More dynamic activity scores

This introduces a more dynamic system of activity scoring, to improve
the way bubbles "bubble up" due to their activity. There are a few
different parts we can tune here, and it's likely we'll need to make
adjustments once we get a feel for how this works in practice.

The basic idea here is:

- We assign points for certain types of event that happen on a bubble. A
  boost gets 1 point, a comment gets 10 points, and so on.
- These points decay over time, at a rate of 50% per day. So old
  activity is worth much less than new activity. Bubbles should rise up
  quickly when acted upon, bit will float back down if left idle.
- Some comments can score higher than others: the first comment from
  each person on a bubble is worth more (20) because it signals that
  more people are getting involved; and comments that follow a comment
  by a different author are also worth more (15) because that signals
  there's ongoing conversation between people, not just a series of
  notes being left by one individual.

In terms of implementation, we persist the score on the bubble
whenever it changes, but we handle the decay on the client side. That
allows us to cache the bubble representation without having to
continually change it while its activity decays.

We also keep a separate `activity_score_order` attribute on the model.
This can be used to sort the bubbles in order of "most active", without
having to think about the decay.

app/helpers/bubbles_helper.rb

@@ -10,17 +10,4 @@ module BubblesHelper
 
     "--bubble-rotate: #{value}deg;"
   end
-
-  def bubble_size(bubble)
-    rank =
-      case bubble.activity_score
-      when 0..5   then "one"
-      when 6..10  then "two"
-      when 11..25 then "three"
-      when 26..50 then "four"
-      else             "five"
-      end
-
-    "--bubble-size: var(--bubble-size-#{rank});"
-  end
 end

app/javascript/controllers/bubble_size_controller.js

@@ -0,0 +1,43 @@
+import { Controller } from "@hotwired/stimulus"
+
+const SIZES = [ "one", "two", "three", "four", "five" ]
+
+export default class extends Controller {
+  static targets = [ "bubble" ]
+
+  connect() {
+    this.resize()
+  }
+
+  resize() {
+    const [ min, max ] = this.#getScoreRange()
+
+    this.bubbleTargets.forEach(bubble => {
+      const score = this.#currentBubbleScore(bubble)
+      const idx = Math.round((score - min) / (max - min) * (SIZES.length - 1))
+
+      bubble.style.setProperty("--bubble-size", `var(--bubble-size-${SIZES[idx]})`)
+    })
+  }
+
+  #getScoreRange() {
+    var min = 0, max = 1;
+
+    this.bubbleTargets.forEach(bubble => {
+      const score = this.#currentBubbleScore(bubble)
+
+      min = Math.min(min, score)
+      max = Math.max(max, score)
+    })
+
+    return [ min, max ]
+  }
+
+  #currentBubbleScore(el) {
+    const score = el.dataset.activityScore
+    const scoreAt = el.dataset.activityScoreAt
+    const daysAgo = (Date.now() / 1000 - scoreAt) / (60 * 60 * 24)
+
+    return score / (2**daysAgo)
+  }
+}

app/models/bubble.rb

@@ -1,6 +1,6 @@
 class Bubble < ApplicationRecord
   include Assignable, Boostable, Colored, Commentable, Eventable,
-    Messages, Notifiable, Poppable, Searchable, Staged, Statuses, Taggable, Watchable
+    Messages, Notifiable, Poppable, Scorable, Searchable, Staged, Statuses, Taggable, Watchable
 
   belongs_to :bucket, touch: true
   belongs_to :creator, class_name: "User", default: -> { Current.user }
@@ -14,7 +14,6 @@ class Bubble < ApplicationRecord
 
   scope :reverse_chronologically, -> { order created_at: :desc, id: :desc }
   scope :chronologically, -> { order created_at: :asc, id: :asc }
-  scope :ordered_by_activity, -> { order activity_score: :desc }
   scope :in_bucket, ->(bucket) { where bucket: bucket }
 
   scope :indexed_by, ->(index) do
@@ -28,10 +27,6 @@ class Bubble < ApplicationRecord
     end
   end
 
