--[[
 Expected slot assignment/content:
 Slot 1: 64 Torches
 Slot 2: 1 Cobble (reserved for cobble compare)
 Slot 3: Enderchest
--]]

-- Parameters

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 enderDumpInterval = 100 -- Dump content into an enderchest every 100 blocks mined

-- Variables

local doProcessContent = false
local depth = 0
local collected = 0
local itemsToEnder = 0
local cobbleDumped = 0

-- Process commandline

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

-- Main 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 dumpCobble()
    for slot=3,16 do
        turtle.select(slot)
        local slotQuantity=turtle.getItemCount(slot)
        if slotQuantity > 0 then
            if turtle.compareTo(cobbleSlot) then
                cobbleDumped = cobbleDumped + slotQuantity
                turtle.drop()
            end
        end
    end
end
local function dropCobbleWhenNecessary()
    if math.fmod(collected,frequencyOfCobbleRemoval)==0 then
       dumpCobble()
    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 placeEnderChest()
    turtle.select(enderChestSlot)
    turtle.placeDown()
end
local function retrieveEnderChest()
    turtle.select(enderChestSlot)
    turtle.digDown()
end
local function processContent()
    if (turtle.getItemCount(enderChestSlot)==0) then
        print("No enderchest found in slot"..enderChestSlot.."!")
        return false
    end
    dumpCobble()
    placeEnderChest()
    for slot=3,16 do
        turtle.select(slot)
        local slotQuantity=turtle.getItemCount(slot)
        itemsToEnder = itemsToEnder + slotQuantity
        turtle.dropDown()
    end
    retrieveEnderChest()
end
local function DumpStatistics()
    print( "Statistics:")
    print( string.rep("=",20))
    print( "Mined "..collected.." blocks total." )
    print( "Discarded "..cobbleDumped.." pieces of cobble.")
    print( itemsToEnder.." items send to storage.")
    print( string.rep("=",20))
end
local function mine()
    print( "Tunneling..." )
    local rotation=0
    for m=1,width do
        for n=1,length-1 do
            tryDigUp()
            tryDigDown()
            if  doProcessContent and (math.fmod(collected+1,enderDumpInterval)==0) then
                processContent()
            end
            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()
    return true
end

if mine() then
    print( "Tunnel complete." )
else
    print( "Tunnel aborted prematurely.")
end