Support different types of speed restrictions; add documentation

6 files changed, 197 insertions, 3 deletions

diff --git a/advtrains/doc/advtrains_speed_lessp.3advtrains.md b/advtrains/doc/advtrains_speed_lessp.3advtrains.md
new file mode 100644
index 0000000..165d028
--- /dev/null
+++ b/advtrains/doc/advtrains_speed_lessp.3advtrains.md
@@ -0,0 +1,15 @@
+% advtrains.speed.lessp(3advtrains) | Advtrains Developer's Manual
+
+# NAME
+`advtrains.speed.lessp`, `advtrains.speed.greaterp`, `advtrains.speed.not_lessp`, `advtrains.speed_not_greaterp`, `advtrains.speed.equalp`, `advtrains.speed.not_equalp`, `advtrains.speed.max`, `advtrains.speed.min` - speed restriction comparison functions
+
+# SYNOPSIS
+Each function takes two arguments and returns a boolean or (for `advtrains.speed.max` and `advtrains.speed.min`) a valid speed limit
+
+# DESCRIPTION
+
+The functions above correspond to the arithmetic `<`, `>`, `>=`, `<=`, `==`, `~=` operators and the `math.max` and `math.min` functions, respectively. The constants `nil` and `false` are treated as -1.
+
+# NOTES
+
+These functions are trivial to implement and the implementation can be easily embedded into existing code. They are simply provided for convenience.
diff --git a/advtrains/doc/advtrains_speed_merge_aspect.3advtrains.md b/advtrains/doc/advtrains_speed_merge_aspect.3advtrains.md
new file mode 100644
index 0000000..02e83ea
--- /dev/null
+++ b/advtrains/doc/advtrains_speed_merge_aspect.3advtrains.md
@@ -0,0 +1,18 @@
+% advtrains.speed.set_restriction(3advtrains) | Advtrains Developer's Manual
+
+# NAME
+`advtrains.speed.set_restriction`, `advtrains.speed.merge_aspect` - modify speed restriction
+
+# SYNOPSIS
+* `advtrains.speed.set_restriction(train, rtype, rval)`
+* `advtrains.speed.merge_aspect(train, asp)`
+
+# DESCRIPTION
+
+The `advtrains.speed.set_restriction` function sets the speed restriction of type `rtype` of `train` to `rval` and updates the speed restriction value to the strictest speed restriction in the table, or `nil` if all speed restrictions are `nil` or `-1`. If the speed restriction table does not exist, it is created with the `"main"` speed restriction being the speed restriction value of `train`.
+
+The `advtrains.speed.merge_aspect` function merges the main aspect of `asp` into the speed restriction table with the same procedure described above. If the signal aspect table does not provide the type of speed restriction, the restriction type `"main"` is assumed.
+
+# SIDE EFFECTS
+
+Both functions modify `train.speed_restriction` and `train.speed_restrictions_t`.
diff --git a/advtrains/init.lua b/advtrains/init.lua
index 0882237..a7e5764 100644
--- a/advtrains/init.lua
+++ b/advtrains/init.lua
@@ -198,6 +198,8 @@ advtrains.meseconrules =
 
 advtrains.fpath=minetest.get_worldpath().."/advtrains"
 
