local min_empty = 1         -- The least amount of free slots before inv is regarded as full

local FUEL  = 1
local TORCH = 2
local FREE  = 3

local torch_interval = 6
local torch_current = 1
local pos_total = 0
local pos_current = 0

term.clear()
term.setCursorPos(1, 1)

function torch()
    torching = true
    turtle.select(TORCH)
    turtle.turnLeft()
    turtle.place()
    turtle.turnRight()
    torching = false
end

function full_inv()
    if turtle.getItemCount(16) > 0 then
        return true
    end
end

function empty_inv()
	for i=FREE,16 do
		turtle.select(i)
		turtle.dropUp()
	end
end

function refuel()
    -- This beast is designed to run on coal
    if turtle.getFuelLevel() <= 20 then
        turtle.select(FUEL)
        return turtle.refuel(1)
    end
    return true
end

function mine_chunk()
	print("Mining chunk nr: ")
	print(pos_current)

	while turtle.detect() do
            turtle.dig()
        end
	turtle.forward()

	pos_current = pos_current + 1
	pos_total = pos_total + 1
	torch_current = torch_current + 1

	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.up()
	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.down()
	turtle.turnLeft()
	while turtle.detect() do
            turtle.dig()
        end
	turtle.forward()
	turtle.turnRight()

	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.up()
	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.down()
	turtle.turnLeft()
	while turtle.detect() do
            turtle.dig()
        end
	turtle.forward()
	turtle.turnRight()

	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.up()
	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.down()
	turtle.turnLeft()
	while turtle.detect() do
            turtle.dig()
        end
	turtle.forward()
	turtle.turnRight()

	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.up()
	while turtle.detectUp() do
            turtle.digUp()
        end
	turtle.down()

	turtle.turnRight()
	turtle.forward()
	turtle.forward()
	turtle.forward()
	turtle.turnLeft()

	print("Mined chunk nr: ")
	print(pos_current)
end

function return_and_empty()
	print("Emptying...")

	while pos_current ~= 0 do

	        turtle.back()
	        pos_current = pos_current - 1

	end

	empty_inv()

	while pos_current ~= pos_total do

	        turtle.forward()
	        pos_current = pos_current + 1

	end

	print("Emptied. Returning")
end

function main_loop()
        -- refuel()
	mine_chunk()

	if full_inv() == true then
	        return_and_empty()
	end

	if torch_current == torch_interval then
	        torch()
	        torch_current = 1
	end

	main_loop()
end

print("Starting the tunnel")
main_loop()