-- Active slaves which will activate an engine next to it (to get content of a chest)
-- Slaves should be aligned with the master
-- It leaks at the moment (because engines have a cool down and pipes are slow)

-- Possible other (simpler) slave: use the turtle as a chest and put it next to a diamond pipe
-- (this requires more diamond, but less redstone engines/chests and probably wont leak)


local args = { ... }
local threshold = 5

local function count_total()
	local c = 0
	for i = 1, 9 do c = c + turtle.getItemCount(i) end
	return c
end

local function count_space()
	local c = 0
	for i = 1, 9 do c = c + turtle.getItemSpace(i) end
	return c
end

rednet.open("right")
while true do
	-- we are using wireless to get the distance
	-- so the master should be aligned with the slaves
	local id, mess, dist = rednet.receive(1)
	if mess == args[1] then
		if count_total() < threshold then
			rednet.send(id, "empty")
		else
			rednet.send(id, "ack")

			-- Wait for the pipes to be empty (and not leak)
			-- TODO: find out magic value to wait...
			rs.setOutput("left", false)
			sleep(2)

			-- GO!!!
			turtle.up()
			for i = 1, dist do turtle.forward() end

			print("I will leave again in 5 seconds...")
			sleep(5)
			print("Bye!")

			for i = 1, dist do turtle.back() end
			turtle.down()
			rednet.send(id, "return")
			print("Back home :)")
		end
	end

	-- This will power the engine next to the turtle
	-- We don't want to fill if we're full
	-- NOTE: we can't use the side of the modem...
	if count_space() > threshold then
		rs.setOutput("left", true)
	else
		rs.setOutput("left", false)
	end
end