Shop Manager Implementation

app.rb

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+require_relative "lib/application"
+
+database = "shop_manager"
+
+app = Application.new(database)
+
+app.run

lib/application.rb

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+require_relative "./item_repository"
+require_relative "./order_repository"
+
+class Application
+  def initialize(
+    database_name,
+    io = Kernel,
+    item_repository = ItemRepository.new,
+    order_repository = OrderRepository.new
+  )
+    DatabaseConnection.connect(database_name)
+    @io = io
+    @item_repository = item_repository
+    @order_repository = order_repository
+  end
+
+  def run
+    print_welcome_options
+    choice = @io.gets.chomp
+    process_user_input(choice)
+  end
+
+  private
+
+  def process_user_input(choice)
+    case choice
+    when "1"
+      print_all_items
+    when "2"
+      add_new_item
+    when "3"
+      print_all_orders
+    when "4"
+      add_new_order
+    end
+  end
+
+  def add_new_order
+    add_order_to_database(*new_order_from_user)
+  end
+
+  def new_order_from_user
+    @io.print "What's the customer name of the new order: "
+    customer = @io.gets.chomp
+    @io.print "What's the date this order was placed: "
+    date = @io.gets.chomp
+    [customer, date]
+  end
+
+  def add_order_to_database(customer, date)
+    order = Order.new
+    order.customer_name = customer
+    order.date_placed = date
+    @order_repository.create(order)
+  end
+
+  def add_new_item
+    name, price, quantity = new_item_from_user
+    add_item_to_database(name, price, quantity)
+  end
+
+  def new_item_from_user
+    @io.print "What's the name of the new item: "
+    name = @io.gets.chomp
+    @io.print "What's the unit price of the new item: "
+    price = @io.gets.chomp
+    @io.print "What's the quantity of the new item: "
+    quantity = @io.gets.chomp
+    [name, price, quantity]
+  end
+
+  def add_item_to_database(name, price, quantity)
+    item = Item.new
+    item.name = name
+    item.unit_price = price
+    item.quantity = quantity
+    @item_repository.create(item)
+  end
+
+  def print_all_items
+    items = @item_repository.all
+    @io.puts("Here's a list of all shop items:\n")
+    items.each_with_index do |item, i|
+      @io.puts "##{i + 1} #{item.name} - " +
+        "Unit price: #{format_price(item.unit_price)} - " +
+        "Quantity: #{item.quantity}"
+    end
+  end
+
+  def format_price(price)
+    pounds = (price.to_i / 100).to_s
+    pence = (price.to_i % 100).to_s
+    pence = "0" + pence if pence.length == 1
+    "£#{pounds}.#{pence}"
+  end
+
+  def print_all_orders
+    orders = @order_repository.all_with_items
+    @io.puts "Here's a list of all orders:\n"
+    orders.each_with_index do |order, i|
+      @io.puts "##{i + 1} Customer: #{order.customer_name} - Date placed: #{order.date_placed}"
+      order.items.each do |item|
+        @io.puts "    #{item.name} - Unit price: #{format_price(item.unit_price)}"
+      end
+      @io.puts ""
+    end
+  end
+
+  def print_welcome_options
+    @io.puts("Welcome to the shop management program!\n")
+    @io.puts("What do you want to do?")
+    @io.puts("  1 = list all shop items")
+    @io.puts("  2 = create a new item")
+    @io.puts("  3 = list all orders")
+    @io.puts("  4 = create a new order")
+    @io.puts("")
+  end
+end

lib/database_connection.rb

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+require "pg"
+
+class DatabaseConnection
+  def self.connect(database_name)
+    @connection = PG.connect({ host: "127.0.0.1", dbname: database_name })
+  end
+
+  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/item.rb

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+class Item
+  attr_accessor :id, :name, :unit_price, :quantity
+end

lib/item_repository.rb

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+require_relative "./database_connection"
+require_relative "./item"
+
+class ItemRepository
+  def all
+    sql = "SELECT * FROM items;"
+    records = DatabaseConnection.exec_params(sql, [])
+    records.map { |record| convert_record_to_item(record) }
+  end
+
+  def create(item)
+    sql = "INSERT INTO items (name, unit_price, quantity)
+    VALUES ($1, $2, $3);"
+    params = [item.name, item.unit_price, item.quantity]
+    DatabaseConnection.exec_params(sql, params)
+  end
+
+  private
+
+  def convert_record_to_item(record)
+    item = Item.new
+    item.id = record["id"]
+    item.name = record["name"]
+    item.unit_price = record["unit_price"]
+    item.quantity = record["quantity"]
+    item
+  end
+end

lib/order.rb

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+class Order
+  attr_accessor :id, :customer_name, :date_placed, :items
+
+  def initialize
+    @items = []
+  end
+end

lib/order_repository.rb

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+require_relative "./order"
+
+class OrderRepository
+  def all
+    sql = "SELECT * FROM orders;"
+    records = DatabaseConnection.exec_params(sql, [])
+    records.map { |record| record_to_order(record) }
+  end
+
+  def all_with_items
+    sql = "SELECT id FROM orders;"
+    records = DatabaseConnection.exec_params(sql, [])
+    orders = []
+    records.each do |record|
+      id = (record["id"]).to_i
+      order = find_with_items(id)
+      orders << order
+    end
+    orders
+  end
+
+  def find(id)
+    sql = "SELECT * FROM orders WHERE id = $1;"
+    records = DatabaseConnection.exec_params(sql, [id])
+    record_to_order(records.first)
+  end
+
+  def find_with_items(id)
+    sql = "SELECT orders.id AS id, customer_name, date_placed,
+            items.id AS items_id, name, unit_price, quantity
+          FROM orders JOIN items_orders ON orders.id = items_orders.order_id
+            JOIN items ON items.id = items_orders.item_id
+          WHERE orders.id = $1;"
+
+    records = DatabaseConnection.exec_params(sql, [id])
+    return find(id) if records.ntuples.zero?
+    order = record_to_order(records.first)
+    records.each { |record| order.items << record_to_item(record) }
+    order
+  end
+
+  def create(order)
+    sql = "INSERT INTO orders (customer_name, date_placed)
+    VALUES ($1, $2)"
+    params = [order.customer_name, order.date_placed]
+    DatabaseConnection.exec_params(sql, params)
+  end
+
+  private
+
+  def record_to_order(record)
+    order = Order.new
+    order.id = record["id"]
+    order.customer_name = record["customer_name"]
+    order.date_placed = record["date_placed"]
+    order
+  end
+
+  def record_to_item(record)
+    item = Item.new
+    item.id = record["items_id"]
+    item.name = record["name"]
+    item.unit_price = record["unit_price"]
+    item.quantity = record["quantity"]
+    item
+  end
+end

seeds.sql

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+CREATE TABLE items (
+    id SERIAL PRIMARY KEY,
+    name text,
+    unit_price int,
+    quantity int
+);
+
+CREATE TABLE orders (
+    id SERIAL PRIMARY KEY,
+    customer_name text,
+    date_placed date
+);
+
+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)
+);