-  def rescore
-    update! activity_score: boosts_count + comments_count
-  end
-
   private
     def track_due_date_change
       if due_on.present?

app/models/bubble/scorable.rb

@@ -0,0 +1,58 @@
+module Bubble::Scorable
+  extend ActiveSupport::Concern
+
+  REFERENCE_DATE = Time.utc(2025, 1, 1)
+
+  included do
+    scope :ordered_by_activity, -> { order activity_score_order: :desc }
+  end
+
+  def rescore
+    score = calculate_activity_score
+    score_at = last_scorable_activity_at
+
+    update! \
+      activity_score: score,
+      activity_score_at: score_at,
+      activity_score_order: event_score_reference(score, score_at)
+  end
+
+  private
+    def calculate_activity_score
+      scorable_events.sum { |event| event_score(event) }
+    end
+
+    def event_score(event)
+      days_ago = (last_scorable_activity_at - event.created_at) / 1.day
+      event_weight(event) / (2**days_ago)
+    end
+
+    def event_weight(event)
+      case
+      when event.boosted? then 1
+      when event.comment&.first_by_author_on_bubble? then 20
+      when event.comment&.follows_comment_by_another_author? then 15
+      when event.commented? then 10
+      else 0
+      end
+    end
+
+    def event_score_reference(score, activity_at)
+      # The reference score is used to make the activity score comparable
+      # across different bubbles, since it represents the bubble's activity
+      # level at a consistent point in time.
+      #
+      # We store this as log2 to tame the huge/tiny numbers we'd otherwise get
+      # when activity is far from the reference date.
+      days_diff = (activity_at - REFERENCE_DATE) / 1.day
+      Math.log2(score) + days_diff
+    end
+
+    def last_scorable_activity_at
+      scorable_events.maximum(:created_at) || created_at
+    end
+
+    def scorable_events
+      events.where(action: [ :commented, :boosted ])
+    end
+end

app/models/comment.rb

@@ -10,6 +10,14 @@ class Comment < ApplicationRecord
 
   before_destroy :cleanup_events
 
+  def first_by_author_on_bubble?
+    bubble_comments.many? && bubble_comments_prior.where(creator_id: creator_id).none?
+  end
+
+  def follows_comment_by_another_author?
+    bubble_comments.many? && bubble_comments_prior.last&.creator != creator
+  end
+
   private
 
   def cleanup_events
@@ -21,4 +29,12 @@ class Comment < ApplicationRecord
     # Delete events that reference directly in particulars
     Event.where(particulars: { comment_id: id }).destroy_all
   end
+
+  def bubble_comments_prior
+    bubble_comments.where(created_at: ...created_at)
+  end
+
+  def bubble_comments
+    Comment.joins(:message).where(messages: { bubble: bubble })
+  end
 end

app/models/event.rb

@@ -12,9 +12,18 @@ class Event < ApplicationRecord
   scope :chronologically, -> { order created_at: :asc, id: :desc }
   scope :non_boosts, -> { where.not action: :boosted }
   scope :boosts, -> { where action: :boosted }
+  scope :comments, -> { where action: :commented }
 
   after_create -> { bubble.update_auto_pop_at(created_at) }
 
+  def boosted?
+    action == "boosted"
+  end
+
+  def commented?
+    action == "commented"
+  end
+
   def generate_notifications
     Notifier.for(self)&.generate
   end

app/views/bubbles/_bubble.html.erb

@@ -1,6 +1,9 @@
 <% cache bubble do %>
   <div class="<%= class_names("bubble", drafted: bubble.drafted?, popped: bubble.popped?) %>"
-    style="view-transition-name: bubble-<%= bubble.id -%>; --bubble-color: <%= bubble.color %>; <%= bubble_rotation(bubble) %> <%= bubble_size(bubble) %>"
+    style="view-transition-name: bubble-<%= bubble.id -%>; --bubble-color: <%= bubble.color %>; <%= bubble_rotation(bubble) %>"
+    data-bubble-size-target="bubble"
+    data-activity-score="<%= bubble.activity_score %>"
+    data-activity-score-at="<%= bubble.activity_score_at.to_i %>"
     data-controller="animation upload-preview"
     data-animation-play-class="bubble--wobble"
     data-animation-play-on-load-value="true"

