3x3 Tunnel

--[[
    3x3
    By Coaster3000

    3x3 is licensed under the Creative Commons Attribution-ShareAlike 3.0 United States License.
    To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/us/.

    Extra Permissions: You can freely extract the api for turtle movement tracking. Do note...
    You are required to follow iNav's Licensing. As this part of code is based off of it.
    This is simply a remake of it.

-- Link: http://pastebin.com/3KHq3K2R
-- Maker of iNav dd4235
]]

local x,z,y = 0,0,0
local dir = 0

local count = 0

local function dig()
    while turtle.dig() do
        count = count + 1
        sleep(0.5)
    end
    return true
end
local function digUp()
    while turtle.digUp() do
        count = count + 1
        sleep(0.5)
    end
    return true
end
local function digDown()
    while turtle.digDown() do
        count = count + 1
        sleep(0.5)
    end
    return true
end

local function hasFuel( ammount )
    ammount = ammount or 1
    return turtle.getFuelLevel() >= ammount
end

local function refuel( ammount )
    ammount = ammount or (turtle.getFuelLevel() + 1)
    if turtle.getFuelLevel() > ammount then
        return true
    end
    for i=1,16 do
        turtle.select(i)
        while turtle.getItemCount(i) > 0 do
            if not turtle.refuel(0) then
                break
            end
            if hasFuel(ammount) then
                turtle.select(1)
                return true
            else
                turtle.refuel(1)
            end
        end
    end
    turtle.select(1)
    return false
end

local function forward()
    local good = turtle.forward()
    if good then
        if dir % 4 == 0 then x = x + 1 end
        if dir % 4 == 1 then z = z + 1 end
        if dir % 4 == 2 then x = x - 1 end
        if dir % 4 == 3 then z = z - 1 end
    end
    return good
end

local function back()
    local good = turtle.back()
    if good then
        if dir % 4 == 0 then x = x - 1 end
        if dir % 4 == 1 then z = z - 1 end
        if dir % 4 == 2 then x = x + 1 end
        if dir % 4 == 3 then z = z + 1 end
    end
    return good
end


local function turnRight()
    local good = turtle.turnRight()
    if good then
        dir = dir + 1
    end
    return good
end
local function turnAround()
    turnRight()
    turnRight()
end

local function turnLeft()
    local good = turtle.turnLeft()
    if good then
        dir = dir - 1
    end
    return good
end
local function up()
    local good = turtle.up()
    if good then
        y = y + 1
    end
    return good
end

local function down()
    local good = turtle.down()
    if good then
        y = y - 1
    end
    return good
end

length = nil
local args = {...}
lastx = 0

function resume()
    while (x < lastx) do
        if not forward() then
            break
        end
    end
end

if #args > 0 then
    length = tonumber(args[1]) or nil
    if #args > 1 then
        lastx = tonumber(args[2]) or 0
        resume()
    end
end

local function layer()
    turnLeft()
    dig()
    turnAround()
    dig()
    turnLeft()
end
fuelNeeded = 0

function checkLength()
    while not length do
        term.clear()
        term.setCursorPos(1, 1)
        write("Enter Length: ")
        local d = tonumber(read())
        if (d) and (d > 0) then
            length = d
        else
            print("Invalid Input... Please type a number...")
            sleep(3)
        end
    end
     fuelNeeded = 2 + length * 2 + (length * 4) -- Formula is expanded to show those not soo good at math what calculation is
     if lastx then
        fuelNeeded = fuelNeeded + (lastx * 2)
    end
    while not refuel(fuelNeeded) do
        term.clear()
        term.setCursorPos(1, 1)
        print("Turtle needs more fuel.")
        print(turtle.getFuelLevel().."/"..fuelNeeded)
        print("Press any key to continue refueling")
        os.pullEvent("key")
    end
end

function run()

    checkLength()
    for i=1,length do
        up()
        up()
        dig()
        forward()
        layer()
        -- Bottom Layer
        digDown()
        down()
        layer()
        -- Mid Layer
        digDown()
        down()
        layer()
    end
    lastx = x

    while x > 0 do
        while dir % 4 ~= 0 do
            turnRight()
        end
        back()
    end
    endscreen()
end


function endscreen()
    term.clear()
    term.setCursorPos(1, 1)
    print("Total Blocks Dug: "..count)
    print("Current Fuel Level: "..turtle.getFuelLevel())
    write("Resume? (Y/N): ")
    length = nil
    local b = read()
    if (b == "y") or (b =="Y") then
        checkLength()
        resume()
        run()
    else
        term.clear()
        term.setCursorPos(1, 1)
    end
end
checkLength()
if lastx then
    resume()
end
run()