S.P.L.U.R.T-Station-13/code/modules/atmospherics/machinery/components/binary_devices/passive_gate.dm

/*

Passive gate is similar to the regular pump except:
* It doesn't require power
* Can not transfer low pressure to higher pressure (so it's more like a valve where you can control the flow)

*/

/obj/machinery/atmospherics/components/binary/passive_gate
	icon_state = "passgate_map"

	name = "passive gate"
	desc = "A one-way air valve that does not require power."

	can_unwrench = TRUE

	var/on = FALSE
	var/target_pressure = ONE_ATMOSPHERE

	var/frequency = 0
	var/id = null
	var/datum/radio_frequency/radio_connection

	construction_type = /obj/item/pipe/directional
	pipe_state = "passivegate"

/obj/machinery/atmospherics/components/binary/passive_gate/Destroy()
	SSradio.remove_object(src,frequency)
	return ..()

/obj/machinery/atmospherics/components/binary/passive_gate/update_icon_nopipes()
	if(!on)
		icon_state = "passgate_off"
		cut_overlays()
		return

	add_overlay(getpipeimage('icons/obj/atmospherics/components/binary_devices.dmi', "passgate_on"))

/obj/machinery/atmospherics/components/binary/passive_gate/process_atmos()
	..()
	if(!on)
		return

	var/datum/gas_mixture/air1 = airs[1]
	var/datum/gas_mixture/air2 = airs[2]

	var/output_starting_pressure = air2.return_pressure()
	var/input_starting_pressure = air1.return_pressure()

	if(output_starting_pressure >= min(target_pressure,input_starting_pressure-10))
		//No need to pump gas if target is already reached or input pressure is too low
		//Need at least 10 KPa difference to overcome friction in the mechanism
		return

	//Calculate necessary moles to transfer using PV = nRT
	if((air1.total_moles() > 0) && (air1.temperature>0))
		var/pressure_delta = min(target_pressure - output_starting_pressure, (input_starting_pressure - output_starting_pressure)/2)
		//Can not have a pressure delta that would cause output_pressure > input_pressure

		var/transfer_moles = pressure_delta*air2.volume/(air1.temperature * R_IDEAL_GAS_EQUATION)

		//Actually transfer the gas
		var/datum/gas_mixture/removed = air1.remove(transfer_moles)
		air2.merge(removed)

		update_parents()


//Radio remote control

/obj/machinery/atmospherics/components/binary/passive_gate/proc/set_frequency(new_frequency)
	SSradio.remove_object(src, frequency)
	frequency = new_frequency
	if(frequency)
		radio_connection = SSradio.add_object(src, frequency, filter = GLOB.RADIO_ATMOSIA)

/obj/machinery/atmospherics/components/binary/passive_gate/proc/broadcast_status()
	if(!radio_connection)
		return

	var/datum/signal/signal = new
	signal.transmission_method = 1 //radio signal
	signal.source = src

	signal.data = list(
		"tag" = id,
		"device" = "AGP",
		"power" = on,
		"target_output" = target_pressure,
		"sigtype" = "status"
	)

	radio_connection.post_signal(src, signal, filter = GLOB.RADIO_ATMOSIA)

/obj/machinery/atmospherics/components/binary/passive_gate/ui_interact(mob/user, ui_key = "main", datum/tgui/ui = null, force_open = FALSE, \
																		datum/tgui/master_ui = null, datum/ui_state/state = GLOB.default_state)
	ui = SStgui.try_update_ui(user, src, ui_key, ui, force_open)
	if(!ui)
		ui = new(user, src, ui_key, "atmos_pump", name, 335, 115, master_ui, state)
		ui.open()

/obj/machinery/atmospherics/components/binary/passive_gate/ui_data()
	var/data = list()
	data["on"] = on
	data["pressure"] = round(target_pressure)
	data["max_pressure"] = round(MAX_OUTPUT_PRESSURE)
	return data

/obj/machinery/atmospherics/components/binary/passive_gate/ui_act(action, params)
	if(..())
		return
	switch(action)
		if("power")
			on = !on
			investigate_log("was turned [on ? "on" : "off"] by [key_name(usr)]", INVESTIGATE_ATMOS)
			. = TRUE
		if("pressure")
			var/pressure = params["pressure"]
			if(pressure == "max")
				pressure = MAX_OUTPUT_PRESSURE
				. = TRUE
			else if(pressure == "input")
				pressure = input("New output pressure (0-[MAX_OUTPUT_PRESSURE] kPa):", name, target_pressure) as num|null
				if(!isnull(pressure) || !..())
					. = TRUE
			else if(text2num(pressure) != null)
				pressure = text2num(pressure)
				. = TRUE
			if(.)
				target_pressure = CLAMP(pressure, 0, MAX_OUTPUT_PRESSURE)
				investigate_log("was set to [target_pressure] kPa by [key_name(usr)]", INVESTIGATE_ATMOS)
	update_icon()

/obj/machinery/atmospherics/components/binary/passive_gate/atmosinit()
	..()
	if(frequency)
		set_frequency(frequency)

/obj/machinery/atmospherics/components/binary/passive_gate/receive_signal(datum/signal/signal)
	if(!signal.data["tag"] || (signal.data["tag"] != id) || (signal.data["sigtype"]!="command"))
		return

	var/old_on = on //for logging

	if("power" in signal.data)
		on = text2num(signal.data["power"])

	if("power_toggle" in signal.data)
		on = !on

	if("set_output_pressure" in signal.data)
		target_pressure = CLAMP(text2num(signal.data["set_output_pressure"]),0,ONE_ATMOSPHERE*50)

	if(on != old_on)
		investigate_log("was turned [on ? "on" : "off"] by a remote signal", INVESTIGATE_ATMOS)

	if("status" in signal.data)
		broadcast_status()
		return

	broadcast_status()
	update_icon()

/obj/machinery/atmospherics/components/binary/passive_gate/power_change()
	..()
	update_icon()

/obj/machinery/atmospherics/components/binary/passive_gate/can_unwrench(mob/user)
	. = ..()
	if(. && on)
		to_chat(user, "<span class='warning'>You cannot unwrench [src], turn it off first!</span>")
		return FALSE