Refactors to Metrics::Algorithms

Moves both types of metrics on algorithms to use a single class and
associated database table.

Creating the namespace `Metrics` should allow us to better organize code
associated with various metrics into a common space that is both
intuitive and useful.

Relevant ticket(s):
https://mitlibraries.atlassian.net/browse/TCO-17

app/models/metrics/algorithms.rb

@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: metrics_algorithms
+#
+#  id         :integer          not null, primary key
+#  month      :date
+#  doi        :integer
+#  issn       :integer
+#  isbn       :integer
+#  pmid       :integer
+#  unmatched  :integer
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+module Metrics
+  # Algorithms aggregates statistics for matches for all SearchEvents
+  class Algorithms < ApplicationRecord
+    self.table_name = 'metrics_algorithms'
+
+    # generate metrics data about SearchEvents matches
+    #
+    # @note This is expected to only be run once per month per type of aggregation (once with no month supplied, once
+    #   with a month supplied), ideally at the beginning of the following month to ensure as
+    #   accurate as possible statistics. Running further from the month in question will work, but matches will use the
+    #   current versions of all algorithms which may not match the algorithm in place during the month the SearchEvent
+    #   occurred.
+    # @note We don't currently prevent this running more than once per month per type of aggregation.
+    # @param month [DateTime] A DateTime object within the `month` to be generated. Defaults to nil will runs is how
+    #   total algorithm statistics are created.
+    # @example
+    #   # Generate metrics for all SearchEvents
+    #   Metrics::Algorithms.new.generate
+    #
+    #   # Generate metrics for all SearchEvents last month
+    #   Metrics::Algorithms.new.generate(1.month.ago)
+    # @return [Metrics::Algorithms] The created Metrics::Algorithms object.
+    def generate(month = nil)
+      matches = if month.present?
+                  count_matches(SearchEvent.single_month(month).includes(:term))
+                else
+                  count_matches(SearchEvent.all.includes(:term))
+                end
+      Metrics::Algorithms.create(month:, doi: matches[:doi], issn: matches[:issn], isbn: matches[:isbn],
+                                 pmid: matches[:pmid], unmatched: matches[:unmatched])
+    end
+
+    # Counts matches supplied events
+    #
+    # @note We currently only have StandardIdentifiers to match. As we add new algorithms, this method will need to
+    #   expand to handle additional match types.
+    # @param events [Array of SearchEvents] An array of SearchEvents to check for matches.
+    # @return [Hash] A Hash with keys for each known algorithm and the count of matched SearchEvents.
+    def count_matches(events)
+      matches = Hash.new(0)
+      known_ids = %i[unmatched pmid isbn issn doi]
+
+      events.each do |event|
+        ids = StandardIdentifiers.new(event.term.phrase)
+
+        matches[:unmatched] += 1 if ids.identifiers.blank?
+
+        known_ids.each do |id|
+          matches[id] += 1 if ids.identifiers[id].present?
+        end
+      end
+
+      matches
+    end
+  end
+end

db/migrate/20240621132136_create_monthly_matches.rb → db/migrate/20240621132136_create_metrics_algorithms.rb

@@ -1,6 +1,6 @@
-class CreateMonthlyMatches < ActiveRecord::Migration[7.1]
+class CreateMetricsAlgorithms < ActiveRecord::Migration[7.1]
   def change
-    create_table :monthly_matches do |t|
+    create_table :metrics_algorithms do |t|
       t.date :month
       t.integer :doi
       t.integer :issn