app/views/bubbles/index.html.erb

@@ -29,7 +29,7 @@
   </nav>
 <% end %>
 
-<section class="bubbles flex-inline flex-wrap gap justify-center align-end" style="view-transition-name: bubbles_<%= @filter.id %>">
+<section class="bubbles flex-inline flex-wrap gap justify-center align-end" style="view-transition-name: bubbles_<%= @filter.id %>" data-controller="bubble-size" data-action="turbo:morph@window->bubble-size#resize">
   <% if @bubbles.any? %>
     <%= render partial: "bubbles/bubble", collection: @bubbles.limit(10), cached: true %>
   <% else %>

app/views/buckets/_bucket.html.erb

@@ -2,7 +2,10 @@
   <%= link_to bubbles_path(bucket_ids: [ bucket ]), class: "border border-radius margin-block-end-half bubbles__container flex justify-center align-center position-relative" do %>
     <div class="bubbles bucket__bubbles flex flex-wrap gap justify-center align-end" style="view-transition-name: bubbles_<%= bucket.id %>">
       <% bucket.bubbles.active.published_or_drafted_by(Current.user).ordered_by_activity.limit(10).each do |bubble| %>
-        <div class="<%= class_names("bubble", drafted: bubble.drafted?) %>" style="--bubble-color: <%= bubble.color %>; <%= bubble_rotation(bubble) %> <%= bubble_size(bubble) %>">
+        <div class="<%= class_names("bubble", drafted: bubble.drafted?) %>" style="--bubble-color: <%= bubble.color %>; <%= bubble_rotation(bubble) %>"
+          data-bubble-size-target="bubble"
+          data-activity-score="<%= bubble.activity_score %>"
+          data-activity-score-at="<%= bubble.activity_score_at.to_i %>">
           <span class="bubble__shape"></span>
         </div>
       <% end %>

app/views/buckets/index.html.erb

@@ -22,10 +22,10 @@
   </nav>
 <% end %>
 
-<div class="buckets margin-block-double unpad align-start justify-center flex flex-wrap gap">
+<div class="buckets margin-block-double unpad align-start justify-center flex flex-wrap gap" data-controller="bubble-size">
   <%= render @buckets, cached: true %>
 </div>
-<div class="buckets margin-block-double unpad align-start justify-center flex flex-wrap gap">
+<div class="buckets margin-block-double unpad align-start justify-center flex flex-wrap gap" data-controller="bubble-size">
   <%= render @filters %>
 </div>
 

app/views/filters/_filter.html.erb

@@ -3,7 +3,10 @@
     <%= link_to bubbles_path(**filter.as_params), class: "border border-radius margin-block-end-half bubbles__container flex justify-center align-center position-relative" do %>
       <div class="bubbles bucket__bubbles flex flex-wrap gap justify-center align-end" style="view-transition-name: bubbles_<%= filter.id %>">
         <% filter.bubbles.ordered_by_activity.limit(10).each do |bubble| %>
-          <div class="bubble" style="--bubble-color: <%= bubble.color %>; <%= bubble_rotation(bubble) %> <%= bubble_size(bubble) %>">
+          <div class="<%= class_names("bubble", drafted: bubble.drafted?) %>" style="--bubble-color: <%= bubble.color %>; <%= bubble_rotation(bubble) %>"
+            data-bubble-size-target="bubble"
+            data-activity-score="<%= bubble.activity_score %>"
+            data-activity-score-at="<%= bubble.activity_score_at.to_i %>">
             <span class="bubble__shape"></span>
           </div>
         <% end %>

