Keeping things simple

lib/duration.rb

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+# -*- encoding:  utf-8 -*-
+require 'i18n'
+require 'active_support/core_ext'
+
+# Duration objects are simple mechanisms that allow you to operate on durations
+# of time.  They allow you to know how much time has passed since a certain
+# point in time, or they can tell you how much time something is (when given as
+# seconds) in different units of time measurement.  Durations would particularly
+# be useful for those scripts or applications that allow you to know the uptime
+# of themselves or perhaps provide a countdown until a certain event.
+class Duration
+  include Comparable
+
+  UNITS = [:seconds, :minutes, :hours, :days, :weeks]
+
+  MULTIPLES = {:seconds => 1,
+               :minutes => 60,
+               :hours   => 3600,
+               :days    => 86400,
+               :weeks   => 604800,
+               :second  => 1,
+               :minute  => 60,
+               :hour    => 3600,
+               :day     => 86400,
+               :week    => 604800}
+
+  attr_reader :weeks, :days, :hours, :minutes, :seconds, :total
+
+  # Initialize a duration. 'args' can be a hash or anything else.  If a hash is
+  # passed, it will be scanned for a key=>value pair of time units such as those
+  # listed in the Duration::UNITS array or Duration::MULTIPLES hash.
+  #
+  # If anything else except a hash is passed, #to_i is invoked on that object
+  # and expects that it return the number of seconds desired for the duration.
+  def initialize(args = 0)
+    if args.kind_of?(Hash)
+      @seconds = 0
+      MULTIPLES.each do |unit, multiple|
+        unit = unit.to_sym
+        @seconds += args[unit].to_i * multiple if args.key?(unit)
+      end
+    else
+      @seconds = args.to_i
+    end
+
+    calculate!
+  end
+
+  # Compare this duration to another (or objects that respond to #to_i)
+  def <=>(other)
+    return false unless other.is_a?(Duration)
+    @total <=> other.to_i
+  end
+
+  def +(other)
+    Duration.new(@total + other.to_i)
+  end
+
+  def -(other)
+    Duration.new(@total - other.to_i)
+  end
+
+  def *(other)
+    Duration.new(@total * other.to_i)
+  end
+
+  def /(other)
+    Duration.new(@total / other.to_i)
+  end
+
+  def %(other)
+    Duration.new(@total % other.to_i)
+  end
+
+  # Formats a duration in ISO8601.
+  # @see http://en.wikipedia.org/wiki/ISO_8601#Durations
+  def iso8601
+    output = 'P'
+
+    output << "#{weeks}W" if weeks > 0
+    output << "#{days}D" if days > 0
+    if seconds > 0 || minutes > 0 || hours > 0
+      output << 'T'
+      output << "#{hours}H" if hours > 0
+      output << "#{minutes}M" if minutes > 0
+      output << "#{seconds}S" if seconds > 0
+    end
+
+    output
+  end
+
+  # @return true if total is 0
+  def blank?
+    @total == 0
+  end
+
+  # @return true if total different than 0
+  def present?
+    !blank?
+  end
+
+  # Format a duration into a human-readable string.
+  #
+  #   %w  => weeks
+  #   %d  => days
+  #   %h  => hours
+  #   %m  => minutes
+  #   %s  => seconds
+  #   %t  => total seconds
+  #   %H  => zero-padded hours
+  #   %M  => zero-padded minutes
+  #   %S  => zero-padded seconds
+  #   %~s => locale-dependent "seconds" terminology
+  #   %~m => locale-dependent "minutes" terminology
+  #   %~h => locale-dependent "hours" terminology
+  #   %~d => locale-dependent "days" terminology
+  #   %~w => locale-dependent "weeks" terminology
+  #
+  # You can also use the I18n support.
+  # The %~s, %~m, %~h, %~d and %~w can be translated with I18n.
+  # If you are using Ruby on Rails, the support is ready out of the box, so just change your locale file. Otherwise you can try:
+  #
+  #   I18n.load_path << "path/to/your/locale"
+  #   I18n.locale = :your_locale
+  # 
+  # And you must use the following structure (example) for your locale file:
+  #   pt:
+  #     ruby_duration:
+  #       second: segundo
+  #       seconds: segundos
+  #       minute: minuto
+  #       minutes: minutos
+  #       hour: hora
+  #       hours: horas
+  #       day: dia
+  #       days: dias
+  #       week: semana
+  #       weeks: semanas
+  #
+  def format(format_str)
+    identifiers = {
+      'w'  => @weeks,
+      'd'  => @days,
+      'h'  => @hours,
+      'm'  => @minutes,
+      's'  => @seconds,
+      't'  => @total,
+      'H'  => @hours.to_s.rjust(2, '0'),
+      'M'  => @minutes.to_s.rjust(2, '0'),
+      'S'  => @seconds.to_s.rjust(2, '0'),
+      '~s' => i18n_for(:second),
+      '~m' => i18n_for(:minute),
+      '~h' => i18n_for(:hour),
+      '~d' => i18n_for(:day),
+      '~w' => i18n_for(:week)
+    }
+
+    format_str.gsub(/%?%(w|d|h|m|s|t|H|M|S|~(?:s|m|h|d|w))/) do |match|
+      match['%%'] ? match : identifiers[match[1..-1]]
+    end.gsub('%%', '%')
+  end
+
+  alias_method :to_i, :total
+  alias_method :strftime, :format
+
+private
+
+  # Calculates the duration from seconds and figures out what the actual
+  # durations are in specific units.  This method is called internally, and
+  # does not need to be called by user code.
+  def calculate!
+    multiples = [MULTIPLES[:weeks], MULTIPLES[:days], MULTIPLES[:hours], MULTIPLES[:minutes], MULTIPLES[:seconds]]
+    units     = []
+    @total    = @seconds.to_f.round
+    multiples.inject(@total) do |total, multiple|
+      # Divide into largest unit
+      units << total / multiple
+      total % multiple # The remainder will be divided as the next largest
+    end
+
+    # Gather the divided units
+    @weeks, @days, @hours, @minutes, @seconds = units
+  end
+
+  def i18n_for(singular)
+    plural = "#{singular}s"
+    label = send(plural) == 1 ? singular : plural
+
+    I18n.t(label, :scope => :ruby_duration, :default => label.to_s)
+  end
+end

lib/duration/mongoid.rb

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+require "#{File.dirname(__FILE__)}/../duration"
+
+# Mongoid serialization support for Duration type.
+module Mongoid
+  module Fields
+    module Serializable
+      class Duration
+        include Serializable
+
+        # Deserialize a Duration given the amount of seconds stored by Mongodb
+        #
+        # @param [Integer, nil] duration in seconds
+        # @return [Duration] deserialized Duration
+        def deserialize(seconds)
+          return if !seconds
+          ::Duration.new(seconds)
+        end
+
+        # Serialize a Duration or a Hash (with duration units) or a amount of seconds to
+        # a BSON serializable type.
+        #
+        # @param [Duration, Hash, Integer] value
+        # @return [Integer] duration in seconds
+        def serialize(value)
+          return if value.blank?
+          if value.is_a?(Hash)
+            value.delete_if{|k, v| v.blank? || !::Duration::UNITS.include?(k.to_sym)}
+            return if value.blank?
+            ::Duration.new(value).to_i
+          elsif value.respond_to?(:to_i)
+            value.to_i
+          end
+        end
+      end
+    end
+  end
+end

lib/duration/version.rb

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+class Duration
+  VERSION = "2.0.0"
+end