Rewrite pipe construction

- Moved pipe construction defines into __defines/construction.dm
- Unified pipe *unwrenching* by creating a standard proc along with the `construction_type` var.
- Eliminated the pipe fitting name & icon_state lookup tables by adding `pipe_state` var on atmos machinery and referencing that.
    - Each pipe which can be made from a fitting object should override `pipe_state` with the icon state to be used on the pipe fitting object.
- Eliminated the giant switch statement of doom in pipe construction by delegating that work to `on_construction` proc.
    - To make this work, every pipe must implement `get_neighbor_nodes_for_init` which returns a list of nodes which should be re-initialized on that pipe's construction.
- Combined the SCRUBBERS, SUPPLY and REGULAR pipe fitting classes together by storing the `piping_layer` variable and using the `setPipingLayer` procs
- Standardized the code for searching for node neighbors into the `can_be_node` proc.
    - This proc is also improved in that is a mutual check, `check_connectable` is called on BOTH objects, so they have to mutually agree to connect as nodes. Eliminates lots of special edge case logic.
    - Updated all the `amos_init` procs to use `can_be_node`.  In the most common cases, even that boilerplate code is consolidated into the `STANDARD_ATMOS_CHOOSE_NODE` macro.
- Implemented `pipe_flags` which lets pipes declare (or override) certain requirements.
- Adds a "pipe_recipe" datum to help out things that construct pipes.  By taking it out of the dispenser, we open the road for multiple dispenser types.  No, no RPD yet.  Soon.
    - Enhances the pipe dispenser to operate on pipe recipe datums instead of hard coded lists of pipes it can construct.   These datums are also (partially) initialized from the pipe machine types themselves, reducing having to define stuff in multiple places.
    - Switched pipe dispenser UI to use browse().   Not a NanoUI, but makes it a bit prettier with low effort.
    - Changed pipe dispenser to use a button selector to switch between Regular/Scrubbers/Supply instead of having separate list items.
- Added icon states to HE pipes to support the "connected on neither side" state.

code/ATMOSPHERICS/_atmos_setup.dm

@@ -15,11 +15,6 @@
 #define	PIPE_COLOR_BLACK	"#444444"
 #define	PIPE_COLOR_PURPLE	"#5c1ec0"
 
-#define CONNECT_TYPE_REGULAR	1
-#define CONNECT_TYPE_SUPPLY		2
-#define CONNECT_TYPE_SCRUBBER	4
-#define CONNECT_TYPE_HE			8
-
 var/global/list/pipe_colors = list("grey" = PIPE_COLOR_GREY, "red" = PIPE_COLOR_RED, "blue" = PIPE_COLOR_BLUE, "cyan" = PIPE_COLOR_CYAN, "green" = PIPE_COLOR_GREEN, "yellow" = PIPE_COLOR_YELLOW, "black" = PIPE_COLOR_BLACK, "purple" = PIPE_COLOR_PURPLE)
 
 /proc/pipe_color_lookup(var/color)

code/ATMOSPHERICS/atmospherics.dm

@@ -19,8 +19,12 @@ Pipelines + Other Objects -> Pipe network
 
 	layer = 2.4 //under wires with their 2.44
 
+	var/pipe_flags = PIPING_DEFAULT_LAYER_ONLY // Allow other layers by exception basis.
 	var/connect_types = CONNECT_TYPE_REGULAR
+	var/piping_layer = PIPING_LAYER_DEFAULT // This will replace icon_connect_type at some point ~Leshana
 	var/icon_connect_type = "" //"-supply" or "-scrubbers"
+	var/construction_type = null // Type path of the pipe item when this is deconstructed.
+	var/pipe_state // icon_state as a pipe item
 
 	var/initialize_directions = 0
 	var/pipe_color
@@ -46,6 +50,10 @@ Pipelines + Other Objects -> Pipe network
 /obj/machinery/atmospherics/proc/init_dir()
 	return
 
+// Get ALL initialize_directions - Some types (HE pipes etc) combine two vars together for this.
+/obj/machinery/atmospherics/proc/get_init_dirs()
+	return initialize_directions
+
 // Get the direction each node is facing to connect.
 // It now returns as a list so it can be fetched nicely, each entry corresponds to node of same number.
 /obj/machinery/atmospherics/proc/get_node_connect_dirs()
@@ -59,6 +67,14 @@ Pipelines + Other Objects -> Pipe network
 /obj/machinery/atmospherics/proc/atmos_init()
 	return
 
+/** Check if target is an acceptable target to connect as a node from this machine. */
+/obj/machinery/atmospherics/proc/can_be_node(obj/machinery/atmospherics/target, node_num)
+	return (target.initialize_directions & get_dir(target,src)) && check_connectable(target) && target.check_connectable(src)
+
+/** Check if this machine is willing to connect with the target machine. */
+/obj/machinery/atmospherics/proc/check_connectable(obj/machinery/atmospherics/target)
+	return (src.connect_types & target.connect_types)
+
 /obj/machinery/atmospherics/attackby(atom/A, mob/user as mob)
 	if(istype(A, /obj/item/device/pipe_painter))
 		return
@@ -82,12 +98,6 @@ Pipelines + Other Objects -> Pipe network
 	else
 		return 0
 
