src/timetable: Add new_from_timestamp function

[etc/awesome.git] / src / timetable.lua

diff --git a/src/timetable.lua b/src/timetable.lua
index 81fcbf8acd6ff9e75ff5c3fad70732c916e9a80f..887ee94d689344d48e869d9036e2e40cd7078c0a 100644 (file)
--- 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 )
@@ -96,23 +99,91 @@ 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 ;
+       __lt = function ( a , b )
+               return a:timestamp() < b:timestamp()
+       end ;
+}
+
+local function cast_timetable ( tm )
+       return setmetatable ( tm , timetable_mt )
+end
+
+local function new_timetable ( year , month , day , hour , min , sec )
+       return cast_timetable {
+               year  = year ;
+               month = month ;
+               day   = day ;
+               hour  = hour ;
+               min   = min ;
+               sec   = 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 ;
 }