-- simple program for mining turtles to mine a 3x3 tunnel (as opposed to the default
-- tunnel app, which mines a 3x2)
-- adapted from user FutileFreedom's 3x3 "tunneler" program, posted on the ComputerCraft
-- forums: http://www.computercraft.info/forums2/index.php?/topic/3044-turtle-cc-14-3x3-tunnel/

-- ---------------- config options
-- specify the slot for chests to place for unloading items when the turtles
-- inventory gets full. Set to 0 to disable this feature altogether.
local CHEST_SLOT = 16

-- specify the slot for torches. Set to 0 to disable altogether.
local TORCH_SLOT = 15

-- if TORCH_SLOT is non-zero, then torches will be placed on the right wall of
-- the excavated tunnel every TORCH_STEP blocks
local TORCH_STEP = 6

-- if you're using an ender chest, set this to true
-- otherwise, provide a stack of chests in slot CHEST_SLOT and the turtle will
-- leave a trail of chests behind
local RECOLLECT_CHEST = false

-- how low our fuel level gets before we try to refuel off of anything in
-- our inv slots (except for CHEST_SLOT)
local REFUEL_LEVEL = 100

-- how long to wait between actions
local SLEEP_INT = 0.5

-- sometimes gravel that falls while the turtle is mining a top block gets missed
-- set this to true to snag that sneaky gravel, with the tradeoff that it adds a few
-- seconds to each layer/iteration
local GET_SNEAKY_GRAVEL = true


-- -------------- initialization
local tArgs = { ... }
if #tArgs ~= 1 then
    print( "Usage: tunnel3 <length>" )
    return
end

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

-- -------------- digging
local function oneeighty()
    turtle.turnLeft()
    turtle.turnLeft()
end

local collected = 0
local function collect()
    collected = collected + 1
    if math.fmod(collected, 25) == 0 then
        print( "Mined "..collected.." blocks." )
    end
    if math.fmod(collected, 300) == 0 then
        print( "Fuel level="..turtle.getFuelLevel())
    end
end

local function tryDig()
    while turtle.dig() do
        collect()
        sleep(SLEEP_INT)
        if not turtle.detect() then
            return true
        end
    end
    return not turtle.detect()
end

local function tryDigUp()
    while turtle.digUp() do
        collect()
        sleep(SLEEP_INT)
        if not turtle.detectUp() then
            return true
        end
    end
    return not turtle.detectUp()
end

-- --------------- fuel management
local function needToRefuel()
    return turtle.getFuelLevel() < REFUEL_LEVEL
end

local function doRefuel(amount, once)
    amount = amount or 10
    once = once or false
    for slot=1,16 do
        if slot ~= CHEST_SLOT then
            turtle.select(slot)
            if turtle.refuel(amount) and (turtle.getFuelLevel() > (REFUEL_LEVEL * 2) or once) then
                break
            end
        end
    end
    print("Refueling complete; new fuel level="..turtle.getFuelLevel())
    turtle.select(1)
end

-- -------------- inventory management
local function hasSpace()
    local space = 0
    for slot=1,16 do
        if slot ~= CHEST_SLOT and slot ~= TORCH_SLOT then
            space = space + turtle.getItemSpace(slot)
        end
    end
    if space < 32 then
        return false
    end
    return true
end

local function hasEmptySlots()
    local emptySlots = 0
    for slot=1,16 do
        if slot ~= CHEST_SLOT and slot ~= TORCH_SLOT then
            if turtle.getItemCount(slot) == 0 then
                emptySlots = emptySlots + turtle.getItemSpace(slot)
            end
        end
    end
    if emptySlots < 2 then
        return false
    end
    return true
end

local function unloadToChest(isComplete)
    isComplete = isComplete or false
    oneeighty()
    turtle.select(CHEST_SLOT)
    if not turtle.place() then
        print("Couldn't place chest! Not unloading current inventory..")
        return false
    end
    sleep(SLEEP_INT)
    for slot=1,16 do
        if slot ~= CHEST_SLOT and slot ~= TORCH_SLOT then
            turtle.select(slot)
            if not turtle.drop(turtle.getItemCount(slot)) then
                print("Couldn't drop off inventory - invalid target or target is full")
                return false
            end
        end
        sleep(SLEEP_INT)
    end
    if RECOLLECT_CHEST and not isComplete then
        turtle.select(CHEST_SLOT)
        turtle.dig()
    end
    turtle.select(1)
    oneeighty()
    return true
end

local function checkUnloadToChest()
    if CHEST_SLOT > 0 and (not hasSpace() or not hasEmptySlots()) then
        print("Inv space low - dumping to chest...")
        -- do a small refuel with anything we happen to have before we dump it
        doRefuel(5, true)
        unloadToChest()
        if not hasSpace() or not hasEmptySlots() then
            -- see if we weren't able to unload enough material to the chest
            print("Doh - still no inventory space; aborting! (Is the chest full?)")
            return false
        end
    end
    return true
end

-- ----------------- torches
local function checkPlaceTorch()
    -- if so configured, place a torch
    if TORCH_SLOT > 0 and steps % TORCH_STEP == 0 then
        turtle.select(TORCH_SLOT)
        if not turtle.place() then
            -- couldnt place it on the right; try on the left
            oneeighty()
            if not turtle.place() then
                print('Weird: couldnt place torch')
            end
            oneeighty()
        end
        if turtle.getItemCount(TORCH_SLOT) == 0 then
            print('Out of torches! Disabling torch placement')
            TORCH_SLOT = 0
        end
    end
end

-- ----------------- Main Program for digging the tunnel
local function tunnelize(tunnelLength)
    --[[
    -- Mine out a 3x3 tunnel for tunnelLength blocks:
    --   1 2 3
    -- A x x x
    -- B x x x
    -- C x S x
    -- ...assuming that the turtle starts in position S
    --]]
    print("Tunneling for "..tunnelLength.." blocks")
    steps = 0
    for n=0,length do
        turtle.select(1)
        if not checkUnloadToChest() then
            -- we were supposed to unload to a chest but
            -- couldnt for some reason ..so abort
            break
        end
        if needToRefuel() then
            print("Fuel low ("..turtle.getFuelLevel().."<"..REFUEL_LEVEL.."); refueling..")
            doRefuel()
        end
        -- C1
        turtle.turnLeft()
        tryDig()
        -- B2
        tryDigUp()
        turtle.up()
        -- B1
        tryDig()
        -- A2
        tryDigUp()
        turtle.up()
        -- A1
        tryDig()
        oneeighty()
        -- A3
        tryDig()
        while not turtle.down() do
            sleep(SLEEP_INT)
            turtle.digDown()
        end
        -- B3
        tryDig()
        while not turtle.down() do
            sleep(SLEEP_INT)
            turtle.digDown()
        end
        -- C3
        tryDig()
        checkPlaceTorch()
        turtle.turnLeft()

        if GET_SNEAKY_GRAVEL then
            -- check for gravel that we might have missed back at C1
            turtle.turnLeft()
            if turtle.detect() then
                tryDig()
            end
            -- start over
            turtle.turnRight()
        end

        -- done?
        if n == tunnelLength then
            -- call unloadToChest with isComplete=True so we leave the chest placed in the world
            if CHEST_SLOT > 0 then
                unloadToChest(true)
            end
            print("Tunnel complete")
            print("Blocks mined="..collected)
            print("Fuel level="..turtle.getFuelLevel())
            return
        end
        -- start the next layer
        tryDig()
        if not turtle.forward() then
            print("Aborting Tunnel!")
            break
        end
        steps = steps + 1
    end
end

tunnelize(length)