Flexible rails scope for date-attributes in a PostgreSQL table

date_scope.rb

# 
# Scopes for date attribute
# https://gist.github.com/2235839
# 
module Common::DateScope
  extend ActiveSupport::Concern
  
  included do
    
    unless respond_to?(:year)
      scope :year,  ->(year) do
        year = year.year if year.is_a?(Date)
        where "EXTRACT(YEAR FROM date) = ?", year.to_s
      end
    end
    
    unless respond_to?(:month)
      scope :month, ->(month) do
        month = month.month if month.is_a?(Date)
        where "EXTRACT(MONTH FROM date) = ?", month.to_s
      end
    end
    
    # Date instance => specific year
    # Date range    => days included in the range
    # 'YYYY'        => Scope for year
    # 'YYYY-MM'     => Scope for year and month
    # 'YYYY-MM-DD'  => Scope for exact date
    # 'YYYY-MM-DD..YY-MM-DDDD' => Scope for date range
    scope :date, ->(date) do
      if date.respond_to?(:begin) && date.respond_to?(:end)
        # Range instance
        where "date >= ? AND date <= ?", date.begin, date.end
      elsif date.is_a?(String) && date.include?("..")
        # Range expressed by string
        min, max = date.split("..")
        
        Date.parse(min) rescue (raise ArgumentError, "Invalid start date '#{min}'")
        Date.parse(max) rescue (raise ArgumentError, "Invalid end date '#{max}'")
        
        where "date >= ? AND date <= ?", min, max
      elsif date.is_a?(String) && date.length < 10
        # YYYY(-MM)
        y, m = date.split("-")
        if m
          year(y).month(m)
        else
          year(y)
        end
      else
        # YYYY-MM-DD
        where :date => date
      end
    end
  end
  
end