Draft API to get all collections by an account (#37139)

app/controllers/api/v1_alpha/collections_controller.rb

@@ -3,20 +3,34 @@
 class Api::V1Alpha::CollectionsController < Api::BaseController
   include Authorization
 
+  DEFAULT_COLLECTIONS_LIMIT = 40
+
   rescue_from ActiveRecord::RecordInvalid, Mastodon::ValidationError do |e|
     render json: { error: ValidationErrorFormatter.new(e).as_json }, status: 422
   end
 
   before_action :check_feature_enabled
 
+  before_action -> { authorize_if_got_token! :read, :'read:collections' }, only: [:index, :show]
   before_action -> { doorkeeper_authorize! :write, :'write:collections' }, only: [:create, :update, :destroy]
 
   before_action :require_user!, only: [:create, :update, :destroy]
 
+  before_action :set_account, only: [:index]
+  before_action :set_collections, only: [:index]
   before_action :set_collection, only: [:show, :update, :destroy]
 
+  after_action :insert_pagination_headers, only: [:index]
+
   after_action :verify_authorized
 
+  def index
+    cache_if_unauthenticated!
+    authorize Collection, :index?
+
+    render json: @collections, each_serializer: REST::BaseCollectionSerializer
+  end
+
   def show
     cache_if_unauthenticated!
     authorize @collection, :show?
@@ -50,6 +64,18 @@ class Api::V1Alpha::CollectionsController < Api::BaseController
 
   private
 
+  def set_account
+    @account = Account.find(params[:account_id])
+  end
+
+  def set_collections
+    @collections = @account.collections
+                           .with_item_count
+                           .order(created_at: :desc)
+                           .offset(offset_param)
+                           .limit(limit_param(DEFAULT_COLLECTIONS_LIMIT))
+  end
+
   def set_collection
     @collection = Collection.find(params[:id])
   end
@@ -65,4 +91,24 @@ class Api::V1Alpha::CollectionsController < Api::BaseController
   def check_feature_enabled
     raise ActionController::RoutingError unless Mastodon::Feature.collections_enabled?
   end
+
+  def next_path
+    return unless records_continue?
+
+    api_v1_alpha_account_collections_url(@account, pagination_params(offset: offset_param + limit_param(DEFAULT_COLLECTIONS_LIMIT)))
+  end
+
+  def prev_path
+    return if offset_param.zero?
+
+    api_v1_alpha_account_collections_url(@account, pagination_params(offset: offset_param - limit_param(DEFAULT_COLLECTIONS_LIMIT)))
+  end
+
+  def records_continue?
+    ((offset_param * limit_param(DEFAULT_COLLECTIONS_LIMIT)) + @collections.size) < @account.collections.size
+  end
+
+  def offset_param
+    params[:offset].to_i
+  end
 end

app/models/collection.rb

@@ -39,6 +39,11 @@ class Collection < ApplicationRecord
   validate :items_do_not_exceed_limit
 
   scope :with_items, -> { includes(:collection_items).merge(CollectionItem.with_accounts) }
+  scope :with_item_count, lambda {
+    select('collections.*, COUNT(collection_items.id)')
+      .left_joins(:collection_items)
+      .group(collections: :id)
+  }
 
   def remote?
     !local?

app/serializers/rest/base_collection_serializer.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class REST::BaseCollectionSerializer < ActiveModel::Serializer
+  attributes :uri, :name, :description, :local, :sensitive, :discoverable,
+             :item_count, :created_at, :updated_at
+
+  belongs_to :tag, serializer: REST::StatusSerializer::TagSerializer
+
+  def item_count
+    object.respond_to?(:item_count) ? object.item_count : object.collection_items.count
+  end
+end

app/serializers/rest/collection_serializer.rb

@@ -1,11 +1,7 @@
 # frozen_string_literal: true
 
-class REST::CollectionSerializer < ActiveModel::Serializer
-  attributes :uri, :name, :description, :local, :sensitive, :discoverable,
-             :created_at, :updated_at
-
+class REST::CollectionSerializer < REST::BaseCollectionSerializer
   belongs_to :account, serializer: REST::AccountSerializer
-  belongs_to :tag, serializer: REST::StatusSerializer::TagSerializer
 
