Shop manager challenge

Gemfile

@@ -1,15 +1,14 @@
 source 'https://rubygems.org'
 
-ruby '3.0.2'
-
 group :test do
   gem 'rspec'
   gem 'simplecov', require: false
   gem 'simplecov-console', require: false
 end
 
 group :development, :test do
-  gem 'rubocop', '1.20'
+  gem 'rubocop', '1.51'
 end
 
-gem "pg", "~> 1.3"
+gem "pg", "~> 1.5.3"
+gem 'colorize'

Gemfile.lock

@@ -3,41 +3,44 @@ GEM
   specs:
     ansi (1.5.0)
     ast (2.4.2)
-    diff-lcs (1.4.4)
+    colorize (0.8.1)
+    diff-lcs (1.5.0)
     docile (1.4.0)
-    parallel (1.20.1)
-    parser (3.0.2.0)
+    json (2.6.3)
+    parallel (1.23.0)
+    parser (3.2.2.1)
       ast (~> 2.4.1)
-    pg (1.3.5)
-    rainbow (3.0.0)
-    regexp_parser (2.1.1)
+    pg (1.5.3)
+    rainbow (3.1.1)
+    regexp_parser (2.8.0)
     rexml (3.2.5)
-    rspec (3.10.0)
-      rspec-core (~> 3.10.0)
-      rspec-expectations (~> 3.10.0)
-      rspec-mocks (~> 3.10.0)
-    rspec-core (3.10.1)
-      rspec-support (~> 3.10.0)
-    rspec-expectations (3.10.1)
+    rspec (3.12.0)
+      rspec-core (~> 3.12.0)
+      rspec-expectations (~> 3.12.0)
+      rspec-mocks (~> 3.12.0)
+    rspec-core (3.12.2)
+      rspec-support (~> 3.12.0)
+    rspec-expectations (3.12.3)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.10.0)
-    rspec-mocks (3.10.2)
+      rspec-support (~> 3.12.0)
+    rspec-mocks (3.12.5)
       diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.10.0)
-    rspec-support (3.10.2)
-    rubocop (1.20.0)
+      rspec-support (~> 3.12.0)
+    rspec-support (3.12.0)
+    rubocop (1.51.0)
+      json (~> 2.3)
       parallel (~> 1.10)
-      parser (>= 3.0.0.0)
+      parser (>= 3.2.0.0)
       rainbow (>= 2.2.2, < 4.0)
       regexp_parser (>= 1.8, < 3.0)
-      rexml
-      rubocop-ast (>= 1.9.1, < 2.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.28.0, < 2.0)
       ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 1.4.0, < 3.0)
-    rubocop-ast (1.11.0)
-      parser (>= 3.0.1.1)
-    ruby-progressbar (1.11.0)
-    simplecov (0.21.2)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.28.1)
+      parser (>= 3.2.1.0)
+    ruby-progressbar (1.13.0)
+    simplecov (0.22.0)
       docile (~> 1.1)
       simplecov-html (~> 0.11)
       simplecov_json_formatter (~> 0.1)
@@ -46,23 +49,21 @@ GEM
       simplecov
       terminal-table
     simplecov-html (0.12.3)
-    simplecov_json_formatter (0.1.3)
-    terminal-table (3.0.1)
+    simplecov_json_formatter (0.1.4)
+    terminal-table (3.0.2)
       unicode-display_width (>= 1.1.1, < 3)
-    unicode-display_width (2.0.0)
+    unicode-display_width (2.4.2)
 
 PLATFORMS
-  ruby
+  arm64-darwin-22
 
 DEPENDENCIES
-  pg (~> 1.3)
+  colorize
+  pg (~> 1.5.3)
   rspec
-  rubocop (= 1.20)
+  rubocop (= 1.51)
   simplecov
   simplecov-console
 
