BuildWall

function isEmpty(i)
    if turtle.getItemCount(i)==0 then
        print("Empty")
        return true
    end
end

function shiftLeft()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnRight()
end

function shiftRight()
    turtle.turnRight()
    turtle.forward()
    turtle.turnLeft()
end

function widthCheck(a, b)
    if a == b then
        return true
    end
    return false
end

function shiftDirection(d)
    if d == "left" then
        shiftLeft()
    end
    if d == "right" then
        shiftRight()
    end
end

--Main

io.write("Enter Length: ")
height = tonumber(io.read())
io.write("Enter Width: ")
width = tonumber(io.read())
io.write("Direction- left or right: ")
direction = string.lower(io.read())

itemIndex = 1
turtle.select(itemIndex)
widthCount = 0

while true do
    for i=1, height-1 do
        if isEmpty(itemIndex) then
            itemIndex = itemIndex + 1
            turtle.select(itemIndex)
        end
        turtle.place()
        turtle.up()
    end
    if isEmpty(itemIndex) then
        itemIndex = itemIndex + 1
        turtle.select(itemIndex)
    end
    turtle.place()
    widthCount = widthCount+1
    if widthCheck(widthCount, width) then
        break
    end

    shiftDirection(direction)



    for i=1, height-1 do
        if isEmpty(itemIndex) then
            itemIndex = itemIndex + 1
            turtle.select(itemIndex)
        end
        turtle.place()
        turtle.down()
    end
    if isEmpty(itemIndex) then
        itemIndex = itemIndex + 1
        turtle.select(itemIndex)
    end
    turtle.place()
    widthCount = widthCount+1
    if widthCheck(widthCount, width) then
        break
    end
    shiftDirection(direction)

end

if (width%2) > 0 then
    for i=1, height do
        turtle.down()
    end
end