Build Rectangle V0.1

--Build Rectangle V0.1 by QQII
--Declerations
local Arguments = { ... }       --Program arguments
local length = tonumber(Arguments[1]) or 0
local width = tonumber(Arguments[2]) or length

--Functions
local function refuel()
    while turtle.getFuelLevel() <= 0 do
        shell.run("refuel", "all")
        if turtle.getFuelLevel() <= 0 then
            print("ERROR: out of fuel")
            read()
        end
    end
    turtle.select(1)
end

local function forward()        --Moves forward
    refuel()
    while not turtle.forward() do
        if not turtle.dig() then
            turtle.attack()
        end
    end
end

local function inventory_sort()     --Fills the first slot with items from the other slots
    for i = 2, 16 do
        if turtle.getItemSpace(1) == 0 then
            break
        end
        turtle.select(i)
        turtle.transferTo(1, turtle.getItemCount(i))
    end
    turtle.select(1)
end

local function place_down()     --Places a block below the turtle
    while not turtle.detectDown() do
        while not turtle.placeDown() do
            inventory_sort()
            if turtle.getItemCount(1) == 0 then
                print("ERROR: out of items")
                read()
            end
        end
    end
end

local function line(l)          --Places a line of size l
    for i = 2, l do
        place_down()
        forward()
    end
    place_down()
end

--User Inputs
print("The turtle will build a rectangle")
if length <= 0 then
    io.write("Length: ")
    while length <= 0 do
        length = tonumber(read())
    end
else
    print("Length: " .. length)
end
if  width <= 0 then
    io.write("Width: ")
    while width <= 0 do
        width = tonumber(read())
    end
else
    print("Width: " .. width)
end

--Main Script
refuel()
for i = 2, width do
    line(length)
    if i % 2 ~= 0 then
        turtle.turnLeft()
        forward()
        turtle.turnLeft()
    elseif i % 2 == 0 then
        turtle.turnRight()
        forward()
        turtle.turnRight()
    end
end
line(length)