FEATURE: add a Top Categories section to the user summary page, showing the categories in which a user has the most activity

app/assets/javascripts/discourse/templates/user/summary.hbs

@@ -115,6 +115,35 @@
     {{/user-summary-section}}
   </div>
 
+  {{#if model.top_categories.length}}
+    <div class='top-section top-categories-section'>
+      {{#user-summary-section title="top_categories" class="summary-category-list pull-left"}}
+        <table>
+          <thead>
+            <th class="category-link"></th>
+            <th class='topic-count'>{{i18n "user.summary.topics"}}</th>
+            <th class='reply-count'>{{i18n "user.summary.replies"}}</th>
+          </thead>
+          <tbody>
+            {{#each model.top_categories as |category|}}
+              <tr>
+                <td class="category-link">
+                  {{category-link category allowUncategorized="true" hideParent=false}}
+                </td>
+                <td class='topic-count'>
+                  {{category.topic_count}}
+                </td>
+                <td class='reply-count'>
+                  {{category.post_count}}
+                </td>
+              </tr>
+            {{/each}}
+          </tbody>
+        </table>
+      {{/user-summary-section}}
+    </div>
+  {{/if}}
+
   {{#if siteSettings.enable_badges}}
     <div class='top-section badges-section'>
       <h3 class='stats-title'>{{i18n "user.summary.top_badges"}}</h3>

app/assets/stylesheets/common/base/user.scss

@@ -502,6 +502,23 @@
   }
 }
 
+.top-categories-section {
+  table {
+    max-width: 95%;
+    tr {
+      border: none;
+    }
+    td,
+    th {
+      padding: 0.5em;
+      &.topic-count,
+      &.reply-count {
+        text-align: center;
+      }
+    }
+  }
+}
+
 .summary-user-list {
   li {
     height: 40px;

app/models/user_summary.rb

@@ -155,6 +155,56 @@ class UserSummary
     @user.recent_time_read
   end
 
+  class CategoryWithCounts < OpenStruct
+    include ActiveModel::SerializerSupport
+    KEYS = [:id, :name, :color, :text_color, :slug, :read_restricted, :parent_category_id]
+  end
+
+  def top_categories
+    post_count_query = Post
+      .joins(:topic)
+      .includes(:topic)
+      .secured(@guardian)
+      .merge(Topic.listable_topics.visible.secured(@guardian))
+      .where(user: @user)
+      .group('topics.category_id')
+      .order('COUNT(*) DESC')
+
+    top_categories = {}
+
+    Category.where(id: post_count_query.limit(MAX_SUMMARY_RESULTS).pluck('category_id'))
+      .pluck(:id, :name, :color, :text_color, :slug, :read_restricted, :parent_category_id)
+      .each do |c|
+        top_categories[c[0].to_i] = CategoryWithCounts.new(
+          Hash[CategoryWithCounts::KEYS.zip(c)].merge(
+            topic_count: 0,
+            post_count: 0
+          )
+        )
+      end
+
+    post_count_query.where('post_number > 1')
+      .where('topics.category_id in (?)', top_categories.keys)
+      .pluck('category_id, COUNT(*)')
+      .each do |r|
+        top_categories[r[0].to_i].post_count = r[1]
+      end
+
+    Topic.listable_topics.visible.secured(@guardian)
+      .where('topics.category_id in (?)', top_categories.keys)
+      .where(user: @user)
+      .group('topics.category_id')
+      .order('COUNT(*) DESC')
+      .pluck('category_id, COUNT(*)')
+      .each do |r|
+        top_categories[r[0].to_i].topic_count = r[1]
+      end
+
+    top_categories.values.sort_by do |r|
+      -(r[:post_count] + r[:topic_count])
+    end
+  end
+
   delegate :likes_given,
            :likes_received,
            :days_visited,

app/serializers/user_summary_serializer.rb

@@ -22,6 +22,12 @@ class UserSummarySerializer < ApplicationSerializer
     attributes :count, :name
   end
 
+  class CategoryWithCountsSerializer < ApplicationSerializer
+    attributes :topic_count, :post_count,
+      :id, :name, :color, :text_color, :slug,
+      :read_restricted, :parent_category_id
+  end
+
   has_many :topics, serializer: TopicSerializer
   has_many :replies, serializer: ReplySerializer, embed: :object
   has_many :links, serializer: LinkSerializer, embed: :object
@@ -29,6 +35,7 @@ class UserSummarySerializer < ApplicationSerializer
   has_many :most_liked_users, serializer: UserWithCountSerializer, embed: :object
   has_many :most_replied_to_users, serializer: UserWithCountSerializer, embed: :object
   has_many :badges, serializer: UserBadgeSerializer, embed: :object
+  has_many :top_categories, serializer: CategoryWithCountsSerializer, embed: :object
 
   attributes :likes_given,
              :likes_received,

config/locales/client.en.yml

@@ -1004,7 +1004,9 @@ en:
         most_liked_users: "Most Liked"
         most_replied_to_users: "Most Replied To"
         no_likes: "No likes yet."
-
+        top_categories: "Top Categories"
+        topics: "Topics"
+        replies: "Replies"
 
       associated_accounts: "Logins"
       ip_address:

spec/models/user_summary_spec.rb

@@ -11,16 +11,21 @@ describe UserSummary do
 
     expect(summary.topics.length).to eq(1)
     expect(summary.replies.length).to eq(1)
+    expect(summary.top_categories.length).to eq(1)
+    expect(summary.top_categories.first[:topic_count]).to eq(1)
+    expect(summary.top_categories.first[:post_count]).to eq(1)
 
     topic.update_columns(deleted_at: Time.now)
 
     expect(summary.topics.length).to eq(0)
     expect(summary.replies.length).to eq(0)
+    expect(summary.top_categories.length).to eq(0)
 
     topic.update_columns(deleted_at: nil, visible: false)
 
     expect(summary.topics.length).to eq(0)
     expect(summary.replies.length).to eq(0)
+    expect(summary.top_categories.length).to eq(0)
 
     category = Fabricate(:category)
     topic.update_columns(category_id: category.id, deleted_at: nil, visible: true)
@@ -30,7 +35,7 @@ describe UserSummary do
 
     expect(summary.topics.length).to eq(0)
     expect(summary.replies.length).to eq(0)
-
+    expect(summary.top_categories.length).to eq(0)
   end
 
 end

test/javascripts/acceptance/user-test.js.es6

@@ -46,5 +46,9 @@ QUnit.test("Viewing Summary", assert => {
     assert.ok(exists(".liked-by-section .user-info"), "liked by");
     assert.ok(exists(".liked-section .user-info"), "liked");
     assert.ok(exists(".badges-section .badge-card"), "badges");
+    assert.ok(
+      exists(".top-categories-section .category-link"),
+      "top categories"
+    );
   });
 });

test/javascripts/helpers/create-pretender.js.es6

@@ -88,7 +88,20 @@ export default function() {
           most_replied_to_users: [{ id: 333 }],
           most_liked_by_users: [{ id: 333 }],
           most_liked_users: [{ id: 333 }],
-          badges: [{ badge_id: 444 }]
+          badges: [{ badge_id: 444 }],
+          top_categories: [
+            {
+              id: 1,
+              name: "bug",
+              color: "e9dd00",
+              text_color: "000000",
+              slug: "bug",
+              read_restricted: false,
+              parent_category_id: null,
+              topic_count: 1,
+              post_count: 1
+            }
+          ]
         },
         badges: [{ id: 444, count: 1 }],
         topics: [{ id: 1234, title: "cool title", url: "/t/1234/cool-title" }]