scottohara/loot

# Copyright (c) 2016 Scott O'Hara, oharagroup.net
# frozen_string_literal: true

# Measurable
module Measurable
    extend ::ActiveSupport::Concern

    Frequency = ::Struct.new :advance_by, :periods_since
    private_constant :Frequency

    FREQUENCIES = {
        Weekly: Frequency.new({weeks: 1}, :weeks_since),
        Fortnightly: Frequency.new({weeks: 2}, :fortnights_since),
        Monthly: Frequency.new({months: 1}, :months_since),
        Bimonthly: Frequency.new({months: 2}, :bimonths_since),
        Quarterly: Frequency.new({months: 3}, :quarters_since),
        Yearly: Frequency.new({years: 1}, :years_since)
    }.freeze

    private_constant :FREQUENCIES

    # Methods for measuring things, in particular date periods
    class_methods do
        # Weeks since a given date
        def weeks_since(date)
            ((::Time.zone.today - date) / 7).to_i
        end

        # Fortnights since a given date
        def fortnights_since(date)
            ((::Time.zone.today - date) / 14).to_i
        end

        # Months since a given date
        def months_since(date)
            months = ((::Time.zone.today.year - date.year) * 12) + (::Time.zone.today.month - date.month)
            months -= 1 if ::Time.zone.today.day < date.day
            months
        end

        # Bimonths since a given date
        def bimonths_since(date)
            (months_since(date) / 2).to_i
        end

        # Quarters since a given date
        def quarters_since(date)
            (months_since(date) / 3).to_i
        end

        # Years since a given date
        def years_since(date)
            (months_since(date) / 12).to_i
        end

        def periods_since(frequency, date)
            public_send FREQUENCIES[frequency.to_sym].periods_since, date
        end

        def advance_by(frequency, date)
            date.advance FREQUENCIES[frequency.to_sym].advance_by
        end
    end
end