-obj/machinery/atmospherics/proc/check_connect_types(obj/machinery/atmospherics/atmos1, obj/machinery/atmospherics/atmos2)
-	return (atmos1.connect_types & atmos2.connect_types)
-
-/obj/machinery/atmospherics/proc/check_connect_types_construction(obj/machinery/atmospherics/atmos1, obj/item/pipe/pipe2)
-	return (atmos1.connect_types & pipe2.connect_types)
-
 /obj/machinery/atmospherics/proc/check_icon_cache(var/safety = 0)
 	if(!istype(icon_manager))
 		if(!safety) //to prevent infinite loops
@@ -146,4 +156,60 @@ obj/machinery/atmospherics/proc/check_connect_types(obj/machinery/atmospherics/a
 	var/datum/gas_mixture/env_air = loc.return_air()
 	if((int_air.return_pressure()-env_air.return_pressure()) > 2*ONE_ATMOSPHERE)
 		return 0
-	return 1
+	return 1
+
+// Deconstruct into a pipe item.
+/obj/machinery/atmospherics/proc/deconstruct()
+	if(QDELETED(src))
+		return
+	if(construction_type)
+		var/obj/item/pipe/I = new construction_type(loc, null, null, src)
+		I.setPipingLayer(piping_layer)
+		transfer_fingerprints_to(I)
+	qdel(src)
+
+// Return a list of nodes which we should call atmos_init() and build_network() during on_construction()
+/obj/machinery/atmospherics/proc/get_neighbor_nodes_for_init()
+	return null
+
+// Called on construction (i.e from pipe item) but not on initialization
+/obj/machinery/atmospherics/proc/on_construction(obj_color, set_layer)
+	pipe_color = obj_color
+	setPipingLayer(set_layer)
+	// TODO - M.connect_types = src.connect_types - Or otherwise copy from item? Or figure it out from piping layer?
+	var/turf/T = get_turf(src)
+	level = !T.is_plating() ? 2 : 1
+	atmos_init()
+	if(QDELETED(src))
+		return // TODO - Eventually should get rid of the need for this.
+	build_network()
+	var/list/nodes = get_neighbor_nodes_for_init()
+	for(var/obj/machinery/atmospherics/A in nodes)
+		A.atmos_init()
+		A.build_network()
+	// TODO - Should we do src.build_network() before or after the nodes?
+	// We've historically done before, but /tg does after. TODO research if there is a difference.
+
+// This sets our piping layer.  Hopefully its cool.
+/obj/machinery/atmospherics/proc/setPipingLayer(new_layer)
+	if(pipe_flags & (PIPING_DEFAULT_LAYER_ONLY|PIPING_ALL_LAYER))
+		new_layer = PIPING_LAYER_DEFAULT
+	piping_layer = new_layer
+	// Do it the Polaris way
+	switch(piping_layer)
+		if(PIPING_LAYER_SCRUBBER)
+			icon_state = "[icon_state]-scrubbers"
+			connect_types = CONNECT_TYPE_SCRUBBER
+			layer = 2.38
+			icon_connect_type = "-scrubbers"
+		if(PIPING_LAYER_SUPPLY)
+			icon_state = "[icon_state]-supply"
+			connect_types = CONNECT_TYPE_SUPPLY
+			layer = 2.39
+			icon_connect_type = "-supply"
+	if(pipe_flags & PIPING_ALL_LAYER)
+		connect_types = CONNECT_TYPE_REGULAR|CONNECT_TYPE_SUPPLY|CONNECT_TYPE_SCRUBBER
+	// Or if we were to do it the TG way...
+	// pixel_x = PIPE_PIXEL_OFFSET_X(piping_layer)
+	// pixel_y = PIPE_PIXEL_OFFSET_Y(piping_layer)
+	// layer = initial(layer) + PIPE_LAYER_OFFSET(piping_layer)

code/ATMOSPHERICS/components/binary_devices/binary_atmos_base.dm

@@ -30,6 +30,9 @@
 			initialize_directions = EAST|WEST
 
 // Housekeeping and pipe network stuff below
+/obj/machinery/atmospherics/binary/get_neighbor_nodes_for_init()
+	return list(node1, node2)
+
 /obj/machinery/atmospherics/binary/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node1)
 		network1 = new_network
@@ -64,17 +67,8 @@
 	var/node2_connect = dir
 	var/node1_connect = turn(dir, 180)
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,node1_connect))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
-
-	for(var/obj/machinery/atmospherics/target in get_step(src,node2_connect))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node2 = target
-				break
+	STANDARD_ATMOS_CHOOSE_NODE(1, node1_connect)
+	STANDARD_ATMOS_CHOOSE_NODE(2, node2_connect)
 
 	update_icon()
 	update_underlays()

code/ATMOSPHERICS/components/binary_devices/circulator.dm

@@ -9,6 +9,7 @@
 	icon = 'icons/obj/pipes.dmi'
 	icon_state = "circ-off"
 	anchored = 0
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY|PIPING_ONE_PER_TURF
 
 	var/kinetic_efficiency = 0.04 //combined kinetic and kinetic-to-electric efficiency
 	var/volume_ratio = 0.2

code/ATMOSPHERICS/components/binary_devices/dp_vent_pump.dm

@@ -24,6 +24,7 @@
 	idle_power_usage = 150		//internal circuitry, friction losses and stuff
 	power_rating = 7500			//7500 W ~ 10 HP
 
