Instructor steps

01_inventory/Gemfile

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+source 'https://rubygems.org'
+gem "sinatra"
+gem "rspec"
+
+gem 'activerecord'
+gem 'activesupport'
+gem 'sqlite3'

01_inventory/Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    activemodel (4.2.6)
+      activesupport (= 4.2.6)
+      builder (~> 3.1)
+    activerecord (4.2.6)
+      activemodel (= 4.2.6)
+      activesupport (= 4.2.6)
+      arel (~> 6.0)
+    activesupport (4.2.6)
+      i18n (~> 0.7)
+      json (~> 1.7, >= 1.7.7)
+      minitest (~> 5.1)
+      thread_safe (~> 0.3, >= 0.3.4)
+      tzinfo (~> 1.1)
+    arel (6.0.3)
+    builder (3.2.2)
+    diff-lcs (1.2.5)
+    i18n (0.7.0)
+    json (1.8.3)
+    minitest (5.9.0)
+    rack (1.6.4)
+    rack-protection (1.5.3)
+      rack
+    rspec (3.2.0)
+      rspec-core (~> 3.2.0)
+      rspec-expectations (~> 3.2.0)
+      rspec-mocks (~> 3.2.0)
+    rspec-core (3.2.0)
+      rspec-support (~> 3.2.0)
+    rspec-expectations (3.2.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.2.0)
+    rspec-mocks (3.2.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.2.0)
+    rspec-support (3.2.1)
+    sinatra (1.4.7)
+      rack (~> 1.5)
+      rack-protection (~> 1.4)
+      tilt (>= 1.3, < 3)
+    sqlite3 (1.3.11)
+    thread_safe (0.3.5)
+    tilt (1.3.3)
+    tzinfo (1.2.2)
+      thread_safe (~> 0.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  activerecord
+  activesupport
+  rspec
+  sinatra
+  sqlite3

01_inventory/Rakefile

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+require "active_record"
+require "active_support/all"
+
+namespace :db do
+  desc "migrate your database"
+  task :migrate do
+    require "./store/db_store/config"
+    ActiveRecord::Migrator.migrate('store/db_store/migrate')
+  end
+end

01_inventory/app.rb

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+require "sinatra"
+require_relative "lib/inventory"
+require_relative "store/db_store/config"
+require_relative "store/db_store"
+
+store = DbStore.new
+inventory = Inventory.new(store)
+
+get '/' do
+  @articles = inventory.articles_list
+  erb :index
+end
+
+get '/articles/new' do
+  @form = inventory.new_article_form
+  erb :new_article
+end
+
+post '/articles' do
+  status = inventory.add_article(params)
+
+  if status.success?
+    redirect "/"
+  else
+    @form = status.form_with_errors
+    erb :new_article
+  end
+end
+
+post '/articles/:code/increment' do
+  inventory.increment_article_quantity(params[:code])
+  redirect "/"
+end
+
+post '/articles/:code/decrement' do
+  inventory.decrement_article_quantity(params[:code])
+  redirect "/"
+end
+
+after do
+  ActiveRecord::Base.clear_active_connections!
+end

01_inventory/lib/inventory.rb

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+require "ostruct"
+
+class Inventory
+  def initialize(store)
+    @store = store
+  end
+
+  def articles_list
+    store.all_articles.map { |raw| Article.new(raw) }
+  end
+
+  def new_article_form
+    ArticleForm.new(Article.new)
+  end
+
+  def add_article(params)
+    article = Article.new(params)
+    errors = ArticleValidator.new(article, store).validate!
+
+    if errors.empty?
+      store.create(article.to_h)
+      SuccessArticleStatus.new
+    else
+      ErrorArticleStatus.new(ArticleForm.new(article, errors))
+    end
+  end
+
+  def increment_article_quantity(code)
+    article = Article.new(store.find_with_code(code))
+    article.increment_quantity!
+    store.update(article.to_h)
+  end
+
+  def decrement_article_quantity(code)
+    article = Article.new(store.find_with_code(code))
+    article.decrement_quantity! do |article|
+      store.update(article.to_h)
+    end
+  end
+
+  private
+
+  attr_reader :store
+end
+
+module Presence
+  def present?(attr)
+    !attr.nil? && attr != ""
+  end
+end
+
+module Delegate
+  def delegate(*keys, to:, sufix: false)
+    keys.each do |key|
+      method_name = sufix && "#{key}_#{to}" || key
+      define_method method_name do
+        self.send(to).send(key)
+      end
+    end
+  end
+end
+
+class ArticleValidator
+  include Presence
+
+  def initialize(article, store)
+    @store = store
+    @article = article
+  end
+
+  def validate!
+    self.errors = {}
+    validate_presence_of! :name, :code, :quantity
+    validate_uniqness_of_code!
+    validate_quantity_is_greater_than_or_equals_than_zero!
+    errors
+  end
+
+  private
+
+  attr_reader :article, :store
+  attr_accessor :errors
+
+  def validate_presence_of!(*attr_keys)
+    attr_keys.each do |attr_key|
+      unless present?(article.send(attr_key))
+        errors[attr_key] = "can't be blank"
+      end
+    end
+  end
+
+  def validate_uniqness_of_code!
+    if present?(article.code) && store.find_with_code(article.code)
+      errors[:code] = "already taken"
+    end
+  end
+
+  def validate_quantity_is_greater_than_or_equals_than_zero!
+    if present?(article.quantity) && article.quantity < 0
+      errors[:quantity] = "should be greater or equals than 0"
+    end
+  end
+end
+
+class ArticleForm
+  extend Delegate
+
+  delegate :name, :code, :quantity, to: :article
+  delegate :name, :code, :quantity, to: :errors, sufix: true
+
+  def initialize(article, errors = {})
+    @article = article
+    @errors = OpenStruct.new(errors)
+  end
+
+  private
+
+  attr_reader :article, :errors
+end
+
+class ErrorArticleStatus
+  attr_reader :form_with_errors
+
+  def initialize(form)
+    @form_with_errors = form
+  end
+
+  def success?
+    false
+  end
+end
+
+class SuccessArticleStatus
+  def success?
+    true
+  end
+end
+
+class Article
+  include Presence
+
+  attr_reader :name, :code, :quantity
+
+  def initialize(data = {})
+    @name = data["name"]
+    @code = data["code"]
+    self.quantity = data["quantity"]
+  end
+
+  def to_h
+    {"name" => name,
+     "code" => code,
+     "quantity" => quantity}
+  end
+
+  def increment_quantity!
+    self.quantity = quantity + 1
+  end
+
+  def decrement_quantity!(&block)
+    if quantity > 0
+      self.quantity = quantity - 1
+      block.call(self)
+    end
+  end
+
+  private
+
+  def quantity=(value)
+    @quantity = value.to_i if present?(value)
+  end
+end