API: Add pagination to articles (#4483)

* Add pagination to articles

* Refactoring

* Update specs

app/services/article_api_index_service.rb

@@ -1,5 +1,8 @@
 class ArticleApiIndexService
-  attr_accessor :tag, :username, :page, :state, :top, :collection_id
+  attr_accessor :tag, :username, :page, :state, :top, :collection_id, :per_page
+
+  DEFAULT_PER_PAGE = 30
+  MAX_PER_PAGE = 1000
 
   def initialize(params)
     @page = params[:page]
@@ -8,6 +11,7 @@ class ArticleApiIndexService
     @state = params[:state]
     @top = params[:top]
     @collection_id = params[:collection_id]
+    @per_page = params[:per_page]
   end
 
   def get
@@ -32,9 +36,9 @@ class ArticleApiIndexService
 
   def username_articles
     num = if @state == "all"
-            1000
+            MAX_PER_PAGE
           else
-            30
+            DEFAULT_PER_PAGE
           end
 
     if (user = User.find_by(username: username))
@@ -42,13 +46,13 @@ class ArticleApiIndexService
         includes(:organization).
         order("published_at DESC").
         page(page).
-        per(num)
+        per(per_page || num)
     elsif (organization = Organization.find_by(slug: username))
       organization.articles.published.
         includes(:user).
         order("published_at DESC").
         page(page).
-        per(num)
+        per(per_page || num)
     else
       Article.none
     end
@@ -66,12 +70,12 @@ class ArticleApiIndexService
                  articles.order("hotness_score DESC")
                end
 
-    articles.page(page).per(30)
+    articles.page(page).per(per_page || DEFAULT_PER_PAGE)
   end
 
   def top_articles
     Article.published.order("positive_reactions_count DESC").where("published_at > ?", top.to_i.days.ago).
-      page(page).per(30)
+      page(page).per(per_page || DEFAULT_PER_PAGE)
   end
 
   def state_articles(state)
@@ -90,7 +94,7 @@ class ArticleApiIndexService
       includes(:user, :organization).
       order("published_at").
       page(page).
-      per(30)
+      per(per_page || DEFAULT_PER_PAGE)
   end
 
   def base_articles
@@ -99,6 +103,6 @@ class ArticleApiIndexService
       includes(:user, :organization).
       order("hotness_score DESC").
       page(page).
-      per(30)
+      per(per_page || DEFAULT_PER_PAGE)
   end
 end

spec/requests/api/v0/articles_spec.rb

@@ -9,74 +9,132 @@ RSpec.describe "Api::V0::Articles", type: :request do
   end
 
   describe "GET /api/articles" do
-    it "returns json response" do
-      get api_articles_path
-      expect(response.content_type).to eq("application/json")
+    context "without params" do
+      it "returns json response" do
+        get api_articles_path
+        expect(response.content_type).to eq("application/json")
+      end
+
+      it "returns featured articles if no param is given" do
+        article.update_column(:featured, true)
+        get api_articles_path
+        expect(json_response.size).to eq(1)
+      end
+
+      it "supports pagination" do
+        create_list(:article, 2, featured: true)
+        get api_articles_path, params: { page: 1, per_page: 2 }
+        expect(json_response.length).to eq(2)
+        get api_articles_path, params: { page: 2, per_page: 2 }
+        expect(json_response.length).to eq(1)
+      end
+
+      it "returns flare tag in the response" do
+        get api_articles_path
+        response_article = JSON.parse(response.body)[0]
+        expect(response_article["flare_tag"]).to be_present
+        expect(response_article["flare_tag"].keys).to eq(%w[name bg_color_hex text_color_hex])
+        expect(response_article["flare_tag"]["name"]).to eq("discuss")
+      end
     end
 
-    it "returns featured articles if no param is given" do
-      article.update_column(:featured, true)
-      get api_articles_path
-      expect(json_response.size).to eq(1)
+    context "with username param" do
+      it "returns user's articles for the given username" do
+        create(:article, user: article.user)
+        get api_articles_path(username: article.user.username)
+        expect(json_response.size).to eq(2)
+      end
+
+      it "returns nothing if given user is not found" do
+        get api_articles_path(username: "foobar")
+        expect(json_response.size).to eq(0)
+      end
+
+      it "returns org's articles if org's slug is given" do
+        create(:article, user: article.user, organization: organization)
+        get api_articles_path(username: organization.slug)
+        expect(json_response.size).to eq(1)
+      end
+
+      it "supports pagination" do
+        create_list(:article, 2, user: article.user)
+        get api_articles_path(username: article.user.username), params: { page: 1, per_page: 2 }
+        expect(json_response.length).to eq(2)
+        get api_articles_path(username: article.user.username), params: { page: 2, per_page: 2 }
+        expect(json_response.length).to eq(1)
+      end
     end
 
