Turtle GPS

Directions = {
    Forward = 0,
    Right = 1,
    Backwards = 2,
    Left = 3
}
local file_position = "saves/position"

Direction = Directions.Forward -- 0 the default moveForward direction (direction placed), 1 right, 2 back, 3 left
Local_x = 0
Local_y = 0
Local_z = 0

Auto_refuel = true

LastPos = {
    Local_x = 0,
    Local_y = 0,
    Local_z = 0,
    Direction = Directions.Forward
}

function SetLastPosition()
    if LastPos.Local_x == 0 and LastPos.Local_y == 0 and LastPos.Local_z == 0 then
        LastPos.Local_x = Local_x
        LastPos.Local_y = Local_y
        LastPos.Local_z = Local_z
        LastPos.Direction = Direction
    end
end

function MoveToLastPos(order)
    if LastPos.Local_x ~= 0 or LastPos.Local_y ~= 0 or LastPos.Local_z ~= 0 then

        moveTo(LastPos.Local_x, LastPos.Local_y, LastPos.Local_z, order)
        turnToDirection(LastPos.Direction)

        LastPos = {
            Local_x = 0,
            Local_y = 0,
            Local_z = 0,
            Direction = Directions.Forward
        }
    end
end

function moveForward()
    while not turtle.forward() do
        print("Obstructed. Couldn't move forward")
        turtle.attack()
        turtle.dig()
        CheckFuel()
    end

    if Direction == 0 then
        Local_x = Local_x + 1
    elseif Direction == 1 then
        Local_y = Local_y + 1
    elseif Direction == 2 then
        Local_x = Local_x - 1
    elseif Direction == 3 then
        Local_y = Local_y - 1
    end

    _persist_position()
end

function turnRight()
    turtle.turnRight()
    Direction = (Direction + 1) % 4
    _persist_position()
end
function turnLeft()
    turtle.turnLeft()
    Direction = (Direction + 3) % 4
    _persist_position()
end

function moveUp()
    while not turtle.up() do
        print("Obstructed. Couldn't move up")
        turtle.attackUp()
        turtle.digUp()
        CheckFuel()
    end
    Local_z = Local_z + 1
    _persist_position()
end
function moveDown()
    while not turtle.down() do
        print("Obstructed. Couldn't move down")
        turtle.attackDown()
        turtle.digDown()
        CheckFuel()
    end
    Local_z = Local_z - 1
    _persist_position()
end

function moveTo(x, y, z, order)
    for i = 1, string.len(order) do
        char = string.sub(order, i, i)

        if char == "x" then
            moveToX(x)
        elseif char == "y" then
            moveToY(y)
        elseif char == "z" then
            moveToZ(z)
        end
    end
end

function moveToX(x)
    while Local_x ~= x do
        if Local_x > x then
            turnToDirection(Directions.Backwards)
            moveForward()
        else
            turnToDirection(Directions.Forward)
            moveForward()
        end
    end
end

function moveToY(y)
    while Local_y ~= y do
        if Local_y > y then
            turnToDirection(Directions.Left)
            moveForward()
        else
            turnToDirection(Directions.Right)
            moveForward()
        end
    end
end

function moveToZ(z)
    while Local_z ~= z do
        if Local_z > z then
            moveDown()
        else
            moveUp()
        end
    end
end


function turnToDirection(direction)
    if Direction == direction then
        return
    elseif (Direction + 1) % 4 == direction then
        turnRight()
    elseif (Direction + 3) % 4 == direction then
        turnLeft()
    else
        turnRight()
        turnRight()
    end
end

function CheckFuel()
    if turtle.getFuelLevel() == 0 and Auto_refuel then
        print("Out of fuel. Feed me!")
        while turtle.getFuelLevel() == 0 do
            for i = 5, 15 do
                if turtle.getItemCount(i) > 0 then
                    turtle.select(i)
                    turtle.refuel()
                end
            end
            sleep(5)
        end
    end
end

function _persist_position()
    position = {
        Local_x = Local_x,
        Local_y = Local_y,
        Local_z = Local_z,
        Direction = Direction,
        LastPos = LastPos,
        Auto_refuel = Auto_refuel
    }

    save_data(file_position, position)
end

function read_position()
    position = read_data(file_position)

    if position ~= nil then
        if position.Local_x ~= nil then
            Local_x = position.Local_x
        end
        if position.Local_y ~= nil then
            Local_y = position.Local_y
        end
        if position.Local_z ~= nil then
            Local_z = position.Local_z
        end
        if position.Direction ~= nil then
            Direction = position.Direction
        end
        if position.LastPos ~= nil then
            LastPos = position.LastPos
        end
        if position.Auto_refuel ~= nil then
            Auto_refuel = position.Auto_refuel
        end
    end
end

function save_data(filename, obj)
    file = io.open(filename, "w")
    file:write(textutils.serialise(obj, { compact = true }))

    file:close()
end

function read_data(filename)
    file = io.open(filename, "r")
    obj = {}

    if file ~= nil then
        obj = textutils.unserialise(file:read())

        file:close()
    end

    return obj
end