db/migrate/20250304140641_add_activity_score_at_to_bubbles.rb

@@ -0,0 +1,11 @@
+class AddActivityScoreAtToBubbles < ActiveRecord::Migration[8.1]
+  def change
+    change_table :bubbles do |t|
+      t.datetime :activity_score_at
+      t.float :activity_score_order, null: false, default: 0
+      t.change :activity_score, :float, null: false, default: 0
+
+      t.index :activity_score_order, order: :desc
+    end
+  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[8.1].define(version: 2025_02_24_152047) do
+ActiveRecord::Schema[8.1].define(version: 2025_03_04_140641) do
   create_table "accesses", force: :cascade do |t|
     t.integer "bucket_id", null: false
     t.integer "user_id", null: false
@@ -105,9 +105,12 @@ ActiveRecord::Schema[8.1].define(version: 2025_02_24_152047) do
     t.integer "boosts_count", default: 0, null: false
     t.integer "stage_id"
     t.integer "comments_count", default: 0, null: false
-    t.integer "activity_score", default: 0, null: false
+    t.float "activity_score", default: 0.0, null: false
     t.text "status", default: "creating", null: false
     t.datetime "auto_pop_at", null: false
+    t.datetime "activity_score_at"
+    t.float "activity_score_order", default: 0.0, null: false
+    t.index ["activity_score_order"], name: "index_bubbles_on_activity_score_order", order: :desc
     t.index ["auto_pop_at"], name: "index_bubbles_on_auto_pop_at"
     t.index ["bucket_id"], name: "index_bubbles_on_bucket_id"
     t.index ["stage_id"], name: "index_bubbles_on_stage_id"

test/models/bubble/scorable_test.rb

@@ -0,0 +1,56 @@
+require "test_helper"
+
+class Bubble::ScorableTest < ActiveSupport::TestCase
+  test "a bubble has a score that increases with activity" do
+    bubble = bubbles(:logo)
+
+    score = bubble.activity_score
+    assert_operator score, :>, 0
+
+    with_current_user :kevin do
+      bubble.capture Comment.create(body: "This is exciting!")
+    end
+
+    assert_operator bubble.activity_score, :>, score
+  end
+
+  test "commenting on a bubble boosts its score more than boosting it" do
+    bubble = bubbles(:logo)
+    bubble.rescore
+
+    comment_change = capture_change -> { bubble.activity_score } do
+      with_current_user :kevin do
+        bubble.capture Comment.create(body: "This is exciting!")
+      end
+    end
+
+    boost_change = capture_change -> { bubble.activity_score } do
+      with_current_user :kevin do
+        bubble.boost!
+      end
+    end
+
+    assert_operator comment_change, :>, boost_change
+  end
+
+  test "recent activity counts more than older activity in the ordering" do
+    with_current_user :kevin do
+      travel_to 5.days.ago
+      bubble_old = buckets(:writebook).bubbles.create! status: :published, title: "old"
+      bubble_mid = buckets(:writebook).bubbles.create! status: :published, title: "mid"
+      bubble_new = buckets(:writebook).bubbles.create! status: :published, title: "new"
+
+      bubble_old.boost!
+      bubble_old.boost!
+
+      travel_back
+      travel_to 2.days.ago
+      bubble_mid.boost!
+
+      travel_back
+      bubble_new.boost!
+
+      assert_equal [ bubble_new, bubble_mid, bubble_old ], Bubble.where(id: [ bubble_old, bubble_mid, bubble_new ]).ordered_by_activity
+    end
+  end
+end

test/models/bubble_test.rb

@@ -14,8 +14,10 @@ class BubbleTest < ActiveSupport::TestCase
   end
 
   test "boosting" do
-    assert_difference %w[ bubbles(:logo).boosts_count bubbles(:logo).activity_score Event.count ], +1 do
+    assert_changes -> { bubbles(:logo).activity_score } do
-      bubbles(:logo).boost!(bubbles(:logo).boosts_count+ 1)
+      assert_difference -> { bubbles(:logo).boosts_count }, +1 do
+        bubbles(:logo).boost!(bubbles(:logo).boosts_count+ 1)
+      end
     end
   end
 
