Trend reports are based on distribution/donation/purchase issued date

app/services/historical_trend_service.rb

@@ -4,26 +4,36 @@ def initialize(organization_id, type)
     @type = type
   end
 
+  # Returns: [{:name=>"Adult Briefs (XXL)", :data=>[0, 0, 0, 0, 0, 0, 0, 0, 0, 416, 0, 0], :visible=>false}]
+  # :data contains quantity from 11 months ago to current month
   def series
-    # Preload line_items with a single query to avoid N+1 queries.
-    items_with_line_items = @organization.items.active
-      .includes(:line_items)
-      .where(line_items: {itemizable_type: @type, created_at: 1.year.ago.beginning_of_month..Time.current})
-      .order(:name)
+    type_symbol = @type.tableize.to_sym # :distributions, :donations, :purchases
+    records_for_type = @organization.send(type_symbol)
+      .includes(items: :line_items)
+      .where(issued_at: 1.year.ago.beginning_of_month..Time.current)
 
-    month_offset = [*1..12].rotate(Time.zone.today.month)
-    default_dates = (1..12).index_with { |i| 0 }
+    array_of_items = []
 
-    items_with_line_items.each_with_object([]) do |item, array_of_items|
-      dates = default_dates.deep_dup
+    records_for_type.each do |record|
+      index = record.issued_at.month - Date.current.month - 1
 
-      item.line_items.each do |line_item|
-        month = line_item.created_at.month
-        index = month_offset.index(month) + 1
-        dates[index] = dates[index] + line_item.quantity
-      end
+      record.line_items.each do |line_item|
+        name = line_item.item.name
+        quantity = line_item.quantity
+        next if quantity.zero?
 
-      array_of_items << {name: item.name, data: dates.values, visible: false} unless dates.values.sum.zero?
+        existing_item = array_of_items.find { |item| item[:name] == name }
+        if existing_item
+          quantity_per_month = existing_item[:data]
+          quantity_per_month[index] += quantity
+        else
+          quantity_per_month = Array.new(12, 0)
+          quantity_per_month[index] += quantity
+          array_of_items << {name:, data: quantity_per_month, visible: false}
+        end
+      end
     end
+
+    array_of_items.sort_by { |item| item[:name] }
   end
 end

spec/services/historical_trend_service_spec.rb

@@ -4,22 +4,29 @@
   let(:service) { described_class.new(organization.id, type) }
 
   describe "#series" do
-    let!(:item1) { create(:item, organization: organization, name: "Item 1") }
-    let!(:item2) { create(:item, organization: organization, name: "Item 2") }
+    let(:item1) { create(:item, organization: organization, name: "Item 1") }
+    let(:item2) { create(:item, organization: organization, name: "Item 2") }
+    let(:donation1) { create(:donation, organization:, issued_at: Date.current) }
+    let(:donation2) { create(:donation, organization:, issued_at: 2.months.ago) }
     let!(:line_items) do
       (0..11).map do |n|
-        create(:line_item, item: item1, itemizable_type: type, quantity: 10 * (n + 1), created_at: n.months.ago)
+        create(:line_item, item: item1, itemizable_type: type, itemizable_id: donation1.id, quantity: 10, created_at: n.months.ago)
       end
     end
-    let!(:line_item2) { create(:line_item, item: item2, itemizable_type: type, quantity: 60, created_at: 6.months.ago) }
-    let!(:line_item3) { create(:line_item, item: item2, itemizable_type: type, quantity: 30, created_at: 3.months.ago) }
+    let!(:line_item2) { create(:line_item, item: item2, itemizable_type: type, itemizable_id: donation2.id, quantity: 60, created_at: 6.months.ago) }
+    let!(:line_item3) { create(:line_item, item: item2, itemizable_type: type, itemizable_id: donation2.id, quantity: 30, created_at: 3.months.ago) }
 
     it "returns an array of items with their monthly data" do
       expected_result = [
-        {name: "Item 1", data: [120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 10], visible: false},
-        {name: "Item 2", data: [0, 0, 0, 0, 0, 60, 0, 0, 30, 0, 0, 0], visible: false}
+        {name: "Item 1", data: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 120], visible: false},
+        {name: "Item 2", data: [0, 0, 0, 0, 0, 0, 0, 0, 0, 90, 0, 0], visible: false}
       ]
       expect(service.series).to eq(expected_result)
     end
+
+    it "the last data point is the quantity for the current month" do
+      item1_quantities = service.series.first[:data]
+      expect(item1_quantities.last).to be(line_items.pluck(:quantity).sum)
+    end
   end
 end