t

x = 0
y = 0
z = 0
dir = 0

-- check fuel
function fuel()
    if turtle.getFuelLevel() <= 100 then
        turtle.select(16)
        turtle.refuel(1)
        print("Refueled. Fuel level is :".. turtle.getFuelLevel())
    end
end

-- up
function up()
    fuel()
    if turtle.up() then
        return true
    end
    return false
end

-- down
function dn()
    fuel()
    if turtle.down() then
        return true
    end
    return false
end

-- turnLeft
function lt()
    if turtle.turnLeft() then
        dir = dir - 1
        if dir < 0 then
            dir = 3
        end
        return true
    end
    return false
end

-- turnRight
function rt()
    if turtle.turnRight() then
        dir = dir + 1
        if dir > 3 then
            dir = 0
        end
        return true
    end
    return false
end

-- forward
function fd()
    fuel()
    if turtle.forward() then
        changePos("fd")
        return true
    end
    return false
end

-- back
function bk()
    fuel()
    if turtle.back() then
        changePos("bk")
        return true
    end
    return false
end

-- get location by gps
function gpsUpdate()
    x, y, z = gps.locate(5)
    if x == nil then
        return false
    end
    return true
end

-- direction
function checkDir()
    turtle.forward()
    turtle.forward()
    cx, cy, cz = gps.locate(1)
    if (x - cx) == 2 then
        print("W")
        dir = 3
    end

    if (z - cz) == 2 then
        print("N")
        dir = 0
    end

    if (x - cx) == -2 then
        print("E")
        dir = 1
    end

    if (z - cz) == -2 then
        print("S")
        dir = 2
    end

    turtle.back()
    turtle.back()
end

function getDir()
    print(dir)
end

-- change pos
function changePos(command)
    if command == "fd" then
        if dir == 0 then
            z = z - 1
        end
        if dir == 1 then
            x = x + 1
        end
        if dir == 2 then
            z = z + 1
        end
        if dir == 3 then
            x = x - 1
        end
    end

    if command == "bk" then
        if dir == 0 then
            z = z + 1
        end
        if dir == 1 then
            x = x - 1
        end
        if dir == 2 then
            z = z - 1
        end
        if dir == 3 then
            x = x + 1
        end
    end
end

-- get positions
function getPos()
    print(x..","..y..","..z)
end