@@ -72,11 +74,6 @@ class BubbleTest < ActiveSupport::TestCase
     assert_includes Bubble.search("haggis"), bubble
   end
 
-  test "ordering by activity" do
-    bubbles(:layout).tap { |b| b.update!(boosts_count: 1_000) }.rescore
-    assert_equal bubbles(:layout, :logo, :shipping, :text), Bubble.ordered_by_activity
-  end
-
   test "ordering by comments" do
     assert_equal bubbles(:logo, :layout, :shipping, :text), Bubble.ordered_by_comments
   end

test/models/comment_test.rb

@@ -12,12 +12,54 @@ class CommentTest < ActiveSupport::TestCase
   end
 
   test "updating bubble counter" do
-    assert_difference %w[ bubbles(:logo).comments_count bubbles(:logo).activity_score ], +1 do
+    assert_difference -> { bubbles(:logo).comments_count } do
-      bubbles(:logo).capture Comment.new(body: "I'd prefer something more rustic")
+      assert_changes -> { bubbles(:logo).activity_score } do
+        bubbles(:logo).capture Comment.new(body: "I'd prefer something more rustic")
+      end
     end
 
-    assert_difference %w[ bubbles(:logo).comments_count bubbles(:logo).activity_score ], -1 do
+    assert_difference -> { bubbles(:logo).comments_count }, -1 do
-      bubbles(:logo).messages.comments.last.destroy
+      assert_changes -> { bubbles(:logo).activity_score } do
+        bubbles(:logo).messages.comments.last.destroy
+      end
+    end
+  end
+
+  test "first_by_author_on_bubble?" do
+    assert_not Comment.new.first_by_author_on_bubble?
+
+    with_current_user :david do
+      comment = Comment.new.tap { |c| bubbles(:logo).capture c }
+      assert comment.first_by_author_on_bubble?
+
+      comment = Comment.new.tap { |c| bubbles(:logo).capture c }
+      assert_not comment.first_by_author_on_bubble?
+    end
+
+    with_current_user :kevin do
+      comment = Comment.new.tap { |c| bubbles(:logo).capture c }
+      assert_not comment.first_by_author_on_bubble?
+    end
+  end
+
+  test "follows_comment_by_another_author?" do
+    assert_not Comment.new.follows_comment_by_another_author?
+
+    bubble = buckets(:writebook).bubbles.create!
+
+    with_current_user :david do
+      comment = Comment.new.tap { |c| bubble.capture c }
+      assert_not comment.follows_comment_by_another_author?
+    end
+
+    with_current_user :kevin do
+      comment = Comment.new.tap { |c| bubble.capture c }
+      assert comment.follows_comment_by_another_author?
+    end
+
+    with_current_user :david do
+      comment = Comment.new.tap { |c| bubble.capture c }
+      assert comment.follows_comment_by_another_author?
     end
   end
 end

test/models/filter_test.rb

@@ -26,7 +26,7 @@ class FilterTest < ActiveSupport::TestCase
     assert_equal [ @new_bubble ], filter.bubbles
 
     filter = users(:david).filters.new terms: [ "haggis" ]
-    assert_equal bubbles(:logo, :layout), filter.bubbles
+    assert_equal bubbles(:logo, :layout).sort, filter.bubbles.sort
 
     filter = users(:david).filters.new terms: [ "haggis", "love" ]
     assert_equal [ bubbles(:logo) ], filter.bubbles

test/test_helper.rb

@@ -10,6 +10,6 @@ module ActiveSupport
     # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
     fixtures :all
 
-    include SessionTestHelper
+    include ChangeTestHelper, SessionTestHelper
   end
 end

test/test_helpers/change_test_helper.rb

@@ -0,0 +1,8 @@
+module ChangeTestHelper
+  def capture_change(target)
+    before = target.call
+    yield
+    after = target.call
+    after - before
+  end
+end