Xukun Liu's backend technical challenge

Gemfile

@@ -26,6 +26,11 @@ gem "stimulus-rails"
 # Build JSON APIs with ease [https://github.com/rails/jbuilder]
 gem "jbuilder"
 
+gem "bootstrap", "~> 5.1.3"
+
+gem 'jquery-rails'
+
+gem 'concurrent-ruby'
 # Use Redis adapter to run Action Cable in production
 # gem "redis", ">= 4.0.1"
 

Gemfile.lock

@@ -77,11 +77,17 @@ GEM
       tzinfo (~> 2.0)
     addressable (2.8.6)
       public_suffix (>= 2.0.2, < 6.0)
+    autoprefixer-rails (10.4.16.0)
+      execjs (~> 2)
     base64 (0.2.0)
     bigdecimal (3.1.5)
     bindex (0.8.1)
     bootsnap (1.17.0)
       msgpack (~> 1.2)
+    bootstrap (5.1.3)
+      autoprefixer-rails (>= 9.1.0)
+      popper_js (>= 2.9.3, < 3)
+      sassc-rails (>= 2.0.0)
     builder (3.2.4)
     capybara (3.39.2)
       addressable
@@ -102,6 +108,8 @@ GEM
     drb (2.2.0)
       ruby2_keywords
     erubi (1.12.0)
+    execjs (2.9.1)
+    ffi (1.16.3)
     globalid (1.2.1)
       activesupport (>= 6.1)
     i18n (1.14.1)
@@ -117,6 +125,10 @@ GEM
     jbuilder (2.11.5)
       actionview (>= 5.0.0)
       activesupport (>= 5.0.0)
+    jquery-rails (4.6.0)
+      rails-dom-testing (>= 1, < 3)
+      railties (>= 4.2.0)
+      thor (>= 0.14, < 2.0)
     loofah (2.22.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
@@ -149,6 +161,7 @@ GEM
       racc (~> 1.4)
     nokogiri (1.15.5-x86_64-linux)
       racc (~> 1.4)
+    popper_js (2.11.8)
     psych (5.1.1.1)
       stringio
     public_suffix (5.0.4)
@@ -201,6 +214,14 @@ GEM
     rexml (3.2.6)
     ruby2_keywords (0.0.5)
     rubyzip (2.3.2)
+    sassc (2.4.0)
+      ffi (~> 1.9)
+    sassc-rails (2.1.2)
+      railties (>= 4.0.0)
+      sassc (>= 2.0)
+      sprockets (> 3.0)
+      sprockets-rails
+      tilt
     selenium-webdriver (4.9.0)
       rexml (~> 3.2, >= 3.2.5)
       rubyzip (>= 1.2.2, < 3.0)
@@ -220,6 +241,7 @@ GEM
       railties (>= 6.0.0)
     stringio (3.1.0)
     thor (1.3.0)
+    tilt (2.3.0)
     timeout (0.4.1)
     turbo-rails (1.5.0)
       actionpack (>= 6.0.0)
@@ -252,10 +274,13 @@ PLATFORMS
 
 DEPENDENCIES
   bootsnap
+  bootstrap (~> 5.1.3)
   capybara
+  concurrent-ruby
   debug
   importmap-rails
   jbuilder
+  jquery-rails
   puma (>= 5.0)
   rails (~> 7.1.2)
   selenium-webdriver

README.md

@@ -1,3 +1,23 @@
+## What I did
+
+- **MVC Architecture:** Follows the standard Model-View-Controller (MVC) pattern.
+- **Search Functionality:** Users can search for articles using keywords.
+- **Frontend:** Implemented using jQuery and Bootstrap for a responsive and interactive user interface.
+- **Caching:** Utilizes file-based caching to improve performance and reduce database load.
+- **Rate Limiting:** Protects the application from excessive use of the create article endpoint.
+- **Concurrency:** Handles write operations using a multithreading approach.
+
+## What I could do more
+
+- Add Redis to handle cache more efficiently
+- Add message queue to better handle more write requests
+
+# Instruction on how to run
+1. Clone this repo
+2. Navitage to the repo and perform `bundle install` then `rails server` to start the server
+3. Go to http://127.0.0.1:3000/articles, the default link, and open it to access the UI
+
+
 # Technical Instructions
 1. Fork this repo to your local Github account.
 2. Create a new branch to complete all your work in.