+	pipe_flags = PIPING_ALL_LAYER
 	connect_types = CONNECT_TYPE_REGULAR|CONNECT_TYPE_SUPPLY|CONNECT_TYPE_SCRUBBER //connects to regular, supply and scrubbers pipes
 
 	var/pump_direction = 1 //0 = siphoning, 1 = releasing

code/ATMOSPHERICS/components/binary_devices/passive_gate.dm

@@ -5,6 +5,8 @@
 /obj/machinery/atmospherics/binary/passive_gate
 	icon = 'icons/atmos/passive_gate.dmi'
 	icon_state = "map"
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "passivegate"
 	level = 1
 
 	name = "pressure regulator"
@@ -257,8 +259,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 #undef REGULATE_NONE
 #undef REGULATE_INPUT

code/ATMOSPHERICS/components/binary_devices/pipeturbine.dm

@@ -139,6 +139,9 @@
 		src.set_dir(turn(src.dir, 90))
 
 //Goddamn copypaste from binary base class because atmospherics machinery API is not damn flexible
+	get_neighbor_nodes_for_init()
+		return list(node1, node2)
+
 	network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 		if(reference == node1)
 			network1 = new_network

code/ATMOSPHERICS/components/binary_devices/pump.dm

@@ -15,6 +15,8 @@ Thus, the two variables affect pump operation are set in New():
 /obj/machinery/atmospherics/binary/pump
 	icon = 'icons/atmos/pump.dmi'
 	icon_state = "map_off"
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "pump"
 	level = 1
 
 	name = "gas pump"
@@ -236,5 +238,4 @@ Thus, the two variables affect pump operation are set in New():
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()

code/ATMOSPHERICS/components/binary_devices/volume_pump.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/binary/pump/high_power
 	icon = 'icons/atmos/volume_pump.dmi'
 	icon_state = "map_off"
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "volumepump"
 	level = 1
 
 	name = "high power gas pump"

code/ATMOSPHERICS/components/omni_devices/filter.dm

@@ -4,6 +4,7 @@
 /obj/machinery/atmospherics/omni/atmos_filter
 	name = "omni gas filter"
 	icon_state = "map_filter"
+	pipe_state = "omni_filter"
 
 	var/list/atmos_filters = new()
 	var/datum/omni_port/input

code/ATMOSPHERICS/components/omni_devices/mixer.dm

@@ -4,6 +4,7 @@
 /obj/machinery/atmospherics/omni/mixer
 	name = "omni gas mixer"
 	icon_state = "map_mixer"
+	pipe_state = "omni_mixer"
 
 	use_power = 1
 	idle_power_usage = 150		//internal circuitry, friction losses and stuff

code/ATMOSPHERICS/components/omni_devices/omni_base.dm

@@ -7,6 +7,7 @@
 	icon_state = "base"
 	use_power = 1
 	initialize_directions = 0
+	construction_type = /obj/item/pipe/quaternary
 	level = 1
 
 	var/configuring = 0
@@ -93,8 +94,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 /obj/machinery/atmospherics/omni/can_unwrench()
 	var/int_pressure = 0
@@ -222,6 +222,11 @@
 
 
 // Housekeeping and pipe network stuff below
+/obj/machinery/atmospherics/omni/get_neighbor_nodes_for_init()
+	var/list/neighbor_nodes = list()
+	for(var/datum/omni_port/P in ports)
+		neighbor_nodes += P.node
+	return neighbor_nodes
 
 /obj/machinery/atmospherics/omni/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	for(var/datum/omni_port/P in ports)
@@ -252,10 +257,9 @@
 		if(P.node || P.mode == 0)
 			continue
 		for(var/obj/machinery/atmospherics/target in get_step(src, P.dir))
-			if(target.initialize_directions & get_dir(target,src))
-				if (check_connect_types(target,src))
-					P.node = target
-					break
+			if(can_be_node(target, 1))
+				P.node = target
+				break
 
 	for(var/datum/omni_port/P in ports)
 		P.update = 1

code/ATMOSPHERICS/components/portables_connector.dm

@@ -7,6 +7,9 @@
 
 	dir = SOUTH
 	initialize_directions = SOUTH
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "connector"
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY|PIPING_ONE_PER_TURF
 
 	var/obj/machinery/portable_atmospherics/connected_device
 
@@ -47,6 +50,9 @@
 	return 1
 
 // Housekeeping and pipe network stuff below
+/obj/machinery/atmospherics/portables_connector/get_neighbor_nodes_for_init()
+	return list(node)
+
 /obj/machinery/atmospherics/portables_connector/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node)
 		network = new_network
@@ -77,10 +83,9 @@
 	var/node_connect = dir
 
 	for(var/obj/machinery/atmospherics/target in get_step(src,node_connect))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node = target
-				break
+		if(can_be_node(target, 1))
+			node = target
+			break
 
 	update_icon()
 	update_underlays()
@@ -146,5 +151,4 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()

code/ATMOSPHERICS/components/trinary_devices/filter.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/trinary/atmos_filter
 	icon = 'icons/atmos/filter.dmi'
 	icon_state = "map"
+	construction_type = /obj/item/pipe/trinary/flippable
+	pipe_state = "filter"
 	density = 0
 	level = 1
 

code/ATMOSPHERICS/components/trinary_devices/mixer.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/trinary/mixer
 	icon = 'icons/atmos/mixer.dmi'
 	icon_state = "map"
+	construction_type = /obj/item/pipe/trinary/flippable
+	pipe_state = "mixer"
 	density = 0
 	level = 1
 
