Roofer.lua

function Prepare(height)
    print("Positioning for Roofing...")
    for i=1,height do
        while not turtle.up() do
            turtle.digUp()
        end
    end
end

function Done()
    print("Finished roofing!")
    print("Fuel remaining:")
    print(turtle.getFuelLevel())
end

function ResetPosition(width,height)
    print("Moving back to starting position...")
    turtle.turnRight()
    for i=1,width do
        while not turtle.forward() do
            turtle.dig()
        end
    end
    for i=1,height do
        while not turtle.down() do
            turtle.digDown()
        end
    end
    turtle.turnLeft()
end

function NextLine()
    print("Preparing for next line...")
    turtle.turnRight()
    while not turtle.forward() do
        turtle.dig()
    end
    turtle.turnRight()
end

function TurnBack(length)
    print("Returning...")
    turtle.turnLeft()
    turtle.turnLeft()
    for i=1,length do
        while not turtle.forward() do
            turtle.dig()
        end
    end
end

function Roofing(length,width)
    print("building roof...")
    local stack = 0
    local itemIndex = 2

    turtle.select(itemIndex)
    for i=1,width do
        for e=1,length do
            if stack == 64 then
                itemIndex = itemIndex + 1
                turtle.select(itemIndex)
                stack = 0
            end
            if turtle.placeUp() then
                stack = stack + 1
            end
            while not turtle.forward() do
                turtle.dig()
            end
        end
        TurnBack(length)
        NextLine()
    end
end

function Start()
    local roof = RequestInput()

    if (CheckBuildLimit(roof)) then
        print("Area is too big!")
        return
    end
    Prepare(roof[3])
    Roofing(roof[1],roof[2])
    ResetPosition(roof[2],roof[3])
    Done()
end

function CheckBuildLimit(roof)
    if (roof[1] * roof[2]) + roof[3] > 64*15 then
        return true
    end
    return false
end

function RequestInput()
    io.write("Enter length of roof:")
    local length = io.read()
    io.write("Enter width of roof:")
    local width = io.read()
    io.write("Enter height of roof (Excluding turtle position):")
    local height = io.read()

    local roof = {tonumber(length),tonumber(width),tonumber(height)}

    return roof
end

Start()