Blood moon and Ashenvale: fix handling time zones for start time

Turns out GetServerTime() does not return server time but local time. Which
is fine because synchronized clocks are a thing. But we need to adjust for
server time zone.

The previous logic just relying on GetGameTime() got this right, but it was
unreliable because GetGameTime() sucks in other ways.

.luacheckrc

@@ -42,6 +42,7 @@ globals = {
 	"C_AreaPoiInfo",
 	"C_ChatInfo",
 	"C_CurrencyInfo",
+	"C_DateAndTime",
 	"C_DeathInfo",
 	"C_GossipInfo",
 	"C_Map",

DBM-PvP/Ashenvale.lua

@@ -4,6 +4,8 @@ end
 local MAP_ASHENVALE = 1440
 local mod = DBM:NewMod("m" .. MAP_ASHENVALE, "DBM-PvP")
 
+local pvpMod = DBM:GetModByName("PvPGeneral")
+
 mod:SetRevision("@file-date-integer@")
 -- TODO: we could teach this thing to handle outdoor zones instead of only instances
 -- when implementing this make sure that the stop functions are called properly, i.e., that ZONE_CHANGED_NEW_AREA still fires when leaving
@@ -27,13 +29,6 @@ local widgetIDs = {
 -- Observed start times:
 -- 16:00:12
 
--- See BloodMoon.lua for some comments on how timing works.
-local function getTimeUntilNextEvent()
-	local time = date("*t", GetServerTime())
-	local hour = time.hour + time.min / 60 + time.sec / 60 / 60
-	return (3 - ((hour - 1) % 3)) * 60 * 60 + 20
-end
-
 local function debugTimeString()
 	local time = date("*t", GetServerTime())
 	local gameHour, gameMin = GetGameTime()
@@ -46,7 +41,7 @@ function mod:updateStartTimer()
 		-- (yes, this happened)
 		return
 	end
-	local remaining = getTimeUntilNextEvent()
+	local remaining = pvpMod:GetTimeUntilWorldPvpEvent(1)
 	local total = 3 * 60 * 60
 	if remaining < 2.75 * 60 * 60 then
 		startTimer:Update(total - remaining, total)

DBM-PvP/BloodMoon.lua

@@ -5,6 +5,8 @@ local MAP_STRANGLETHORN = 1434
 local mod = DBM:NewMod("m" .. MAP_STRANGLETHORN, "DBM-PvP")
 local L = mod:GetLocalizedStrings()
 
+local pvpMod = DBM:GetModByName("PvPGeneral")
+
 mod:SetRevision("@file-date-integer@")
 mod:SetZone(DBM_DISABLE_ZONE_DETECTION)
 mod:RegisterEvents(
@@ -23,7 +25,7 @@ local widgetIDs = {
 	[5609] = true, -- Event not active
 }
 
--- Observed start and end times (GetServerTime()), seems to be exactly 30 minutes
+-- Observed start and end times (GetServerTime()), seems to be exactly 30 minutes but start/end is a bit random
 -- 18:00:58 to 18:30:58
 -- 21:00:48 to 21:30:47
 -- 12:00:?? to 12:30:36
@@ -32,23 +34,8 @@ local widgetIDs = {
 -- 12:00:16 to 12:30:17
 -- 15:00:12 to 15:30:12
 