-RUBY VERSION
-   ruby 3.0.2p107
-
 BUNDLED WITH
-   2.2.26
+   2.4.13

items_orders.sql

@@ -0,0 +1,23 @@
+-- Create the first table.
+CREATE TABLE items (
+  id SERIAL PRIMARY KEY,
+  name text,
+  price numeric,
+  quantity int
+);
+
+-- Create the second table.
+CREATE TABLE orders (
+  id SERIAL PRIMARY KEY,
+  customer_name text,
+  date date
+);
+
+-- Create the join table.
+CREATE TABLE items_orders (
+  item_id int,
+  order_id int,
+  constraint fk_item foreign key(item_id) references items(id) on delete cascade,
+  constraint fk_order foreign key(order_id) references orders(id) on delete cascade,
+  PRIMARY KEY (item_id, order_id)
+);

lib/app.rb

@@ -0,0 +1,138 @@
+require_relative 'database_connection'
+require_relative 'item_repository'
+require_relative 'item'
+require_relative 'order'
+require_relative 'order_repository'
+require_relative 'format'
+
+class Application
+  def initialize(database_name, io, order_repository, item_repository)
+    DatabaseConnection.connect(database_name)
+    @io = io
+    @order_repository = order_repository
+    @item_repository = item_repository
+    @format = Format.new
+  end
+
+  def show_menu(forever = true)
+    running = true
+
+    @io.puts @format.header("Welcome to the shop management program!")
+    while running do
+      @io.puts @format.string("Choose from one of these options:", :cyan, :before)
+      @io.puts "  1. List all items"
+      @io.puts "  2. Create new item"
+      @io.puts "  3. List all orders"
+      @io.puts "  4. Create new order"
+      @io.puts "  5. View all items in an order"
+      @io.puts "  6. Exit"
+      input = @io.gets.chomp
+      process_selection(input)
+      running = forever
+    end
+  end
+
+  def process_selection(input)
+    case input
+    when "1"
+      show_all_items
+    when "2"
+      create_new_item
+    when "3"
+      show_all_orders
+    when "4"
+      create_new_order
+    when "5"
+      view_order_items
+    when "6"
+      exit # TODO: need to test for exiting
+    end
+  end
+
+  def show_all_items(header = true)
+    @io.puts @format.header("All items") if header == true
+    items = @item_repository.all
+    items.each do |item|
+      @io.puts "  #{item.id}: #{item.name} – #{@format.currency(item.price)} (#{item.quantity} in stock)"
+    end
+  end
+
+  def create_new_item
+    @io.puts @format.header("Add a new item")
+    @io.puts @format.string("Enter the item's details", :cyan)
+    @io.puts "Item name:"
+    name = @io.gets.chomp
+    @io.puts "Item price (e.g. 3.25):"
+    price = @io.gets.chomp
+    @io.puts "Quantity in stock:"
+    quantity = @io.gets.chomp
+
+    item = Item.new
+    item.name = name
+    item.price = price
+    item.quantity = quantity
+    @item_repository.create(item)
+
+    @io.puts @format.string("#{name} added to the databse", :green, :pad)
+  end
+
+  def show_all_orders
+    @io.puts @format.header("All orders")
+    orders = @order_repository.all
+    orders.each do |order|
+      @io.puts "  Order ##{order.id}: #{order.date} – #{order.customer_name}"
+    end
+  end
+
+  def create_new_order
+    @io.puts @format.header("New order")
+    @io.puts @format.string("Enter the order details", :cyan)
+    @io.puts "Your name:"
+    name = @io.gets.chomp
+    @io.puts "Select order items (press enter after each selection, and enter on its own to end):"
+    order_items = choose_order_items
+    order = Order.new
+    order.customer_name = name
+    order.date = Time.now
+    order.items = order_items
+    @order_repository.create(order)
+    @io.puts @format.string("Order placed", :green, :pad)
+  end
+
+  def choose_order_items
+    items = []
+    loop do
+      show_all_items(false)
+      input = @io.gets.chomp
+      return items if input == ""
+      item = @item_repository.find(input.to_i)
+      if item.quantity.to_i.zero?
+        @io.puts @format.string("Sorry, #{item.name} is out of stock. Choose something different.", :red, :pad)
+        next
+      end
+      @item_repository.update_quantity(input.to_i)
+      items << input.to_i
+    end
+  end
+
+  def view_order_items
+    @io.puts @format.string("Which order ID do you want to view items for?", :cyan, :pad)
+    input = @io.gets.chomp.to_i
+    items = @order_repository.find_items_by_order(input)
+    @io.puts @format.header("Items in order ##{input}")
+    items.each do |item|
+      @io.puts "#{item.id}: #{item.name} – #{@format.currency(item.price)}"
+    end
+  end
+
+end
+
+if __FILE__ == $0
+  app = Application.new(
+    'shop_manager',
+    Kernel,
+    OrderRepository.new,
+    ItemRepository.new
+  )
+  app.show_menu
+end

