X-Git-Url: https://git.madduck.net/etc/awesome.git/blobdiff_plain/cf0cc951c06f50ff9390eca662f13d4887c83114..86e57ee7249734545974d4b8ba2de3bcea6575a3:/src/timetable.lua

diff --git a/src/timetable.lua b/src/timetable.lua
index df78b15..e7f2816 100644
--- a/src/timetable.lua
+++ b/src/timetable.lua
@@ -27,9 +27,13 @@ local function month_length ( m , y )
 	end
 end
 
+local function leap_years_since ( year )
+	return idiv ( year , 4 ) - idiv ( year , 100 ) + idiv ( year , 400 )
+end
+
 local function doomsday ( year )
 	return ( 3 -- Tuesday
-		- 1 + year + idiv ( year , 4 ) - idiv ( year , 100 ) + idiv ( year , 400 ) )
+		- 1 + year + leap_years_since ( year ) )
 		% 7 + 1
 end
 local doomsday_cache = setmetatable ( { } , {
@@ -72,9 +76,8 @@ local function unpack_tm ( tm )
 		tm.sec  or 0
 end
 
-local function normalise ( tm )
-	local year , month , day , hour , min , sec = unpack_tm ( tm )
-
+-- Modify parameters so they all fit within the "normal" range
+local function normalise ( year , month , day , hour , min , sec )
 	min  , sec  = increment ( min  , sec  , 60 ) -- TODO: consider leap seconds?
 	hour , min  = increment ( hour , min  , 60 )
 	day  , hour = increment ( day  , hour , 24 )
@@ -96,22 +99,60 @@ local function normalise ( tm )
 	year , month = increment ( year , month - 1 , 12 )
 	month = month + 1
 
-	tm.sec   = sec
-	tm.min   = min
-	tm.hour  = hour
-	tm.day   = day
-	tm.month = month
-	tm.year  = year
+	return year , month , day , hour , min , sec
+end
+
+local leap_years_since_1970 = leap_years_since ( 1970 )
+local function timestamp ( year , month , day , hour , min , sec )
+	year , month , day , hour , min , sec = normalise ( year , month , day , hour , min , sec )
+
+	local days_since_epoch = day_of_year ( day , month , year )
+		+ 365 * ( year - 1970 )
+		-- Each leap year adds one day
+		+ ( leap_years_since ( year - 1 ) - leap_years_since_1970 ) - 1
+
+	return days_since_epoch * 60*60*24
+		+ hour  * (60*60)
+		+ min   * 60
+		+ sec
+end
+
+
+local timetable_methods = { }
+
+function timetable_methods:normalise ( )
+	local year , month , day
+	year , month , day , self.hour , self.min , self.sec = normalise ( unpack_tm ( self ) )
+
+	self.day   = day
+	self.month = month
+	self.year  = year
 
 	local yday = day_of_year ( day , month , year )
 	local wday = day_of_week ( yday , year )
 
-	tm.yday = yday
-	tm.wday = wday
+	self.yday = yday
+	self.wday = wday
+
+	return self
+end
+timetable_methods.normalize = timetable_methods.normalise -- American English
 
-	return tm
+function timetable_methods:timestamp ( )
+	return timestamp ( unpack_tm ( self ) )
 end
+
+function timetable_methods:rfc_3339 ( )
+	-- %06.4g gives 3 (=6-4+1) digits after decimal
+	return strformat ( "%04u-%02u-%02uT%02u:%02u:%06.4g" , unpack_tm ( self ) )
+end
+
 local timetable_mt = {
+	__index    = timetable_methods ;
+	__tostring = timetable_methods.rfc_3339 ;
+	__eq = function ( a , b )
+		return a:timestamp() < b:timestamp()
+	end ;
 }
 
 local function cast_timetable ( tm )
@@ -132,6 +173,7 @@ end
 return {
 	doomsday  = doomsday ;
 	normalise = normalise ;
+	timestamp = timestamp ;
 
 	new = new_timetable ;
 	cast = cast_timetable ;