101 lines
2.9 KiB
Ruby
101 lines
2.9 KiB
Ruby
# frozen_string_literal: true
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class CohortsService
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MONTHS_INCLUDED = 12
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def execute
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{
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months_included: MONTHS_INCLUDED,
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cohorts: cohorts
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}
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end
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# Get an array of hashes that looks like:
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#
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# [
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# {
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# registration_month: Date.new(2017, 3),
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# activity_months: [3, 2, 1],
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# total: 3
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# inactive: 0
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# },
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# etc.
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#
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# The `months` array is always from oldest to newest, so it's always
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# non-strictly decreasing from left to right.
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def cohorts
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months = Array.new(MONTHS_INCLUDED) { |i| i.months.ago.beginning_of_month.to_date }
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Array.new(MONTHS_INCLUDED) do
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registration_month = months.last
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activity_months = running_totals(months, registration_month)
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# Even if no users registered in this month, we always want to have a
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# value to fill in the table.
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inactive = counts_by_month[[registration_month, nil]].to_i
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months.pop
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{
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registration_month: registration_month,
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activity_months: activity_months[1..],
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total: activity_months.first[:total],
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inactive: inactive
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}
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end
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end
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private
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# Calculate a running sum of active users, so users active in later months
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# count as active in this month, too. Start with the most recent month first,
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# for calculating the running totals, and then reverse for displaying in the
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# table.
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#
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# Each month has a total, and a percentage of the overall total, as keys.
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def running_totals(all_months, registration_month)
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month_totals =
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all_months
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.map { |activity_month| counts_by_month[[registration_month, activity_month]] }
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.reduce([]) { |result, total| result << result.last.to_i + total.to_i }
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.reverse
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overall_total = month_totals.first
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month_totals.map do |total|
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{ total: total, percentage: total == 0 ? 0 : 100 * total / overall_total }
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end
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end
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# Get a hash that looks like:
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#
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# {
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# [created_at_month, last_activity_on_month] => count,
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# [created_at_month, last_activity_on_month_2] => count_2,
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# # etc.
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# }
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#
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# created_at_month can never be nil, but last_activity_on_month can (when a
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# user has never logged in, just been created). This covers the last
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# MONTHS_INCLUDED months.
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# rubocop: disable CodeReuse/ActiveRecord
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def counts_by_month
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@counts_by_month ||=
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begin
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created_at_month = column_to_date('created_at')
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last_activity_on_month = column_to_date('last_activity_on')
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User
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.where('created_at > ?', MONTHS_INCLUDED.months.ago.end_of_month)
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.group(created_at_month, last_activity_on_month)
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.reorder(Arel.sql("#{created_at_month} ASC, #{last_activity_on_month} ASC"))
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.count
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end
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end
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# rubocop: enable CodeReuse/ActiveRecord
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def column_to_date(column)
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"CAST(DATE_TRUNC('month', #{column}) AS date)"
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end
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end
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