lib/database_connection.rb

@@ -0,0 +1,26 @@
+require 'pg'
+
+# This class is a thin "wrapper" around the
+# PG library. We'll use it in our project to interact
+# with the database using SQL.
+
+class DatabaseConnection
+  # This method connects to PostgreSQL using the 
+  # PG gem. We connect to 127.0.0.1, and select
+  # the database name given in argument.
+  def self.connect(database_name)
+    @connection = PG.connect({ host: '127.0.0.1', dbname: database_name })
+  end
+
+  # This method executes an SQL query 
+  # on the database, providing some optional parameters
+  # (you will learn a bit later about when to provide these parameters).
+  def self.exec_params(query, params)
+    if @connection.nil?
+      raise 'DatabaseConnection.exec_params: Cannot run a SQL query as the connection to'\
+      'the database was never opened. Did you make sure to call first the method '\
+      '`DatabaseConnection.connect` in your app.rb file (or in your tests spec_helper.rb)?'
+    end
+    @connection.exec_params(query, params)
+  end
+end

lib/format.rb

@@ -0,0 +1,19 @@
+require 'colorize'
+
+class Format
+  def string(text = "", color = :default, spacing = "")
+    return if text == ""
+    text = text.colorize(color)
+    text = "\n#{text}" if spacing == :pad || spacing == :before
+    text = "#{text}\n" if spacing == :pad || spacing == :after
+    return text
+  end
+
+  def currency(price)
+    return sprintf("£%.2f", price)
+  end
+
+  def header(text)
+    return string("====== #{text} ======", :red, :before)
+  end
+end

lib/item.rb

@@ -0,0 +1,3 @@
+class Item
+  attr_accessor :id, :name, :price, :quantity
+end

lib/item_repository.rb

@@ -0,0 +1,44 @@
+require_relative 'item'
+
+class ItemRepository
+  def all
+    sql = 'SELECT id, name, price, quantity FROM items ORDER BY id;'
+    results = DatabaseConnection.exec_params(sql, [])
+
+    items = []
+    results.each do |result|
+      item = Item.new
+      item.id = result['id']
+      item.name = result['name']
+      item.price = result['price']
+      item.quantity = result['quantity']
+
+      items << item
+    end
+
+    return items
+  end
+
+  def create(item)
+    sql = 'INSERT INTO items (name, price, quantity) VALUES($1, $2, $3);'
+    DatabaseConnection.exec_params(sql, [item.name, item.price, item.quantity])
+  end
+
+  def find(id)
+    sql = 'SELECT id, name, price, quantity FROM items WHERE id = $1;'
+    result = DatabaseConnection.exec_params(sql, [id])
+
+    item = Item.new
+    item.id = result.first['id']
+    item.name = result.first['name']
+    item.price = result.first['price']
+    item.quantity = result.first['quantity']
+
+    return item
+  end
+
+  def update_quantity(id)
+    sql = 'UPDATE items SET quantity = quantity - 1 WHERE id = $1;'
+    result = DatabaseConnection.exec_params(sql, [id])
+  end
+end

lib/order.rb

@@ -0,0 +1,3 @@
+class Order
+  attr_accessor :id, :customer_name, :date, :items
+end