Implement API endpoints for Categories and Products (#4)

* chore: Switch from jbuilder to jsonapi-serializer

This change came about after a number of research. I found that JSON:API
 standard follows best practices and it's something I want to become
 very good at.

 Also, based on the benchmark tests, it is way faster than jbuilder and
 the alternatives I found.

* feat: Update schema to make category_id optional on products

This update makes the `category_id` on the `products` to be optional so
that it doesn't need to be provided when a product does not fit into a
category yet.

It also ensures that when a category is deleted, the products that
depend will have their `category_id` field set to null.

Finally, `available` and `currency` have been introduced to the
`products` to table to help know the availability status of a product
and the currency it uses.

* test: Add tests for updates and deletion for products and category
models

* chore: Add default URLs to test and development environments

* feat: Add helper to retrieve response body

* test: Add test for controller routing to endpoints

* chore: Include RequestsHelper in spec_helper.rb file

* feat: Add routes for version 1 of categories and unmatched endpoints

* feat: Add error handling and JsonResponse helper for API responses

* chore: Add coverage for tests

* chore: Ignore coverage directory

* chore: Add 'simplecov' configuration to spec_helper.rb

* refactor: Update error handling for controllers

* feat: Add serializer for Category model

* feat: Add JsonResponse and PaginationHelper for API responses

* test: Add unit tests for CategoriesController to validate all actions

* feat: Add controller for category API operations

* style: Update code style

* test: Add unit tests for validating filtering by name and search
keywords

* feat: Implement filtering based on name and search keywords

* refactor: Move authentication validation to application controller

* refactor: Update error handling responses and include Authentication
mixin

* feat: Add an authentication module to validate dev tokens and user IDs

* feat: Add endpoints for products API operations

* chore: Add database cleaner for active record

* refactor: Update application_controller.rb to handle validation error

* refactor: Update developer token and user ID retrieval

* refactor: Add status code success metadata for successful JSON responses

* refactor: Update to mock the valid_developer_token to return true always

* feat: Add redis and HTTParty

* test: Fix test cases for categories_controller.rb

* feat: Update schema to include app ID

* feat: Update authentication.rb to use the user service for validations

* refactor: Improve pagination response

* feat: Implement a method to handle bad requests.

* feat: Add Redis as the caching store

* feat: Add caching for single results

* test: Add tests for route matching for products API endpoints

* feat: Implement user service client to validate user, app and developer
details

* test: Add tests for UserServiceClient

* feat: Add database_cleaner and shared_context.rb files

* feat: Fix failing tests after adding mandatory app_id field

* feat: Add authentication helper for request to spec_helper.rb

* refactor: Move authentication helper to a separate module

* feat: Update shared_contexts.rb to retrieve valid data

* style: Rubocop style fixes

* feat: Add logic for filtering products

* feat: Add the AuthenticationHelper for request type tests

* test: Add tests for product operation endpoints

* feat: Add controller actions for Product endpoints

* feat: Add serializer for products

* style: Rubocop style fixes

.gitignore

@@ -32,3 +32,4 @@
 # Ignore master key for decrypting credentials and more.
 /config/master.key
 .idea/
+/coverage/

Gemfile

@@ -8,10 +8,8 @@ gem 'rails', '~> 7.2.1'
 gem 'pg', '~> 1.1'
 # Use the Puma web server [https://github.com/puma/puma]
 gem 'puma', '>= 5.0'
-# Build JSON APIs with ease [https://github.com/rails/jbuilder]
-gem 'jbuilder'
 # Use Redis adapter to run Action Cable in production
-# gem "redis", ">= 4.0.1"
+gem 'redis', '>= 4.0.1'
 
 # Use Kredis to get higher-level data types in Redis [https://github.com/rails/kredis]
 # gem "kredis"
@@ -46,9 +44,21 @@ group :development, :test do
   gem 'factory_bot_rails'
 
   gem 'dotenv-rails'
+
+  # code coverage
+  gem 'simplecov', require: false
 end
 
 gem 'uuid7', '~> 0.2.0'
 
 # for pagination
 gem 'kaminari'
+
+# for JSON response serialization
+gem 'jsonapi-serializer'
+
+group :test do
+  gem 'database_cleaner-active_record'
+end
+
+gem 'httparty', '~> 0.22.0'

