Show admin heading stats for the current budget

To get the heading where a user voted, we were relying on the
`balloted_heading_id` field.

Our guess is this was done so the total number of users is the same as
the sum of users who voted on a heading. That is, if 2000 people voted
just on the "All city" heading, 1000 voted just on the "North district"
heading, and 500 people voted on both, instead of showing "3500 people
voted in total, 2500 voted in all city, 1500 voted in north district",
we show something like "3500 people voted in total, 2250 voted in all
city, and 1250 voted in north district".

However, this approach has some disadvantages.

The first disadvantage is, the stats aren't correct. In the case above,
2500 voted on the "All city heading", so the statistics for this heading
don't show reality.

The second one is we weren't considering the last heading where users
voted inside the budget being displayed, but the last heading where
users voted, period. That means that, if all the people above voted on a
later budget, the stats for the budget above would become "3500 people
voted in total, 0 voted in all city, and 0 voted in north district".
That also means we were including headings from previous budgets in the
statistics for more recent budgets when people hadn't voted on the
recent ones.

So we're removing the `balloted_heading_id` since its data is lost once
people vote on a new budget. And, in order to show the right stats and
simplify the code, we're no longer trying to add votes just to one
heading when users vote on several headings.

Co-Authored-By: Julian Nicolas Herrero <microweb10@gmail.com>

app/components/admin/stats/budget_balloting_component.html.erb

@@ -45,7 +45,7 @@
   </tbody>
 </table>
 
-<table class="investment-projects-summary">
+<table class="investment-projects-summary user-count-by-heading">
   <thead>
     <tr><th colspan="2"><%= t("admin.stats.budget_balloting.participants_per_district") %></th></tr>
   </thead>

app/components/admin/stats/budget_balloting_component.rb

@@ -20,6 +20,10 @@ class Admin::Stats::BudgetBallotingComponent < ApplicationComponent
     end
 
     def user_count_by_heading
-      User.where.not(balloted_heading_id: nil).group(:balloted_heading_id).count.map { |k, v| [Budget::Heading.find(k).name, v] }.sort
+      budget.headings.map do |heading|
+        ballots = budget.ballots.joins(:lines).where(budget_ballot_lines: { heading_id: heading })
+
+        [heading.name, ballots.select(:user_id).distinct.count]
+      end.select { |_, count| count > 0 }.sort
     end
 end

app/models/budget/ballot/line.rb

@@ -16,7 +16,6 @@ class Budget
       scope :by_investment, ->(investment_id) { where(investment_id: investment_id) }
 
       before_validation :set_denormalized_ids
-      after_save :store_user_heading
 
       def check_enough_resources
         ballot.lock!
@@ -43,10 +42,6 @@ class Budget
           self.group_id   ||= investment&.group_id
           self.budget_id  ||= investment&.budget_id
         end
-
-        def store_user_heading
-          ballot.user.update(balloted_heading_id: heading.id) unless ballot.physical == true
-        end
     end
   end
 end

db/migrate/20230206141152_remove_balloted_heading_id_from_users.rb

@@ -0,0 +1,5 @@
+class RemoveBallotedHeadingIdFromUsers < ActiveRecord::Migration[6.0]
+  def change
+    remove_column :users, :balloted_heading_id, :integer
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2022_12_03_140136) do
+ActiveRecord::Schema.define(version: 2023_02_06_141152) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_trgm"
@@ -1637,7 +1637,6 @@ ActiveRecord::Schema.define(version: 2022_12_03_140136) do
     t.boolean "created_from_signature", default: false
     t.integer "failed_email_digests_count", default: 0
     t.text "former_users_data_log", default: ""
-    t.integer "balloted_heading_id"
     t.boolean "public_interests", default: false
     t.boolean "recommended_debates", default: true
     t.boolean "recommended_proposals", default: true