@@ -133,6 +135,8 @@
 //
 obj/machinery/atmospherics/trinary/mixer/t_mixer
 	icon_state = "tmap"
+	construction_type = /obj/item/pipe/trinary  // Can't flip a "T", its symmetrical
+	pipe_state = "t_mixer"
 	dir = SOUTH
 	initialize_directions = SOUTH|EAST|WEST
 	tee = TRUE

code/ATMOSPHERICS/components/trinary_devices/trinary_base.dm

@@ -2,6 +2,7 @@
 	dir = SOUTH
 	initialize_directions = SOUTH|NORTH|WEST
 	use_power = 0
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY|PIPING_ONE_PER_TURF
 
 	var/mirrored = FALSE
 	var/tee = FALSE
@@ -64,10 +65,12 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 // Housekeeping and pipe network stuff below
+/obj/machinery/atmospherics/trinary/get_neighbor_nodes_for_init()
+	return list(node1, node2, node3)
+
 /obj/machinery/atmospherics/trinary/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node1)
 		network1 = new_network
@@ -113,21 +116,9 @@
 
 	var/list/node_connects = get_node_connect_dirs()
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,node_connects[1]))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
-	for(var/obj/machinery/atmospherics/target in get_step(src,node_connects[2]))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node2 = target
-				break
-	for(var/obj/machinery/atmospherics/target in get_step(src,node_connects[3]))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node3 = target
-				break
+	STANDARD_ATMOS_CHOOSE_NODE(1, node_connects[1])
+	STANDARD_ATMOS_CHOOSE_NODE(2, node_connects[2])
+	STANDARD_ATMOS_CHOOSE_NODE(3, node_connects[3])
 
 	update_icon()
 	update_underlays()

code/ATMOSPHERICS/components/tvalve.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/tvalve
 	icon = 'icons/atmos/tvalve.dmi'
 	icon_state = "map_tvalve0"
+	construction_type = /obj/item/pipe/trinary/flippable
+	pipe_state = "mtvalve"
 
 	name = "manual switching valve"
 	desc = "A pipe valve"
@@ -12,6 +14,7 @@
 	var/state = 0 // 0 = go straight, 1 = go to side
 
 	var/mirrored = FALSE
+	var/tee = FALSE // Note: Tee not actually supported for T-valves: no sprites
 
 	// like a trinary component, node1 is input, node2 is side output, node3 is straight output
 	var/obj/machinery/atmospherics/node3
@@ -47,6 +50,9 @@
 /obj/machinery/atmospherics/tvalve/init_dir()
 	initialize_directions = get_initialize_directions_trinary(dir, mirrored)
 
+/obj/machinery/atmospherics/tvalve/get_neighbor_nodes_for_init()
+	return list(node1, node2, node3)
+
 /obj/machinery/atmospherics/tvalve/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node1)
 		network_node1 = new_network
@@ -178,21 +184,9 @@
 
 	var/list/node_connects = get_node_connect_dirs()
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,node_connects[1]))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
-	for(var/obj/machinery/atmospherics/target in get_step(src,node_connects[2]))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node2 = target
-				break
-	for(var/obj/machinery/atmospherics/target in get_step(src,node_connects[3]))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node3 = target
-				break
+	STANDARD_ATMOS_CHOOSE_NODE(1, node_connects[1])
+	STANDARD_ATMOS_CHOOSE_NODE(2, node_connects[2])
+	STANDARD_ATMOS_CHOOSE_NODE(3, node_connects[3])
 
 	update_icon()
 	update_underlays()
@@ -262,6 +256,7 @@
 	name = "digital switching valve"
 	desc = "A digitally controlled valve."
 	icon = 'icons/atmos/digital_tvalve.dmi'
+	pipe_state = "dtvalve"
 
 	var/frequency = 0
 	var/id = null
@@ -348,8 +343,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 /obj/machinery/atmospherics/tvalve/mirrored
 	icon_state = "map_tvalvem0"

code/ATMOSPHERICS/components/unary/cold_sink.dm

@@ -38,18 +38,15 @@
 	var/node_connect = dir
 
 	for(var/obj/machinery/atmospherics/target in get_step(src, node_connect))
-		if(target.initialize_directions & get_dir(target, src))
+		if(can_be_node(target, 1))
 			node = target
 			break
 
-	//copied from pipe construction code since heaters/freezers don't use fittings and weren't doing this check - this all really really needs to be refactored someday.
-	//check that there are no incompatible pipes/machinery in our own location
-	for(var/obj/machinery/atmospherics/M in src.loc)
-		if(M != src && (M.initialize_directions & node_connect) && M.check_connect_types(M,src))	// matches at least one direction on either type of pipe & same connection type
-			node = null
-			break
+	if(check_for_obstacles())
+		node = null
 
-	update_icon()
+	if(node)
+		update_icon()
 