   has_many :items, serializer: REST::CollectionItemSerializer
 

config/routes/api.rb

@@ -6,6 +6,10 @@ namespace :api, format: false do
 
   # Experimental JSON / REST API
   namespace :v1_alpha do
+    resources :accounts, only: [] do
+      resources :collections, only: [:index]
+    end
+
     resources :async_refreshes, only: :show
 
     resources :collections, only: [:show, :create, :update, :destroy]

spec/requests/api/v1_alpha/collections_spec.rb

@@ -5,6 +5,58 @@ require 'rails_helper'
 RSpec.describe 'Api::V1Alpha::Collections', feature: :collections do
   include_context 'with API authentication', oauth_scopes: 'read:collections write:collections'
 
+  describe 'GET /api/v1_alpha/accounts/:account_id/collections' do
+    subject do
+      get "/api/v1_alpha/accounts/#{account.id}/collections", headers: headers, params: params
+    end
+
+    let(:params) { {} }
+
+    let(:account) { Fabricate(:account) }
+
+    before { Fabricate.times(3, :collection, account:) }
+
+    it 'returns all collections for the given account and http success' do
+      subject
+
+      expect(response).to have_http_status(200)
+      expect(response.parsed_body.size).to eq 3
+    end
+
+    context 'with limit param' do
+      let(:params) { { limit: '1' } }
+
+      it 'returns only a single result' do
+        subject
+
+        expect(response).to have_http_status(200)
+        expect(response.parsed_body.size).to eq 1
+
+        expect(response)
+          .to include_pagination_headers(
+            next: api_v1_alpha_account_collections_url(account, limit: 1, offset: 1)
+          )
+      end
+    end
+
+    context 'with limit and offset params' do
+      let(:params) { { limit: '1', offset: '1' } }
+
+      it 'returns the correct result and headers' do
+        subject
+
+        expect(response).to have_http_status(200)
+        expect(response.parsed_body.size).to eq 1
+
+        expect(response)
+          .to include_pagination_headers(
+            prev: api_v1_alpha_account_collections_url(account, limit: 1, offset: 0),
+            next: api_v1_alpha_account_collections_url(account, limit: 1, offset: 2)
+          )
+      end
+    end
+  end
+
   describe 'GET /api/v1_alpha/collections/:id' do
     subject do
       get "/api/v1_alpha/collections/#{collection.id}", headers: headers

spec/serializers/rest/base_collection_serializer_spec.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe REST::BaseCollectionSerializer do
+  subject do
+    serialized_record_json(collection, described_class, options: {
+      scope: current_user,
+      scope_name: :current_user,
+    })
+  end
+
+  let(:current_user) { nil }
+
+  let(:tag) { Fabricate(:tag, name: 'discovery') }
+  let(:collection) do
+    Fabricate(:collection,
+              name: 'Exquisite follows',
+              description: 'Always worth a follow',
+              local: true,
+              sensitive: true,
+              discoverable: false,
+              tag:)
+  end
+
+  it 'includes the relevant attributes' do
+    expect(subject)
+      .to include(
+        'name' => 'Exquisite follows',
+        'description' => 'Always worth a follow',
+        'local' => true,
+        'sensitive' => true,
+        'discoverable' => false,
+        'tag' => a_hash_including('name' => 'discovery'),
+        'created_at' => match_api_datetime_format,
+        'updated_at' => match_api_datetime_format
+      )
+  end
+
+  describe 'Counting items' do
+    before do
+      Fabricate.times(2, :collection_item, collection:)
+    end
+
+    it 'can count items on demand' do
+      expect(subject['item_count']).to eq 2
+    end
+
+    it 'can use precalculated counts' do
+      collection.define_singleton_method :item_count, -> { 8 }
+
+      expect(subject['item_count']).to eq 8
+    end
+  end
+end