-    it "returns user's articles for the given username" do
-      create(:article, user: article.user)
-      get api_articles_path(username: article.user.username)
-      expect(json_response.size).to eq(2)
+    context "with tag param" do
+      it "returns tag's articles" do
+        get api_articles_path(tag: article.tag_list.first)
+        expect(json_response.size).to eq(1)
+      end
+
+      it "returns top tag articles if tag and top param is present" do
+        get api_articles_path(tag: article.tag_list.first, top: "7")
+        expect(json_response.size).to eq(1)
+      end
+
+      it "returns not tag articles if article and tag are not approved" do
+        article.update_column(:approved, false)
+        tag = Tag.find_by(name: article.tag_list.first)
+        tag.update(requires_approval: true)
+
+        get api_articles_path(tag: tag.name)
+        expect(JSON.parse(response.body).size).to eq(0)
+      end
+
+      it "supports pagination" do
+        create_list(:article, 2, tags: "discuss")
+        get api_articles_path(tag: article.tag_list.first), params: { page: 1, per_page: 2 }
+        expect(json_response.length).to eq(2)
+        get api_articles_path(tag: article.tag_list.first), params: { page: 2, per_page: 2 }
+        expect(json_response.length).to eq(1)
+      end
     end
 
-    it "returns nothing if given user is not found" do
-      get api_articles_path(username: "foobar")
-      expect(json_response.size).to eq(0)
+    context "with top param" do
+      it "only returns fresh top articles if top param is present" do
+        # TODO: slight duplication, test should be removed
+        old_article = create(:article)
+        old_article.update_column(:published_at, 10.days.ago)
+        get api_articles_path(top: "7")
+        expect(json_response.size).to eq(1)
+      end
+
+      it "supports pagination" do
+        old_articles = create_list(:article, 2, featured: true)
+        old_articles.each do |old_article|
+          old_article.update_column(:published_at, 10.days.ago)
+        end
+        get api_articles_path(top: "11"), params: { page: 1, per_page: 2 }
+        expect(json_response.length).to eq(2)
+        get api_articles_path(top: "11"), params: { page: 2, per_page: 2 }
+        expect(json_response.length).to eq(1)
+      end
     end
 
-    it "returns org's articles if org's slug is given" do
-      create(:article, user: article.user, organization: organization)
-      get api_articles_path(username: organization.slug)
-      expect(json_response.size).to eq(1)
-    end
+    context "with collection_id param" do
+      it "returns a collection id" do
+        collection = create(:collection, user: article.user)
+        article.update_columns(collection_id: collection.id)
+        get api_articles_path(collection_id: collection.id)
+        expect(json_response[0]["collection_id"]).to eq collection.id
+      end
 
-    it "returns tag's articles" do
-      get api_articles_path(tag: article.tag_list.first)
-      expect(json_response.size).to eq(1)
-    end
-
-    it "returns top tag articles if tag and top param is present" do
-      get api_articles_path(tag: article.tag_list.first, top: "7")
-      expect(json_response.size).to eq(1)
-    end
-
-    it "only returns fresh top articles if top param is present" do
-      # TODO: slight duplication, test should be removed
-      old_article = create(:article)
-      old_article.update_column(:published_at, 10.days.ago)
-      get api_articles_path(top: "7")
-      expect(json_response.size).to eq(1)
-    end
-
-    it "returns not tag articles if article and tag are not approved" do
-      article.update_column(:approved, false)
-      tag = Tag.find_by(name: article.tag_list.first)
-      tag.update(requires_approval: true)
-
-      get api_articles_path(tag: tag.name)
-      expect(JSON.parse(response.body).size).to eq(0)
-    end
-
-    it "returns flare tag in the response" do
-      get api_articles_path
-      response_article = JSON.parse(response.body)[0]
-      expect(response_article["flare_tag"]).to be_present
-      expect(response_article["flare_tag"].keys).to eq(%w[name bg_color_hex text_color_hex])
-      expect(response_article["flare_tag"]["name"]).to eq("discuss")
-    end
-
-    it "returns a collection id" do
-      collection = create(:collection, user: article.user)
-      article.update_columns(collection_id: collection.id)
-      get api_articles_path(collection_id: collection.id)
-      expect(json_response[0]["collection_id"]).to eq collection.id
+      it "supports pagination" do
+        collection = create(:collection, user: article.user)
+        article.update_columns(collection_id: collection.id)
+        collection_articles = create_list(:article, 2, featured: true)
+        collection_articles.each do |collection_article|
+          collection_article.update_columns(collection_id: collection.id)
+        end
+        get api_articles_path(collection_id: collection.id), params: { page: 1, per_page: 2 }
+        expect(json_response.length).to eq(2)
+        get api_articles_path(collection_id: collection.id), params: { page: 2, per_page: 2 }
+        expect(json_response.length).to eq(1)
+      end
     end
   end