end
    redstone.setAnalogOutput("front",message)
    sleep(0.1)
    redstone.setAnalogOutput("front",cNone)
end

function forward()
    sendMessageToPartner(cForward)
    while turtle.forward()==false do
        sleep(0.1)
    end
    if settings["rightNext"]==true then
        turtle.turnRight()
        settings["rightNext"]=false
    end
    if settings["leftNext"]==true then
        turtle.turnLeft()
        settings["leftNext"]=false
    end
    saveSettings()
end

function readyCharge()
    sendMessageToPartner(cReadyCharge)
    while turtle.back()==false do
        sleep(0.1)
    end
    settings["nextStep"]="wait-forward"
    saveSettings()
    waitForward()
end

function waitForward()
    sleep(2)
    while turtle.detect()==true do
        sleep(0.1)
    end
    sleep(2)
    while turtle.forward()==false do
        sleep(0.1)
    end
    settings["nextStep"]=nil
    saveSettings()
    sendMessageToPartner(cComplete)
end

function powerUp()
    turtle.select(1)
    turtle.digDown()
    sendMessageToPartner(cPowerUp)
end

function powerDown()
    turtle.select(1)
    while turtle.placeDown()==false and turtle.getItemCount(1)>0 do
            sleep(0.1)
    end
    sendMessageToPartner(cPowerDown)
end

function waitForMessageFromPartner()
    if settings["debug"]==true then
        print("Waiting for message")
    end
    os.pullEvent("redstone")

    --check to see if Box has turned and moved - only works on left turns :(
    local msg=redstone.getAnalogInput("front")

    if msg==cPowerDown then
        powerDown()
    elseif msg==cPowerUp then
        powerUp()
    elseif msg==cRight then
        settings["rightNext"]=true
        saveSettings()
        sendMessageToPartner(cRight)
    elseif msg==cLeft then
        settings["leftNext"]=true
        saveSettings()
        sendMessageToPartner(cLeft)
    elseif msg==cForward then
        forward()
    elseif msg==cClearSettings then
        shell.run("clearsettings")
    elseif msg==cShutdown then
        os.shutdown()
    elseif msg==cReboot then
        os.reboot()
    elseif msg==cNeedFuel then
        needFuel()
    elseif msg==cReadyCharge then
        readyCharge()
    end
end

function checkResume()
    local file=fs.open("SnapBoxSettings","r")
    if file==nil then
        return false
    else
        file.close()
        return true
    end
end


-----MAIN PROGRAM
--Hack to fix situations where Snap gets left behind
turtle.forward()

term.clear()
term.setCursorPos(1,1)

--Check for a resume
if checkResume()==false then
    --Check to make sure it has all the items it needs
    checkStatus()

    --initial refuel
    turtle.select(16)
    turtle.refuel()
    turtle.select(1)

    --wait to find partner
    waitForPartner()
    saveSettings()
else
    print("Resuming")
    loadSettings()
end

while true do
    if settings["nextStep"]=="wait-forward" then
        waitForward()
    end
    waitForMessageFromPartner()
end