ReplaceBlock

function isEmpty(i)
    if turtle.getItemCount(i)==0 then
        print("Slot empty. Changing Slot")
        return true
    else
        return false
    end
end

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

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

function checkFront()
    if turtle.detect() then
        turtle.dig()
    end
end

function compareDown(i)
    turtle.select(16)
    if turtle.compareDown() then
        turtle.select(i)
        return true
    else
        turtle.select(i)
        return false
    end
end

function digDown()
    turtle.digDown()
end

function dig()
    turtle.dig()
end

function placeDown()
    turtle.placeDown()
end


--Main


io.write("Enter Length: ")
length = tonumber(io.read())
io.write("Enter Width: ")
width = tonumber(io.read())


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

while true do
    for l=1, (length) do
        if (compareDown(itemIndex)~=true) then
            digDown()
            if isEmpty(itemIndex) then
                itemIndex = itemIndex+1
                turtle.select(itemIndex)
            end
            placeDown()
        end
        checkFront()
        turtle.forward()
        if (compareDown(itemIndex)~=true) then
            digDown()
            if isEmpty(itemIndex) then
                itemIndex = itemIndex+1
                turtle.select(itemIndex)
            end
            placeDown()
        end
    end

    widthCount = widthCount+1
    if widthCount==width then
        break
    end

    shiftRight()

    for l=1, (length) do
        if (compareDown(itemIndex)~=true) then
            digDown()
            if isEmpty(itemIndex) then
                itemIndex = itemIndex+1
                turtle.select(itemIndex)
            end
            placeDown()
        end
        checkFront()
        turtle.forward()
        if (compareDown(itemIndex)~=true) then
            digDown()
            if isEmpty(itemIndex) then
                itemIndex = itemIndex+1
                turtle.select(itemIndex)
            end
            placeDown()
        end
    end

    widthCount = widthCount+1
    if widthCount==width then
        break
    end

    shiftLeft()
end

if (width%2)~=0 then
    for i=1, length do
        turtle.back()
    end
end



--[[
function isEmpty(i)
    if turtle.getItemCount(i)==1 then
        print("Empty")
        return true
    end
end

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

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

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



--Main

io.write("Enter Length: ")
length = tonumber(io.read())
io.write("Enter Width: ")
width = tonumber(io.read())


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

while true do
    for l=1, length do
        if turtle.detect() then
            turtle.dig()
        end
        if (turtle.compareDown() == false) then
            turtle.digDown()
            if isEmpty(itemIndex) then
                itemIndex = itemIndex + 1
                turtle.select(itemIndex)
            end
            turtle.placeDown()
        end
    end
    widthCount = widthCount+1
    if widthCheck(widthCount, width) then
        break
    end
    shiftRight()



    for l=1, length do
        if turtle.detect() then
            turtle.dig()
        end
        if (turtle.compareDown() == false) then
            turtle.digDown()
            if isEmpty(itemIndex) then
                itemIndex = itemIndex + 1
                turtle.select(itemIndex)
            end
            turtle.placeDown()
        end
    end
    widthCount = widthCount+1
    if widthCheck(widthCount, width) then
        break
    end
    shiftLeft()
end

if (width%2) > 0 then
    for i=1, length do
        turtle.back()
    end
end
--]]