Gemfile.lock

@@ -82,11 +82,17 @@ GEM
     concurrent-ruby (1.3.4)
     connection_pool (2.4.1)
     crass (1.0.6)
+    csv (3.3.0)
+    database_cleaner-active_record (2.2.0)
+      activerecord (>= 5.a)
+      database_cleaner-core (~> 2.0.0)
+    database_cleaner-core (2.0.1)
     date (3.3.4)
     debug (1.9.2)
       irb (~> 1.10)
       reline (>= 0.3.8)
     diff-lcs (1.5.1)
+    docile (1.4.1)
     dotenv (3.1.2)
     dotenv-rails (3.1.2)
       dotenv (= 3.1.2)
@@ -100,16 +106,19 @@ GEM
       railties (>= 5.0.0)
     globalid (1.2.1)
       activesupport (>= 6.1)
-    i18n (1.14.6)
+    httparty (0.22.0)
+      csv
+      mini_mime (>= 1.0.0)
+      multi_xml (>= 0.5.2)
+    i18n (1.14.5)
       concurrent-ruby (~> 1.0)
     io-console (0.7.2)
     irb (1.14.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
-    jbuilder (2.13.0)
-      actionview (>= 5.0.0)
-      activesupport (>= 5.0.0)
     json (2.7.2)
+    jsonapi-serializer (2.2.0)
+      activesupport (>= 4.2)
     kaminari (1.2.2)
       activesupport (>= 4.1.0)
       kaminari-actionview (= 1.2.2)
@@ -136,6 +145,8 @@ GEM
     mini_mime (1.1.5)
     minitest (5.25.1)
     msgpack (1.7.2)
+    multi_xml (0.7.1)
+      bigdecimal (~> 3.1)
     net-imap (0.4.16)
       date
       net-protocol
@@ -209,6 +220,10 @@ GEM
     rake (13.2.1)
     rdoc (6.7.0)
       psych (>= 4.0.0)
+    redis (5.3.0)
+      redis-client (>= 0.22.0)
+    redis-client (0.22.2)
+      connection_pool
     regexp_parser (2.9.2)
     reline (0.5.10)
       io-console (~> 0.5)
@@ -259,6 +274,12 @@ GEM
       rubocop-rails
     ruby-progressbar (1.13.0)
     securerandom (0.3.1)
+    simplecov (0.22.0)
+      docile (~> 1.1)
+      simplecov-html (~> 0.11)
+      simplecov_json_formatter (~> 0.1)
+    simplecov-html (0.12.3)
+    simplecov_json_formatter (0.1.4)
     stringio (3.1.1)
     thor (1.3.2)
     timeout (0.4.1)
@@ -285,16 +306,20 @@ PLATFORMS
 DEPENDENCIES
   bootsnap
   brakeman
+  database_cleaner-active_record
   debug
   dotenv-rails
   factory_bot_rails
-  jbuilder
+  httparty (~> 0.22.0)
+  jsonapi-serializer
   kaminari
   pg (~> 1.1)
   puma (>= 5.0)
   rails (~> 7.2.1)
+  redis (>= 4.0.1)
   rspec-rails (~> 7.0)
   rubocop-rails-omakase
+  simplecov
   tzinfo-data
   uuid7 (~> 0.2.0)
 

app/controllers/api/v1/categories_controller.rb

@@ -0,0 +1,128 @@
+# frozen_string_literal: true
+
+module Api
+  module V1
+    # Controller for version of Categories side of Product Management Service
+    # This controller handles CRUD operations for categories.
+    class CategoriesController < ApplicationController
+      # Before actions to set up authorization and category object
+      before_action :set_api_v1_category, only: %i[show update destroy]
+
+      # GET /api/v1/categories
+      # GET /api/v1/categories.json
+      # Retrieves a paginated list of categories filtered by developer token
+      def index
+        categories = Category.all
+
+        categories = perform_filtering(categories)
+
+        paginated_categories = categories.page(params[:page]).per(page_size)
+
+        render json: json_response(
+          paginated_categories, serializer:,
+                                message: 'Categories retrieved successfully'
+        )
+      end
+
+      # GET /api/v1/categories/:id
+      # GET /api/v1/categories/:id.json
+      # Retrieves a specific category by ID
+      def show
+        # Render the JSON response with the category
+        render json: json_response(
+          category, serializer:,
+                    message: 'Category retrieved successfully'
+        )
+      end
+
+      # POST /api/v1/categories
+      # POST /api/v1/categories.json
+      # Creates a new category
+      def create
+        @category = Category.new(api_v1_category_params)
+
+        @category.save! # Raise an error when the category could not be saved
+
+        # Render the JSON response with the created category
+        render json: json_response(@category,
+                                   message: 'Category created successfully',
+                                   serializer:), status: :created
+      end
+
+      # PATCH/PUT /api/v1/categories/:id
+      # PATCH/PUT /api/v1/categories/:id.json
+      # Updates an existing category
+      def update
+        if @category.update!(api_v1_category_params)
+          # Render the JSON response with the updated category
+          render json: json_response(@category,
+                                     serializer:,
+                                     message: 'Category updated successfully')
+        else
+          # Render an error response if the category could not be updated
+          render json: category.errors, status: :unprocessable_content
+        end
+      end
+
+      # DELETE /api/v1/categories/:id
+      # DELETE /api/v1/categories/:id.json
+      #
+      # Deletes a specific category by ID
+      def destroy
+        @category.destroy!
+        # Respond with no content status
+        head :no_content
+      end
+
+      private
+
+        # Reader method for the category instance variable
+        attr_reader :category
+
+        # Sets the category instance variable based on the ID and developer
+        # token
+        def set_api_v1_category
+          cache_key = "category/#{params[:id]}_#{developer_id}"
+          @category = Rails.cache.fetch(cache_key, expires_in: 12.hours) do
+            Category.find_by!(
+              id: params[:id],
+              developer_id:
+            )
+          end
+        end
+
+        # Only allow a list of trusted parameters through.
+        # Permits the name and description parameters and merges the developer
+        # token
+        def api_v1_category_params
+          params.require(:category)
+                .permit(:name, :description)
+                .merge(developer_id:)
+        end
+
+        # Returns the serializer class for the category
+        def serializer
+          CategorySerializer
+        end
+
+        def perform_filtering(categories)
+          # Filter categories by developer token
+          categories = categories.where(developer_id:)
+
+          # Filter categories by name
+          if params[:name].present?
+            categories = categories.where('name ILIKE ?', "%#{params[:name]}%")
+          end
+
+          # filter categories by the search term, so any category that
+          # has the search term in its name or description will be returned
+          return categories if params[:search].blank?
+
+          categories.where(
+            'name ILIKE :search OR description ILIKE :search',
+            search: "%#{params[:search]}%"
+          )
+        end
+    end
+  end
+end