X-Git-Url: https://git.madduck.net/etc/awesome.git/blobdiff_plain/81eaf243f3f28403292343af73e178f79ab5c0b3..6db06b57e851ec08d5355f015d6df1ebe58b4982:/src/timetable.lua

diff --git a/src/timetable.lua b/src/timetable.lua
index 9af7994..d1cd534 100644
--- a/src/timetable.lua
+++ b/src/timetable.lua
@@ -1,3 +1,4 @@
+local strformat = string.format
 local floor = math.floor
 local function idiv ( n , d )
 	return floor ( n / d )
@@ -20,6 +21,7 @@ local function year_length ( y )
 end
 
 local function month_length ( m , y )
+	m = ( m - 1 ) % 12 + 1
 	if m == 2 then
 		return is_leap ( y ) and 29 or 28
 	else
@@ -27,9 +29,13 @@ 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 ( { } , {
@@ -63,14 +69,19 @@ local function increment ( tens , units , base )
 	return tens , units
 end
 
-local function normalise ( tm )
-	local sec   = tm.sec  or 0
-	local min   = tm.min  or 0
-	local hour  = tm.hour or 12
-	local day   = assert ( tm.day   , "day required" )
-	local month = assert ( tm.month , "month required" )
-	local year  = assert ( tm.year  , "year required" )
+local function unpack_tm ( tm )
+	return assert ( tm.year  , "year required" ) ,
+		assert ( tm.month , "month required" ) ,
+		assert ( tm.day   , "day required" ) ,
+		tm.hour or 12 ,
+		tm.min  or 0 ,
+		tm.sec  or 0 ,
+		tm.yday ,
+		tm.wday
+end
 
+-- 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 )
@@ -92,23 +103,106 @@ 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
+
+function timetable_methods:timestamp ( )
+	return timestamp ( unpack_tm ( self ) )
+end
 
-	return tm
+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
+
+local function coerce_arg ( t )
+	if getmetatable ( t ) == timetable_mt then
+		return t:timestamp ( )
+	end
+	return t
+end
+
+timetable_mt = {
+	__index    = timetable_methods ;
+	__tostring = timetable_methods.rfc_3339 ;
+	__eq = function ( a , b )
+		return coerce_arg ( a ) == coerce_arg ( b )
+	end ;
+	__lt = function ( a , b )
+		return coerce_arg ( a ) < coerce_arg ( b )
+	end ;
+}
+
+local function cast_timetable ( tm )
+	return setmetatable ( tm , timetable_mt )
+end
+
+local function new_timetable ( year , month , day , hour , min , sec , yday , wday )
+	return cast_timetable {
+		year  = year ;
+		month = month ;
+		day   = day ;
+		hour  = hour ;
+		min   = min ;
+		sec   = sec ;
+		yday  = yday ;
+		wday  = wday ;
+	}
+end
+
+function timetable_methods:clone ( )
+	return new_timetable ( unpack_tm ( self ) )
+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 ;
 }