root/lu/LUDate.lua

--------------------------------------------------------------------------------
-- Title:               LUDate.lua
-- Description:         Like a square peg in a round hole
-- Author:              Raphaël Szwarc http://alt.textdrive.com/lua/
-- Creation Date:       February 1, 2005
-- Legal:               Copyright (C) 2005 Raphaël Szwarc
--------------------------------------------------------------------------------

-- import dependencies
local LUObject = require( "LUObject" )
local LUString = require( "LUString" )
local math = require( "math" )
local os = require( "os" )

-- constant(s)
local Second = 1
local Minute = 60 * Second
local Hour = 60 * Minute
local Day = 24 * Hour
local Week = 7 * Day
local Month = 31 * Day
local Year = 365 * Day
local Durations = { Y = Year, M = Month, W = Week, D = Day, h = Hour, m = Minute, s = Second }

-- define the class
local super = LUObject
local self = super()

-- initialization method
function self:init( aTime )
        self = super.init( self )

        self._time = aTime
        
        return self
end

-- method to access this date time
function self:time()
        if self._time == nil then
                self._time = os.time()
        end
        
        return self._time
end

-- method to access this date's date table
function self:date()
        if self._date == nil then
                self._date = os.date( "*t", self:time() )
        end

        return self._date
end

-- method to compare the given object with this object
function self:compare( anObject )
        return self:time() < anObject:time()
end

 -- method for equality
function self:equals( anObject )
        if self:isKindOf( anObject ) == true then
                if self:time() == anObject:time() then
                        return true
                end
        end

        return false
end

-- method for hashing
function self:hashCode()
        return self:time()
end

-- method to access this date year
function self:year()
        return self:date()[ "year" ]
end

-- method to access this date month
function self:month()
        return self:date()[ "month" ]
end

-- method to access this date week
function self:week()
        return tonumber( self:toString( "%U" ) )
end

-- method to access this month number of weeks
function self:weeksInMonth()
        return self:monthEndDate():week() - self:monthDate():week() + 1
end

-- method to access this date day
function self:day()
        return self:date()[ "day" ]
end

-- method to access this date day of year
function self:dayOfYear()
        return self:date()[ "yday" ]
end

-- method to access this date day of week
function self:dayOfWeek()
        return self:date()[ "wday" ]
end

-- method to access this date hour
function self:hour()
        return self:date()[ "hour" ]
end

-- method to access this date minute
function self:minute()
        return self:date()[ "min" ]
end

-- method to access this date second
function self:second()
        return self:date()[ "sec" ]
end

-- method to access this date day saving time
function self:isDST()
        return self:date()[ "isdst" ]
end

-- method to access this date UTC time
function self:utc()
        local anOffset = self:timeZoneOffset()
        
        if anOffset ~= nil then
                return self:time() - anOffset
        end
        
        return self:time()
end

-- method to access this date UTC date
function self:utcDate()
        return self:new( self:utc() )
end

-- method to access the day date
function self:dayDate()
        local someValues = { year = self:year(), month = self:month(), day = self:day(), hour = 0, min = 0, sec = 0 }
        
        return self:dateWithValues( someValues )
end

-- method to access the week date
function self:weekDate()
        local someValues = { year = self:year(), month = self:month(), day = self:day() - self:dayOfWeek() + 1, hour = 0, min = 0, sec = 0 }
        
        return self:dateWithValues( someValues )
end

-- method to access the month date
function self:monthDate()
        local someValues = { year = self:year(), month = self:month(), day = 1, hour = 0, min = 0, sec = 0 }
        
        return self:dateWithValues( someValues )
end

-- method to access the year date
function self:yearDate()
        local someValues = { year = self:year(), month = 1, day = 1, hour = 0, min = 0, sec = 0 }
        
        return self:dateWithValues( someValues )
end

-- method to access the end of the day date
function self:dayEndDate()
        local someValues = { year = self:year(), month = self:month(), day = self:day(), hour = 23, min = 59, sec = 59 }
        
        return self:dateWithValues( someValues )
end

-- method to access the end of the week date
function self:weekEndDate()
        local someValues = { year = self:year(), month = self:month(), day = self:day() + 7 - self:dayOfWeek(), hour = 23, min = 59, sec = 59 }
        
