Break too long lines and simplify the code

- Add boost_cart:get_rail_groups to get the default rail groups
- Remove duplicated code
- Do not boost the cart backwards when the brake rail gets activated
- Attempt to fix the cart swing problem
- Trim tailings and tidy up code
- TODO: Document all the stuff

detector.lua

@@ -15,7 +15,7 @@ function boost_cart:signal_detector_rail(pos)
 	if minetest.get_item_group(node.name, "detector_rail") ~= 1 then
 		return
 	end
-	--minetest.log("action", "Signaling detector at " .. minetest.pos_to_string(pos))
+
 	if node.name == "boost_cart:detectorrail" then
 		minetest.swap_node(pos, {name = "boost_cart:detectorrail_on", param2=node.param2})
 	end
@@ -25,19 +25,27 @@ end
 
 boost_cart:register_rail("boost_cart:detectorrail", {
 	description = "Detector rail",
-	tiles = {"carts_rail_dtc.png", "carts_rail_curved_dtc.png", "carts_rail_t_junction_dtc.png", "carts_rail_crossing_dtc.png"},
+	tiles = {
-	groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1, detector_rail = 1},
+		"carts_rail_dtc.png", "carts_rail_curved_dtc.png",
+		"carts_rail_t_junction_dtc.png", "carts_rail_crossing_dtc.png"
+	},
+	groups = boost_cart:get_rail_groups({detector_rail = 1}),
 
-	mesecons = {receptor = {state = "off", rules = mesecons_rules }},
+	mesecons = {receptor = {state = "off", rules = mesecons_rules}},
 })
 
 boost_cart:register_rail("boost_cart:detectorrail_on", {
 	description = "Detector rail ON (you hacker you)",
-	tiles = {"carts_rail_dtc_on.png", "carts_rail_curved_dtc_on.png", "carts_rail_t_junction_dtc_on.png", "carts_rail_crossing_dtc_on.png"},
+	tiles = {
-	groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1, detector_rail = 1, not_in_creative_inventory = 1},
+		"carts_rail_dtc_on.png", "carts_rail_curved_dtc_on.png",
+		"carts_rail_t_junction_dtc_on.png", "carts_rail_crossing_dtc_on.png"
+	},
+	groups = boost_cart:get_rail_groups({
+		detector_rail = 1, not_in_creative_inventory = 1
+	}),
 	drop = "boost_cart:detectorrail",
 
-	mesecons = {receptor = {state = "on", rules = mesecons_rules }},
+	mesecons = {receptor = {state = "on", rules = mesecons_rules}},
 })
 
 minetest.register_craft({

functions.lua

@@ -213,3 +213,14 @@ function boost_cart:register_rail(name, def)
 
 	minetest.register_node(name, def)
 end
+
+function boost_cart:get_rail_groups(additional_groups)
+	-- Get the default rail groups and add more when a table is given
+	local groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1}
+	if type(additional_groups) == "table" then
+		for k, v in pairs(additional_groups) do
+			groups[k] = v
+		end
+	end
+	return groups
+end

init.lua

@@ -194,7 +194,9 @@ function boost_cart.cart:on_step(dtime)
 	if self.old_pos then
 		-- Detection for "skipping" nodes
 		local expected_pos = vector.add(self.old_pos, self.old_dir)
-		local found_path = boost_cart:pathfinder(pos, expected_pos, self.old_dir, ctrl, self.old_switch, self.railtype)
+		local found_path = boost_cart:pathfinder(
+			pos, expected_pos, self.old_dir, ctrl, self.old_switch, self.railtype
+		)
 
 		if not found_path then
 			-- No rail found: reset back to the expected position
@@ -203,20 +205,12 @@ function boost_cart.cart:on_step(dtime)
 		end
 	end
 
-	if vel.y == 0 then
-		-- Stop cart completely (do not swing)
-		for _,v in ipairs({"x", "z"}) do
-			if vel[v] ~= 0 and math.abs(vel[v]) < 0.9 then
-				vel[v] = 0
-				update.vel = true
-			end
-		end
-	end
-
 	local cart_dir = boost_cart:velocity_to_dir(vel)
 	local max_vel = boost_cart.speed_max
 	if not dir then
-		dir, last_switch = boost_cart:get_rail_direction(pos, cart_dir, ctrl, self.old_switch, self.railtype)
+		dir, last_switch = boost_cart:get_rail_direction(
+			pos, cart_dir, ctrl, self.old_switch, self.railtype
+		)
 	end
 
 	local new_acc = {x=0, y=0, z=0}
@@ -253,30 +247,35 @@ function boost_cart.cart:on_step(dtime)
 		local speed_mod = tonumber(speed_mod_string)
 		if speed_mod_string == "halt" then
 			vel = {x=0, y=0, z=0}
-			acc = {x=0, y=0, z=0}
+			acc = 0
-			dir = {x=0, y=0, z=0}
 			pos = vector.round(pos)
 			update.pos = true
 			update.vel = true
 		elseif speed_mod and speed_mod ~= 0 then
-			if speed_mod > 0 then
-				for _,v in ipairs({"x","y","z"}) do
-					if math.abs(vel[v]) >= max_vel then
-						speed_mod = 0
-						break
-					end
-				end
-			end
 			-- Try to make it similar to the original carts mod
 			acc = acc + (speed_mod * 10)
 		else
 			acc = acc - 0.4
 			-- Handbrake
-			if ctrl and ctrl.down and math.abs(vel.x + vel.z) > 1.2 then
+			if ctrl and ctrl.down then
 				acc = acc - 1.2
 			end
 		end
 
