DurationHelper#format_duration

duration_helper.rb

module DurationHelper

  # Takes a number of seconds as input and returns a formatted string. See
  # tests for examples.
  def format_duration(seconds, options = {})
    return "0 seconds" if seconds.floor == 0
    options.reverse_merge!(:parts_to_show => 4, :word_style => :short, :specific_end => false)

    description = (options[:word_style] == :short) ?
                    [ ['sec',    60], ['min',    60], ['hr',   24], ['day'] ] :
                    [ ['second', 60], ['minute', 60], ['hour', 24], ['day'] ]

    components = []
    units = seconds.floor
    description.each do |component, max|
      if max
        components.unshift([units % max, component])
        break unless units >= max
        units = units.to_f / max
      else
        components.unshift([units, component])
      end
    end

    parts_shown = 0
    results = components.map do |c|
      next if parts_shown >= options[:parts_to_show]
      parts_shown += 1
      number = c.first
      if options[:specific_end].present? && parts_shown == options[:parts_to_show] && c.last =~ /^(hr|hour|day)/
        number = number.round_at(1).to_i_if_whole
      else
        number = number.floor
      end
      next if number == 0
      "#{number} #{number == 1 ? c.last : c.last.pluralize}"
    end
    results.compact.join(' ')
  end

end

duration_helper_spec.rb

describe DurationHelper, "#format_duration" do
  it "returns the correct string for many different durations" do
    helper.format_duration(212751).should == "2 days 11 hrs 5 mins 51 secs"
    helper.format_duration(79805).should  == "22 hrs 10 mins 5 secs"
    helper.format_duration(2730).should   == "45 mins 30 secs"
    helper.format_duration(142800).should == "1 day 15 hrs 40 mins"
    helper.format_duration(352800).should == "4 days 2 hrs"
    helper.format_duration(345600).should == "4 days"
    helper.format_duration(32).should     == "32 secs"
    helper.format_duration(32.9).should   == "32 secs"
    helper.format_duration(0).should      == "0 seconds"
    helper.format_duration(0.5).should    == "0 seconds"
  end

  it "excludes least-significant units using the :parts_to_show option"do
    helper.format_duration(212751, :parts_to_show => 1).should == "2 days"
    helper.format_duration(212751, :parts_to_show => 2).should == "2 days 11 hrs"
    helper.format_duration(212751, :parts_to_show => 3).should == "2 days 11 hrs 5 mins"
    helper.format_duration(212751, :parts_to_show => 0).should == ""
  end

  it "counts a zero component that's not shown in :parts_to_show" do
    # By using :parts_to_show => 3, that means we want days, hours, and minutes;
    # but if hours turns out to be zero, then we'll actually just show 2 parts.
    helper.format_duration(1.day + 1.minute + 1.second, :parts_to_show => 3).should == "1 day 1 min"
  end

  it "uses short duration words with :word_style => :short" do
    helper.format_duration(2730, :word_style => :short).should == "45 mins 30 secs"
  end

  it "uses long duration words with :word_style => :long" do
    helper.format_duration(2730, :word_style => :long).should == "45 minutes 30 seconds"
  end

  it "uses a float for a least-significant part in days or hours with :specific_end => true" do
    helper.format_duration(352800, :specific_end => true).should == "4 days 2 hrs"
    helper.format_duration(352800, :parts_to_show => 1, :specific_end => true).should == "4.1 days"
    helper.format_duration(352835, :parts_to_show => 2, :specific_end => true).should == "4 days 2 hrs"
    helper.format_duration(79805,  :parts_to_show => 1, :specific_end => true).should  == "22.2 hrs"
    helper.format_duration(79805,  :parts_to_show => 2, :specific_end => true).should  == "22 hrs 10 mins"
    helper.format_duration(79805,  :parts_to_show => 3, :specific_end => true).should  == "22 hrs 10 mins 5 secs"
    helper.format_duration(79200,  :parts_to_show => 1, :specific_end => true).should  == "22 hrs"
  end
end