local has_monitoring_mod = minetest.get_modpath("monitoring")

local switches = {} -- pos_hash -> { time = time_us }

local function get_switch_data(pos)
	local hash = minetest.hash_node_position(pos)
	local switch = switches[hash]

	if not switch then
		switch = {
			time = 0,
			skip = 0
		}
		switches[hash] = switch
	end

	return switch
end

local active_switching_stations_metric, switching_stations_usage_metric

if has_monitoring_mod then
	active_switching_stations_metric = monitoring.gauge(
		"technic_active_switching_stations",
		"Number of active switching stations"
	)

	switching_stations_usage_metric = monitoring.counter(
		"technic_switching_stations_usage",
		"usage in microseconds cpu time"
	)
end

-- collect all active switching stations
minetest.register_abm({
	nodenames = {"technic:switching_station"},
	label = "Switching Station",
	interval   = 1,
	chance     = 1,
	action = function(pos)
		local switch = get_switch_data(pos)
		switch.time = minetest.get_us_time()
	end
})


-- the interval between technic_run calls
local technic_run_interval = 1.0

-- iterate over all collected switching stations and execute the technic_run function
local timer = 0
minetest.register_globalstep(function(dtime)
	timer = timer + dtime
	if timer < technic_run_interval then
		return
	end
	timer = 0

	local max_lag = technic.get_max_lag()
	-- slow down technic execution if the lag is higher than usual
	if max_lag > 5.0 then
		technic_run_interval = 5.0
	elseif max_lag > 2.0 then
			technic_run_interval = 4.0
	elseif max_lag > 1.5 then
			technic_run_interval = 3.0
	elseif max_lag > 1.0 then
			technic_run_interval = 1.5
	else
		-- normal run_interval
		technic_run_interval = 1.0
	end

	local now = minetest.get_us_time()

	local off_delay_seconds = tonumber(minetest.settings:get("technic.switch.off_delay_seconds") or "1800")
	local off_delay_micros = off_delay_seconds*1000*1000

	local active_switches = 0

	for hash, switch in pairs(switches) do
		local pos = minetest.get_position_from_hash(hash)
		local diff = now - switch.time

		minetest.get_voxel_manip(pos, pos)
		local node = minetest.get_node(pos)

		if node.name ~= "technic:switching_station" then
			-- station vanished
			switches[hash] = nil

		elseif diff < off_delay_micros then
			-- station active
			active_switches = active_switches + 1

			if switch.skip < 1 then

				local start = minetest.get_us_time()
				technic.switching_station_run(pos)
				local switch_diff = minetest.get_us_time() - start


				local meta = minetest.get_meta(pos)

				-- set lag in microseconds into the "lag" meta field
				meta:set_int("lag", switch_diff)

				-- overload detection
				if switch_diff > 250000 then
					switch.skip = 30
				elseif switch_diff > 150000 then
					switch.skip = 20
				elseif switch_diff > 75000 then
					switch.skip = 10
				elseif switch_diff > 50000 then
					switch.skip = 2
				end

				if switch.skip > 0 then
					-- calculate efficiency in percent and display it
					local efficiency = math.floor(1/switch.skip*100)
					meta:set_string("infotext", "Polyfuse triggered, current efficiency: " ..
						efficiency .. "% generated lag : " .. math.floor(switch_diff/1000) .. " ms")

					-- remove laggy switching station from active index
					-- it will be reactivated when a player is near it
					-- laggy switching stations won't work well in unloaded areas this way
					switches[hash] = nil
				end

			else
				switch.skip = math.max(switch.skip - 1, 0)
			end


		else
			-- station timed out
			switches[hash] = nil

		end
	end

	local time_usage = minetest.get_us_time() - now

	if has_monitoring_mod then
		active_switching_stations_metric.set(active_switches)
		switching_stations_usage_metric.inc(time_usage)
	end


end)


minetest.register_chatcommand("technic_flush_switch_cache", {
	description = "removes all loaded switching stations from the cache",
	privs = { server = true },
	func = function()
		switches = {}
	end
})