FEATURE: AI Usage page (#964)

- Added a new admin interface to track AI usage metrics, including tokens, features, and models.
- Introduced a new route `/admin/plugins/discourse-ai/ai-usage` and supporting API endpoint in `AiUsageController`.
- Implemented `AiUsageSerializer` for structuring AI usage data.
- Integrated CSS stylings for charts and tables under `stylesheets/modules/llms/common/usage.scss`.
- Enhanced backend with `AiApiAuditLog` model changes: added `cached_tokens` column  (implemented with OpenAI for now) with relevant DB migration and indexing.
- Created `Report` module for efficient aggregation and filtering of AI usage metrics.
- Updated AI Bot title generation logic to log correctly to user vs bot
- Extended test coverage for the new tracking features, ensuring data consistency and access controls.

Author: SamSaffron

admin/assets/javascripts/discourse/routes/admin-plugins-show-discourse-ai-usage.js

@@ -0,0 +1,11 @@
+import { service } from "@ember/service";
+import { ajax } from "discourse/lib/ajax";
+import DiscourseRoute from "discourse/routes/discourse";
+
+export default class DiscourseAiUsageRoute extends DiscourseRoute {
+  @service store;
+
+  model() {
+    return ajax("/admin/plugins/discourse-ai/ai-usage.json");
+  }
+}

admin/assets/javascripts/discourse/templates/admin-plugins/show/discourse-ai-usage.hbs

@@ -0,0 +1 @@
+<AiUsage @model={{this.model}} />

app/controllers/discourse_ai/admin/ai_usage_controller.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module DiscourseAi
+  module Admin
+    class AiUsageController < ::Admin::AdminController
+      requires_plugin "discourse-ai"
+
+      def show
+        render json: AiUsageSerializer.new(create_report, root: false)
+      end
+
+      private
+
+      def create_report
+        report =
+          DiscourseAi::Completions::Report.new(
+            start_date: params[:start_date]&.to_date || 30.days.ago,
+            end_date: params[:end_date]&.to_date || Time.current,
+          )
+
+        report = report.filter_by_feature(params[:feature]) if params[:feature].present?
+        report = report.filter_by_model(params[:model]) if params[:model].present?
+        report
+      end
+    end
+  end
+end

app/models/ai_api_audit_log.rb

@@ -3,6 +3,7 @@
 class AiApiAuditLog < ActiveRecord::Base
   belongs_to :post
   belongs_to :topic
+  belongs_to :user
 
   module Provider
     OpenAI = 1
@@ -43,3 +44,10 @@ def prev_log_id
 #  feature_name         :string(255)
 #  language_model       :string(255)
 #  feature_context      :jsonb
+#  cached_tokens        :integer
+#
+# Indexes
+#
+#  index_ai_api_audit_logs_on_created_at_and_feature_name    (created_at,feature_name)
+#  index_ai_api_audit_logs_on_created_at_and_language_model  (created_at,language_model)
+#

app/serializers/ai_usage_serializer.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+class AiUsageSerializer < ApplicationSerializer
+  attributes :data, :features, :models, :users, :summary, :period
+
+  def data
+    object.tokens_by_period.as_json(
+      only: %i[period total_tokens total_cached_tokens total_request_tokens total_response_tokens],
+    )
+  end
+
+  def period
+    object.guess_period
+  end
+
+  def features
+    object.feature_breakdown.as_json(
+      only: %i[
+        feature_name
+        usage_count
+        total_tokens
+        total_cached_tokens
+        total_request_tokens
+        total_response_tokens
+      ],
+    )
+  end
+
+  def models
+    object.model_breakdown.as_json(
+      only: %i[
+        llm
+        usage_count
+        total_tokens
+        total_cached_tokens
+        total_request_tokens
+        total_response_tokens
+      ],
+    )
+  end
+
+  def users
+    object.user_breakdown.map do |user|
+      {
+        avatar_template: User.avatar_template(user.username, user.uploaded_avatar_id),
+        username: user.username,
+        usage_count: user.usage_count,
+        total_tokens: user.total_tokens,
+        total_cached_tokens: user.total_cached_tokens,
+        total_request_tokens: user.total_request_tokens,
+        total_response_tokens: user.total_response_tokens,
+      }
+    end
+  end
+
+  def summary
+    {
+      total_tokens: object.total_tokens,
+      total_cached_tokens: object.total_cached_tokens,
+      total_request_tokens: object.total_request_tokens,
+      total_response_tokens: object.total_response_tokens,
+      total_requests: object.total_requests,
+      date_range: {
+        start: object.start_date,
+        end: object.end_date,
+      },
+    }
+  end
+end

assets/javascripts/discourse/admin-discourse-ai-plugin-route-map.js

@@ -18,5 +18,6 @@ export default {
       this.route("new");
       this.route("show", { path: "/:id" });
     });
+    this.route("discourse-ai-usage", { path: "ai-usage" });
   },
 };