X-Git-Url: https://git.madduck.net/etc/awesome.git/blobdiff_plain/d431ae6abaf5b0814389f2adf6069915d2e983c2..f0b23dea771e2d9cb9a672a147c946f1ad539082:/luatz/timetable.lua

diff --git a/luatz/timetable.lua b/luatz/timetable.lua
index 8c44f2f..10af170 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 )
@@ -135,12 +128,8 @@ function timetable_methods:normalise ( )
 	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
@@ -155,6 +144,10 @@ function timetable_methods:rfc_3339 ( )
 	return strformat ( "%04u-%02u-%02uT%02u:%02u:%06.3f" , self:unpack ( ) )
 end
 
+function timetable_methods:strftime ( format_string )
+	return strftime ( format_string , self )
+end
+
 local timetable_mt
 
 local function coerce_arg ( t )
@@ -168,10 +161,13 @@ 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 ;
+	__sub = function ( a , b )
+		return coerce_arg ( a ) - coerce_arg ( b )
 	end ;
 }
 
@@ -201,7 +197,8 @@ 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 ;