 /obj/machinery/atmospherics/unary/freezer/update_icon()
 	if(node)

code/ATMOSPHERICS/components/unary/heat_exchanger.dm

@@ -2,6 +2,7 @@
 
 	icon = 'icons/obj/atmospherics/heat_exchanger.dmi'
 	icon_state = "intact"
+	pipe_state = "heunary"
 	density = 1
 
 	name = "Heat Exchanger"
@@ -83,5 +84,4 @@
 				"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 				"<span class='notice'>You have unfastened \the [src].</span>", \
 				"You hear a ratchet.")
-			new /obj/item/pipe(loc, make_from=src)
-			qdel(src)
+			deconstruct()

code/ATMOSPHERICS/components/unary/heat_source.dm

@@ -39,18 +39,15 @@
 
 	//check that there is something to connect to
 	for(var/obj/machinery/atmospherics/target in get_step(src, node_connect))
-		if(target.initialize_directions & get_dir(target, src))
+		if(can_be_node(target, 1))
 			node = target
 			break
 
-	//copied from pipe construction code since heaters/freezers don't use fittings and weren't doing this check - this all really really needs to be refactored someday.
-	//check that there are no incompatible pipes/machinery in our own location
-	for(var/obj/machinery/atmospherics/M in src.loc)
-		if(M != src && (M.initialize_directions & node_connect) && M.check_connect_types(M,src))	// matches at least one direction on either type of pipe & same connection type
-			node = null
-			break
+	if(check_for_obstacles())
+		node = null
 
-	update_icon()
+	if(node)
+		update_icon()
 
 
 /obj/machinery/atmospherics/unary/heater/update_icon()

code/ATMOSPHERICS/components/unary/outlet_injector.dm

@@ -5,6 +5,7 @@
 /obj/machinery/atmospherics/unary/outlet_injector
 	icon = 'icons/atmos/injector.dmi'
 	icon_state = "map_injector"
+	pipe_state = "injector"
 	layer = 3
 
 	name = "air injector"

code/ATMOSPHERICS/components/unary/unary_base.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/unary
 	dir = SOUTH
 	initialize_directions = SOUTH
+	construction_type = /obj/item/pipe/directional
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY|PIPING_ONE_PER_TURF
 	//layer = TURF_LAYER+0.1
 
 	var/datum/gas_mixture/air_contents
@@ -21,6 +23,9 @@
 	initialize_directions = dir
 
 // Housekeeping and pipe network stuff below
+/obj/machinery/atmospherics/unary/get_neighbor_nodes_for_init()
+	return list(node)
+
 /obj/machinery/atmospherics/unary/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node)
 		network = new_network
@@ -48,10 +53,9 @@
 	var/node_connect = dir
 
 	for(var/obj/machinery/atmospherics/target in get_step(src,node_connect))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node = target
-				break
+		if(can_be_node(target, 1))
+			node = target
+			break
 
 	update_icon()
 	update_underlays()
@@ -93,4 +97,19 @@
 	update_icon()
 	update_underlays()
 
-	return null
+	return null
+
+// Check if there are any other atmos machines in the same turf that will block this machine from initializing.
+// Intended for use when a frame-constructable machine (i.e. not made from pipe fittings) wants to wrench down and connect.
+// Returns TRUE if something is blocking, FALSE if its okay to continue.
+/obj/machinery/atmospherics/unary/proc/check_for_obstacles()
+	for(var/obj/machinery/atmospherics/M in loc)
+		if((M.pipe_flags & pipe_flags & PIPING_ONE_PER_TURF))	//Only one dense/requires density object per tile, eg connectors/cryo/heater/coolers.
+			visible_message("<span class='warning'>\The [src]'s cannot be connected, something is hogging the tile!</span>")
+			return TRUE
+		if((M.piping_layer != piping_layer) && !((M.pipe_flags | flags) & PIPING_ALL_LAYER)) // Pipes on different layers can't block each other unless they are ALL_LAYER
+			continue
+		if(M.get_init_dirs() & get_init_dirs())	// matches at least one direction on either type of pipe
+			visible_message("<span class='warning'>\The [src]'s connector can't be connected, there is already a pipe at that location!</span>")
+			return TRUE
+	return FALSE

code/ATMOSPHERICS/components/unary/vent_pump.dm

@@ -10,6 +10,7 @@
 /obj/machinery/atmospherics/unary/vent_pump
 	icon = 'icons/atmos/vent_pump.dmi'
 	icon_state = "map_vent"
+	pipe_state = "uvent"
 
 	name = "Air Vent"
 	desc = "Has a valve and pump attached to it"
@@ -410,8 +411,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 #undef DEFAULT_PRESSURE_DELTA
 

code/ATMOSPHERICS/components/unary/vent_scrubber.dm

@@ -1,6 +1,7 @@
 /obj/machinery/atmospherics/unary/vent_scrubber
 	icon = 'icons/atmos/vent_scrubber.dmi'
 	icon_state = "map_scrubber_off"
+	pipe_state = "scrubber"
 
 	name = "Air Scrubber"
 	desc = "Has a valve and pump attached to it"
@@ -283,8 +284,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 /obj/machinery/atmospherics/unary/vent_scrubber/examine(mob/user)
 	if(..(user, 1))

code/ATMOSPHERICS/components/valve.dm

@@ -1,6 +1,8 @@
 /obj/machinery/atmospherics/valve
 	icon = 'icons/atmos/valve.dmi'
 	icon_state = "map_valve0"
+	construction_type = /obj/item/pipe/binary
+	pipe_state = "mvalve"
 
 	name = "manual valve"
 	desc = "A pipe valve"
@@ -45,6 +47,9 @@
 		if(EAST || WEST)
 			initialize_directions = EAST|WEST
 
