X-Git-Url: https://git.madduck.net/etc/awesome.git/blobdiff_plain/e5c87b4489b0881b7b9903733478f0d11ac96ab7..bbc7e867d92c185d6316bdd222202f357f8253a3:/luatz/timetable.lua

diff --git a/luatz/timetable.lua b/luatz/timetable.lua
index 3b3b2ed..6a39a13 100644
--- a/luatz/timetable.lua
+++ b/luatz/timetable.lua
@@ -1,3 +1,4 @@
+local strftime = require "luatz.strftime".strftime
 local strformat = string.format
 local floor = math.floor
 local function idiv ( n , d )
@@ -11,6 +12,8 @@ local months_to_days_cumulative = { 0 }
 for i = 2, 12 do
 	months_to_days_cumulative [ i ] = months_to_days_cumulative [ i-1 ] + mon_lengths [ i-1 ]
 end
+-- For Sakamoto's Algorithm (day of week)
+local sakamoto = {0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4};
 
 local function is_leap ( y )
 	return (y % 4) == 0 and (y % 100) ~= 0 or (y % 400) == 0
@@ -32,19 +35,6 @@ 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 + leap_years_since ( year ) )
-		% 7 + 1
-end
-local doomsday_cache = setmetatable ( { } , {
-	__index = function ( cache , year )
-		local d = doomsday ( year )
-		cache [ year ] = d
-		return d
-	end ;
-} )
-
 local function day_of_year ( day , month , year )
 	local yday = months_to_days_cumulative [ month ]
 	if month > 2 and is_leap ( year ) then
@@ -53,8 +43,11 @@ local function day_of_year ( day , month , year )
 	return yday + day
 end
 
-local function day_of_week ( yday , year )
-	return ( yday - doomsday_cache [ year ] - 1 ) % 7 + 1
+local function day_of_week ( day , month , year )
+	if month < 3 then
+		year = year - 1
+	end
+	return ( year + leap_years_since ( year ) + sakamoto[month] + day ) % 7 + 1
 end
 
 local function increment ( tens , units , base )
@@ -68,17 +61,6 @@ local function increment ( tens , units , base )
 	return tens , units
 end
 
-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?
@@ -128,50 +110,52 @@ end
 
 local timetable_methods = { }
 
+function timetable_methods:unpack ( )
+	return assert ( self.year  , "year required" ) ,
+		assert ( self.month , "month required" ) ,
+		assert ( self.day   , "day required" ) ,
+		self.hour or 12 ,
+		self.min  or 0 ,
+		self.sec  or 0 ,
+		self.yday ,
+		self.wday
+end
+
 function timetable_methods:normalise ( )
 	local year , month , day
-	year , month , day , self.hour , self.min , self.sec = normalise ( unpack_tm ( self ) )
+	year , month , day , self.hour , self.min , self.sec = normalise ( self:unpack ( ) )
 
 	self.day   = day
 	self.month = month
 	self.year  = year
-
-	local yday = day_of_year ( day , month , year )
-	local wday = day_of_week ( yday , year )
-
-	self.yday = yday
-	self.wday = wday
+	self.yday  = day_of_year ( day , month , year )
+	self.wday  = day_of_week ( day , month , year )
 
 	return self
 end
 timetable_methods.normalize = timetable_methods.normalise -- American English
 
 function timetable_methods:timestamp ( )
-	return timestamp ( unpack_tm ( self ) )
+	return timestamp ( self:unpack ( ) )
 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 ) )
+	-- %06.3f gives 3 (=6-3) digits after decimal
+	return strformat ( "%04u-%02u-%02uT%02u:%02u:%06.3f" , self:unpack ( ) )
 end
 
-local timetable_mt
-
-local function coerce_arg ( t )
-	if getmetatable ( t ) == timetable_mt then
-		return t:timestamp ( )
-	end
-	return t
+function timetable_methods:strftime ( format_string )
+	return strftime ( format_string , self )
 end
 
-timetable_mt = {
+local timetable_mt = {
 	__index    = timetable_methods ;
 	__tostring = timetable_methods.rfc_3339 ;
 	__eq = function ( a , b )
-		return coerce_arg ( a ) == coerce_arg ( b )
+		return a:timestamp ( ) == b:timestamp ( )
 	end ;
 	__lt = function ( a , b )
-		return coerce_arg ( a ) < coerce_arg ( b )
+		return a:timestamp ( ) < b:timestamp ( )
 	end ;
 }
 
@@ -193,7 +177,7 @@ local function new_timetable ( year , month , day , hour , min , sec , yday , wd
 end
 
 function timetable_methods:clone ( )
-	return new_timetable ( unpack_tm ( self ) )
+	return new_timetable ( self:unpack ( ) )
 end
 
 local function new_from_timestamp ( ts )
@@ -201,7 +185,8 @@ local function new_from_timestamp ( ts )
 end
 
 return {
-	doomsday  = doomsday ;
+	day_of_year = day_of_year ;
+	day_of_week = day_of_week ;
 	normalise = normalise ;
 	timestamp = timestamp ;