[CC] lavaElevator (rewritten)

--[[
--
-- There are config variables below.
--
-- Modified to use a file to
-- 'remember' what action it was doing
-- when the world stopped existing.
--
-- Fair warning, I have not tested
-- this code.
--
-- Also, you should really make things
-- local, it keeps the computer global
-- memory cleaner.
--
-- 39 characters are not enough width.
-- http://computercraft.info/wiki/Resolution#Turtle_resolution
--
-- I've practically rewritten this
-- entirely, feel free to not use it
-- because of this.
--
-- If you need me to explain the code
-- then feel free to ask me to do so.
--
-- Lupus590
--
-- P.S. I'm part way through this
-- rewrite and I'm realising that I
-- may be doing a lot of tricks which
-- you may not know about, I've tried
-- my best to comment regularly.
--
-- P.P.S. You have some odd logic.
--
-- ]]
--[[ multi line comment
I've done it oddly above as I believe
ComputerCraft reacts funny.
It might only be the syntax highlighter
that goes funny, which this would
demonstrate if on an advanced system. ]]



------------
-- Config --
------------

local targetFuelLevel = 1000
  -- turtle will try to keep at this fuel level by using lava
  -- increase if turtle runs out of fuel and has no lava
  -- decrease if it keeps drinking it all

local stateFileName = "lavaElelvatorState"

----------
-- Code --
----------

local currentState
local state = {}
state.descend = "descend"
state.goToLava = "goToLava"
state.getLava = "getLava"
state.goToShaftBottom = "goToShaftBottom"
state.ascend = "ascend"
state.giveLava = "giveLava"
local action = {} -- corresponds to the states above
action.descend
action.goToLava
action.getLava
action.goToShaftBottom
action.ascend
action.giveLava


local function findResumeActions() -- figures out what the turtle was doing before chunk unload so that the turtle can continue efficiently
  -- print("Running findResumeActions...")

  -- resume sequence { action.descend, action.goToLava, action.getLava, action.goToShaftBottom, action.ascend,  action.giveLava}

  if fs.exists(stateFileName) then
    local stateFile = fs.open(stateFileName, "r")
    currentState = stateFile.readLine()
    stateFile.close()
    if currentState == state.descend then
      return "continue" -- default actions are fine

    elseif currentState == state.goToLava then
      return {action.goToLava, action.getLava, action.goToShaftBottom, action.ascend, action.giveLava}

    elseif currentState == state.getLava then
      return {action.getLava, action.goToShaftBottom, action.ascend, action.giveLava}

    elseif currentState == state.goToShaftBottom then
      return {action.goToShaftBottom, action.ascend, action.giveLava}

    elseif currentState == state.ascend then
      return {action.ascend, action.giveLava}

    elseif currentState == state.givLava then
      return {action.giveLava}

    else
      error("Unexpected value in file: "..stateFileName)
    end
  end


  print("Could not find file: "..stateFileName)
  print("Assistance required to start")
  print("Please place turtle to the shaft bottom and then restart this program")
  print("If the turtle is already there then type in 'Y', any other input will quit this program")

  if string.lower(read()) == "y" then
    return "continue"
  else
    return "quit"
  end
end

local function saveState(state)
  local stateFile = fs.open(stateFileName, "w")
  stateFile.writeLine(state) -- could error here if for some reason the file can't be opened
  stateFile.close()
  --print("state saved")
end

local function selectEmptySlot()
  for i = 1, 16 do
    turtle.select(i)
    if turtle.getItemCount() == 0 then
      return true
     end
  end
  return false -- could not find an empty slot
end

local function checkFuel() -- true = lava used
  local currentSlot = 1
  local drank = false
  while turtle.getFuelLevel < targetFuelLevel do
    turtle.select(currentSlot)
    if not turtle.refuel(1) then -- if we can't refuel from it
      if currentSlot ~= 16 then
        currentSlot = currentSlot + 1 -- select the next slot
      else
        break -- exit the while loop as we have ran out of slots to try to refuel from
      end
    else
      drank = true -- we refuelled from something
    end
  end
  return drank
end

function action.descend()
  --print("Running action.descend...")
  saveState(state.descending)
  while turtle.down() do -- if we can go down then we do, otherwise we must be at the bottom
    -- would check fuel but no lava on board so we are stuck anyway
  end
end


function action.goToLava()
  --print("Running action.goToLava...")
  saveState(state.goToLava)
  while turtle.forward() do
    -- would check fuel but no lava on board so we are stuck anyway
  end
end


function action.getLava()
  --print("Running action.getLava...")
  saveState(state.getLava)
  -- drop off empty buckets
  for i = 1,16 do
    turtle.select(i)
    local _, item = turtle.getItemDetail()
    if item.name = "minecraft:bucket" then
      turtle.drop()
    end
  end

  -- pick up full buckets
  while selectEmptySlot() do
    turtle.suck()

    -- check that the item we got is not an empty bucket
    local _, item = turtle.getItemDetail()
    if item.name = "minecraft:bucket" then
      turtle.drop() -- if it is an empty bucket, put it back
      sleep(10) -- sleep a bit so the other turtle has time to fill the bucket
    end

    -- let's check our fuel while we have lava near us
    if checkFuel() then
      -- we just refuelled, may as well replace the empty bucket/s while we are here
      return action.getLava() -- trick: by returning we don't use another 'slot' on the function stack
    end
  end
end


function action.goToShaftBottom()
  --print("Running action.goToShaftBottom...")
  saveState(state.goToShaftBottom)
  checkFuel()
  while turtle.back() do
    checkFuel() -- have lava, don't want to get stuck
  end
end


function action.ascend()
  --print("Running action.ascend...")
  saveState(state.ascend)

  local _, blockInFront = turtle.inspect()
  local foundChest = blockInFront == "minecraft:chest" -- this should work
  while not foundChest do
    checkFuel()
    turtle.up()
    _, blockInFront = turtle.inspect() -- reusing the old variables
    foundChest = blockInFront == "minecraft:chest"
  end
end

function action.giveLava()
 --print("Running action.giveLava...")
  saveState(state.giveLava)

  checkFuel() -- just before we do, lets be a selfish turtle

  -- drop off full buckets
  for i = 1,16 do
    turtle.select(i)
    local _, item = turtle.getItemDetail()
    if item.name = "minecraft:lava_bucket" then
      turtle.drop()
    end
  end

  -- pick up empty buckets
  while selectEmptySlot() do
    turtle.suck()
    -- check that the item we got is not a full bucket
    local _, item = turtle.getItemDetail()
    if item.name = "minecraft:lava_bucket" then
      turtle.drop() -- if it is a full bucket, put it back
      sleep(10) -- sleep a bit so the quarry has time to drink
    end
  end
end


------------------
-- Main Program --
------------------


local resumeActions = findResumeActions() -- returns a table (usually)
if type(resumeActions) == "table" and #resumeActions > 0 then -- is it a table and does it have stuff in
  for _,v in ipairs(resumeActions) do -- go through each key in the table and put the value in v
    v() -- the value should be a function, run it. If it ends up not being a function the script will error here
  end
elseif type(resumeActions) == "string"
  if resumeActions == "quit" then
    return
  elseif resumeActions == "continue" then
    -- continue to while true loop
  else
    error("Unexpected string from findResumeActions")
  end
else
  error("Unexpected return value from findResumeActions")
end

while true do
  action.descend()
  action.goToLava()
  action.getLava()
  action.goToShaftBottom()
  action.ascend()
  action.goToQuarry()
  action.giveLava()
  action.goToShaftTop()
end