From be2f37a0678c66278d1c491b8f1250a8a3be9feb Mon Sep 17 00:00:00 2001
From: ywang <yw05@forksworld.de>
Date: Wed, 3 Nov 2021 18:55:31 +0100
Subject: Support different types of speed restrictions; add documentation

---
 advtrains/speed.lua | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 advtrains/speed.lua

(limited to 'advtrains/speed.lua')

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,
+}
-- 
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