spec/components/admin/stats/budget_balloting_component_spec.rb

@@ -2,7 +2,7 @@ require "rails_helper"
 
 describe Admin::Stats::BudgetBallotingComponent do
   let(:budget) { create(:budget, :balloting) }
-  let(:heading) { create(:budget_heading, budget: budget) }
+  let(:heading) { create(:budget_heading, budget: budget, name: "Main heading") }
   let(:investment) { create(:budget_investment, :feasible, :selected, heading: heading) }
 
   it "shows the number of votes in investment projects" do
@@ -25,4 +25,56 @@ describe Admin::Stats::BudgetBallotingComponent do
 
     expect(page).to have_css "p", exact_text: "Participants 2", normalize_ws: true
   end
+
+  it "does not show participants per district from old budgets" do
+    old_budget = create(:budget, :balloting)
+    old_heading = create(:budget_heading, budget: old_budget, name: "Old Heading")
+    old_investment = create(:budget_investment, :feasible, :selected, heading: old_heading)
+    create(:user, ballot_lines: [old_investment])
+    create(:user, ballot_lines: [old_investment])
+
+    create(:user, ballot_lines: [investment])
+
+    render_inline Admin::Stats::BudgetBallotingComponent.new(budget)
+
+    expect(page).to have_css "p", exact_text: "Votes 1", normalize_ws: true
+    expect(page).to have_css "p", exact_text: "Participants 1", normalize_ws: true
+    expect(page).not_to have_content "Old Heading"
+  end
+
+  it "keeps votes on old budgets when there are new votes" do
+    old_budget = create(:budget, :balloting)
+    old_heading = create(:budget_heading, budget: old_budget, name: "Old Heading")
+    old_investment = create(:budget_investment, :feasible, :selected, heading: old_heading)
+    user = create(:user)
+
+    create(:budget_ballot, user: user, budget: old_budget, investments: [old_investment])
+    create(:budget_ballot, user: user, budget: budget, investments: [investment])
+
+    render_inline Admin::Stats::BudgetBallotingComponent.new(old_budget)
+
+    expect(page).to have_css "p", exact_text: "Votes 1", normalize_ws: true
+    expect(page).to have_css "p", exact_text: "Participants 1", normalize_ws: true
+
+    page.find ".user-count-by-heading tbody" do |table_body|
+      expect(table_body).to have_css "tr", exact_text: "Old Heading 1", normalize_ws: true
+    end
+  end
+
+  it "counts a participant in all headings where the participant voted" do
+    another_heading = create(:budget_heading, budget: budget, name: "Another heading")
+    another_investment = create(:budget_investment, :selected, heading: another_heading)
+
+    create(:user, ballot_lines: [investment, another_investment])
+
+    render_inline Admin::Stats::BudgetBallotingComponent.new(budget)
+
+    expect(page).to have_css "p", exact_text: "Votes 2", normalize_ws: true
+    expect(page).to have_css "p", exact_text: "Participants 1", normalize_ws: true
+
+    page.find ".user-count-by-heading tbody" do |table_body|
+      expect(table_body).to have_css "tr", exact_text: "Main heading 1", normalize_ws: true
+      expect(table_body).to have_css "tr", exact_text: "Another heading 1", normalize_ws: true
+    end
+  end
 end

spec/models/budget/ballot/line_spec.rb

@@ -88,18 +88,6 @@ describe Budget::Ballot::Line do
     end
   end
 
-  describe "#store_user_heading" do
-    it "stores the heading where the user has voted" do
-      user = create(:user, :level_two)
-      investment = create(:budget_investment, :selected)
-      ballot = create(:budget_ballot, user: user, budget: investment.budget)
-
-      create(:budget_ballot_line, ballot: ballot, investment: investment)
-
-      expect(user.reload.balloted_heading_id).to eq(investment.heading.id)
-    end
-  end
-
   describe "scopes" do
     describe "by_investment" do
       it "returns ballot lines for an investment" do