+/obj/machinery/atmospherics/valve/get_neighbor_nodes_for_init()
+	return list(node1, node2)
+
 /obj/machinery/atmospherics/valve/network_expand(datum/pipe_network/new_network, obj/machinery/atmospherics/pipe/reference)
 	if(reference == node1)
 		network_node1 = new_network
@@ -153,16 +158,8 @@
 			else if (!node2_dir)
 				node2_dir = direction
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,node1_dir))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
-	for(var/obj/machinery/atmospherics/target in get_step(src,node2_dir))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node2 = target
-				break
+	STANDARD_ATMOS_CHOOSE_NODE(1, node1_dir)
+	STANDARD_ATMOS_CHOOSE_NODE(2, node2_dir)
 
 	build_network()
 
@@ -224,6 +221,7 @@
 	name = "digital valve"
 	desc = "A digitally controlled valve."
 	icon = 'icons/atmos/digital_valve.dmi'
+	pipe_state = "dvalve"
 
 	var/frequency = 0
 	var/id = null
@@ -306,8 +304,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		qdel(src)
+		deconstruct()
 
 /obj/machinery/atmospherics/valve/examine(mob/user)
 	..()

code/ATMOSPHERICS/mainspipe.dm

@@ -92,6 +92,9 @@ obj/machinery/atmospherics/mains_pipe
 
 		else return 1
 
+	get_neighbor_nodes_for_init()
+		return nodes
+
 	disconnect()
 		..()
 		for(var/obj/machinery/atmospherics/pipe/mains_component/node in nodes)

code/ATMOSPHERICS/pipes/cap.dm

@@ -14,6 +14,9 @@
 	dir = SOUTH
 	initialize_directions = SOUTH
 
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "cap"
+
 	var/obj/machinery/atmospherics/node
 
 /obj/machinery/atmospherics/pipe/cap/init_dir()
@@ -56,10 +59,9 @@
 
 /obj/machinery/atmospherics/pipe/cap/atmos_init()
 	for(var/obj/machinery/atmospherics/target in get_step(src, dir))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node = target
-				break
+		if (can_be_node(target, 1))
+			node = target
+			break
 
 	var/turf/T = src.loc			// hide if turf is not intact
 	if(level == 1 && !T.is_plating()) hide(1)

code/ATMOSPHERICS/pipes/he_pipes.dm

@@ -8,6 +8,10 @@
 	color = "#404040"
 	level = 2
 	connect_types = CONNECT_TYPE_HE
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY
+	construction_type = /obj/item/pipe/binary/bendable
+	pipe_state = "he"
+
 	layer = 2.41
 	var/initialize_directions_he
 	var/surface = 2	//surface area in m^2
@@ -27,6 +31,16 @@
 /obj/machinery/atmospherics/pipe/simple/heat_exchanging/init_dir()
 	..()
 	initialize_directions_he = initialize_directions	// The auto-detection from /pipe is good enough for a simple HE pipe
+	initialize_directions = 0
+
+/obj/machinery/atmospherics/pipe/simple/heat_exchanging/get_init_dirs()
+	return ..() | initialize_directions_he
+
+// Use initialize_directions_he to connect to neighbors instead.
+/obj/machinery/atmospherics/pipe/simple/heat_exchanging/can_be_node(var/obj/machinery/atmospherics/pipe/simple/heat_exchanging/target)
+	if(!istype(target))
+		return FALSE
+	return (target.initialize_directions_he & get_dir(target,src)) && check_connectable(target) && target.check_connectable(src)
 
 /obj/machinery/atmospherics/pipe/simple/heat_exchanging/atmos_init()
 	normalize_dir()
@@ -41,11 +55,11 @@
 				node2_dir = direction
 
 	for(var/obj/machinery/atmospherics/pipe/simple/heat_exchanging/target in get_step(src,node1_dir))
-		if(target.initialize_directions_he & get_dir(target,src))
+		if(can_be_node(target, 1))
 			node1 = target
 			break
 	for(var/obj/machinery/atmospherics/pipe/simple/heat_exchanging/target in get_step(src,node2_dir))
-		if(target.initialize_directions_he & get_dir(target,src))
+		if(can_be_node(target, 2))
 			node2 = target
 			break
 	if(!node1 && !node2)
@@ -117,6 +131,8 @@
 	pipe_icon = "hejunction"
 	level = 2
 	connect_types = CONNECT_TYPE_REGULAR|CONNECT_TYPE_HE
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "junction"
 	minimum_temperature_difference = 300
 	thermal_conductivity = WALL_HEAT_TRANSFER_COEFFICIENT
 
@@ -136,6 +152,18 @@
 			initialize_directions = EAST
 			initialize_directions_he = WEST
 
+	// Allow ourselves to make connections to either HE or normal pipes depending on which node we are doing.
+/obj/machinery/atmospherics/pipe/simple/heat_exchanging/junction/can_be_node(obj/machinery/atmospherics/target, node_num)
+	var/target_initialize_directions
+	switch(node_num)
+		if(1)
+			target_initialize_directions = target.initialize_directions // Node1 is towards normal pipes
+		if(2)
+			var/obj/machinery/atmospherics/pipe/simple/heat_exchanging/H = target
+			if(!istype(H))
+				return FALSE
+			target_initialize_directions = H.initialize_directions_he  // Node2 is towards HE pies.
+	return (target_initialize_directions & get_dir(target,src)) && check_connectable(target) && target.check_connectable(src)
 
