3 files changed, 162 insertions, 3 deletions
diff --git a/advtrains_interlocking/database.lua b/advtrains_interlocking/database.lua
index e9e484c..f4a6871 100644
--- a/advtrains_interlocking/database.lua
+++ b/advtrains_interlocking/database.lua
@@ -382,7 +382,7 @@ end
 
 -- Utilize the traverser to find the track section at the specified position
 -- Returns:
--- ts_id - the first found ts
+-- ts_id, origin - the first found ts and the sigd of the found tcb
 -- nil - there were no TCBs in TRAVERSER_MAX range of the position, or track ends were reached
 -- false - the first found TCB stated End-Of-Interlocking
 function ildb.get_ts_at_pos(pos)
@@ -397,7 +397,7 @@ function ildb.get_ts_at_pos(pos)
 			local tcbs = ildb.get_tcbs(found_tcbs[1])
 			local ts
 			if tcbs.ts_id then
-				return tcbs.ts_id
+				return tcbs.ts_id, found_tcbs[1]
 			else
 				return false
 			end
diff --git a/advtrains_interlocking/tcb_ts_ui.lua b/advtrains_interlocking/tcb_ts_ui.lua
index 7e4d904..0ebe767 100644
--- a/advtrains_interlocking/tcb_ts_ui.lua
+++ b/advtrains_interlocking/tcb_ts_ui.lua
@@ -244,6 +244,15 @@ function advtrains.interlocking.show_ts_form(ts_id, pname, sel_tcb)
 		form = form.."button[5.5,5;4,1;del_tcb;Unlink selected TCB]"
 		hint = 2
 	end
+	
+	-- occupying trains
+	if ts.trains and #ts.trains>0 then
+		form = form.."label[0.5,6.1;Trains on this section:]"
+		form = form.."textlist[0.5,6.7;3,2;trnlist;"..table.concat(ts.trains, ",").."]"
+	else
+		form = form.."label[0.5,6.1;No trains on this section.]"
+	end
+	
 	if hint == 1 then
 		form = form.."label[0.5,0.75;Use the 'Join' button to designate rail crosses and link not listed far-away TCBs]"
 	elseif hint == 2 then
@@ -327,7 +336,7 @@ minetest.register_entity("advtrains_interlocking:tcbmarker", {
 })
 
 function advtrains.interlocking.show_tcb_marker(pos)
-	atdebug("showing tcb marker",pos)
+	--atdebug("showing tcb marker",pos)
 	local tcb = advtrains.interlocking.db.get_tcb(pos)
 	if not tcb then return end
 	local node_ok, conns, rhe = advtrains.get_rail_info_at(pos, advtrains.all_tracktypes)
diff --git a/advtrains_interlocking/train_related.lua b/advtrains_interlocking/train_related.lua
index 3e1c05b..3d7e280 100644
--- a/advtrains_interlocking/train_related.lua
+++ b/advtrains_interlocking/train_related.lua
@@ -1,2 +1,152 @@
 -- train_related.lua
 -- Occupation of track sections - mainly implementation of train callbacks
+
+--[[
+Track section occupation is saved as follows
+
+In train:
+train.il_sections = {
+	[n] = {ts_id = <...> (origin = <sigd>)}
+}
+-- "origin" is the TCB (signal describer) the train initially entered this section
+
+In track section
+ts.trains = {
+	[n] = <train_id>
+}
+
+When any inconsistency is detected, we will assume the most restrictive setup.
+It will be possible to indicate a section "free" via the GUI.
+]]
+
+local ildb = advtrains.interlocking.db
+
+
+local function itexist(tbl, com)
+	for _,item in ipairs(tbl) do
+		if (item==com) then
+			return true
+		end
+	end
+	return false
+end
+local function itkexist(tbl, ikey, com)
+	for _,item in ipairs(tbl) do
+		if item[ikey] == com then
+			return true
+		end
+	end
+	return false
+end
+
+local function itremove(tbl, com)
+	local i=1
+	while i <= #tbl do
+		if tbl[i] == com then
+			table.remove(tbl, i)
+		else
+			i = i + 1
+		end
+	end
+end
+local function itkremove(tbl, ikey, com)
+	local i=1
+	while i <= #tbl do
+		if tbl[i][ikey] == com then
+			table.remove(tbl, i)
+		else
+			i = i + 1
+		end
+	end
+end
+
+local function setsection(tid, train, ts_id, ts, origin)
+	-- train
+	if not train.il_sections then train.il_sections = {} end
+	if not itkexist(train.il_sections, "ts_id", ts_id) then
+		table.insert(train.il_sections, {ts_id = ts_id, origin = origin})
+	end
+	
+	-- ts
+	if not ts.trains then ts.trains = {} end
+	if not itexist(ts.trains, tid) then
+		table.insert(ts.trains, tid)
+	end
+	
+end
+
+local function freesection(tid, train, ts_id, ts)
+	-- train
+	if not train.il_sections then train.il_sections = {} end
+	itkremove(train.il_sections, "ts_id", ts_id)
+	
+	-- ts
+	if not ts.trains then ts.trains = {} end
+	itremove(ts.trains, tid)
+	
+end
+
+
+-- This is regular operation
+-- The train is on a track and drives back and forth
+
+-- This sets the section for both directions, to be failsafe
+advtrains.tnc_register_on_enter(function(pos, id, train, index)
+	local tcb = ildb.get_tcb(pos)
+	if tcb then
+		for connid=1,2 do
+			local ts = tcb[connid].ts_id and ildb.get_ts(tcb[connid].ts_id)
+			if ts then
+				setsection(id, train, tcb[connid].ts_id, ts, {p=pos, s=connid})
+			end
+		end
+	end
+end)
+
+
+-- this time, of course, only clear the backside (cp connid)
+advtrains.tnc_register_on_leave(function(pos, id, train, index)
+	local tcb = ildb.get_tcb(pos)
+	if tcb and train.path_cp[index] then
+		local connid = train.path_cp[index]
+		local ts = tcb[connid].ts_id and ildb.get_ts(tcb[connid].ts_id)
+		if ts then
+			freesection(id, train, tcb[connid].ts_id, ts)
+		end
+	end
+end)
+
+-- those callbacks are needed to account for created and removed trains (also regarding coupling)
+
+advtrains.te_register_on_create(function(id, train)
+	-- let's see what track sections we find here
+	local index = atround(train.index)
+	local pos = advtrains.path_get(train, index)
+	local ts_id, origin = ildb.get_ts_at_pos(pos)
+	if ts_id then
+		local ts = ildb.get_ts(ts_id)
+		if ts then
+			setsection(id, train, ts_id, ts, origin)
+		else
+			atwarn("ILDB corruption: TCB",origin," has invalid TS reference")
+		end
+	elseif ts_id==nil then
+		atwarn("Train",id,": Unable to determine whether to block a track section!")
+	else
+		atdebug("Train",id,": Outside of interlocked area!")
+	end
+end)
+
+advtrains.te_register_on_remove(function(id, train)
+	if train.il_sections then
+		for idx, item in ipairs(train.il_sections) do
+			
+			local ts = item.ts_id and ildb.get_ts(item.ts_id)
+			
+			if ts and ts.trains then
+				itremove(ts.trains, id)
+			end
+		end
+		train.il_sections = nil
+	end
+end)