--[[
 Expected slot assignment/content

 Slot 1: 64 Torches
 Slot 2: 1 Cobble (reserved for cobble compare)
 Slot 3: Enderchest
--]]

--Variables

local torchSlot = 1                     -- Inventory slot of torches
local cobbleSlot = 2                    -- Inventory slot of atleast one cobble
local enderChestSlot = 3                -- Inventory slot of enderchest to be used for offloading
local frequencyOfCobbleRemoval = 30     -- Remove cobble every n blocks mined
local doProcessContent = false
local depth = 0
local collected = 0

-- Parameters

local tArgs = { ... }
if #tArgs < 2 then
    print( "Usage: Area <length> <width> [Process]" )
    print( "======================================" )
    print( "Process If true, content -> Enderchest")
    print( "")
    print( "Expected content in inventory of turtle:" )
    print( "Slot 1: Torches" )
    print( "Slot 2: Cobble (at least 1)")
    print( "Slot 3: Enderchest (only if Process=true)")
    return
end

local length = tonumber( tArgs[1] )
if length < 1 then
    print( "Area length must be 1+" )
    return
end

local width = 1

if #tArgs > 1 then
    width = tonumber( tArgs[2] )
    if width < 1 then
        print( "Area width must be 1+" )
        return
    end
    if #tArgs > 2 then
        doProcessContent = tArgs[3]:lower()=="true"
    end
end

local function checkSlot(slotNr,description)
   if turtle.getItemCount(slotNr)==0 then
      print("Expected item '"..description.."' in slot "..slotNr..".")
      return false
   end
   return true
end

-- Check slots

if not checkSlot(torchSlot,"torches") then return end
if not checkSlot(cobbleSlot,"cobbleStone (atleast 1)") then return end
if doProcessContent then
   if not checkSlot(enderChestSlot,"enderChest") then return end
end

-- Code

local function collect()

    collected = collected + 1
    if math.fmod(collected, 25) == 0 then
        print( "Mined "..collected.." items." )
    end
end
local function refuel()
    local fuelLevel = turtle.getFuelLevel()
    if fuelLevel == "unlimited" or fuelLevel > 0 then
        return
    end

    local function tryRefuel()
        for n=1,16 do
            if turtle.getItemCount(n) > 0 then
                turtle.select(n)
                if turtle.refuel(1) then
                    turtle.select(1)
                    return true
                end
            end
        end
        turtle.select(1)
        return false
    end

    if not tryRefuel() then
        print( "Add more fuel to continue." )
        while not tryRefuel() do
            sleep(1)
        end
        print( "Resuming Tunnel." )
    end
end
local function tryDig()
    while turtle.detect() do
        if turtle.dig() then
            collect()
            sleep(0.5)
        else
            return false
        end
    end
    return true
end
local function tryDigUp()
    while turtle.detectUp() do
        if turtle.digUp() then
            collect()
            sleep(0.5)
        else
            return false
        end
    end
    return true
end
local function tryDigDown()
 while turtle.detectDown() do
  if turtle.digDown() then
    collect()
    sleep(0.5)
 else
   return false
  end
 end
 return true
end
local function tryUp()
    refuel()
    while not turtle.up() do
        if turtle.detectUp() then
            if not tryDigUp() then
                return false
            end
        elseif turtle.attackUp() then
            collect()
        else
            sleep( 0.5 )
        end
    end
    return true
end
local function tryDown()
    refuel()
    while not turtle.down() do
        if turtle.detectDown() then
            if not tryDigDown() then
                return false
            end
        elseif turtle.attackDown() then
            collect()
        else
            sleep( 0.5 )
        end
    end
    return true
end
local function tryForward()

    refuel()
    while not turtle.forward() do
        if turtle.detect() then
            if not tryDig() then
                return false
            end
        elseif turtle.attack() then
            collect()
        else
            sleep( 0.5 )
        end
    end
    return true
end

local function dropCobbleWhenNecessary(x)
    if math.fmod(collected,frequencyOfCobbleRemoval)==0 then
        for n=3,16 do
            turtle.select(n)
            if turtle.compareTo(cobbleSlot) then
                turtle.drop()
            end
        end
    end
end
local function placeTorchWhenNecessary(x,y)
    if math.fmod(x,8)==1 and math.fmod(y,8)==1 then
        turtle.select(1)
        if (turtle.getItemCount(torchSlot)==0) then
            print("Out of torches, please resupply!")
            return false
        else
            turtle.placeDown()
        end
    end
    return true
end
local function processContent()
    if not doProcessContent then
       return
    end

    if (turtle.getItemCount(torchSlot)==0) then
        print("No enderchest found Out of torches, please resupply!")
        return false
    end

    -- place chest
    turtle.select(enderChestSlot)
    turtle.placeDown()
    --
    for slot=3,16 do
        turtle.select(n)
        if turtle.compareTo(cobbleSlot) then
            turtle.drop()
        else
            turtle.dropDown()
        end
    end
    --retrieve chest
    turtle.select(enderChestSlot)
    turtle.digDown()
end

local function mine()
    print( "Tunneling..." )
    local rotation=0
    for m=1,width do
        for n=1,length-1 do
            tryDigUp()
            tryDigDown()
            dropCobbleWhenNecessary(n)
            placeTorchWhenNecessary(n,m)
            tryDig()
            if not tryForward() then
                return false
            end
        end
        tryDigUp()
        tryDigDown()
        if m < width then
            if rotation==0 then
                turtle.turnRight()
            else
                turtle.turnLeft()
            end
            tryDig()
            if not tryForward() then
                return false
            end
            if rotation==0 then
                turtle.turnRight()
            else
                turtle.turnLeft()
            end
            rotation = 1 - rotation
        end
    end
    processContent()
end

if mine() then
    print( "Tunnel complete." )
else
    print( "Tunnel aborted prematurely.")
end
print( "Mined "..collected.." blocks total." )