 /obj/machinery/atmospherics/pipe/simple/heat_exchanging/junction/atmos_init()
 	for(var/obj/machinery/atmospherics/target in get_step(src,initialize_directions))

code/ATMOSPHERICS/pipes/manifold.dm

@@ -12,6 +12,9 @@
 	dir = SOUTH
 	initialize_directions = EAST|NORTH|WEST
 
+	construction_type = /obj/item/pipe/trinary
+	pipe_state = "manifold"
+
 	var/obj/machinery/atmospherics/node3
 
 	level = 1
@@ -116,11 +119,10 @@
 	for(var/direction in cardinal)
 		if(direction&connect_directions)
 			for(var/obj/machinery/atmospherics/target in get_step(src,direction))
-				if(target.initialize_directions & get_dir(target,src))
-					if (check_connect_types(target,src))
-						node1 = target
-						connect_directions &= ~direction
-						break
+				if (can_be_node(target, 1))
+					node1 = target
+					connect_directions &= ~direction
+					break
 			if (node1)
 				break
 
@@ -128,11 +130,10 @@
 	for(var/direction in cardinal)
 		if(direction&connect_directions)
 			for(var/obj/machinery/atmospherics/target in get_step(src,direction))
-				if(target.initialize_directions & get_dir(target,src))
-					if (check_connect_types(target,src))
-						node2 = target
-						connect_directions &= ~direction
-						break
+				if (can_be_node(target, 2))
+					node2 = target
+					connect_directions &= ~direction
+					break
 			if (node2)
 				break
 
@@ -140,11 +141,10 @@
 	for(var/direction in cardinal)
 		if(direction&connect_directions)
 			for(var/obj/machinery/atmospherics/target in get_step(src,direction))
-				if(target.initialize_directions & get_dir(target,src))
-					if (check_connect_types(target,src))
-						node3 = target
-						connect_directions &= ~direction
-						break
+				if (can_be_node(target, 3))
+					node3 = target
+					connect_directions &= ~direction
+					break
 			if (node3)
 				break
 

code/ATMOSPHERICS/pipes/manifold4w.dm

@@ -12,6 +12,9 @@
 	dir = SOUTH
 	initialize_directions = NORTH|SOUTH|EAST|WEST
 
+	construction_type = /obj/item/pipe/quaternary
+	pipe_state = "manifold4w"
+
 	var/obj/machinery/atmospherics/node3
 	var/obj/machinery/atmospherics/node4
 
@@ -127,29 +130,25 @@
 
 /obj/machinery/atmospherics/pipe/manifold4w/atmos_init()
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,1))
-		if(target.initialize_directions & 2)
-			if (check_connect_types(target,src))
-				node1 = target
-				break
+	for(var/obj/machinery/atmospherics/target in get_step(src, NORTH))
+		if (can_be_node(target, 1))
+			node1 = target
+			break
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,2))
-		if(target.initialize_directions & 1)
-			if (check_connect_types(target,src))
-				node2 = target
-				break
+	for(var/obj/machinery/atmospherics/target in get_step(src, SOUTH))
+		if (can_be_node(target, 2))
+			node2 = target
+			break
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,4))
-		if(target.initialize_directions & 8)
-			if (check_connect_types(target,src))
-				node3 = target
-				break
+	for(var/obj/machinery/atmospherics/target in get_step(src, EAST))
+		if (can_be_node(target, 3))
+			node3 = target
+			break
 
-	for(var/obj/machinery/atmospherics/target in get_step(src,8))
-		if(target.initialize_directions & 4)
-			if (check_connect_types(target,src))
-				node4 = target
-				break
+	for(var/obj/machinery/atmospherics/target in get_step(src, WEST))
+		if (can_be_node(target, 4))
+			node4 = target
+			break
 
 	if(!node1 && !node2 && !node3 && !node4)
 		qdel(src)

code/ATMOSPHERICS/pipes/pipe_base.dm

@@ -10,6 +10,8 @@
 	layer = 2.4 //under wires with their 2.44
 	use_power = 0
 
+	pipe_flags = 0 // Does not have PIPING_DEFAULT_LAYER_ONLY flag.
+
 	var/alert_pressure = 80*ONE_ATMOSPHERE
 		//minimum pressure before check_pressure(...) should be called
 
@@ -31,6 +33,10 @@
 /obj/machinery/atmospherics/pipe/proc/pipeline_expansion()
 	return null
 
+// For pipes this is the same as pipeline_expansion()
+/obj/machinery/atmospherics/pipe/get_neighbor_nodes_for_init()
+	return pipeline_expansion()
+
 /obj/machinery/atmospherics/pipe/proc/check_pressure(pressure)
 	//Return 1 if parent should continue checking other pipes
 	//Return null if parent should stop checking other pipes. Recall: qdel(src) will by default return null
@@ -69,7 +75,11 @@
 	qdel_null(parent)
 	if(air_temporary)
 		loc.assume_air(air_temporary)
-
+	for(var/obj/machinery/meter/meter in loc)
+		if(meter.target == src)
+			var/obj/item/pipe_meter/PM = new /obj/item/pipe_meter(loc)
+			meter.transfer_fingerprints_to(PM)
+			qdel(meter)
 	. = ..()
 
