ioquatix/periodical

# Copyright, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# THE SOFTWARE.

require 'date'

module Periodical
    Duration = Struct.new(:from, :to) do
        def days
            to - from
        end
        
        def weeks
            days / 7
        end
        
        def whole_months
            (to.year * 12 + to.month) - (from.year * 12 + from.month)
        end
        
        def months
            whole = self.whole_months
            
            partial_start = from >> whole
            partial_end = from >> whole + 1
            
            return whole + (to - partial_start) / (partial_end - partial_start)
        end
        
        def whole_years
            to.year - from.year
        end
        
        def years
            whole = self.whole_years
            
            partial_start = from >> (whole * 12)
            partial_end = from >> ((whole + 1) * 12)
            
            return whole + (to - partial_start) / (partial_end - partial_start)
        end
        
        # Calculate the number of periods between from and to
        def / period
            self.send(period.unit) / period.count
        end
    end
end