--- Note on game time and server time.
--- Contrary to popular opinion the event start time is not synced to GetGameTime(), it seems a bit random.
--- Also, GetGameTime() is only available with minute granularity and the updates of minutes on game time as visible by the API does not seem to be synchronized to actual time.
--- This GetGameTime() randomness seems to be just be a weird effect due to how the time between client and server are synchronized.
--- The exact time at which the minute for GetGameTime updates changes between relogs, so there doesn't seem to be any meaning to the exact point in time when this happens.
-
-local function getTimeUntilNextEvent()
-	-- C_DateAndTime.GetServerTimeLocal() returns a time zone that is neither the server's time nor my time?
-	-- GetServerTime() returns something that looks like local time and is 0.5-1.5 minutes ahead of GetGameTime() (but GetGameTime() is somewhat random between relogs)
-	-- So we just show a timer targeting xx:00:30 ServerTime (whatever ServerTime means) because that seems to be close enough (+/- 30 seconds)
-	local time = date("*t", GetServerTime())
-	local hour = time.hour + time.min / 60 + time.sec / 60 / 60
-	return (3 - (hour % 3)) * 60 * 60 + 30
-end
-
 function mod:updateStartTimer()
-	local remaining = getTimeUntilNextEvent()
+	local remaining = pvpMod:GetTimeUntilWorldPvpEvent()
 	local total = 3 * 60 * 60
 	if remaining < 2.5 * 60 * 60 then
 		startTimer:Update(total - remaining, total)
@@ -79,7 +66,7 @@ function mod:startEvent(timeRemaining)
 			-- For example, event triggers like this are common:
 			-- 3 minute at 28:35 server time, 1 minute at 29:38 server time, ended at 30:36 (2 min update was just skipped)
 			-- 3 minute at 28:10 server time, 2 minute at 29:13 server time, 1 minute at 30:15 server time, ended at 30:17
-			local remaining = getTimeUntilNextEvent() - 2.5 * 60 * 60
+			local remaining = pvpMod:GetTimeUntilWorldPvpEvent() - 2.5 * 60 * 60
 			eventRunningTimer:Update(30 * 60 - remaining, 30 * 60)
 		end
 	end

DBM-PvP/PvPGeneral.lua

@@ -681,3 +681,45 @@ do
 	end
 	mod.UPDATE_UI_WIDGET = mod.AREA_POIS_UPDATED
 end
+
+-- Note on game time and server time.
+-- Contrary to popular opinion the event start time is not synced to GetGameTime(), it seems a bit random.
+-- Also, GetGameTime() is only available with minute granularity and the updates of minutes on game time as visible by the API does not seem to be synchronized to actual time.
+-- This GetGameTime() randomness seems to be just be a weird effect due to how the time between client and server are synchronized.
+-- The exact time at which the minute for GetGameTime updates changes between relogs, so there doesn't seem to be any meaning to the exact point in time when this happens.
+-- Earlier versions of this mod just used GetGameTime() and attempted to adjust for seconds from local but it was often off by a whole minute,
+-- this implementation is only off by at most 30 seconds, but usually at most 15 seconds (if your clock is synchronized)
+
+-- Get current time in server time zone
+function mod:GetServerTime()
+	-- C_DateAndTime.GetServerTimeLocal() returns a time zone that is neither the server's time nor my time?
+	-- GetGameTime() returns server time but is updated once per minute and the update interval is synchronized to actual server time, i.e., it will be off by up to a minute and the update time differs between relogs
+	-- Also there is GetLocalGameTime() which seems to be identical to GetGameTime()?
+	-- GetServerTime() looks like it returns local time, but good thing everyone has synchronized clocks nowadays, so this is fine to use
+	-- We just need to handle time zones, i.e., find the diff between what GetGameTime() says and what is local time
+	local gameHours, gameMinutes = GetGameTime()
+	-- The whole date logic could probably be avoided with some clever modular arithmetic, but whatever, we know the date
+	local gameDate = C_DateAndTime.GetTodaysDate() -- Yes, this is server date
+	local localSeconds = GetServerTime() -- Yes, that is local time
+	local gameSeconds = time({
+		year = gameDate.year,
+		month = gameDate.month,
+		day = gameDate.day,
+		hour = gameHours,
+		min = gameMinutes
+	})
+	local timeDiff = localSeconds - gameSeconds
+	-- Time zones can be in 15 minute increments, so round to that
+	return localSeconds - math.floor(timeDiff / (15 * 60) + 0.5) * 15 * 60
+end
+
+-- Time until world pvp events (Season of Discovery) that ocur every `interval` hours at an offset of `offet` hours
+---@return number
+function mod:GetTimeUntilWorldPvpEvent(offset, interval)
+	offset = offset or 0
+	interval = interval or 3
+	local time = date("*t", self:GetServerTime())
+	local hour = time.hour + time.min / 60 + time.sec / 60 / 60
+	return (interval - ((hour - offset) % interval)) * 60 * 60 + 30
+end
+