os.loadAPI("/apis/storage")
os.loadAPI("/apis/position")
local db = storage
position.hook()

local t = turtle

function invFull ()
  for i = 2, 16 do
    if 0 == t.getItemCount(i) then
      return false
    end
  end
  return true
end

function face (dir)
  local F = position.get.F;
  ({
    function () end,
    t.turnLeft,
    function ()
      t.turnRight()
      t.turnRight()
    end,
    t.turnRight
  })[(F() + 4 - dir) % 4 + 1]()
end

local function goto (axis, N)
  local get = position.get
  if get[axis]() == N then return end
  local f
  if "Y" == axis then
    f = ({ [1] = t.up, [2] = t.down })
      [get[axis]() < N and 1 or 2]
  else
    face(({ ["X"] = {3, 1}, ["Z"] = {0, 2} })
      [axis][get[axis]() < N and 1 or 2])
    f = t.forward
  end
  repeat f() until get[axis]() == N
end

function goHome ()
  print("going home")
  goto("Y", 0)
  goto("X", 0)
  goto("Z", 0)
end

local bookmark = {}
for i, v in ipairs({
  "X", "Y", "Z", "F"
}) do
  bookmark[v] = (
    db.get("bookmark/"..v) or 0
  ) - 0
end

local function resume ()
  print("resuming")
  local get = position.get
  goto("Z", bookmark.Z)
  goto("X", bookmark.X)
  goto("Y", bookmark.Y)
  face(bookmark.F)
  db.clear("bookmark")
end

local function pause ()
  db.create("bookmark")
  for _, axis in ipairs({
    "X", "Y", "Z", "F"
  }) do
    bookmark[axis] = position.get[axis]()
    db.set("bookmark/"..axis, bookmark[axis])
  end
end

function emptyInv ()
  for i = 2, 16 do
    if 0 < t.getItemCount(i) then
      t.select(i)
      if not t.dropUp() then
        print("dropoff full, waiting...")
        repeat sleep(1) until t.dropUp()
      end
    end
  end
  t.select(1)
end

function refuel ()
  local fuelLevel = t.getFuelLevel()
  local fuelValue, softLimit
  for i = 2, 16 do
    t.select(i)
    if t.refuel(1) then
      fuelValue = t.getFuelLevel() - fuelLevel
      softLimit = t.getFuelLimit() - fuelValue
      repeat t.refuel(1)
      until t.getFuelLevel() > softLimit
        or 0 == t.getItemCount()
      if t.getFuelLevel() > softLimit then break end
    end
  end
  t.select(1)
  if softLimit and t.getFuelLevel() > softLimit then
    print("Refueling complete. Please take any leftover fuel back.")
    return true
  end
  return false
end

function sane_p2 (op)
  goHome()
  emptyInv()
  if 0 == t.getItemCount(1) then
    print("need torches")
    repeat sleep(1)
    until 0 < t.getItemCount(1)
  end
  if 400 > t.getFuelLevel() then
    print("need fuel")
    repeat sleep(1)
    until refuel()
  end
  storage.clear("autohome")
  resume()
  t.forward()
end

function sane (op)
  if 0 == t.getItemCount(1)
    or invFull() then
    storage.set("autohome", true)
    t.back()
    pause()
    sane_p2()
  end
  return (turtle.sane or turtle)[op]()
end

function dig ()
  return sane("dig")
end

function digUp ()
  return sane("digUp")
end

function digDown ()
  return sane("digDown")
end

function hook ()
  if t.sane then return false end
  t.sane = {}
  for _, f in ipairs({
    "dig", "digUp", "digDown"
  }) do
    t.sane[f] = t[f]
    t[f] = function ()
      return sane(f)
    end
  end
end

if storage.get("autohome") then
  sane_p2()
end

if storage.get("bookmark") then
  resume()
end

--]]