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

-- Mine in a quarry pattern until we hit something we can't dig
local length = tonumber( tArgs[1] )
if length < 1 then
        print( "Tunnel length must be positive" )
        return
end

local depth = 0
local collected = 0

local function tryPlaceTorch()
  turtle.select(2)
  turtle.place()
end


local function collect()
        collected = collected + 1
        if math.fmod(collected, 25) == 0 then
                print( "Mined "..collected.." items." )
        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 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 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

print( "Tunnelling..." )

for n=1,length do
	tryForward()
        tryDigUp()
 	 if n % 5 == 0 then
   		turtle.turnLeft()
		turtle.turnLeft()
		tryPlaceTorch()
		turtle.turnLeft()
		turtle.turnLeft()
	end
  		   
end


print( "Returning to start..." )

-- Return to where we started
tryUp()
turtle.turnLeft()
turtle.turnLeft()
while length > 0 do
        if tryForward() then
                length = length - 1
        else
                turtle.dig()
        end
end
turtle.turnRight()
turtle.turnRight()
tryDown()

print( "Tunnel complete." )
print( "Mined "..collected.." items total." )