+		if self.old_dir.y == 0 and not self.punched then
+			-- Stop the cart swing between two rail parts (handbrake)
+			if vector.equals(vector.multiply(self.old_dir, -1), dir) then
+				vel = {x=0, y=0, z=0}
+				acc = 0
+				if self.old_pos then
+					pos = vector.new(self.old_pos)
+					update.pos = true
+				end
+				dir = vector.new(self.old_dir)
+				update.vel = true
+			end
+		end
+
 		new_acc = vector.multiply(dir, acc)
 	end
 
@@ -308,6 +307,7 @@ function boost_cart.cart:on_step(dtime)
 					obj_:get_luaentity() and
 					not obj_:get_luaentity().physical_state and
 					obj_:get_luaentity().name == "__builtin:item" then
+
 				obj_:set_attach(self.object, "", {x=0, y=0, z=0}, {x=0, y=0, z=0})
 				self.attached_items[#self.attached_items + 1] = obj_
 			end

rails.lua

@@ -1,7 +1,10 @@
 minetest.register_node(":default:rail", {
 	description = "Rail",
 	drawtype = "raillike",
-	tiles = {"default_rail.png", "default_rail_curved.png", "default_rail_t_junction.png", "default_rail_crossing.png"},
+	tiles = {
+		"default_rail.png", "default_rail_curved.png",
+		"default_rail_t_junction.png", "default_rail_crossing.png"
+	},
 	inventory_image = "default_rail.png",
 	wield_image = "default_rail.png",
 	paramtype = "light",
@@ -12,7 +15,7 @@ minetest.register_node(":default:rail", {
 		type = "fixed",
 		fixed = {-1/2, -1/2, -1/2, 1/2, -1/2+1/16, 1/2},
 	},
-	groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1},
+	groups = boost_cart:get_rail_groups(),
 })
 
 if minetest.get_modpath("moreores") then
@@ -21,8 +24,11 @@ if minetest.get_modpath("moreores") then
 else
 	boost_cart:register_rail(":carts:copperrail", {
 		description = "Copper rail",
-		tiles = {"carts_rail_cp.png", "carts_rail_curved_cp.png", "carts_rail_t_junction_cp.png", "carts_rail_crossing_cp.png"},
+		tiles = {
-		groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1},
+			"carts_rail_cp.png", "carts_rail_curved_cp.png",
+			"carts_rail_t_junction_cp.png", "carts_rail_crossing_cp.png"
+		},
+		groups = boost_cart:get_rail_groups(),
 	})
 
 	minetest.register_craft({
@@ -39,8 +45,11 @@ end
 
 boost_cart:register_rail(":carts:powerrail", {
 	description = "Powered rail",
-	tiles = {"carts_rail_pwr.png", "carts_rail_curved_pwr.png", "carts_rail_t_junction_pwr.png", "carts_rail_crossing_pwr.png"},
+	tiles = {
-	groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1},
+		"carts_rail_pwr.png", "carts_rail_curved_pwr.png",
+		"carts_rail_t_junction_pwr.png", "carts_rail_crossing_pwr.png"
+	},
+	groups = boost_cart:get_rail_groups(),
 
 	after_place_node = function(pos, placer, itemstack)
 		if not mesecon then
@@ -72,19 +81,22 @@ minetest.register_craft({
 
 boost_cart:register_rail(":carts:brakerail", {
 	description = "Brake rail",
-	tiles = {"carts_rail_brk.png", "carts_rail_curved_brk.png", "carts_rail_t_junction_brk.png", "carts_rail_crossing_brk.png"},
+	tiles = {
-	groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1},
+		"carts_rail_brk.png", "carts_rail_curved_brk.png",
+		"carts_rail_t_junction_brk.png", "carts_rail_crossing_brk.png"
+	},
+	groups = boost_cart:get_rail_groups(),
 
 	after_place_node = function(pos, placer, itemstack)
 		if not mesecon then
-			minetest.get_meta(pos):set_string("cart_acceleration", "-0.2")
+			minetest.get_meta(pos):set_string("cart_acceleration", "-0.3")
 		end
 	end,
 
 	mesecons = {
 		effector = {
 			action_on = function(pos, node)
-				boost_cart:boost_rail(pos, -0.2)
+				minetest.get_meta(pos):set_string("cart_acceleration", "-0.3")
 			end,
 
 			action_off = function(pos, node)
@@ -103,10 +115,13 @@ minetest.register_craft({
 	}
 })
 
-boost_cart:register_rail(":boost_cart:startstoprail", {
+boost_cart:register_rail("boost_cart:startstoprail", {
 	description = "Start-stop rail",
-	tiles = {"carts_rail_ss.png", "carts_rail_curved_ss.png", "carts_rail_t_junction_ss.png", "carts_rail_crossing_ss.png"},
+	tiles = {
-	groups = {dig_immediate = 2, attached_node = 1, rail = 1, connect_to_raillike = 1},
+		"carts_rail_ss.png", "carts_rail_curved_ss.png",
+		"carts_rail_t_junction_ss.png", "carts_rail_crossing_ss.png"
+	},
+	groups = boost_cart:get_rail_groups(),
 
 	after_place_node = function(pos, placer, itemstack)
 		if not mesecon then