app/assets/javascripts/application.js

@@ -0,0 +1,5 @@
+//= require rails-ujs
+//= require jquery3
+//= require popper
+//= require bootstrap
+//= require_tree .

app/assets/stylesheets/application.css → app/assets/stylesheets/application.scss

@@ -13,3 +13,4 @@
  *= require_tree .
  *= require_self
  */
+ @import "bootstrap";

app/controllers/articles_controller.rb

@@ -0,0 +1,162 @@
+require 'concurrent'
+class ArticlesController < ApplicationController
+    RATE_LIMIT = 20 # Maximum requests for creating per minute
+    RATE_LIMIT_PERIOD = 60 # Period in seconds
+
+    THREAD_POOL = Concurrent::ThreadPoolExecutor.new(
+        min_threads: 1,
+        max_threads: 5,
+        max_queue: 10,
+        fallback_policy: :caller_runs
+    )
+
+
+    before_action :set_article, only: [:show, :edit, :update, :destroy]
+
+    # GET /articles
+    # Responds to: HTML, JSON
+    def index
+        # Create a unique cache key based on the search term
+        cache_key = params[:search].present? ? "articles_search_#{params[:search]}" : "articles_all"
+
+        # Fetch from cache or perform the search query
+        @articles = Rails.cache.fetch(cache_key, expires_in: 12.hours) do
+          Article.search(params[:search]).to_a
+        end
+
+        respond_to do |format|
+          format.html
+          format.json { render json: @articles }
+        end
+    end
+
+    # GET /articles/:id
+    # Responds to: HTML, JSON
+    def show
+      respond_to do |format|
+        format.html
+        format.json { render json: @article }
+      end
+    end
+
+    # GET /articles/new
+    # Responds to: HTML
+    def new
+      @article = Article.new
+    end
+
+    # POST /articles
+    # Responds to: HTML, JSON
+    def create
+      # in case someone maliciously call our api
+      if rate_limit_exceeded?(request.remote_ip)
+        respond_to do |format|
+            format.html do
+                flash[:alert] = 'Rate limit exceeded. Please try again later.'
+                redirect_to articles_path
+            end
+            format.json { render json: { error: 'Rate limit exceeded' }, status: :too_many_requests }
+        end
+          return
+      end
+
+      @article = Article.new(article_params)
+      # use multi-threading to handle more requests
+      future = Concurrent::Future.execute(executor: THREAD_POOL) do
+        ActiveRecord::Base.connection_pool.with_connection do
+          @article.save
+        end
+      end    
+      future.wait # Wait for the thread to complete
+
+      respond_to do |format|
+        if future.value
+          clear_articles_cache
+          format.html { redirect_to @article, notice: 'Article was successfully created.' }
+          format.json { render json: @article, status: :created, location: @article }
+        else
+          format.html { render :new }
+          format.json { render json: @article.errors, status: :unprocessable_entity }
+        end
+      end
+    end
+
+    # GET /articles/:id/edit
+    # Responds to: HTML
+    def edit
+    end
+
+    # PATCH/PUT /articles/:id
+    # Responds to: HTML, JSON
+    def update
+      respond_to do |format|
+        if @article.update(article_params)
+          clear_articles_cache
+          format.html { redirect_to @article, notice: 'Article was successfully updated.' }
+          format.json { render json: @article }
+        else
+          format.html { render :edit }
+          format.json { render json: @article.errors, status: :unprocessable_entity }
+        end
+      end
+    end
+
+    # DELETE /articles/:id
+    # Responds to: HTML, JSON
+    def destroy
+        begin
+          # Clear cache related to articles before destroying the article
+          Rails.cache.delete_matched("articles_*")
+
+          @article.destroy
+          respond_to do |format|
+            format.html { redirect_to articles_url, notice: 'Article was successfully destroyed.' }
+            format.json { head :no_content }
+          end
+        rescue => e
+          # Handle the exception and provide feedback to the user
+          respond_to do |format|
+            format.html { redirect_to articles_url, alert: "Failed to destroy the article: #{e.message}" }
+            format.json { render json: { error: "Failed to destroy the article: #{e.message}" }, status: :unprocessable_entity }
+          end
+        end
+    end
+
+    private
+        def set_article
+            begin
+            @article = Article.find(params[:id])
+            rescue ActiveRecord::RecordNotFound
+                # Handle the case when the article is not found
+                respond_to do |format|
+                    format.html { redirect_to articles_url, alert: 'Article not found.' }
+                    format.json { render json: { error: 'Article not found.' }, status: :not_found }
+                end
+            end
+        end
+
+      def article_params
+        params.require(:article).permit(:title, :content, :author, :date)
+      end
+
+      def clear_articles_cache
+        # Clear general articles cache
+        Rails.cache.delete("articles_all")
+
+        # Clear caches for specific search terms
+        Rails.cache.delete_matched("articles_search_*")
+      end
+
+      def rate_limit_exceeded?(ip)
+        key = "rate_limit:#{ip}"
+        count = Rails.cache.read(key) || 0
+
+        if count >= RATE_LIMIT
+          true
+        else
+          Rails.cache.write(key, count + 1, expires_in: RATE_LIMIT_PERIOD)
+          false
+        end
+       end
+  end
+

