1 files changed, 133 insertions, 0 deletions
diff --git a/advtrains_line_automation/scheduler.lua b/advtrains_line_automation/scheduler.lua
new file mode 100644
index 0000000..6025b02
--- /dev/null
+++ b/advtrains_line_automation/scheduler.lua
@@ -0,0 +1,133 @@
+-- scheduler.lua
+-- Implementation of a Railway time schedule queue
+-- In contrast to the LuaATC interrupt queue, this one can handle many different
+-- event receivers. This is done by registering a callback with the scheduler
+
+local ln = advtrains.lines
+local sched = {}
+
+local UNITS_THRESH = 10
+local MAX_PER_ITER = 10
+
+local callbacks = {}
+
+-- Register a handler callback to handle scheduler items.
+-- e - a handler identifier (corresponds to "handler" in enqueue() )
+-- func - a function(evtdata) to be executed when a schedule item expires
+--        evtdata - arbitrary data that has been passed into enqueue()
+function sched.register_callback(e, func)
+	callbacks[e] = func
+end
+
+--[[
+{
+	t = <railway time in seconds>
+	e = <handler callback>
+	d = <data table>
+	u = <unit identifier>
+}
+The "unit identifier" is there to prevent schedule overflows. It can be, for example, the position hash
+of a node or a train ID. If the number of schedules for a unit exceeds UNITS_THRESH, further schedules are
+blocked.
+]]--
+local queue = {}
+
+local units_cnt = {}
+
+function sched.load(data)
+	if data then
+		for i,elem in ipairs(data) do
+			table.insert(queue, elem)
+			units_cnt[elem.u] = (units_cnt[elem.u] or 0) + 1
+		end
+		atlog("[lines][scheduler] Loaded the schedule queue,",#data,"items.")
+	end
+end
+function sched.save()
+	return queue
+end
+
+function sched.run()
+	local ctime = ln.rwt.get_time()
+	local cnt = 0
+	local ucn, elem
+	while cnt <= MAX_PER_ITER do
+		elem = queue[1]
+		if elem and elem.t <= ctime then
+			table.remove(queue, 1)
+			if callbacks[elem.e] then
+				-- run it
+				callbacks[elem.e](elem.d)
+			else
+				atwarn("[lines][scheduler] No callback to handle schedule",elem)
+			end
+			cnt=cnt+1
+			ucn = units_cnt[elem.u]
+			if ucn and ucn>0 then
+				units_cnt[elem.u] = ucn - 1
+			end
+		else
+			break
+		end
+	end
+end
+
+-- Enqueue a new scheduled item to be executed at "rwtime"
+-- handler: a string identifying the handler to use (registered with sched.register_callback())
+-- evtdata: Arbitrary Lua data to be passed to the handler callback
+-- unitid: An arbitrary string uniquely identifying the thing that is issuing this enqueue.
+--    used to prevent expotentially growing "scheduler bombs"
+-- unitlim: Custom override for UNITS_THRESH (see there)
+function sched.enqueue(rwtime, handler, evtdata, unitid, unitlim)
+	local qtime = ln.rwt.to_secs(rwtime)
+	assert(type(handler)=="string")
+	assert(type(unitid)=="string")
+	assert(type(unitlim)=="number")
+	
+	local cnt=1
+	local ucn, elem
+	
+	ucn = (units_cnt[unitid] or 0)
+	local ulim=(unitlim or UNITS_THRESH)
+	if ucn >= ulim then
+		atlog("[lines][scheduler] discarding enqueue for",handler,"(limit",ulim,") because unit",unitid,"has already",ucn,"schedules enqueued")
+		return false
+	end
+	
+	while true do
+		elem = queue[cnt]
+		if not elem or elem.t > qtime then
+			table.insert(queue, cnt, {
+					t=qtime,
+					e=handler,
+					d=evtdata,
+					u=unitid,
+				})
+			units_cnt[unitid] = ucn + 1
+			return true
+		end
+		cnt = cnt+1
+	end
+end
+
+-- See enqueue(). Same meaning, except that rwtime is relative to now.
+function sched.enqueue_in(rwtime, handler, evtdata, unitid, unitlim)
+	local ctime = ln.rwt.get_time()
+	local rwtime_s = ln.rwt.to_secs(rwtime)
+	sched.enqueue(ctime + rwtime_s, handler, evtdata, unitid, unitlim)
+end
+
+-- Discards all schedules for unit "unitid" (removes them from the queue)
+function sched.discard_all(unitid)
+	local i = 1
+	while i<=#queue do
+		if queue[i].u == unitid then
+			table.remove(queue,i)
+		else
+			i=i+1
+		end
+	end
+	units_cnt[unitid] = 0
+end
+
+ln.sched = sched