+advtrains.speed = dofile(advtrains.modpath.."/speed.lua")
+
 dofile(advtrains.modpath.."/path.lua")
 dofile(advtrains.modpath.."/trainlogic.lua")
 dofile(advtrains.modpath.."/trainhud.lua")
@@ -467,7 +469,7 @@ advtrains.avt_save = function(remove_players_from_wagons)
 				"trainparts", "recently_collided_with_env",
 				"atc_brake_target", "atc_wait_finish", "atc_command", "atc_delay", "door_open",
 				"text_outside", "text_inside", "line", "routingcode",
-				"il_sections", "speed_restriction", "is_shunt",
+				"il_sections", "speed_restriction", "speed_restrictions_t", "is_shunt",
 				"points_split", "autocouple", "atc_wait_autocouple", "ars_disable",
 			})
 			--then save it
diff --git a/advtrains/spec/speed_spec.lua b/advtrains/spec/speed_spec.lua
new file mode 100644
index 0000000..0f0365f
--- /dev/null
+++ b/advtrains/spec/speed_spec.lua
@@ -0,0 +1,70 @@
+package.path = "../?.lua;" .. package.path
+advtrains = {}
+_G.advtrains = advtrains
+local speed = require("speed")
+
+describe("Arithmetic functions on speed restrictions", function()
+	it("should work", function()
+		local a = math.random()
+		local b = math.random(20)
+		-- This test is basically a "typo check"
+		assert.is_true (speed.lessp(a, b))
+		assert.is_false(speed.greaterp(a, b))
+		assert.is_false(speed.not_lessp(a, b))
+		assert.is_true (speed.not_greaterp(a, b))
+		assert.is_false(speed.lessp(a, a))
+		assert.is_false(speed.greaterp(a, a))
+		assert.is_true (speed.equalp(a, a))
+		assert.is_false(speed.not_equalp(a, a))
+		assert.equal(b, speed.max(a, b))
+		assert.equal(a, speed.min(a, b))
+	end)
+	it("should handle -1", function()
+		assert.is_false(speed.lessp(-1, math.random()))
+	end)
+	it("should handle nil", function()
+		assert.is_false(speed.greaterp(nil, math.random()))
+	end)
+	it("should handle mixed nil and -1", function()
+		assert.is_true(speed.equalp(nil, -1))
+	end)
+end)
+
+describe("The speed restriction setter", function()
+	it("should set the signal aspect", function()
+		local t = {speed_restrictions_t = {x = 5, y = 9}}
+		local u = {speed_restrictions_t = {x = 7, y = 9}, speed_restriction = 7}
+		speed.merge_aspect(t, {main = 7, type = "x"})
+		assert.same(u, t)
+	end)
+	it("should work with existing signal aspect tables", function()
+		local t = {speed_restrictions_t = {main = 5, foo = 3}}
+		local u = {speed_restrictions_t = {main = 7, foo = 3}, speed_restriction = 3}
+		speed.merge_aspect(t, {main = 7})
+		assert.same(u, t)
+	end)
+	it("should work with distant signals", function()
+		local t = {speed_restrictions_t = {main = 5}}
+		local u = {speed_restrictions_t = {main = 5}, speed_restriction = 5}
+		speed.merge_aspect(t, {})
+		assert.same(u, t)
+	end)
+	it("should create the restriction table if necessary", function()
+		local t = {speed_restriction = 5}
+		local u = {speed_restriction = 3, speed_restrictions_t = {main = 5, foo = 3}}
+		speed.merge_aspect(t, {main = 3, type = "foo"})
+		assert.same(u, t)
+	end)
+	it("should also create the restriction table for trains without any speed limit", function()
+		local t = {}
+		local u = {speed_restrictions_t = {}}
+		speed.merge_aspect(t, {})
+		assert.same(u, t)
+	end)
+	it("should set the speed restriction to nil if that is the case", function()
+		local t = {speed_restriction = math.random(20)}
+		local u = {speed_restrictions_t = {main = -1}}
+		speed.merge_aspect(t, {main = -1})
+		assert.same(u, t)
+	end)
+end)
diff --git a/advtrains/speed.lua b/advtrains/speed.lua
new file mode 100644
index 0000000..ec4f928
--- /dev/null
+++ b/advtrains/speed.lua
@@ -0,0 +1,88 @@
+-- auxiliary functions for the reworked speed restriction system
+
+local function s_lessp(a, b)
+	if not a or a == -1 then
+		return false
+	elseif not b or b == -1 then
+		return true
+	else
+		return a < b
+	end
+end
+
+local function s_greaterp(a, b)
+	return s_lessp(b, a)
+end
+
+local function s_not_lessp(a, b)
+	return not s_lessp(a, b)
+end
+
+local function s_not_greaterp(a, b)
+	return not s_greaterp(a, b)
+end
+
+local function s_equalp(a, b)
+	return (a or -1) == (b or -1)
+end
+
+local function s_not_equalp(a, b)
+	return (a or -1) ~= (b or -1)
+end
+
+local function s_max(a, b)
+	if s_lessp(a, b) then
+		return b
+	else
+		return a
+	end
+end
+
+local function s_min(a, b)
+	if s_lessp(a, b) then
+		return a
+	else
+		return b
+	end
+end
+
+local function get_speed_restriction_from_table (tbl)
+	local strictest = -1
+	for _, v in pairs(tbl) do
+		strictest = s_min(strictest, v)
+	end
+	if strictest == -1 then
+		return nil
+	end
+	return strictest
+end
+
+local function set_speed_restriction (tbl, rtype, rval)
+	if rval then
+		tbl[rtype or "main"] = rval
+	end
+	return tbl
+end
+
+local function set_speed_restriction_for_train (train, rtype, rval)
+	local t = train.speed_restrictions_t or {main = train.speed_restriction}
+	train.speed_restrictions_t = set_speed_restriction(t, rtype, rval)
+	train.speed_restriction = get_speed_restriction_from_table(t)
+end
+
+local function merge_speed_restriction_from_aspect_to_train (train, asp)
+	return set_speed_restriction_for_train(train, asp.type, asp.main)
+end
+
+return {
+	lessp = s_lessp,
+	greaterp = s_greaterp,
+	not_lessp = s_not_lessp,
+	not_greaterp = s_not_greaterp,
+	equalp = s_equalp,
+	not_equalp = s_not_equalp,
+	max = s_max,
+	min = s_min,
+	set_restriction = set_speed_restriction_for_train,
+	merge_aspect = merge_speed_restriction_from_aspect_to_train,
+}
diff --git a/advtrains/trainlogic.lua b/advtrains/trainlogic.lua
index e7f2fd4..10af567 100644
--- a/advtrains/trainlogic.lua
+++ b/advtrains/trainlogic.lua
@@ -1168,6 +1168,7 @@ function advtrains.split_train_at_index(train, index)
 	newtrain.line = train.line
 	newtrain.routingcode = train.routingcode
 	newtrain.speed_restriction = train.speed_restriction
+	newtrain.speed_restrictions_t = table.copy(train.speed_restrictions_t)
 	newtrain.is_shunt = train.is_shunt
 	newtrain.points_split = advtrains.merge_tables(train.points_split)
 	newtrain.autocouple = train.autocouple
@@ -1210,10 +1211,10 @@ function advtrains.invert_train(train_id)
 	-- If interlocking present, check whether this train is in a section and then set as shunt move after reversion
 	if advtrains.interlocking and train.il_sections and #train.il_sections > 0 then
 		train.is_shunt = true
-		train.speed_restriction = advtrains.SHUNT_SPEED_MAX
+		advtrains.speed.set_restriction(train, "main", advtrains.SHUNT_SPEED_MAX)
 	else
 		train.is_shunt = false
-		train.speed_restriction = nil
+		advtrains.speed.set_restriction(train, "main", -1)
 	end
 end