Breaking down a timeframe into the optimal number of parts.

timeframe_breakdown.rb

starts_on                           = Date.parse("March 19, 2009")
ends_on                             = Date.parse("July 15, 2011")

first_beginning_of_day_interval     = starts_on.beginning_of_day
first_end_of_day_interval           = nil
first_beginning_of_month_interval   = starts_on.next_month.beginning_of_month.beginning_of_day
first_end_of_month_interval         = nil
beginning_of_year_interval          = starts_on.next_year.beginning_of_year.beginning_of_day
end_of_year_interval                = nil
last_beginning_of_month_interval    = ends_on.beginning_of_year.beginning_of_day
last_end_of_month_interval          = ends_on.prev_month.end_of_month.end_of_day
last_beginning_of_day_interval      = ends_on.beginning_of_month.beginning_of_day
last_end_of_day_interval            = ends_on.end_of_day
same_year                           = starts_on.year == ends_on.year
same_month                          = same_year && starts_on.month == ends_on.month

if same_month
  # interval == ("day", first_beginning_of_day_interval, last_end_of_day_interval)
elsif same_year
  if first_beginning_of_day_interval < first_beginning_of_month_interval
    first_end_of_day_interval         = starts_on.end_of_month.end_of_day
  else
    first_beginning_of_day_interval   = nil
  end

  if first_beginning_of_day_interval
    # interval == ("day", first_beginning_of_day_interval, first_end_of_day_interval)
  end
  if first_beginning_of_month_interval
    # interval == ("month", first_beginning_of_month_interval, last_end_of_month_interval)
  end
  if last_beginning_of_day_interval
    # interval == ("day", last_beginning_of_day_interval, last_end_of_day_interval)
  end
else
  # if "oct 3, 2009" <  "nov 1, 2009"
  #   first_end_of_day_interval = "oct 31, 2009"
  # else
  #   first day is the first of the month, so there will be no day intervals
  if first_beginning_of_day_interval < first_beginning_of_month_interval
    first_end_of_day_interval         = starts_on.end_of_month.end_of_day
  else
    first_beginning_of_day_interval   = nil
  end

  # if "nov 1, 2009" <  "jan 1, 2010"
  #   first_end_of_month_interval = "dec 31, 2009"
  # else
  #   first day of the month is the new year, so there are no months
  if first_beginning_of_month_interval < beginning_of_year_interval
    first_end_of_month_interval       = first_beginning_of_month_interval.end_of_year.end_of_day
  else
    first_beginning_of_month_interval = nil
  end

  # if "jan 1, 2011" >  "jan 1, 2010"
  #   end_of_year_interval = "dec 31, 2010"
  # else
  #   first day of the year is the first day of the starting year, so there are no years
  if last_beginning_of_month_interval > beginning_of_year_interval
    end_of_year_interval              = ends_on.prev_year.end_of_year.end_of_day
  else
    beginning_of_year_interval        = nil
  end

  # if "march 1, 2011" > "jan 1, 2011"
  #   last_end_of_month_interval = "feb 28, 2011"
  # else
  #   the last day is within the first month of the year, so there are no months
  if last_beginning_of_day_interval > last_beginning_of_month_interval
    last_end_of_month_interval        = ends_on.prev_month.end_of_month.end_of_day
  else
    last_beginning_of_month_interval  = nil
  end

  if first_beginning_of_day_interval
    # interval == ("day", first_beginning_of_day_interval, first_end_of_day_interval)
  end
  if first_beginning_of_month_interval
    # interval == ("month", first_beginning_of_month_interval, first_end_of_month_interval)
  end
  if beginning_of_year_interval
    # interval == ("year", beginning_of_year_interval, end_of_year_interval)
  end
  if last_beginning_of_month_interval
    # interval == ("month", last_beginning_of_month_interval, last_end_of_month_interval)
  end
  if last_beginning_of_day_interval
    # interval == ("day", last_beginning_of_day_interval, last_end_of_day_interval)
  end
end