app/models/article.rb

@@ -0,0 +1,13 @@
+class Article < ApplicationRecord
+
+    validates :title, presence: true
+    validates :content, presence: true
+
+    def self.search(search_term)
+        if search_term
+            where('title LIKE ? OR content LIKE ?', "%#{search_term}%", "%#{search_term}%")
+        else
+            all
+        end
+    end
+end

app/views/articles/_form.html.erb

@@ -0,0 +1,34 @@
+<%= form_with model: article, local: true, html: { class: 'mb-3' } do |form| %>
+  <% if article.errors.any? %>
+    <div id="error_explanation" class="alert alert-danger">
+      <h2><%= pluralize(article.errors.count, "error") %> prohibited this article from being saved:</h2>
+      <ul>
+        <% article.errors.full_messages.each do |message| %>
+          <li><%= message %></li>
+        <% end %>
+      </ul>
+    </div>
+  <% end %>
+
+  <div class="form-group mb-3">
+    <%= form.label :title %>
+    <%= form.text_field :title, class: 'form-control' %>
+  </div>
+
+  <div class="form-group mb-3">
+    <%= form.label :content %>
+    <%= form.text_area :content, class: 'form-control' %>
+  </div>
+
+  <div class="form-group mb-3">
+    <%= form.label :author %>
+    <%= form.text_field :author, class: 'form-control' %>
+  </div>
+
+  <div class="form-group mb-3">
+    <%= form.label :date %>
+    <%= form.date_select :date, class: 'form-control' %>
+  </div>
+
+  <%= form.submit class: 'btn btn-primary' %>
+<% end %>

app/views/articles/edit.html.erb

@@ -0,0 +1,7 @@
+<div class="container">
+  <h1>Edit Article</h1>
+
+  <%= render 'form', article: @article %>
+
+  <%= link_to 'Back', articles_path, class: 'btn btn-outline-primary' %>
+</div>

app/views/articles/index.html.erb

@@ -0,0 +1,22 @@
+<div class="container">
+  <h1>Articles</h1>
+
+  <%= form_with url: articles_path, method: :get, class: 'form-inline mb-3' do |form| %>
+    <%= form.text_field :search, value: params[:search], placeholder: "Search articles", class: 'form-control mr-sm-2' %>
+    <%= form.submit "Search", class: 'btn btn-outline-success' %>
+  <% end %>
+
+  <%= link_to 'New Article', new_article_path, class: 'btn btn-primary mb-3' %>
+
+  <ul class="list-group">
+    <% @articles.each do |article| %>
+      <li class="list-group-item d-flex justify-content-between align-items-center">
+        <%= link_to article.title, article_path(article) %>
+        <span>
+          <%= link_to 'Edit', edit_article_path(article), class: 'btn btn-outline-secondary btn-sm' %>
+          <%= link_to 'Delete', article_path(article), method: :delete, data: { confirm: 'Are you sure?' }, class: 'btn btn-outline-danger btn-sm' %>
+        </span>
+      </li>
+    <% end %>
+  </ul>
+</div>

app/views/articles/new.html.erb

@@ -0,0 +1,7 @@
+<div class="container">
+  <h1>New Article</h1>
+
+  <%= render 'form', article: @article %>
+
+  <%= link_to 'Back', articles_path, class: 'btn btn-outline-primary' %>
+</div>

app/views/articles/show.html.erb

@@ -0,0 +1,10 @@
+<div class="container">
+  <h1><%= @article.title %></h1>
+
+  <p><%= @article.content %></p>
+
+  <p>Author: <%= @article.author %></p>
+  <p>Date: <%= @article.date %></p>
+
+  <%= link_to 'Back', articles_path, class: 'btn btn-outline-primary' %>
+</div>