X-Git-Url: https://git.madduck.net/etc/awesome.git/blobdiff_plain/3a7693d5c89981e1230d0d49163fc23d02224873..3abaaf68b0945784e3a8968a733bd7f569e4330e:/src/timetable.lua

diff --git a/src/timetable.lua b/src/timetable.lua
index 7e986a1..887ee94 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 ( { } , {
@@ -98,6 +102,21 @@ local function normalise ( year , month , day , hour , min , sec )
 	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 = { }
 
@@ -119,8 +138,24 @@ function timetable_methods:normalise ( )
 end
 timetable_methods.normalize = timetable_methods.normalise -- American English
 
+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 ;
+	__lt = function ( a , b )
+		return a:timestamp() < b:timestamp()
+	end ;
 }
 
 local function cast_timetable ( tm )
@@ -138,11 +173,17 @@ local function new_timetable ( year , month , day , hour , min , sec )
 	}
 end
 
+local function new_from_timestamp ( ts )
+	return new_timetable ( 1970 , 1 , 1 , 0 , 0 , ts )
+end
+
 return {
 	doomsday  = doomsday ;
 	normalise = normalise ;
+	timestamp = timestamp ;
 
 	new = new_timetable ;
+	new_from_timestamp = new_from_timestamp ;
 	cast = cast_timetable ;
 	timetable_mt = timetable_mt ;
 }