[MIRROR] Refactors mothweek check [MDB IGNORE] (#14846)

* Refactors mothweek check (#68280)

* Refactors mothweek check

Mothweek HAS SIDE EFFECTS
Checking it on a day that causes a week offset will currently cause that
week offset to persist
That's dumb.

Also it's not very expansive, only covers a slim set of possibilities.

Instead, lets build something to generate all passing days over a period
of time, maybe 3 months out of 2 years.
Then we'll crosscheck that against some predecided "ok" dates

If either list disagrees with each other, we'll fail. That way we can't
miss an edgecase. or have issues with side effects

I like this pattern.

* Refactors mothweek check

Co-authored-by: LemonInTheDark <58055496+LemonInTheDark@users.noreply.github.com>

code/__HELPERS/time.dm

@@ -59,17 +59,38 @@ GLOBAL_VAR_INIT(rollovercheck_last_timeofday, 0)
 		if (SUNDAY)
 			return 7
 
-///Returns the first day of the given year and month in number format, from 1 (monday) - 7 (sunday).
-/proc/first_day_of_month(year, month)
+///Returns an integer in ISO format 1 (Monday) - 7 (Sunday) as a string day
+/proc/iso_to_weekday(ddd)
+	switch (ddd)
+		if (1)
+			return MONDAY
+		if (2)
+			return TUESDAY
+		if (3)
+			return WEDNESDAY
+		if (4)
+			return THURSDAY
+		if (5)
+			return FRIDAY
+		if (6)
+			return SATURDAY
+		if (7)
+			return SUNDAY
+
+/// Returns the day (mon, tues, wen...) in number format, 1 (monday) - 7 (sunday) from the passed in date (year, month, day)
+/// All inputs are expected indexed at 1
+/proc/day_of_month(year, month, day)
 	// https://en.wikipedia.org/wiki/Zeller%27s_congruence
 	var/m = month < 3 ? month + 12 : month // month (march = 3, april = 4...february = 14)
 	var/K = year % 100 // year of century
 	var/J = round(year / 100) // zero-based century
-	// day 0-6 saturday to sunday:
-	var/h = (1 + round(13 * (m + 1) / 5) + K + round(K / 4) + round(J / 4) - 2 * J) % 7
+	// day 0-6 saturday to friday:
+	var/h = (day + round(13 * (m + 1) / 5) + K + round(K / 4) + round(J / 4) - 2 * J) % 7
 	//convert to ISO 1-7 monday first format
 	return ((h + 5) % 7) + 1
 
+/proc/first_day_of_month(year, month)
+	return day_of_month(year, month, 1)
 
 //Takes a value of time in deciseconds.
 //Returns a text value of that number in hours, minutes, or seconds.

code/modules/holiday/holidays.dm

@@ -794,3 +794,20 @@
 
 /datum/holiday/easter/getStationPrefix()
 	return pick("Fluffy","Bunny","Easter","Egg")
+
+/// Takes a holiday datum, a starting month, ending month, max amount of days to test in, and min/max year as input
+/// Returns a list in the form list("yyyy/m/d", ...) representing all days the holiday runs on in the tested range
+/proc/poll_holiday(datum/holiday/path, min_month, max_month, min_year, max_year, max_day)
+	var/list/deets = list()
+	for(var/year in min_year to max_year)
+		for(var/month in min_month to max_month)
+			for(var/day in 1 to max_day)
+				var/datum/holiday/new_day = new path()
+				if(new_day.shouldCelebrate(day, month, year, iso_to_weekday(day_of_month(year, month, day))))
+					deets += "[year]/[month]/[day]"
+	return deets
+
+/// Does the same as [/proc/poll_holiday], but prints the output to admins instead of returning it
+/proc/print_holiday(datum/holiday/path, min_month, max_month, min_year, max_year, max_day)
+	var/list/deets = poll_holiday(path, min_month, max_month, min_year, max_year, max_day)
+	message_admins("The accepted dates for [path] in the input range [min_year]-[max_year]/[min_month]-[max_month]/1-[max_day] are [deets.Join("\n")]")

code/modules/unit_tests/holidays.dm

@@ -29,8 +29,20 @@
 	TEST_ASSERT(new_year.shouldCelebrate(2, JANUARY, 1983, SUNDAY), "January 2, 1983 was not New Year.")
 
 /datum/unit_test/moth_week_2020/Run()
-	var/datum/holiday/nth_week/moth/moth = new
-	TEST_ASSERT(moth.shouldCelebrate(18, JULY, 2020, SATURDAY), "July 18, 2020 was not Moth Week.")
-	TEST_ASSERT(moth.shouldCelebrate(20, JULY, 2020, MONDAY), "July 20, 2020 was not Moth Week.")
-	TEST_ASSERT(moth.shouldCelebrate(24, JULY, 2020, FRIDAY), "July 24, 2020 was not Moth Week.")
-	TEST_ASSERT(moth.shouldCelebrate(26, JULY, 2020, SUNDAY), "July 26, 2020 was not Moth Week.")
+	// We expect 2 year's worth of moth week, falling on the last full week of july
+	// We test ahead and behind just in case something's fucked
+	// Both lists are in the form yyyy/m/d
+	var/list/produced_moth_days = poll_holiday(/datum/holiday/nth_week/moth, 6, 8, 2020, 2021, 31)
+	var/list/predicted_moth_days = list()
+	for(var/day in 18 to 26) // Last full week of July 2020
+		predicted_moth_days += "2020/7/[day]"
+	for(var/day in 17 to 25) // Last full week of July 2021
+		predicted_moth_days += "2021/7/[day]"
+	var/list/unexpected_moths = produced_moth_days - predicted_moth_days
+	for(var/date in unexpected_moths)
+		TEST_FAIL("[date] was improperly Moth Week")
+
+	var/list/missing_moths = predicted_moth_days - produced_moth_days
+	for(var/date in missing_moths)
+		TEST_FAIL("[date] was not Moth Week")
+