shop manager - week 3 solo project

app.rb

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+require_relative 'lib/order_repository'
+require_relative 'lib/item_repository'
+require_relative 'lib/database_connection'
+
+
+class Application
+  def initialize(database_name, io, item_repository, order_repository)
+    DatabaseConnection.connect(database_name)
+    @io = io
+    @item_repository = item_repository
+    @order_repository = order_repository
+  end
+
+  def run
+    print_menu
+    user_input = @io.gets.chomp.to_i
+
+    case user_input
+    when 1
+      list_all_items
+    when 2
+      create_new_item
+    when 3
+      list_all_orders
+    when 4
+      create_new_order
+    end
+
+  end
+
+  private
+
+  def print_menu
+    @io.puts (
+      "Welcome to the shop management program!
+
+      What do you want to do?
+        1 = list all shop items
+        2 = create a new item
+        3 = list all orders
+        4 = create a new order"
+      )
+  end
+
+  def list_all_items
+    @item_repository.all.each do |record|
+      @io.puts("##{record.id} #{record.name} - Unit price: #{record.unit_price} - Quantity: #{record.quantity}")
+    end
+  end
+
+  def create_new_item
+    new_item = Item.new
+
+    @io.puts "Please enter the new item's name:"
+    new_item.name = @io.gets.chomp
+    @io.puts "Please enter the new item's unit price:"
+    new_item.unit_price = @io.gets.chomp.to_f
+    @io.puts "Please enter the new item's quantity:"
+    new_item.quantity = @io.gets.chomp.to_i
+
+    @item_repository.create(new_item)
+  end
+
+  def list_all_orders
+    @order_repository.all.each do |record|
+      @io.puts("Date: #{record.date} - Order ID #{record.id} - Customer Name: #{record.customer_name} - item_id: #{record.item_id}")
+    end
+  end
+
+  def create_new_order
+    new_order = Order.new
+
+    @io.puts "Please enter the date (YYYY-MM-DD):"
+    new_order.date = @io.gets.chomp
+    @io.puts "Please enter the customer's name:"
+    new_order.customer_name = @io.gets.chomp
+    @io.puts "Please enter the item ID:"
+    new_order.item_id = @io.gets.chomp.to_i
+
+    @order_repository.create(new_order)
+  end
+
+end
+
+if __FILE__ == $0
+  app = Application.new(
+    'shop_manager',
+    Kernel,
+    ItemRepository.new,
+    OrderRepository.new
+  )
+  app.run
+end

lib/database_connection.rb

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+# file: lib/database_connection.rb
+
+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/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
+
+  # Selecting all records
+  # No arguments
+  def all
+    # Executes the SQL query:
+    # SELECT id, name, unit_price, quantity FROM items;
+    sql = 'SELECT id, name, unit_price, quantity FROM items;'
+    sql_params = []
+
+    result_set = DatabaseConnection.exec_params(sql,sql_params)
+
+    items = []
+
+    result_set.each do |record|
+      items << get_item(record)
+    end
+
+    return items
+  end
+
+  # Gets a single record by its ID
+  # One argument: the id (number)
+  def find(id)
+    # Executes the SQL query:
+    # SELECT id, name, unit_cost, quantity FROM items WHERE id = $1;
+    sql = 'SELECT id, name, unit_price, quantity FROM items WHERE id = $1;'
+    sql_params = [id]
+
+    result = DatabaseConnection.exec_params(sql,sql_params)
+
+    return get_item(result[0])
+  end
+
+  def create(item)
+    # Executes the SQL query:
+    # INSERT INTO items (name, unit_cost, quantity) VALUES ($1, $2, $3);
+    sql = 'INSERT INTO items (name, unit_price, quantity) VALUES ($1, $2, $3);'
+    sql_params = [item.name, item.unit_price, item.quantity]
+
+    result = DatabaseConnection.exec_params(sql,sql_params)
+
+    return nil
+  end
+
+  private
+
+  def get_item(record)
+      item = Item.new
+      item.id = record['id'].to_i
+      item.name = record['name']
+      item.unit_price = record['unit_price'].to_f
+      item.quantity = record['quantity'].to_i
+
+      return item
+  end
+
+end

lib/order.rb

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+class Order
+  attr_accessor :id, :customer_name, :date, :item_id
+end

lib/order_repository.rb

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+require_relative 'database_connection'
+require_relative 'order'
+
+class OrderRepository
+
+  # Selecting all records
+  # No arguments
+  def all
+    # Executes the SQL query:
+    # SELECT id, customer_name, date, item_id FROM orders;
+
+    sql = 'SELECT id, customer_name, date, item_id FROM orders;'
+    sql_params = []
+
+    result_set = DatabaseConnection.exec_params(sql,sql_params)
+
+    orders = []
+
+    result_set.each do |record|
+      orders << get_order(record)
+    end
+
+    return orders
+
+  end
+
+  # Gets a single record by its ID
+  # One argument: the id (number)
+  def find(id)
+    # Executes the SQL query:
+    # SELECT id, customer_name, date, item_id FROM orders WHERE id = $1;
+    sql = 'SELECT id, customer_name, date, item_id FROM orders WHERE id = $1;' 
+    sql_params = [id]
+
+    result = DatabaseConnection.exec_params(sql,sql_params)
+
+    return get_order(result[0])
+
+  end
+
+  def create(order)
+    # Executes the SQL query:
+    # INSERT INTO orders (customer_name, date, item_id) VALUES ($1, $2, $3);
+    sql = 'INSERT INTO orders (customer_name, date, item_id) VALUES ($1, $2, $3);'
+    sql_params = [order.customer_name, order.date, order.item_id]
+
+    result = DatabaseConnection.exec_params(sql,sql_params)
+
+    return nil
+
+  end
+
+  private
+
+  def get_order(record)
+    order = Order.new
+    order.id = record['id'].to_i
+    order.customer_name = record['customer_name']
+    order.date = record['date']
+    order.item_id = record['item_id'].to_i
+
+    return order
+  end
+end