xDir = 1
yDir = 0
w = 0
x = 0
y = 0
z = 0
n = 1

for i=1, 65 do
    turtle.digDown()
    turtle.down()
    z=z-1
end

function dig()
    while turtle.detect() do
        turtle.dig()
        sleep(1)
    end
end


function changeDirR()
    if xDir == 1 then
        xDir = 0
        yDir = -1
    end
    if xDir == -1 then
        xDir = 0
        yDir = 1
    end
    if yDir == 1 then
        xDir = 1
        yDir = 0
    end
    if yDir == -1 then
        xDir = -1
        yDir = 0
    end
end

function changePos()
    if xDir == 1 then
        x = x+1
    end
    if xDir == -1 then
        x = x-1
    end
    if yDir == 1 then
        y = y+1
    end
    if yDir == -1 then
        y = y-1
    end
end


function turn()
    turtle.turnRight()
    turtle.turnRight()
end

function goup()
    for h1=1, -z do
        turtle.digup()
        turtle.up()
    end
    unload()
    charge()
    returnDiggin()
end

function godown()
    for h2=1, -z do
        turtle.digdown()
        turtle.down()
    end

    function gox()
        for g1=1, x do
            dig()
            turtle.forward()
        end
    end

    function goy()
        for g2=1, y do
            dig()
            turtle.forward()
        end
    end

    function gonegx()
        for g3=1, -x do
            dig()
            turtle.forward()
        end
    end

    function gonegy()
        for g4=1, -y do
            dig()
            turtle.forward()
        end
    end

    function goToCorner()
        for bn=1, w do
            turtle.forward()
        end
        turn()
        routine()
    end

    function routine()
        while turtle.getItemCount(16) < 1 do
            w = 0
            for p=1, 2 do
                for u=1, n do
                    while turtle.detect() do
                        turtle.dig()
                        sleep(1)
                    end
                    turtle.forward()
                    changePos()
                    w = w+1
                    if enoughFuel() == true then
                        for s=1, 12 do
                            turtle.digUp()
                            turtle.up()
                        end
                        for t=1, 12, 1 do
                            turtle.digDown()
                            turtle.down()
                        end
                    else
                        returnToSurface()
                    end
                end
                turtle.turnRight()
                changeDirR()
            end
            n=n+1
        end
        returnToSurface()
    end


    function returntosurface()
        if xdir==1 then
            turtle.turnRight()
            goy()
            if x<=0 then
                turtle.turnLeft()
                gonegx()
            else
                turtle.turnright()
                gox()
                turn()
            end
        end
        if xdir==-1 then
            turtle.turnRight()
            gonegy()
            if x<=0 then
                turtle.turnRight()
                gonegx()
            else
                turtle.turnLeft()
                gox()
                turn()
            end
        end
        if ydir==1 then
            turtle.turnRight()
            gonegx()
            if y<=0 then
                turtle.turnLeft()
                gonegy()
                turtle.turnright()
            else
                turtle.turnright()
                goy()
                turtle.turnleft()
            end
        end
        if ydir==-1 then
            turtle.turnRight()
            gox()
            if y<=0 then
                turtle.turnRight()
                gonegy()
                turtle.turnright()
            else
                turtle.turnleft()
                goy()
                turtle.turnleft()
            end
        end
        goup()
    end


    function enoughFuel()
        if xDir == 1 or xDir == -1 then
            if x >= 0 then
                if turtle.getFuelLevel() > x+y-z+30 then
                    return 1
                end
            end
            if x < 0 then
                if turtle.getFuelLevel() > -x+y-z+30 then
                    return 1
                end
            end
        end
        if yDir == 1 or yDir == -1 then
            if y >= 0 then
                if turtle.getFuelLevel() > x+y-z+30 then
                    return 1
                end
            end
            if y < 0 then
                if turtle.getFuelLevel() > x-y-z+30 then
                    return 1
                end
            end
        end
        return nil
    end

    function unload()
        for q=1, 16 do
            local itemCount = turtle.getItemCount(q)
            if itemCount > 0 then
                turtle.select(q)
                turtle.drop()
            end
        end
        turtle.select(1)
    end

    function returnDiggin()
        godown()
        if yDir ~= 0 then
            if x >= 0 then
                gox()
                if y > 0 then
                    turtle.turnLeft()
                    goy()
                end
                if y <= 0 then
                    turtle.turnRight()
                    gonegy()
                    turn()
                end
            end
            if x < 0 then
                turn()
                gonegx()
                if y >= 0 then
                    turtle.turnRight()
                    goy()
                    turn()
                end
                if y < 0 then
                    turtle.turnLeft()
                    gonegy()
                end
            end
        end
        if xDir ~= 0 then
            if y >= 0 then
                turtle.turnLeft()
                goy()
                if x >= 0 then
                    turtle.turnRight()
                    gox()
                    turn()
                end
                if x < 0 then
                    turtle.turnLeft()
                    gonegx()
                end
            end
            if y < 0 then
                turtle.turnRigt()
                gonegy()
                if x > 0 then
                    turtle.turnLeft()
                    gox()
                end
                if x < 0 then
                    turtle.turnRight()
                    gonegx()
                end
                turn()
            end
        end
    end
    goToCorner()
end


function charge()
    print ("Out of Fuel!")
end

routine()