Grid Dig

local y = 2
local z = 0
local i = 0
local bedrock = 0
local enderbox = 0
local fuelSlot = 0
local answer = "a"
local function update(strMessage)
    term.clear()
    term.setCursorPos(1,1)
    if strMessage then
        print(strMessage)
    end
end

update("Welcome to core driller!")
os.sleep(3)

repeat
    update("Do you have an Ender Chest in slot 16 to offload resources?")
    answer=read()
    answer=string.lower(answer)
until answer=="y" or answer=="n"
if answer=="y" then
    enderbox = 16
else
    enderbox = 0
end
repeat
    update("Do you have an Ender Chest for fuel in slot 15 for fuel?")
    answer=read()
    answer=string.lower(answer)
until answer=="y" or answer=="n"
if answer=="y" then
    fuelSlot = 15
else
    fuelSlot = 0
end
repeat
    update("Do you have a bucket for fuel in slot 15?")
    answer=read()
    answer=string.lower(answer)
until answer=="y" or answer=="n"
if answer=="y" then
    bucket = 15
else
    bucket = 0
end

turtle.select(1)
local function tf() bedrock = 0 while not turtle.forward() do turtle.attack() turtle.dig() turtle.digUp() RefuelDigger(fuelSlot) end end

local function fuel(slot)
    if slot == 0 then return end
    turtle.select(slot)
    if turtle.place() then
        if not turtle.refuel() then
            turtle.place()
        end
    end
    turtle.select(1)
end

local function loot()
    while turtle.suck() do
        FullStorage(enderbox)
    end
    while turtle.suckUp() do
        FullStorage(enderbox)
    end
    while turtle.suckDown() do
        FullStorage(enderbox)
    end
end

local function search()
    for i = 1, 4 do -- added wrapper loop
        local gooditem = true -- added because 4 checks
        for t = 1, 4 do
            turtle.select(t)
            if turtle.getItemCount(t) > 50 then
                turtle.drop(turtle.getItemCount(t)-1) -- added to discard trash
            end
            if not turtle.detect() or turtle.compare() then -- removed not
                gooditem = false --added
                fuel(bucket)
                break
            end
        end   --added
        if gooditem then --added
            if turtle.getSelectedSlot() ~= 1 then
                turtle.select(1) -- Always want the items to stack.
            end
            FullStorage(enderbox) -- check we have room 1st!
            while turtle.suck() do FullStorage(enderbox) end
            turtle.dig()
        end
        turtle.turnRight()
        end

end

local function td()
 bedrock = 0
  local canGoDown = true
while canGoDown do
  turtle.select(1) -- added so you don't fill inventory with junk.
  if not turtle.down() then
    RefuelDigger(fuelSlot)
    while turtle.suckDown() do FullStorage(enderbox) end
    if turtle.detectDown() and not turtle.digDown() then
      canGoDown = false
    else
    turtle.attackDown()
    end
  else
    bedrock = bedrock + 1
    FullStorage(enderbox)
    search() -- Simplify functionify so less clutter and we can read it.
  end
end -- End of top while loop

for z = 1, bedrock do  -- Added bedrock counter
  while not turtle.up() do --- added sanity check
    turtle.attackUp()
    turtle.select(1) -- always stack items before dig
    turtle.digUp()
    RefuelDigger(fuelSlot) -- Maybe we ran out of gas looping up 10000 blocks?
  end
end -- end of for loop
tf()
end -- end function

function RefuelDigger(nSlot)
if turtle.getFuelLevel() > 256 then
    return
end
if nSlot == 0 then
    if turtle.getFuelLevel() < 256 then
            for i=1,bedrock do
                    while not turtle.up() do --- added sanity check
                        turtle.attackUp()
                        turtle.select(1) -- always stack items before dig
                        turtle.digUp()
                    end
            end
            while turtle.getFuelLevel() < 4000 do
            update("Waiting for fuel...")
            if turtle.refuel() then
                print("Fuel Level " .. turtle.getFuelLevel())
            end
                    os.sleep(5)
            end
            for i=1,bedrock do
                    while not turtle.down() do
                            turtle.attackDown()
                            turtle.select(1)
                            turtle.digDown()
                    end
            end
    end
else
    FullStorage(enderbox)
    turtle.select(nSlot)
    if turtle.placeUp() then
        while turtle.getFuelLevel() < 1000 do
            turtle.suckUp()
            turtle.refuel()
            turtle.dropUp()
        end
        turtle.digUp()
    end
end
end

function FullStorage(nSlot)
update("Full check...")
if nSlot > 0 then
if turtle.getItemCount(nSlot-2) > 0 then
  turtle.select(nSlot)
  if turtle.placeUp() then
   for i = 5, nSlot-2 do
    turtle.select(i)
    turtle.dropUp()
   end
   turtle.select(nSlot)
   turtle.digUp()
  end
end
else
if turtle.getItemCount(16) > 0 then
    for i=1,bedrock do
        while not turtle.up() do --- added sanity check
            turtle.attackUp()
            turtle.select(1) -- always stack items before dig
            turtle.digUp()
        end
    end
    while turtle.getItemCount(16) > 0 do
        os.sleep(1)
    end
    for i=1,bedrock do
        while not turtle.down() do
            turtle.attackDown()
            turtle.select(1)
            turtle.digDown()
        end
    end
end
end
end

local tn = turtle.turnRight
local tCom = {tf,tf,tf,tf,td,tf,tf,tf,tf,td,tf,tf,tf,tf,td,tf,tf,tf,tf,td,tf,tf,tf,tf,td}

local function arrayShift(tMyArray)
for i=1,2 do
  table.insert(tMyArray,1,tMyArray[#tMyArray])
  table.remove(tMyArray,#tMyArray)
end
return tMyArray
end

local function myDoit(tArray,dir)
  if dir ~= 0 then
    for i=1,#tArray do
      tArray[i]()
    end
  else
      for i=#tArray,1, -1 do
        tArray[i]()
      end
  end
end

tf()
for i=1,26 do
  myDoit(tCom,i%2)
  tCom = arrayShift(tCom)
  if i%2 == 0 then
    tn = turtle.turnLeft
  else
    tn = turtle.turnRight
  end
  tn()
  tf()
  tn()
  tf()
end

function empty(nSlot)
update("Going to empty.")
  turtle.select(nSlot)
  if turtle.placeUp() then
   for i = 5, nSlot-2 do
    turtle.select(i)
    turtle.dropUp()
   end
   turtle.select(nSlot)
   turtle.digUp()
  end
turtle.select(1)
end
if enderbox > 0 then
  empty(enderbox)
end