add split_train_at_fc luaatc command

This command splits the train at the second non-empty FC it
encounters, taking with it the first few freight cars that all go to
the same destination.

advtrains/trainlogic.lua

@@ -892,6 +892,36 @@ function advtrains.spawn_wagons(train_id)
 	end
 end
 
+function advtrains.split_train_at_fc(train)
+	-- splits train at first different current FC
+	local train_id = train.id
+	local fc = false
+	local ind = 0
+	for i = 1, #train.trainparts do
+		local w_id = train.trainparts[i]
+		local data = advtrains.wagons[w_id]
+		if data then
+			local wfc = advtrains.get_cur_fc(data)
+			if  wfc ~= "" then
+				if  fc then
+					if fc ~= wfc then
+						ind = i
+						break
+					end
+				else
+					fc = wfc
+				end
+			end
+		end
+	end
+	if ind > 0 then
+		return advtrains.split_train_at_index(train, ind), fc
+	end
+	if fc then
+		return nil, fc
+	end
+end
+
 function advtrains.split_train_at_index(train, index)
 	-- this function splits a train at index, creating a new train from the back part of the train.
 
@@ -1080,7 +1110,10 @@ function advtrains.do_connect_trains(first_id, second_id, vel)
 	end
 	
 	advtrains.remove_train(second_id)
-	
+	if vel < 0 then
+		advtrains.invert_train(first_id)
+		vel = -vel
+	end
 	first.velocity= vel or 0
 	
 	advtrains.update_trainpart_properties(first_id)

advtrains/wagons.lua

@@ -826,10 +826,8 @@ function wagon:show_wagon_properties(pname)
 
 		local cur = data.fc[data.fcind] or ""
 		form=form.."label[1.5,3.75;"..cur.."]"
-		if data.fcind < #data.fc then
 		form=form.."button[3.5,3.5;1,1;fcn;next FC]"
 	end
-	end
 	form=form.."button_exit[0.5,4.5;4,1;save;"..attrans("Save wagon properties").."]"
 	minetest.show_formspec(pname, "advtrains_prop_"..self.id, form)
 end
@@ -851,12 +849,62 @@ local function checklock(pname, own1, own2, wl1, wl2)
 end
 
 function string:split(sep)
-   local sep, fields = sep or ":", {}
+   local fields = {}
    local pattern = string.format("([^%s]+)", sep)
    self:gsub(pattern, function(c) fields[#fields+1] = c end)
    return fields
 end
 
+function wagon.set_fc(data, fcstr)
+	data.fc = string.split(fcstr, "!")
+	if not data.fcind then
+		data.fcind = 1
+	elseif data.fcind > #data.fc then
+		data.fcind = #data.fc
+	end	
+end
+
+function wagon.prev_fc(data)
+	if data.fcind > 1 then
+		data.fcind = data.fcind -1
+	end
+	if data.fcind == 1 and data.fcrev then
+		data.fcrev = nil
+	end
+end
+
+function wagon.next_fc(data)
+	if data.fcrev then
+		wagon.prev_fc(data)
+		return
+	end
+	if data.fcind < #data.fc then
+		data.fcind = data.fcind + 1
+	else
+		data.fcind = 1
+	end
+	if data.fcind == #data.fc and data.fc[data.fcind] == "?" then
+		data.fcrev = true
+		wagon.prev_fc(data)
+		return			
+	end
+end
+
+function advtrains.get_cur_fc(data)
+	if not ( data.fc and data.fcind ) then
+		return ""
+	end
+	return data.fc[data.fcind] or ""
+end
+
+function advtrains.step_fc(data)
+	wagon.next_fc(data)
+end
+
+
+
+
+
 function wagon:show_bordcom(pname)
 	if not self:train() then return end
 	local train = self:train()
@@ -1072,24 +1120,14 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 					data.roadnumber = fields.roadnumber
 				end
 				if fields.fc then
-					data.fc = string.split(fields.fc, "!")
-					if not data.fcind then
-						data.fcind = 1
-					elseif data.fcind > #data.fc then
-						data.fcind = #data.fc
-					end
+					wagon.set_fc(data, fields.fc)
 				end
 				if fields.fcp then
-					if data.fcind > 1 then
-						data.fcind = data.fcind - 1
-					end
+					wagon.prev_fc(data)
 					wagon.show_wagon_properties({id=uid}, pname)
 				end
 				if fields.fcn then
-					if data.fcind < #data.fc then
-						minetest.chat_send_all(data.fcind)
-						data.fcind = data.fcind + 1
-					end
+					wagon.next_fc(data)
 					wagon.show_wagon_properties({id=uid}, pname)
 				end
 			end

advtrains_luaautomation/atc_rail.lua

@@ -66,6 +66,15 @@ function r.fire_event(pos, evtdata)
 			end
 			return false
 		end,
+		split_at_fc = function(cmd)
+			assertt(cmd, "string")
+			if not train_id then return false end
+			local new_id, fc = advtrains.split_train_at_fc(train)
+			if new_id then
+				minetest.after(1,advtrains.atc.train_set_command,advtrains.trains[new_id], cmd, atc_arrow)
+			end
+			return fc
+		end,
 		set_shunt = function()
 			if not train_id then return false end
 			train.autocouple = true