require 'chronic'

module SifttterRedux
  # DateRangeMaker Module
  # Returns a Range of dates based on supplied parameters
  module DateRangeMaker

    # Returns a date range for the last N days (including
    # today's date if specified).
    # @param [Integer} num_days The number of days to look back
    # @param [Boolean] include_today Should today be included?
    # @return [Range]
    def self.last_n_days(num_days, include_today = false)
      if num_days < 0
        error = 'Cannot specify a negative number of days'
        fail ArgumentError, error
      end

      if include_today
        (Date.today - num_days..Date.today)
      else
        (Date.today - num_days...Date.today)
      end
    end

    # Returns a date range for the last N weeks (including
    # today's date if specified).
    # @param [Integer] num_days The number of weeks to look back
    # @param [Boolean] include_today Should today be included?
    # @return [Range]
    def self.last_n_weeks(num_weeks = 0, include_today = false)
      if num_weeks < 0
        error = 'Cannot specify a negative number of weeks'
        fail ArgumentError, error
      end

      beginning_date = Date.today - Date.today.wday + 1
      end_date = Date.today - Date.today.wday + 7

      # We coerce the end date to be today if a date
      # greater than today has been specified.
      end_date = Date.today if end_date > Date.today

      if include_today
        (beginning_date - num_weeks * 7..end_date)
      else
        (beginning_date - num_weeks * 7...end_date)
      end
    end

    # Returns a date range for specified start dates and
    # end dates. Note that specifying an end date greater
    # than today's date will force today to be the end date.
    # @param [Start] start_date The start date
    # @param [Date] end_date The end date
    # @param [Hash] options Miscellaneous options
    # @return [Range]
    def self.range(start_date, end_date, include_today = false)
      if start_date.nil? && !end_date.nil?
        error = "You can't specify -t without specifying -f"
        fail ArgumentError, error
      end

      begin
        chronic_start_date = Chronic.parse(start_date).to_date
      rescue
        unless start_date.nil?
          error = "Invalid date provided to Chronic: #{ start_date }"
          fail ArgumentError, error
        end
        nil
      end

      begin
        chronic_end_date = Chronic.parse(end_date).to_date
      rescue
        unless end_date.nil?
          error = "Invalid date provided to Chronic: #{ end_date }"
          fail ArgumentError, error
        end
        nil
      end

      if chronic_end_date && chronic_start_date > chronic_end_date
        error = 'The start date must be before or equal to the end date'
        fail ArgumentError, error
      end

      unless chronic_start_date.nil?
        if chronic_end_date.nil?
          if include_today
            (chronic_start_date..Date.today)
          else
            (chronic_start_date...Date.today)
          end
        else
          (chronic_start_date..chronic_end_date)
        end
      end
    end

    # Returns a date range for today
    # @return [Range]
    def self.today
      (Date.today..Date.today)
    end

    # Returns a date range for yesterday
    # @return [Range]
    def self.yesterday
      (Date.today - 1..Date.today - 1)
    end
  end
end