 /obj/machinery/atmospherics/pipe/attackby(var/obj/item/weapon/W as obj, var/mob/user as mob)
@@ -96,12 +106,7 @@
 			"<span class='notice'>\The [user] unfastens \the [src].</span>", \
 			"<span class='notice'>You have unfastened \the [src].</span>", \
 			"You hear a ratchet.")
-		new /obj/item/pipe(loc, make_from=src)
-		for (var/obj/machinery/meter/meter in T)
-			if (meter.target == src)
-				new /obj/item/pipe_meter(T)
-				qdel(meter)
-		qdel(src)
+		deconstruct()
 
 /obj/machinery/atmospherics/pipe/proc/change_color(var/new_color)
 	//only pass valid pipe colors please ~otherwise your pipe will turn invisible

code/ATMOSPHERICS/pipes/simple.dm

@@ -13,6 +13,10 @@
 	dir = SOUTH
 	initialize_directions = SOUTH|NORTH
 
+	pipe_flags = PIPING_CARDINAL_AUTONORMALIZE
+	construction_type = /obj/item/pipe/binary/bendable
+	pipe_state = "simple"
+
 	var/minimum_temperature_difference = 300
 	var/thermal_conductivity = 0 //WALL_HEAT_TRANSFER_COEFFICIENT No
 
@@ -47,9 +51,13 @@
 
 /obj/machinery/atmospherics/pipe/simple/init_dir()
 	switch(dir)
-		if(SOUTH || NORTH)
+		if(SOUTH)
 			initialize_directions = SOUTH|NORTH
-		if(EAST || WEST)
+		if(NORTH)
+			initialize_directions = SOUTH|NORTH
+		if(EAST)
+			initialize_directions = EAST|WEST
+		if(WEST)
 			initialize_directions = EAST|WEST
 		if(NORTHEAST)
 			initialize_directions = NORTH|EAST
@@ -124,15 +132,13 @@
 				node2_dir = direction
 
 	for(var/obj/machinery/atmospherics/target in get_step(src,node1_dir))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
+		if(can_be_node(target, 1))
+			node1 = target
+			break
 	for(var/obj/machinery/atmospherics/target in get_step(src,node2_dir))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node2 = target
-				break
+		if(can_be_node(target, 2))
+			node2 = target
+			break
 
 	if(!node1 && !node2)
 		qdel(src)
@@ -248,6 +254,9 @@
 	icon = 'icons/obj/atmospherics/red_pipe.dmi'
 	icon_state = "intact"
 
+	construction_type = /obj/item/pipe/binary/bendable
+	pipe_state = "insulated"
+
 	minimum_temperature_difference = 10000
 	thermal_conductivity = 0
 	maximum_pressure = 1000*ONE_ATMOSPHERE

code/ATMOSPHERICS/pipes/tank.dm

@@ -14,6 +14,7 @@
 	level = 1
 	dir = SOUTH
 	initialize_directions = SOUTH
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY
 	density = 1
 
 /obj/machinery/atmospherics/pipe/tank/New()
@@ -48,10 +49,9 @@
 	var/connect_direction = dir
 
 	for(var/obj/machinery/atmospherics/target in get_step(src,connect_direction))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
+		if (can_be_node(target, 1))
+			node1 = target
+			break
 
 	update_underlays()
 

code/ATMOSPHERICS/pipes/universal.dm

@@ -6,6 +6,9 @@
 	desc = "An adapter for regular, supply and scrubbers pipes"
 	connect_types = CONNECT_TYPE_REGULAR|CONNECT_TYPE_SUPPLY|CONNECT_TYPE_SCRUBBER
 	icon_state = "map_universal"
+	pipe_flags = PIPING_ALL_LAYER|PIPING_CARDINAL_AUTONORMALIZE
+	construction_type = /obj/item/pipe/binary
+	pipe_state = "universal"
 
 /obj/machinery/atmospherics/pipe/simple/visible/universal/update_icon(var/safety = 0)
 	if(!check_icon_cache())
@@ -41,6 +44,9 @@
 	desc = "An adapter for regular, supply and scrubbers pipes"
 	connect_types = CONNECT_TYPE_REGULAR|CONNECT_TYPE_SUPPLY|CONNECT_TYPE_SCRUBBER
 	icon_state = "map_universal"
+	pipe_flags = PIPING_ALL_LAYER|PIPING_CARDINAL_AUTONORMALIZE
+	construction_type = /obj/item/pipe/binary
+	pipe_state = "universal"
 
 /obj/machinery/atmospherics/pipe/simple/hidden/universal/update_icon(var/safety = 0)
 	if(!check_icon_cache())

code/ATMOSPHERICS/pipes/vent.dm

@@ -14,6 +14,9 @@
 
 	dir = SOUTH
 	initialize_directions = SOUTH
+	pipe_flags = PIPING_DEFAULT_LAYER_ONLY
+	construction_type = /obj/item/pipe/directional
+	pipe_state = "passive vent"
 
 	var/build_killswitch = 1
 
@@ -58,10 +61,9 @@
 	var/connect_direction = dir
 
 	for(var/obj/machinery/atmospherics/target in get_step(src,connect_direction))
-		if(target.initialize_directions & get_dir(target,src))
-			if (check_connect_types(target,src))
-				node1 = target
-				break
+		if (can_be_node(target, 1))
+			node1 = target
+			break
 
 	update_icon()