        return self:dateWithValues( someValues )
end

-- method to access the end of the month date
function self:monthEndDate()
        local someValues = { year = self:year(), month = self:month() + 1, day = 0, hour = 23, min = 59, sec = 59 }
        
        return self:dateWithValues( someValues )
end

-- method to access the end of the year date
function self:yearEndDate()
        local someValues = { year = self:year(), month = 12, day = 31, hour = 23, min = 59, sec = 59 }
        
        return self:dateWithValues( someValues )
end

-- method to add year, month, day, hour, minute and second to a date
function self:add( aYear, aMonth, aDay, anHour, aMinute, aSecond )
        local aYear = self:year() + ( aYear or 0 )
        local aMonth = self:month() + ( aMonth or 0 )
        local aDay = self:day() + ( aDay or 0 )
        local anHour = self:hour() + ( anHour or 0 )
        local aMinute = self:minute() + ( aMinute or 0 )
        local aSecond = self:second() + ( aSecond or 0 )
        local someValues = { year = aYear, month = aMonth, day = aDay, hour = anHour, min = aMinute, sec = aSecond }
        
        return self:dateWithValues( someValues )
end

-- method to compute an approximate interval between two dates
function self:interval( aDate, aType )
        local aDuration = Durations[ aType ] or Second
        local anInterval = math.floor( math.abs( self:time() - aDate:time() ) / aDuration )
        
        if self > aDate then
                anInterval = -anInterval
        end
        
        return anInterval
end

-- as per "Frequently Asked Questions about Calendars Version 2.7"
-- "2.16.1 Is there a formula for calculating the Julian day number?"
-- http://www.tondering.dk/claus/cal/node3.html#SECTION003161000000000000000

function self:julianDay()
        local floor = math.floor
        local a = floor( ( 14 - self:month() ) / 12 )
        local y = self:year() + 4800 - a
        local m = self:month() + ( 12 * a ) - 3
        local aDay = self:day() + floor( ( ( 153 * m ) + 2 ) / 5 ) + ( 365 * y ) + floor( y / 4 ) - floor( y / 100 ) + floor( y / 400 ) - 32045
        
        return aDay
end

function self:dateWithJulianDay( aJulianDay )
        local floor = math.floor
        local a = aJulianDay + 32044
        local b = floor( ( ( 4 * a ) + 3 ) / 146097 )
        local c = a - floor( ( 146097 * b ) / 4 )
        local d = floor( ( ( 4 * c ) + 3 ) / 1461 )
        local e = c - floor( ( 1461 * d ) / 4 )
        local m = floor( ( 5 * e + 2 ) / 153 )
        local aDay = e - floor( ( 153 * m + 2 ) / 5 ) + 1
        local aMonth = m + 3 - ( 12 * floor( m / 10 ) )
        local aYear = ( 100 * b ) + d - 4800 + floor( m / 10 )
        local someValues = { year = aYear, month = aMonth, day = aDay, hour = 0, min = 0, sec = 0 }

        return self:dateWithValues( someValues )
end

-- method for string representation
function self:toString( aFormat )
        if aFormat == nil then
                aFormat = "%Y-%m-%d %H:%M:%S"
        end

        return os.date( aFormat, self:time() )
end

-- method to create a date with the given values
function self:dateWithValues( someValues )
        return self:new( os.time( someValues ) )
end

-- method to access the local time zone
function self:timeZone()
        local aValue = os.date( "%Z", os.time() )
        
        if aValue == nil then
                aValue = "UTC"
        end
        
        return aValue
end

-- method to access the local time zone offset
function self:timeZoneOffset()
        local anOffset = os.date( "%z", os.time() )
        
        if anOffset ~= nil then
                local anHour, aMinute = anOffset:match( "(%d%d)(%d%d)" )
                
                if anHour ~= nil and aMinute ~= nil then
                        anHour = tonumber( anHour )
                        aMinute = tonumber( aMinute )
                        
                        do
                                local aValue = ( anHour * 60 * 60 ) + ( aMinute * 60 )
                                
                                if LUString:startsWith( anOffset, "-" ) == true then
                                        aValue = 0 - aValue
                                end

                                return aValue
                        end
                end
        end
        
        return 0
end

return self