1 files changed, 112 insertions, 0 deletions
diff --git a/lib/gitlab/analytics/date_filler.rb b/lib/gitlab/analytics/date_filler.rb
new file mode 100644
index 00000000000..aa3db9f3635
--- /dev/null
+++ b/lib/gitlab/analytics/date_filler.rb
@@ -0,0 +1,112 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Analytics
+    # This class generates a date => value hash without gaps in the data points.
+    #
+    # Simple usage:
+    #
+    # > # We have the following data for the last 5 day:
+    # > input = { 3.days.ago.to_date => 10, Date.today => 5 }
+    #
+    # > # Format this data, so we can chart the complete date range:
+    # > Gitlab::Analytics::DateFiller.new(input, from: 4.days.ago, to: Date.today, default_value: 0).fill
+    # > {
+    # >  Sun, 28 Aug 2022=>0,
+    # >  Mon, 29 Aug 2022=>10,
+    # >  Tue, 30 Aug 2022=>0,
+    # >  Wed, 31 Aug 2022=>0,
+    # >  Thu, 01 Sep 2022=>5
+    # > }
+    #
+    # Parameters:
+    #
+    # **input**
+    # A Hash containing data for the series or the chart. The key is a Date object
+    # or an object which can be converted to Date.
+    #
+    # **from**
+    # Start date of the range
+    #
+    # **to**
+    # End date of the range
+    #
+    # **period**
+    # Specifies the period in wich the dates should be generated. Options:
+    #
+    # - :day, generate date-value pair for each day in the given period
+    # - :week, generate date-value pair for each week (beginning of the week date)
+    # - :month, generate date-value pair for each week (beginning of the month date)
+    #
+    # Note: the Date objects in the `input` should follow the same pattern (beginning of ...)
+    #
+    # **default_value**
+    #
+    # Which value use when the `input` Hash does not contain data for the given day.
+    #
+    # **date_formatter**
+    #
+    # How to format the dates in the resulting hash.
+    class DateFiller
+      DEFAULT_DATE_FORMATTER = -> (date) { date }
+      PERIOD_STEPS = {
+        day: 1.day,
+        week: 1.week,
+        month: 1.month
+      }.freeze
+
+      def initialize(
+        input,
+        from:,
+        to:,
+        period: :day,
+        default_value: nil,
+        date_formatter: DEFAULT_DATE_FORMATTER)
+        @input = input.transform_keys(&:to_date)
+        @from = from.to_date
+        @to = to.to_date
+        @period = period
+        @default_value = default_value
+        @date_formatter = date_formatter
+      end
+
+      def fill
+        data = {}
+
+        current_date = from
+        loop do
+          transformed_date = transform_date(current_date)
+          break if transformed_date > to
+
+          formatted_date = date_formatter.call(transformed_date)
+
+          value = input.delete(transformed_date)
+          data[formatted_date] = value.nil? ? default_value : value
+
+          current_date = (current_date + PERIOD_STEPS.fetch(period)).to_date
+        end
+
+        raise "Input contains values which doesn't fall under the given period!" if input.any?
+
+        data
+      end
+
+      private
+
+      attr_reader :input, :from, :to, :period, :default_value, :date_formatter
+
+      def transform_date(date)
+        case period
+        when :day
+          date.beginning_of_day.to_date
+        when :week
+          date.beginning_of_week.to_date
+        when :month
+          date.beginning_of_month.to_date
+        else
+          raise "Unknown period given: #{period}"
+        end
+      end
+    end
+  end
+end